Abstract - University of Arizona



Sustainability and Affordability:How Single-Family Home Retrofits Can Achieve BothJason GoffMentor: Colby MoellerFall 2015SBE 498Table of Contents TOC \o "1-4" \h \z \u Abstract PAGEREF _Toc436681952 \h 1Introduction PAGEREF _Toc436681953 \h 2Methodology PAGEREF _Toc436681954 \h 3Literature Review PAGEREF _Toc436681955 \h 4Sustainability and the Built Environment PAGEREF _Toc436681956 \h 5The Modern Foundation for Sustainability PAGEREF _Toc436681957 \h 6The Three Pillars and the Built Environment PAGEREF _Toc436681958 \h 6Buildings and the Environment PAGEREF _Toc436681959 \h 7Energy and Pollution PAGEREF _Toc436681960 \h 7Water PAGEREF _Toc436681961 \h 9Building Materials, Waste, and Disposal PAGEREF _Toc436681962 \h 11Land Use PAGEREF _Toc436681963 \h 12Buildings and Society PAGEREF _Toc436681964 \h 14Buildings and Economics PAGEREF _Toc436681965 \h 16The Modern (Re)Built Environment PAGEREF _Toc436681966 \h 17New vs. Retrofit PAGEREF _Toc436681967 \h 20Retrofit Precedent PAGEREF _Toc436681968 \h 21Data & Discussion PAGEREF _Toc436681969 \h 22Sustainability and Affordability in Southern Arizona PAGEREF _Toc436681970 \h 22Case Study: The Tucson House PAGEREF _Toc436681971 \h 25Assets PAGEREF _Toc436681972 \h 26Deficiencies PAGEREF _Toc436681973 \h 27The Base Case Retrofit PAGEREF _Toc436681974 \h 28The Retrofit+Addition PAGEREF _Toc436681975 \h 34Cost PAGEREF _Toc436681977 \h 36Results PAGEREF _Toc436681978 \h 37Conclusions PAGEREF _Toc436681979 \h 41Limitations PAGEREF _Toc436681980 \h 42Recommendations PAGEREF _Toc436681981 \h 43Appendix PAGEREF _Toc436681982 \h iBibliography PAGEREF _Toc436681983 \h iii TOC \h \z \c "Figure" Figure 1. Water Use source: PAGEREF _Toc437631954 \h 10Figure 2: Heat Island Effect PAGEREF _Toc437631955 \h 13Figure 3: Health and Socioeconomic Status PAGEREF _Toc437631956 \h 15Figure 4. Green Home Listings in Tucson, Basic Characteristics PAGEREF _Toc437631957 \h 23Figure 5. Green Home Listings in Tucson: Cost and Availability PAGEREF _Toc437631958 \h 24Figure 6. Mortgage Calculator Results PAGEREF _Toc437631959 \h 24Figure 7. Affordable Home Price on a Median Income PAGEREF _Toc437631960 \h 25Figure 8. Tucson Green Housing Affordability PAGEREF _Toc437631961 \h 25Figure 9. Base Case House: Facing South PAGEREF _Toc437631962 \h 26Figure 10. Climate Consultant 6: Psychrometric Chart PAGEREF _Toc437631963 \h 29Figure 11. Climate Consultant 6: Design Guidelines Chart PAGEREF _Toc437631964 \h 30Figure 12. Base Case ResCheck Compliance Graphic PAGEREF _Toc437631965 \h 30Figure 13. Individual Strategy Comparisons PAGEREF _Toc437631966 \h 31Figure 14. Base Case Retrofit Floorplans PAGEREF _Toc437631967 \h 33Figure 15. Retrofit ResCheck Compliance Graphic PAGEREF _Toc437631968 \h 34Figure 16. Rendering of the Retrofit+Addition PAGEREF _Toc437631969 \h 35Figure 17. The Retrofit+Addition Floor Plans PAGEREF _Toc437631970 \h 36Figure 18. Retrofit+Addition ResCheck Compliance Graphic PAGEREF _Toc437631971 \h 37Figure 19. Construction Costs PAGEREF _Toc437631972 \h 37Figure 20. Base Case vs. Retrofit Annual Energy Use PAGEREF _Toc437631973 \h 38Figure 21. Base Case vs. Retrofit Annual Electricity Use PAGEREF _Toc437631974 \h 39Figure 22. Solar-Estimator Graphic PAGEREF _Toc437631975 \h 40Figure 23. Base Case vs. Retrofit Utilities Use & Cost Comparison PAGEREF _Toc437631976 \h 41Figure 24. Base Case vs. Retrofit Annual Emissions Results PAGEREF _Toc437631977 \h 42Figure 25. Retrofit+Addition Annual Energy Use PAGEREF _Toc437631978 \h 42Figure 26. Side-by-Side Utilities & Cost Comparison - All Three Case Studies PAGEREF _Toc437631979 \h 44Figure 27. Retrofit+Addition Emissions Results PAGEREF _Toc437631980 \h 44Figure 28. Retrofit+Addition Rendering PAGEREF _Toc437631981 \h 45Figure 29. Summary of Results PAGEREF _Toc437631982 \h 45Figure 30. Green Housing Affordability in Southern Arizona PAGEREF _Toc437631983 \h 46Figure 31. Energy & Emissions: 3 Case Studies PAGEREF _Toc437631984 \h 47AbstractClimate change and resource availability are arguably the two biggest challenges humanity faces going forward. An unprecedented body of scientific work has been compiled over the past thirty years that indicates humans have and continue to be the largest driver of these environmental concerns, and therefore must also be responsible for any solutions. Buildings and their construction account for nearly 40% of the total energy consumption and greenhouse gas emissions in the United States. Water consumption by both buildings and thermoelectric power generation is also an issue, especially in the Southwest and Western United States. Green building has been gaining steam in the U.S. for the past two decades, but the primary focus has been in the commercial and industrial sectors. The residential markets have not seen the efficiency gains, primarily due to the perception that the cost isn’t worth the benefit.This project examines the need, feasibility, and potential benefits of sustainably retrofitting existing homes as an alternative to new construction. It provides a broad definition of sustainability and then focuses into a more narrow description of its application within the built environment. Using precedents, 3D modeling, and energy simulation software it compares the energy and water savings of a retrofit versus a base case as well as the performance of the average Southern Arizona home. Finally, this capstone project provides a professional cost estimate for the implementation of the proposed changes and a side-by-side look at the available “green” housing market, the utility cost savings for the homeowner, and the environmental benefits of individual as well as large-scale adoption of sustainable retrofitting practices.IntroductionThe global scientific community has become increasingly certain that human actions are having a direct impact on our planet’s climate CITATION Gar14 \l 1033 (Garfin, 2014). As the global population continues to grow concerns are also being raised over human consumption exceeding the earth’s carrying capacity CITATION Pen12 \l 1033 (Pengra, 2012). As a result, in recent years, the concept of sustainability has become more of a mainstream topic. How to consume less power and produce more renewable energy, the quality and availability of freshwater sources, and resource conservation and reuse have all become higher priorities.Multiple points of attack for these problems have been identified, however a few of these show greater promise for having a larger, faster, and longer lasting impact than the rest. One area of focus is the built environment. According to the United Nations Energy Programme website, “Buildings use about 40% of global energy, 25% of global water, 40% of global resources, and they emit approximately 1/3 of greenhouse gas (GHG) emissions.” CITATION Sus15 \l 1033 (Sustainable Buildings and Climate Initiative, n.d.) In the U.S. buildings consume approximately the same amount of energy, but domestically account for over 70% of electricity usage and produce nearly 40% of the total GHG emissions CITATION Bui09 \l 1033 (Buildings and their Impact on the Environment: A Statistical Summary, 2009). Beyond the environmental implications of a changing climate and a growing population, discussion surrounding sustainability has developed to include social and economic principles. The Three Pillars of Sustainability, or the triple bottom line as it is sometimes described, asserts that for true sustainability to be achieved environmental, economic, and social factors must all be relatively balanced. Balancing the principles makes sense, as adverse environmental consequences are sure to impact economies and societies, but at the same time if a solution to an environmental problem is socially unjust, or economically unsustainable, then it is unlikely to succeed. Arizona and the Southwest present a unique opportunity to take a look at the built environment and its current interaction with the three factors, and what we have to gain by becoming more sustainable. The 3rd U.S. National Climate Assessment describes the challenges facing this region:The Southwest is the hottest and driest region in the United States, where the availability of water has defined its landscapes, history of human settlement, and modern economy. Climate changes pose challenges for an already parched region that is expected to get hotter and, in its southern half, significantly drier. Increased heat and changes to rain and snowpack will send ripple effects throughout the region’s critical agriculture sector, affecting the lives and economies of 56 million people – a population that is expected to increase 68% by 2050, to 94 million. Severe and sustained drought will stress water sources, already over-utilized in many areas, forcing increasing competition among farmers, energy producers, urban dwellers, and plant and animal life for the region’s most precious resource. CITATION Gar14 \l 1033 (Garfin, 2014)The report goes on to cite sea level rise, human health impacts, agricultural productivity, loss of species diversity, and disrupted economies as the other significant casualties of climate change in this region if nothing changes. This capstone will examine one potential piece of the change necessary to avoid these catastrophes. Its goal is to demonstrate that a well thought out sustainable retrofit of an existing home is economically feasible, will make sustainable living more accessible to a larger segment of society, and have a significantly positive impact on the environment. MethodologyThis project will use primarily quantitative analyses to evaluate how well or poorly the average home and the average existing “sustainable” home in Tucson performs using the triple bottom line as a metric. However, certain categories of evaluation, such as land use and house size, are more subjective and require that a qualitative standard be established. Is a net zero house that is 4,000 square feet still sustainable? Is a green home that requires clearing pristine desert to build sustainable? For the purposes of this study, less is more or, “The most sustainable building is the one that isn’t built” ( CITATION Rob07 \l 1033 (Roberts, 2007). Using this data to establish a baseline for improvement, I will then study the feasibility of retrofitting a run-of-the-mill slump block home in Tucson to perform better in all three categories of the triple bottom line. Utility bills, computer energy analysis, and a 3D digital model of the existing structure will provide the base case, and each sustainability upgrade will be quantitatively analyzed in terms of performance and cost, and documented in the model. In addition to the upgraded base case, a second model that includes an addition of a bedroom and bathroom, adding approximately 500 square feet to the original footprint will be included. This will serve to make for a more equal comparison with the current sustainable home offerings, as their square footages are typically larger than older homes. Qualitatively it will also represent a finished product that is more in line with the current home buying trends in the U.S., and hopefully suggest that affordable sustainable home ownership can be more of a lateral move rather than a sacrifice of space or comfort. Literature ReviewUltimately this paper argues that redesigning and redeveloping existing housing to sustainable efficiency standards is not only feasible, but better at achieving the economic, social, and environmental balance needed in the face of climate change and growing populations than current new home design and construction standards, including most so-called green or sustainable homes. The purpose of this literature review will be to provide a modern definition of sustainability and explain the immediate need for its adoption; explain how sustainability is related to the built environment; and to examine studies and precedents of sustainable retrofitting and compare them to current building practices and costs.Sustainability and the Built EnvironmentThe UN Environment Programme’s report, Buildings and Climate Change: Summary for Decision Makers, released ahead of the Copenhagen 2015 conference laid out six key points: 1. The building sector has the most potential for delivering significant and cost-effective GHG emission reductions. 2. Countries will not meet emission reduction targets without supporting energy efficiency gains in the building sector. 3. Proven policies, technologies and knowledge already exist to deliver deep cuts in building related GHG emissions. 4. The building industry is committed to action and in many countries is already playing a leading role. 5. Significant co-benefits including employment will be created by policies that encourage energy efficient and low-emission building activity. 6. Failure to encourage energy-efficiency and low-carbon when building new or retrofitting will lock countries into the disadvantages of poor performing buildings for decades. CITATION Huo09 \l 1033 (Huovila, et al., 2009)This section of the literature review looks at the relationship between sustainability and buildings in terms of the environment, society, and economics and will provide the foundation for the argument that sustainable retrofits can address the six points above as well or better than current building practices. The Modern Foundation for SustainabilityIn 1984 the World Commission on Environment and Development (WCED), formed at the request of the United Nations, set out to examine issues of the environment and development, as well propose solutions. In 1987 the WCED (also known as the Brundtland Commission after its chairman) released the Brundtland Report, titled “Our Common Future”. It was not groundbreaking in the sense that the issues they highlighted were unheard of, but there were four key elements that represented a change in attitudes and thinking and have continued to shape the discussion on humanity and its interaction with the environment and each other. The first major change was that the 21 nations involved with the report were able to come to a consensus, not just on identifying the problems, but also on leveling responsibility and proposing solutions. The second thing the Brundtland Report did was permanently link the environment with development: "...the "environment" is where we live; and "development" is what we all do in attempting to improve our lot within that abode. The two are inseparable." (Brundtland, 1987). No longer could the natural world we live in exist as a separate entity from the environment we create. The third thing the report gave us was a modern definition of sustainable development: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs” (Brundtland, 1987). Finally, and perhaps their most important point of agreement, the Brundtland Commission clearly laid out the connection between environmental health, social justice, and economic prosperity. The three are interdependent, and a sustainable future requires good stewardship of all three (Brundtland, 1987).The Three Pillars and the Built EnvironmentThe built environment, although just one of many pieces of the global sustainability puzzle, has a disproportionately large effect on all three pillars of sustainability. Land use and resource consumption (environment), affordability and availability (social), and material and labor costs as well as market fluctuations (economic) are just some of the many interrelated factors that can work for or against the successful implementation of sustainable buildings. With so many challenges to solve it is reasonable to ask the questions: Are we really living that unsustainably? Is sustainability worth the headache? What risks do maintaining the status quo present? The following review of reports, statistics, and scientific projections will answer these questions, and provide the opportunity to reframe them.The United Nations’ Intergovernmental Panel on Climate Change (IPCC), created in response to the Brundtland Report, has been analyzing and reviewing thousands of scientific papers and reports from across the globe since 1988. A series of five summary reports, the first in 1990 and the latest in 2014, have all been publicly released and are the basis for ongoing international discussions on the causes, the immediate and projected impacts, and solutions to the human contribution to climate change. With each report the degree of certainty that man-made factors have contributed to climate change has increased, with the latest report stating “with 95 percent certainty that human activity is the dominant cause of observed warming since the mid-20th century.” (Climate Change 2013: The Physical Science Basis) The consensus is that human activities have contributed to a 70% increase in global greenhouse gas (GHG) emissions since the 1970s. The next three sections will examine in more detail the interaction between the built environment and society, the economy, and the natural world. While some impacts are specific to one pillar of sustainability, it is important to remember that all three categories are interrelated. What affects one also has consequences for the other two.Buildings and the EnvironmentEnergy and PollutionThe U.S. represents around 4.5% of the world’s population, yet energy consumption by buildings alone in the U.S. accounted for 7% of total global energy use CITATION USD12 \l 1033 (U.S. Dep't of Energy, 2012). Three quarters of the energy consumed by U.S. buildings is produced by fossil fuels, and 84.5% of our total GHG production is energy related CITATION EPA151 \l 1033 (EPA, 2015). Methane emissions attributed to building energy consumption totaled an equivalent to 176 million metric tons of C02 (measurements of GHG emissions are typically standardized by converting to C02 equivalencies) in 2009 and account for only 10% of our GHG production CITATION EPA152 \l 1033 (EPA, 2015). However, according to the Environmental Protection Agency (EPA), “Pound for pound, the comparative impact of CH4 on climate change is 25 times greater than CO2 over a 100-year period.” This is an important point, as methane releases will grow considerably as natural gas is the alternative of choice to coal and government initiatives to reduce C02 emissions have made coal power less profitable for energy companies. Electricity production accounts for 32% of the U.S.’s CO2 production, with 10% added from commercial and residential activities. Methane’s ties to energy lay primarily in resource extraction, with nearly 40% of its atmospheric releases being tied to coal mining and natural gas and petroleum systems (). While design changes in architecture, mechanical systems, and appliance technology have improved building efficiencies by 30% over older building stock, population growth and the subsequent need for more housing, increased home sizes, and the additional power requirements of new personal technology (PCs, laptops, phones, etc.) have increased residential energy consumption by 39%. CITATION Cen15 \l 1033 (Center for Climate and Energy Solutions, 2015)Air pollution and greenhouse gassesare often the focus of pollution discussions given their contributions to climate change, however there are there are risks associated with the built environment that should not be ignored. Material choices, whether in new construction or retrofits, can pose a significant impact to human health. Off-gassing, also called out-gassing, is the result of volatile organic compounds (VOCs) becoming gases at room temperature CITATION Air15 \l 1033 (AirData, 2015). The EPA warns that the concentration of these gases can contribute to eye, nose, and throat irritation as well as the buildup of ground level ozone. Extended exposure to some VOCs, like formaldehyde, have been found to cause cancer CITATION Pen06 \l 1033 (Penafiel, 2006). Found in everything from plywood and wood composites to paint and adhesives, VOCs are hard to avoid in any new building project and extensive remodels, but there are low-VOC products on the market, and several strategies minimize or eliminate the risk of human contact with them.Materials and design choices can also affect our water supply both during construction and occupancy. New site preparation generally involves considerable earth grading and moving, potentially generating runoff sediments that find their way into streams, rivers, and other water bodies that impact marine ecosystems. Roofing materials, concrete, pavement, paint, and even treated wood can release an array of heavy metals and organic compounds into water supply through normal runoff CITATION Cla09 \l 1033 (Clark, 2009). WaterEnergy production and consumption and their attendant pollution are just one of the many environmental impacts of buildings to be considered, however they go hand in hand with water. Often the focus on the built environment is centered on improving energy efficiency, however, the water cost of producing energy is not always equally discussed. Water is used in every method of electricity generation we currently employ in the U.S except for wind and solar. Water is also used in varying amounts during nearly every step of the extraction and refining of fossil fuels, our primary energy source. Even “clean” energy like biomass is exceptionally water intensive. Conversely, we use massive amounts of energy, by one estimate 13% of our total national energy use, for water related energy uses CITATION The09 \l 1033 (Bevan Griffiths-Sattenspiel, 2009). Reciprocity between energy and water makes improving efficiencies and decreasing consumption of both a key component of any discussion about sustainability. The EPA estimates that if 1% of American homes were retrofitted with water-efficient fixtures we would reduce GHG emissions by 80,000 tons and reduce electricity consumption by enough to power 43,000 homes for a month CITATION Wat11 \l 1033 (EPA U. , 2012).The availability of freshwater, particularly in the West and Southwestern United States, has been a major issue for decades, if not longer in some areas. The effects of climate change have intensified the strain on this critical resource in these regions as evidenced by long term extreme drought conditions, record and more regular heat waves, and longer and more destructive wildfire seasons. The climate models don’t bear much good news for the southern and western United States either. A 10-20% reduction of runoff from snowmelt is predicted over the next 50 years; warmer temperatures will increase evaporation leading to less water available for groundwater recharge; and earlier seasonal warming will affect the timing of river and stream flows, affecting the water availability during traditionally peak use periods CITATION Geo14 \l 1033 (Georgakakos, 2014). Despite the visible and measurable evidence that water conservation should be of the utmost importance, the U.S. continues consume more water per capita than any other nation CITATION Fis12 \l 1033 (Fischetti, 2012). Globally irrigation accounts for over 70% of water use, yet the USGS chart below shows the bulk of U.S. groundwater withdrawals is tied up in thermoelectric power production. Figure SEQ Figure \* ARABIC 1. Water Use source: average nationally is that it takes two gallons of water to produce one kilowatt hour (kWh) of electricity, while nearly 4.5 gallons of water are needed in the Western region of the U.S., and in Arizona it requires seven gallons. The differences are due to the varieties of energy sources used. Arizona receives a significant portion of its power from hydroelectric, which ironically is good for clean energy production, but poor (in a hot, arid climate) for evaporation. Lake Powell and Lake Mead, both created by hydroelectric dams along the Colorado River, lose an average of 2.3 billion gallons of water to evaporation each year compared to the natural evaporation rate of the river CITATION PTo03 \l 1033 (P. Torcellini, 2003). In a state where each household’s electricity consumption averages 1000 KWh/month, 7 gal/kWh is significant. Beyond the water embedded in our energy consumption, the average U.S. Household uses around 80-100 gallons per day (gpd), according to the USGS website. Tucson is slightly higher than the national average with 102 gpd, but is a leader in the Southwest when compared to Phoenix at 123 gpd, or California at 360 gpd (or 170 gpd with outdoor watering restrictions in effect). The USGS attributes 13.6% of our groundwater withdrawals to buildings CITATION Wat15 \l 1033 (Water Use in the United States, 2015). It is clear that improving power generation and irrigation water use efficiencies are going to have the greatest effect in assuring our future freshwater supply, yet there are many things that designers, builders, and homeowners can do to reduce the consumption in the building sector. According to the American Water Works Association a 30% reduction in total water consumption by U.S. households could happen by simply switching to water efficient fixtures, resulting in a daily savings of 5.4 billion gallon CITATION Wat151 \l 1033 (Water Use Statistics, 2015).Building Materials, Waste, and DisposalFrom 1900 to 2010 the U.S. consumption of raw materials, any resource other than fuel or food, increased 2.8 times faster than the population grew. At its peak, just before the financial collapse in 2006, three-quarters of that was used in construction, totaling nearly 3 billion metric tons of materials CITATION Mat12 \l 1033 (Matos, 2012). Consumption dropped by 34% during the recession, but is a trend that has already begun reversing as the demand for new construction has begun to pick back up.In 2013, the municipal solid waste (MSW) produced in the U.S. totaled 254.1 million tons, with just over 34% being recovered through recycling and composting CITATION Was15 \l 1033 (Wastes - Non-Hazardous Waste - Municipal Solid Waste, 2015). By comparison, the total construction and demolition (C&D) waste for the same year was 162.2 million tons, with an estimated 20-30% being recycled CITATION EPA15 \l 1033 (EPA, 2015). Of that, approximately 50% was produced by buildings – roads, infrastructure, and “other” account for the rest. A 2009 report by the EPA estimated that residential construction in 2003 accounted for nearly 40 million tons of materials demolitions, while renovations produced 19 million tons of waste. These numbers are expected increase, with an estimate of 82 billion tons to be generated between 2005 and 2030 CITATION Fre11 \l 1033 (Frey, 2011). Economic fluctuations will produce year to year variation in these totals, but on average four pounds of waste are generated per square foot of building, or between two and seven tons for a new, median-sized single family home, and fifteen to seventy pounds of hazardous waste (paint, caulking, aerosols, adhesives, etc.) are normal byproducts of new construction. Not only does C&D waste present the issue of its disposal, it also represents enormous quantities of embodied energy, and even higher life-cycle energy costs. Embodied energy is the amount of energy it takes to create a product. A life-cycle assessment of materials factors in the embodied energy as well as maintenance and eventual disposal of a product for its entire lifespan, also known as cradle to grave. This is a more accurate measure of a building’s contributions to energy consumption, pollution, and overall cost than just looking at a materials invoice and some utility bills. Land UseAfter World War II there was a mass exodus from our city centers out to the new suburbs. We were in a booming post-war economy and homes, cars, and fuel were affordable, and those who had the means saw no problem with commuting. This was the beginning of urban sprawl, and began a period of growth during which “Urban land acreage quadrupled from 1945 to 2007, increasing at about twice the rate of population growth over this period.” This represents a jump from around 15 million acres to over 60 million acres. CITATION Cyn11 \l 1033 (Cynthia Robertson, 2011). Forty-one percent of that acreage was previously forest land, and fifty-two percent of it was rural land previously used for agriculture. Several studies have found that closer proximity to development increases the “…threat from pests, disease, pollution, and fire” to forests as well as “…decrease management, investment, and harvest rates on private forestlands.” CITATION Cyn11 \l 1033 (Cynthia Robertson, 2011) In addition to forest and arable land loss, grasslands, wetlands, and desert have also been impacted. Beyond the biodiversity loss and risks to ecosystems health caused by urban expansion, the encroachment into forests, grasslands, and wetlands also represent reductions of natural carbon sinks. Reductions to natural systems that regulate carbon just accelerate the problem of climate change. Draining wetlands presents the added negative of methanogenesis, or the process of methane being released when organic material is oxidized.Fortunately land use is one area that is beginning to show signs of progress. The trend of outward migration to the suburbs is reversing, with more and more people returning to urban cores. This is good for land conservation efforts, but will present other challenges mostly out of the scope of this paper. One area of consideration is ground cover. In dense urban city centers and sprawling stretches of strip malls and neighborhoods devoid of the native trees they are named after, the proliferation of asphalt, concrete, brick and the noticeable absence of natural vegetation contribute to a couple of problems. This is called impervious ground cover, and it has a couple of consequences. The first is called the heat island effect, a phenomenon resulting from the storage of solar energy in man-made materials throughout the day resulting in even hotter days and, as anyone who has been in Phoenix at night during the summer, not much cooler nights. This causes the temperature to remain higher than it would normally, which means people are using air conditioning more, consuming more energy, thus producing more GHGs, and the cycle just gets worse and worse. Source: Figure SEQ Figure \* ARABIC 2: Heat Island Effect The second problem has to do with the effect of impervious ground cover on water runoff. Precipitation cannot get through the asphalt and concrete that is spread across the surface of the earth, which also means that the natural vegetation has been mostly if not completely removed. This has the effect of altering water runoff and changing natural water flows; it also affects water quality by delivering every pollutant, toxic contaminant, and fertilizer that can be washed onto and off of these surfaces to the nearest watershed. These are problems that should be being tackled by city planners, but developers, builders, and homeowners can also do much to minimize the impacts of single family homes by paying attention to landscaping and material selection.Buildings and SocietyThe built environment affects society everything from social mobility and human health to our relationships with the natural environment and one another. Some of the observed characteristics of homeowners include: a generally higher level of success in labor markets compared to renters; better ability to maintain and improve property; more environmentally conscious than non-homeowners; more politically and socially involved; improved mental and physical health CITATION Die03 \l 1033 (Dietz, 2003). These social benefits are reinforced by the economic incentives provided by federal, state, and local governments for homeownership. However these opportunities have not, and arguably continue to not be, equitably distributed among the U.S. population, particularly along racial lines. Socioeconomic status and the opportunity for ownership has been studied extensively for decades and the consensus is that housing discrimination has contributed to an ever growing income gap with minority groups being disproportionately affected. One Harvard University Law School study found that the median net worth of a homeowner in the U.S. was $171,000, while that of a renter was only $4,800 CITATION Web06 \l 1033 (Webb-Williams, 2006). The relationship between socioeconomic status and health and life expectancy has also been well documented, with a combination of physiological and psychological stresses reducing the productivity and lifespans of those economically disadvantaged CITATION Sap05 \l 1033 (Sapolsky, 2005)Source: Scientific AmericanFigure SEQ Figure \* ARABIC 3: Health and Socioeconomic StatusThe built environment also affects society in subtler ways. Professor Kaveh Samiei, an architect and researcher at Penn State University, believes the built environment can create either a connection or a disconnection between humans and the natural environment. Since the industrial revolution and the advent of the modern city, he believes, humanity has become increasingly separated from the natural world, much to our detriment:Ecosystems provide our basic human and social needs. The biosphere nurtures our mind and soul, as well as our stomachs and lungs. The modern city is organic process, but one with an unhealthy bio system. The biophilia hypothesis suggests that humans have an innate tendency to affiliate with other living organisms and living processes. Humans require contact with a biodiverse world to stimulate the development of their emotional, cognitive, and social potential. As the living community of other organisms is reduced and human interaction with that community is lost, there is an extinction of experience that results in a loss of real ecological knowledge and emotional attachment to nature. CITATION Sam13 \l 1033 (Samiei, 2013)The population of a world facing a climate crisis cannot continue to be indifferent to everything beyond the concrete and asphalt of their immediate surroundings. Humans seem to have an innate ability to avoid being proactive, relying on intellect and technology to reactively solve self-imposed crises. This may prove useful in adapting in the short-term, but a deeper connection to our planet, understanding ourselves to be a part of a single ecosystem and respecting it and caring for it as such, is the only way humanity is going to find the collective will to adopt the sustainable principles necessary for us to avoid producing even greater climate change and its consequences.Buildings and EconomicsTo understand the impact of housing on our economy one only has to look as far back as the most recent recession. Housing is as much a cornerstone of our economic system as it is the American dream. It’s so important that it is federally subsidized – upwards of $121 billion in 2013 alone – through mortgage programs like Fanny Mae and Freddy Mack, and property tax deductions, and capital gains tax exclusions CITATION Har13 \l 1033 (Harris, 2013). Yet even as the government props up the housing market in the interest of economic stability, it ignores a windfall of both public and private benefits to be had by raising standards meaningful on design efficiency and build quality, while at the same time incentivizing that environmental and social responsibility for owners and developers. It’s really simple math: healthier buildings mean a healthier, more productive society; lower energy bills mean more money to be spent or invested in other segments of the economy; a healthier environment benefits human health and reduces the costs of mitigating environmental damage; sustainable design and construction requires new expertise, technology, and innovation which creates new jobs in several sectors; and most importantly it reduces the burden on the generations to come. Unfortunately at this time federal and, in many places, state funding for programs and incentives that promote green building and retrofits is mostly nonexistent for residential construction. The U.S. construction industry across all sectors - commercial, residential, industrial - accounts for 5.5% of the total GDP in the U.S., and green projects have been steadily growing as a share of the market, particularly in commercial and industrial applications. However, the potential for the private home market is enormous. One study estimates the ten year potential for residential retrofits alone could reach $400 billion, creating 280,000 jobs directly and over 660,000 indirectly CITATION Pol09 \l 1033 (Pollin, 2009). The USGBC suggests there is far more money to be made, stating “Current market trends suggest that building owners and managers will invest an estimated $960 billion between now and 2023 on greening their existing built infrastructure.” CITATION USG15 \l 1033 (USGBC, 2015)The Modern (Re)Built EnvironmentThis project’s aim is to prove that existing homes can be retrofitted to become sustainable, which requires a definition of what exactly that means. Unfortunately a single, concise, universally agreed upon definition for a sustainable building does not exist. So it’s no surprise there are as many sets of sustainable building principles, rules, and fundamentals as there are green building and third party certification programs that award recognition for reaching sustainable goals that meet their specific definitions of what it means to be green. Programs such as the EPA’s Energy Star and WaterSense target specific areas of efficiency and conservation. The Energy Star program reviews, rates, and labels everything from light bulbs and appliances to roof coatings and windows, providing consumers with at-a-glance energy efficiency information. WaterSense applies the efficiency principles of Energy Star to plumbing fixtures and water saving products.Perhaps the most well-known green building certification is the U.S. Green Building Council’s program, Leadership in Energy and Environmental Design (LEED), a points based system that focuses on design efficiency, sustainable building practices, materials, building performance, and occupant health. Some critics have pointed out that the points system can sometimes be gamed to achieve certification for buildings that do not perform well. Credits for bicycle racks, limiting the number of parking spaces, LEED accredited team members (required for the certification process anyway), and a handful of other low hanging fruit can gain buildings accreditation while they fall short in other areas. Another criticism is that the certification process can be completed prior to occupancy, so theoretical performance models and not actual energy loads are used to determine whether or not a building receives achieves LEED status.Despite these drawbacks, due to its market-based approach and user input driven revision process, the program has probably been the single greatest influence in the rise of green building in the United States, and each new version of LEED that has been released has become progressively more stringent. The Home Energy Rating System (HERS) is a system developed by the Residential Energy Network (RESNET), a nonprofit founded in 1995 to help owners improve their home’s efficiency and reduce utility bills. Using the U.S. Department of Energy’s assessment that a typical resold home scores 130 on the HERS index and a newly constructed home rates around 100, a baseline is given to begin applying and assessing efficiency strategies. The lower the HERS number the better performing the home CITATION RES15 \l 1033 (RESNET, 2015). Another program, considered by many to be the most difficult to achieve certification in is the Living Building Challenge. Certification requires that attention be paid to the environmental, social, and economic aspects of sustainability and divides its focus among seven “petals” that include Place, Energy, Water, Health & Happiness, Materials, Equity, and Beauty which are further subdivided into twenty Imperatives. The end goal are buildings that more reflect the natural environment in that they are net energy producers, designed with their entire lifecycle in mind - including deconstruction, and promote symbiotic relationships between the ecosystems and social networks they inhabit CITATION Liv51 \l 1033 (Living Building Challenge, 2015).Most of these add up to a lot of good intentions, and generally they do lead to buildings with improved performance, but rarely do they produce a truly sustainable end result. In terms of the IPCC’s definition of “development that meets the needs of the present without compromising the ability of future generations to meet their own needs“ there are common principles among the certification programs that, when applied with the intention of achieving a truly sustainable result instead of just a green label, sustainability can be achieved. The first of these is to use integrated design principles. This means the entire building has to be thought of as the sum of its parts and how well they interact with each other. This requires a higher level of involvement from the owner, designer, builder, and the various subcontractors that will be involved with a project. Together, before the project even begins, they will establish the performance goals for the structure and collaborate on the most effective and efficient strategies to achieve them. A well-integrated design will also consider the life cycle of the building, as well as potential reuse or decommissioning possibilities.The second common principle is to optimize energy performance. Typically energy conservation efforts begin with a base case modeled off of the minimum performance required by building code, then a target percentage for reducing energy consumption is set. A building’s envelope – walls, windows, and roof – is generally where the most cost effective upgrades occur. Insulating walls and the roof can offer substantial energy savings, while high performance windows can be designed for specific climate needs and are crucial to a structure’s energy performance, as inefficient windows can negate any gains upgraded insulation provides. Another envelope consideration is shading. Blocking direct exposure to the sun whether with trees or bushes or built shading structures can greatly improve building envelope performance. The final piece of the envelope puzzle is how tight, or well-sealed, the project is. This is particularly important in older existing buildings that can be quite drafty, increasing the energy load to heat and cool the building.The interior of a building offers energy saving potential in light fixtures, appliances, and mechanical systems. Lighting can be minimized if effective daylighting strategies are used, such as window placement, skylights, and interior walls and color palate that effectively allow natural light to be distributed throughout the interior. The lighting that is required can take advantage of high efficiency, low heat producing LED fixtures and bulbs. The Energy Star website makes it easy to find and compare the top performing appliances on the market, and energy efficient appliances can have a meaningful impact on utility bills. Energy Star also rates climate control systems, and along with a qualified HVAC technician, a properly sized heating and cooling system integrated with a high performance building envelope can substantially reduce the cost of achieving thermal comfort, especially in more extreme climates. If possible, locating all ductwork within the conditioned space, rather than outside or in attic spaces, will also improve HVAC efficiency. Finally, reducing plug loads from TVs, computers, stereos, small appliances, and anything else that can be plugged into an outlet can offer more savings than one might think. One study found that plug loads, even from devices that were “off”, drew 569 kWh in a year ( CITATION Hol09 \l 1033 (Holladay, 2009). In some areas that equates to adding an extra month of electricity consumption to an annual bill.New vs. RetrofitIn from 2005 to 2011 the green building market grew from $10 billion to $78 billion, and is projected to increase to more than $200 billion in 2016. The bulk of the growth has been happening in the commercial and industrial sectors, however the residential market is expected to have an 18% increase from 2012 to 2016, representing 20% of the market CITATION Dod12 \l 1033 (McGraw-Hill: Analytics, 2012). With the U.S. population projected to grow by at least 100 million over the next 35 years, new housing is going to be necessary, and if construction trends stay constant it would not be unreasonable to expect that 50% or more of new homes will be built green by 2050. This is good news, but despite their sustainable labels there are carbon costs to new construction – even in homes that have substantially improved energy performance – that are rarely acknowledged. An in-depth study commissioned by the National Trust for Historic Preservation found that “Building reuse almost always yields fewer environmental impacts than new construction when comparing buildings of similar size and functionality.” The same report found that residential retrofits with energy performance comparable to that of new green construction had 15-17% reduction in climate change related impacts, and were 31-35% less detrimental to their surrounding environments CITATION Fre11 \l 1033 (Frey, 2011). They also discovered that new structures built to be 30% more efficient than International Energy Conservation Code standards, the minimum for a LEED for Homes certification, can take between 10 to 80 years to offset the carbon emissions involved just in their construction. This strongly indicates that while new, green construction will be vital to providing housing and meeting our carbon-reduction goals in the future, it will not immediately minimize construction related carbon emissions. The extent to which we have to rely on new construction to meet our future housing needs will depend on the degree of investment in building reuse and retrofitting we see going forward. The 2015 Residential Vacancies and Homeownership 3rd quarter report released by the Census estimated there are nearly 17.5 million vacant homes in the U.S., and 50% of the U.S. residential building inventory was constructed before 1975. This represents easily 40 million single-family homes nationwide that are potential deep-energy retrofit candidates, and there are likely millions more built after 1975 that would benefit as well (Appendix, Table 1. American Housing Survey). Retrofit PrecedentThe ReVISION House in Las Vegas, Nevada is a 1960s “desert-modern” home designed by William Krisel. Building Media, Inc. and Green Builder? Media, LLC collaborated with the U.S. Department of Energy to perform a deep-energy retrofit that would reduce the home’s current $500/month utility bills by 60% and then with the addition of PV solar bring the house to net-zero energy consumption. The 1,800 ft?, single-story home has low-pitched roofs, wood framing, and lots of windows. An energy audit found that old R-11 wall insulation that performed worse than the wood studs, no roofing insulation, single-paned aluminum framed windows, unsealed ductwork, inefficient HVAC and water heating units, incandescent lighting, and a drafty building envelope contributed to abysmal energy performance. The exterior stucco and sheathing was removed and spray foam was applied to the wall cavity, then the house was re-sheathed and wrapped with weather barrier and an additional layer of rigid foam exterior insulation panels before a new stucco finish and paint was applied to the new R-21.5 walls. All the windows were replaced with triple-paned, fiberglass framed Milgard windows. Eight inches of spray urethane insulation was also used to insulate and seal the rafter bays of the roof, and an integrated air gap and venting system beneath the metal standing seam BattenLok? cool roof created a system that exceeded an R-45 insulation value. All the mechanical systems were upgraded to high efficiency units, and the ductwork was located within the conditioned space, mastic sealed, and insulated to R-8. Solar hot water was added and connected in series with a new tankless water heater programmed to turn on only if the preheated water was below a set temperature. Inside the house several fixtures were upgraded to LEDs and the remaining fixture were upgraded with LED or CFL lightbulbs. A whole house fan was installed to aid in ventilation, expelling warmer air and drawing healthy fresh air into the much tighter sealed home. In an effort to minimize the cost of the retrofit they attempted to do as much of the work from the exterior of the house as possible, minimizing the amount of drywall repair and refinishing required. In addition to the targeted upgrades, the plumbing was inspected and replaced where necessary to avoid future pipe and fixture leakage, and some minor demolition and reframing was performed to improve air circulation. The result of all these upgrades was a home that began with a HERS Index score of 123 improving to a 44 before factoring in PV solar. After solar was added the HERS rating improved to -2, effectively become a net zero home.The estimated cost of the retrofit was $150,000 bringing the total cost of purchase and improvements to $295,000 CITATION Gre10 \l 1033 (Green Builder Media, 2010).Data & DiscussionSustainability and Affordability in Southern ArizonaWith the triple bottom line as a guide, searching the sustainable housing market in the Tucson area leads only to one conclusion: there is very little true sustainable housing. The vast majority of homes listed for sale as being “green” are either unaffordable or unsustainable. An internet search for green/sustainable homes in Southern Arizona turned up a couple of specialty websites and some individual listings from sites such as Zillow and . Sixty homes from Tucson and surrounding areas were compiled into a database that took into account location, age of construction, square footage, number of bedrooms and bathrooms, construction type, sustainable features, net zero performance, green certifications, and cost. (Appendix, Table 2)SizeBedroomsBathsAcreageCostAverage2,182 ft2331.37$344,709Median1,884 ft232.50.14$257,900After considerable searching, only five homes were listed for sale that could be considered truly sustainable, even in just terms of their energy and water use, and their prices ranged from $229,000 to $1.2 million. The two out of those five homes that were under $300,000 were in rural locations. Figures 4 & 5 give some basic statistics for homes listed as green or sustainable in the Tucson area. Figure SEQ Figure \* ARABIC 4. Green Home Listings in Tucson, Basic CharacteristicsLess than one third of the homes incorporated any onsite energy production, however of the sixty surveyed 40% had solar hot water capabilities and around 65% were designed with some type of water saving fixtures, greywater plumbing, or rainwater harvesting systems. Less than 10% were anywhere close to being net zero, and that number would have gone even lower had the sample size been larger. More than 93% of the homes surveyed were new construction. Less than 7% were retrofits. (Appendix, Table 2). CategoryPriceAvailabilityMedian Listing Price of Net Zero Home$390,0008.3%Average Listing Price of Net Zero Home$579,200of sampled listingsMedian Listing Price of Home With PV$382,18131.7%Average Listing Price of Home With PV$289,000of sampled listingsAverage Listing Price of Green Remodel$631,7506.7%Median Listing Price of Green Remodel$524,000of sampled listings Figure SEQ Figure \* ARABIC 5. Green Home Listings in Tucson: Cost and AvailabilityThe three year average median income collected by the Census over the 2011-2013 period for Tucson was $49,774, with a standard error of $2,560. A 2011 Census report showed median unsecured debt (credit cards, student loans, medical bills, small loans, etc.) was around $7,000 CITATION Vor15 \l 1033 (Vornovytskyy, Gottschalk, & Smith, 2011). The average annual property taxes in Tucson are $1,524 and homeowners insurance averaged $540. So how much house can a median income earner with good credit (a 3.85% APR was assumed) and a $10,000 down payment?Figure SEQ Figure \* ARABIC 6. Mortgage Calculator ResultsThe final affordable house prices were determined by entering the income, debt, insurance, and property tax information into five different mortgage calculator programs and taking the average (Appendix, Table 3). Obviously the debt, insurance, and tax categories are subject to variation, so taking the Census estimated medians for each category seemed the fairest starting point for determining affordability. In reality, the affordability on median income would tend to be closer to the “10% below” numbers since unsecured debt doesn’t factor in secured debt such as automobile loans, however for the purposes of this study I think the ranges calculated below (Figure 7) are sufficient for determining the affordability of currently available sustainable housing in southern Arizona, and whether or not sustainable retrofits offer a cost effective alternative.IncomeAnnual Unsecured Debt (est.)Annual Homeowners Insurance (est.)AnnualProperty Taxes (est.)Affordable House Price10% Below Median$44,796$7,000$540$1,524$172,401Median$49,774$7,000$540$1,524$200,74010% Above Median$54,751$7,000$540$1,524$227,834Figure SEQ Figure \* ARABIC 7. Affordable Home Price on a Median IncomeThe affordable price ranges in Figure 7 compared to the median costs of the sampled listings, and the pie chart below (Figure 8) make it pretty clear that a large percentage of sustainable homes are out of reach for those living on a median income, and there is potentially a lot of money to be made in affordable green retrofitting if it can be proven to be cost effective. Figure SEQ Figure \* ARABIC 8. Tucson Green Housing AffordabilityCase Study: The Tucson HouseThe home being studied for a sustainable retrofit is a three bedroom, one bath, 1,344 ft? slump block home on 0.17 acres. It was built in 1954 and is approximately 5 miles east of downtown Tucson. In 2013 the purchase price was $117,500 and other than landscaping the backyard, the addition of a storage shed, and raising the height of the back privacy wall by two feet with corrugated metal panels, no significant work has been done to it since being purchased.AssetsThe house is oriented to the north and south, with a 30 degree turn to the East. There are six windows and a sliding glass door, and all but two windows receive complete summer shade. The roof is less than five years old, and has one layer of 2” rigid foam. The plumbing pipes have been replaced, as has the water main. The back yard landscaping incorporates native or drought tolerant species and earthwork that diverts and collect water. Half of the house has upgraded electrical wiring and outlets. The home has a new 16-SEER split system AC/furnace package and an 80% efficient hot water heater. A 30’ tall mesquite tree that provides a substantial amount of shade for the west side of the house. The interior is for the most part completely remodeled. The owners have some personal preference changes they would like to make, but in general the house is move-in ready. Figure SEQ Figure \* ARABIC 9. Base Case House: Facing SouthDeficienciesThe complete lack of insulation on the shell of this building is its biggest flaw. The south facing wall of this home in particular is its weak spot, followed closely by its windows and roof. The southern wall receives full sun except for the eastern third which is shaded by a patio cover. Even that portion receives sun in the late afternoon when the sun drops low enough. There is a completely unshaded 4’x4’ aluminum-framed window with low-e glass in the middle of this wall. The performance of the low-e glass is handicapped due to the frame not being thermally broken. The window on the west wall is shaded most of the day by the orientation of the building and the mesquite tree but when the afternoon sun drops below the branches of the tree the window receives direct sunlight for a couple of hours. The window is of the same make and materials as the south window. The roof has two deficiencies, the first also being insulation related. It has a single layer of rigid foam, with an R-6 rating at best. The second is less the fault of the roof design as it is a result of block walls, a messy mesquite tree, and the performance properties of cool roof coatings. Much of the electrical wiring runs through conduits mounted across the roof. Code calls for them to be raised so they do not accumulate debris and so potentially pooling water cannot find its way into an improperly sealed conduit, but not everyone does things by the book, especially on a house with 60 plus years of history. The mesquite tree which is fantastic about shading the roof and the west side of the house for much of the day is also very messy, dropping tiny leaves, pollen, and beans often and in large quantities throughout the year. This detritus collects on the roof and if the homeowner is not diligent about cleaning it off piles will form around the conduit. Any moisture that the roof receives will be absorbed into these piles and begin to affect the composition of the roof coating, which is designed to shed water but breaks down in standing water. A new roof was a mandatory component of the upgrade.Also needing to be replaced is the electrical breaker panel. It currently is the code minimum 100 amp service, noticeable whenever the A/C comes on and the interior lights dim. In addition to the panel, the bedrooms in the house all need the wiring and outlets brought up to code; only the kitchen, dining, living, and bathroom have updated wiring and grounded outlets. In the living room ceiling are two of the cheapest polyacrylic and aluminum skylights available. One has a hole in it and both will be replaced.The rest of the windows in the house need to be replaced as well. All have thermally unbroken aluminum frames which are great at conducting heat and cold, but not so good for maintaining reasonable temperatures inside. Other areas that could use improvement are the front yard landscaping, as it currently is the whole property slopes straight to the street. All of the landscaping is native trees and cacti, but the potential to reshape the topography to collect and direct water to more vegetation is there. Additional plants would decrease the reflected heat of the mostly gravel landscaping, as well as gain some cooling benefits from the increased evapotranspiration produced by more greenery. The backyard has been landscaped with native and drought tolerant species, except for a small patch of grass. The newer plants still require some watering, but have are sufficiently established so their watering needs has already gone down. One of the criteria for upgrading the roof will be to implement rainwater collection techniques, including the addition of gutters, directional downspouts, and cisterns. This house also has zero graywater recycling capacities. At the minimum an under-the-sink mounted tank and pump system will be installed to refill the toilet tank and, if it is not cost prohibitive a tie-in to the shower drain that directs graywater to landscaping is also desirable. In the case of the bathroom addition it will be plumbed for graywater. Finally, there has been no attempt to harness the sun for electricity or hot water production. In a location that receives over 300 days of sunshine per year this is a hugely missed opportunity. The Base Case RetrofitIn addition to identifying the assets and deficiencies of the house through visual assessment and interviewing the owners, Climate Consultant 6 (CC6) was used to determine climate specific strategies for improving energy efficiencies. The psychrometric chart below, generated by CC6, quantifies the degree to which specific strategies need to be implemented to maintain thermal comfort in the Southern Arizona climate. A psychrometric chart uses wet bulb and dry bulb temperatures to generate thermal comfort data for a specific climate. The chart CC6 produced relies on a combination of shading, ventilation, passive solar gain, artificial heating and cooling (HVAC), and user adaptation (i.e. season appropriate clothing, raising and lowering the thermostat set points) to achieve 96.4% comfortable hours out of the total annual hours of use. Figure SEQ Figure \* ARABIC 10. Climate Consultant 6: Psychrometric ChartThe Climate Consultant Design Guidelines chart on the following page (Figure 10) lists the top twenty suggested design strategies for the Southern Arizona climate. The green highlighted guidelines are strategies that are absent from the base case and will be implemented during the retrofit. The blue highlights indicate strategies that the base case already incorporates and will be kept in addition to the retrofit. The pink indicates strategies partially incorporated in the base case, but need further development. The red are guidelines that are not incorporated at all in the base case, and are cost prohibitive to implement due to the design of the existing structure. The strategies are listed in order of importance, the numbers to the left are linked to more detailed information about each guideline. Figure SEQ Figure \* ARABIC 11. Climate Consultant 6: Design Guidelines Chart Using the CC6 recommendations and the known assets and deficiencies of the base case home, 3D models of the base case, the Retrofit, and the Retrofit+Addition were created in SketchUp to track design changes and model shading conditions. The construction materials of the home were inspected, measured, and researched so they could be accurately accounted for in the ResCheck and Energy-10 (E-10) energy modeling programs. ResCheck is the Department of Energy’s program that allows a user to build a quick model based on size and material inputs, and determine whether or not a building is energy code compliant for the area it’s going to be built. It uses a simple U-factor x Area (UA) formula, and the base case was 21% higher than the maximum allowable UA, which was to be expected. Figure SEQ Figure \* ARABIC 12. Base Case ResCheck Compliance GraphicThe Energy-10 software allows precise values for walls, windows, roofing, flooring, mechanical systems, and occupant loads as well as shading and solar orientation data to be input. It produces a detailed and accurate prediction of building performance and uses the building specs provided in the base case to create a Low-Energy Case with an array of efficiency upgrades. The program assumes that structures are built new, resulting in Low-Energy Case recommendations that include alternative framing and structural solutions. When testing the retrofit this was not an option, so those suggestions for were ignored. The retrofit strategy was based off of the CC6 guidelines, but first each strategy was tested independently alongside the base case. E-10 generates a total energy use report which converts all energy inputs into kBtu/ft?, the results are shown in the chart below.Strategy TestedBase Case (kBtu/ft?)Base Case SpecsRetrofit (kBtu/ft?)Base Retrofit SpecsEnergy Savings (kBtu/ft?)Walls43.7Uninsulated30.5R-21.3 Exterior, Polyiso Foam13.2Windows43.7Aluminum/no thermal break42.5Vinyl, Dbl. Pane N,W,E=Low-E1.5Roof43.7R-13.3 Built Up40.9R-53.8, Metal roof over existing2.8Infiltration43.70.6 ACH est.41.00.3 ACH est.2.7Thermal Mass43.725% carpeted42.0Remove carpet1.7HVAC43.716 SEER, unsealed ducts, stock fan42.516 SEER, sealed ducts, upgraded fan 1.2Comfort Settings43.7Comfort=70°/75° Setback=68°/78°40.2Comfort=68°/78° Setback=65°/82°3.5Hot Water43.780% eff. gas heat40.2Solar/gas backup3.5Light Bulbs43.7Incandescent42.1LED1.6User Loads43.7Standard appliances/plug loads40.1Energy Star appliances, smart power strips3.6Figure SEQ Figure \* ARABIC 13. Individual Strategy Comparisons The first strategy tested was wall insulation. To slow heat gain through the block walls, it would be applied to the exterior of the house. Three inch polyisocyanurate panels were chosen for their R-value (R-6 to 6.5/inch), reputation for durability, and more environmentally friendly manufacturing process (non-ozone depleting hexane blown panels vs. hydrocarbon blown panels). This tested as the single largest energy saver in the E-10 modeling by far, representing a 30% energy savings over the base case. There was no option in ResCheck or E-10 for taping the seams of the panels for an airtight envelope, but it was included in the price that was quoted. A smooth sand stucco finish would be applied over the new insulation and a light shade of low-VOC paint sprayed over it. Glazing was the next variable to be analyzed. Manipulating the window values in ResCheck demonstrated good savings, however E-10 demonstrated an energy savings of only 3.4%. The fact that the house has relatively few windows and only two of them receive direct sunlight contributed to the low savings. The glazing and window frame construction contribute to overall efficiency, but often older windows are warped or have shifted in the opening due to temperature extremes or the house settling, and replacing them provides the opportunity to improve envelope performance by eliminating air gaps as well as upgrade their performance. For this reason, despite the low performance gains, replacing the windows is still recommended. Top-of-the-line windows can be very expensive, however the performance increase is not often worth the cost. Usually the added cost is for premium materials and custom colors, or options such as triple-paned glazing whose higher insulation values make more sense in cold climates than in the desert. For this house mid-grade, double-paned, vinyl windows were chosen. The east, west, and north windows received low-e glass, as suggested by the Design Guidelines report, and the south side double-paned, regular glazed units. The vinyl was UV resistant to increase the longevity of the window, and the frames were designed with a number of insulating chambers that closely matched the designs of higher end systems. Instead of removing a fairly new roof and sending it to the dump the decision was made to build a new roof over the existing. Due to the intensive maintenance required for the existing roof, as well as the electrical conduit running across its surface the decision was made to install a vented and insulated metal roof system. This turned out to be the most expensive upgrade of the entire retrofit, and there were several options that were cheaper, however the metal roof would not require the regular maintenance other roof types require, and if installed properly would more than likely last for the owner’s lifetime. In addition to the maintenance cost savings and its longevity, the new roof combined with the existing would have an insulation value exceeding R-50. The roof would also be designed with a gutter system designed to direct water towards landscaping features and fill rainwater collection barrels. The old, uninsulated, cracked plastic and metal skylights would also be removed and replaced with slightly larger (1’x3’ vs. 1’x1’) operable, thermally broken aluminum framed units with double-paned low-e glass. The operability would allow hot air to be exhausted and fresh air to enter. Figure SEQ Figure \* ARABIC 14. Base Case Retrofit FloorplansThe mechanical systems had been upgraded prior to the current homeowners purchasing the home. A three-year-old 16-SEER Trane split system handled the heating and cooling and would continue to do so. A tankless gas hot water system was considered, but higher upfront costs, required annual maintenance, and a payback period that can be longer than the life of the unit meant that the existing 80% efficient GE hot water heater would stay CITATION Con08 \l 1033 (Reports, 2008). A solar hot water system would fill the existing unit, only requiring gas heating a small fraction of the year. All of the upgrades in aggregate produced a much higher ResCheck score:Figure SEQ Figure \* ARABIC 15. Retrofit ResCheck Compliance GraphicIn addition to the energy focused upgrades, water savings was also a priority. The homeowners had already purchased new Energy Star appliances, and their clothes washer and dishwasher were both rated to be more water efficient as well. All of the plumbing fixtures would be replaced with low-flow WaterSense labeled products, and the toilet and sink would be outfitted with a Sloan AQUS graywater system that stores water from the bathroom sink to refill the toilet tank. Plumbing the shower for graywater collection proved to be labor intensive and cost prohibitive at the time. It is a possibility if the homeowners decide to do a major bathroom remodel in the future.The Retrofit+AdditionA home has to meet many criteria before it can be truly sustainable, but it also has to be lived in before any of its performance can be put to use. Since the average new home size in the U.S. has risen to well over 2,000 square feet a 1,344 ft? home might have limited appeal for many buyers. The base case home was already occupied, but in the interest of developing a retrofit that would appeal to a larger percentage of home buyers as well as compare more directly with green housing currently available on the market, a model that increased the square footage of the base case was desirable. As it turned out the homeowners of the base case house were new parents and beginning to feel the storage limitations, by today’s standards, of a 1950s designed home. The lack of a second bathroom was also becoming an issue since relatives were in town more often to see the baby. Figure SEQ Figure \* ARABIC 16. Rendering of the Retrofit+AdditionThe new additions were constructed to the same specs as the base retrofit: new exterior insulation and stucco, new metal roof, upgraded windows, and patio cover are all incorporated. The bedroom was designed to maximize daylighting and views of the Catalina Mountains, and improve ventilation through operable clerestory windows. An issue with routing the HVAC ductwork into the new addition meant extending the bedroom back farther than was initially planned. The extra square footage was absorbed into a massive walk-in closet that should alleviate some of the homeowner’s lack-of-storage issues. The bathroom was situated to minimize new plumbing by locating it near the existing bathroom and was designed with water saving fixtures, sink-to-toilet graywater recycling, and a graywater line from the shower would irrigate landscaping in the front yard. The existing HVAC system was found to be oversized for the square footage of the home, so new ducting was all that was required to supply conditioned air to the additions. An optional single car garage adds a little security and value to the home, and gutters, rainwater collection, and graywater plumbing from the new bath will supply the water needs of a redesigned and xeriscaped front yard that homeowners plan to do themselves. The existing floorplan needed to be modified to allow access to the new master bedroom, so the third bedroom of the base case was opened up. The tiny existing bathroom was extended to the west by two and a half feet, adding a linen closet and a little more space. The door to the bathroom was moved from the south wall to the west wall, opening into the former bedroom. This allowed room for a new laundry closet and a slightly larger hot water heater closet. The furnace closet was also demoed and relocated into the former bedroom closet. This along with the new, slightly raised soffit would make the hallway feel a little more spacious and provide a larger entry into the new open office. Since the new bathroom would be blocking the window on the north wall a 2’x4’ operable skylight would be installed to bring in natural light and fresh ventilation.Figure SEQ Figure \* ARABIC 17. The Retrofit+Addition Floor PlansThe floor plans in Figure 16 indicates the addition and the interior design to the base case changes in red. The patio extension added in the base retrofit is also included, as well as a patio covering off of the new master bedroom, but is not indicated on the plans. Both were modeled and tested to provide maximum shading in the summer while allowing for solar gain during the winter time. Despite the square footage increase and extra energy loads for heating, cooling, and electrical, the ResCheck compliance report indicated better code performance than the Retrofit case. Figure 18. Retrofit+Addition ResCheck Compliance GraphicCostThe floor plans and material specifications for the base case, the Base Retrofit, and the Retrofit+Addition were given to Jed Heuberger of Lloyd Construction to review and estimate the costs of both upgrade cases. Mr. Heuberger has eighteen years of experience in the construction industry, and has spent the last thirteen years as a project manager and estimator. The numbers he calculated include materials and labor. Independent estimates were also received for HVAC, roofing, and mechanical systems work. The table below breaks out the costs and gives the final total. Scope of WorkBase RetrofitRetrofit+AdditionDemolition—$500Rough Carpentry$3,045$6,030Metal Roof$24,155*$31,063*Insulation$2,538$3,780Stucco$5,937$7,340Paint$2,711$3,530Electrical$3,000$6,565Windows$5,500*$15,000*Plumbing—$2,500Mechanical$2,600$4,000Grading/Earthwork—$1,200Concrete—$2,525Masonry—$8,410Millwork—$5,740*Doors—$2,650Drywall—$873Flooring—$1,298Tile (Bath)—$1,000Garage Addition—$36,812*Total$49,486$140,816 Figure SEQ Figure \* ARABIC 19. Construction CostsItems marked with asterisks are upgrades that could potentially cost less if alternative materials and methods were used. For example, the quote for the roof was for the top of the line, highest R-value available, heaviest gauge metal roof, while other options could reduce the cost by several thousand dollars without reducing the performance significantly. In this instance the homeowner preferred the metal roof so it was left in the case study.ResultsWhile the ResCheck compliance reports confirmed that the Retrofit and Retrofit+Addition cases performed better than both the base case and the minimum code requirements by a substantial margin, they do not indicate actual energy use. Energy-10 was used to create detailed simulations for each case and examine energy, cost, and emissions savings. To insure the accuracy of Energy-10’s results the actual utility bill energy totals for gas and electric were compared to the E-10’s base case computed annual energy consumption total. There was less than an 8% difference between the two sets of data so the data output was deemed reliable. (Appendix, Table 4.)The Base Case vs. the Base Retrofit: Figure SEQ Figure \* ARABIC 20. Base Case vs. Retrofit Annual Energy UseThe annual energy consumption for the Base Retrofit was a surprising 69.8% less than the base case, dropping from 43.7 kBtu/ft? to 13.2 kBtu/ft? (see Figure 19). Even acknowledging that 16% of the savings is attributed to hypothetical changes in user behavior, it still represents a decrease of more than 50%. Heating and cooling loads were reduced by 75%, greatly contributing to the overall energy savings. Figure SEQ Figure \* ARABIC 21. Base Case vs. Retrofit Annual Electricity UseThe graph above shows the electricity savings from switching to LED lighting, reducing plug loads, and installing a higher efficiency fan. The combination of insulation, upgraded windows, and raising the thermostat from 75°F to 78°F saw a drastic drop in the cooling energy requirements of the home. Combined, these strategies lowered the estimated annual electricity usage from 9,903 kWh to 2,990.71 kWh. To reach net zero energy consumption a roughly 2.75kW PV solar system would be needed CITATION Sol15 \l 1033 (Solar-Estimate, 2015). There are a few ways to go about obtaining solar power to make up the difference. Tucson Electric Power has a program that adds $3 per month to for each block of solar power purchased, and each block covers 300 kWh each month. For the Base Retrofit two blocks would be necessary, one to cover electric usage and the other to offset natural gas consumption (see Appendix 5). This would add $6 dollars to a bill that will average around $33 per month. For an annual total of $468 dollars the Base Retrofit can attain net zero energy consumption using this method. The benefits of going directly through the power company are that they own and operate the solar generating capabilities and they are offsite, so no installation is required. The drawback is that the actual power the home is using may or may not actually be solar, since in reality is what you are paying for is an allotment of their entire electricity generation, and the portion you receive is in theory produced by solar. Another option is buying or financing an adequately sized PV array for the home. Solar- is a website developed with support from the Department of Energy that has a very easy to use calculator. It asks for location, the local electric company, and your monthly electricity consumption and tells you what sized system you need, how much power it will generate, initial cost, and any tax credits available CITATION Sol15 \l 1033 (Solar-Estimate, 2015). The AZ Personal Tax Credit it listed is no longer available, so it is unclear how often the site is updated. The calculator also estimates how long it will take before the system pays for itself, in the Base Retrofit’s case just over 13 years. Figure SEQ Figure \* ARABIC 22. Solar-Estimator GraphicBy comparison, a PV system sized to offset the total energy consumption (gas and electric) of the base case would be sized around 8.2kW and cost more than double what is required for the Base Retrofit. Going the utility provider route would result in a $24 monthly solar premium on top of an average bill of around $109. Even without pursuing any of the various solar options the homeowners will see a noticeable decrease in their annual energy bill. Figure 22 compares the reduction in energy use and cost between the base case and the Base Retrofit (See Appendix, Table 4 for the formulas and values used to create Figure 22). Electric bills will average $76 per month less than what the owners were previously used to, amounting to an annual savings of more than $900. Natural gas bills that average $33.30 will drop by nearly two-thirds. Case StudyElectricity Usage (kWh)Electricity CostNatural Gas Usage (therms | kWh)Natural Gas CostDecrease from Base CaseTotal Utility CostsBase Case9,903.00$1,307.20207 | 6,065.22$471.55-$1,778.75Base Retrofit2,990.71$394.7762.51 | 1,831.58$142.4069.80%$537.17Figure SEQ Figure \* ARABIC 23. Base Case vs. Retrofit Utilities Use & Cost ComparisonThe environmental benefits of the Base Retrofit are also impressive. Energy-10 estimated a substantial 65% reduction in CO2 emissions over the Base Case (Figure 23), essentially mirroring the savings seen in annual energy consumption. By weight, carbon emissions are reduced by 4.8 tons annually through energy efficiency strategies alone. There are also the resource and carbon emissions savings of retrofitting compared to building new that were discussed earlier. Using the 7 gallons per kWh figure CITATION PTo03 \l 1033 (P. Torcellini, 2003) the Base Retrofit is capable of saving nearly 50,000 gallons of water each year just through its energy cuts. Additional savings from the installation of WaterSense labeled fixtures is estimated to save another 30% off of the homeowner’s water bill, reducing consumption by just under 10,000 gallons each year. The owners of the base case are extremely frugal with water and have minimal irrigation requirements for their landscaping resulting in an annual bill that is almost 60% less than average of 82,000 gallons per year in Tucson (see Appendix 4). An average home in this area could expect to savings of nearly 25,000 gallons per year. In terms of cost savings the Base Retrofit case could expect to save around $200 per year, while a home consuming the Tucson average could see savings approaching $550 annually.Figure SEQ Figure \* ARABIC 24. Base Case vs. Retrofit Annual Emissions ResultsRetrofit+Addition:The Base Retrofit is the core of the Retrofit+Addition, so their energy performance was expected to be relatively close, but a -0.75% performance drop was excellent considering the additions added 531 ft? of space requiring lighting, air conditioning, and heating. Since the Base Retrofit has been discussed in detail, this section will focus on the additions and the differences between the Retrofit+Addition, the base case, and the Base Retrofit. Figure SEQ Figure \* ARABIC 25. Retrofit+Addition Annual Energy UseEnergy-10 always runs its own concurrent Low-Energy Case unless the user inputs a second building. Because of the design changes it was impossible to compare the base case and the Retrofit+Addition side-by-side in E-10. For this section ignore the values for the Low-Energy Case as they are not relevant for comparison except to show that the Retrofit+Addition significantly outperforms even the E-10 upgraded case. As Figure 25 shows, the total annual energy use was one tenth of a kBtu higher than the Base Retrofit. The bedroom and bathroom additions were designed with the same envelope as the Base Retrofit, which tested as the highest energy saver of all the strategies implemented. All new glazing was primarily north facing to take advantage of daylighting without any direct solar gain, except for a French door in the south wall of the bedroom. The patio cover was sized to block summer sun, but during the winter time the sun will drop low enough to cast light twelve feet deep into the room, warming the concrete floors. The heating and cooling loads on the Retrofit+Addition are actually lower than the Base Retrofit. The best explanations for this are that A) the bedroom addition and the garage provide some shading that didn’t exist before, and B) the existing HVAC system was oversized by more than a 25% according to the HVAC technician that did the estimating. Oversized systems are as inefficient as undersized, so the extra square footage actually ended up sizing the house properly for the HVAC. Not generally the approach to take, but in this case it worked out well. New lighting was sized for the space and provided by LED fixtures and bulbs, however the interior remodel along with the addition added five more fixtures which was about a third more than the Base Retrofit included, and is reflected in the increased lighting load. The “other” category also had a noticeable increase due to bedroom and bathroom plug loads, and a new bedroom ceiling fan and bathroom exhaust fans (one was added to the existing bathroom). Water consumption was estimated to be around the same as the Base Retrofit. The energy consumption and utility costs differences between the base Retrofit and the Retrofit+Addition are negligible (see Figure 25), and both versions put the base case to shame, but there was one area that there was a noticeable difference.Case StudyElectricity Use (kWh)Electricity CostNatural Gas Use (therms | kWh)Natural Gas CostDecrease from Base CaseTotal Utility CostsBase Case9,903.00$1,307.20207 | 6,065.22$471.55-$1,778.75Base Retrofit2,990.71$394.7762.51 | 1,831.58$142.4069.80%$537.17Retrofit+Addition3,010.51$397.3962.93 | 1843.89$143.3569.60%$540.74Figure SEQ Figure \* ARABIC 26. Side-by-Side Utilities & Cost Comparison - All Three Case StudiesEmissions were the only area where the Base Retrofit significantly outperformed the Retrofit+Addition, which produced nearly 2.5 tons more C02 per year (Figure 25). Still, the Retrofit+Addition saw 2.3 tons annual savings over the base case. On a square footage basis the Base Retrofit was first at 3.82 lbs/ft?, the Retrofit+Addition was second with 5.39 lbs/ft?, and the 10.98 lbs/ ft? of CO2 producing base case was last. Despite the efficiency increases in heating and cooling, the extra space still requires additional conditioning and lighting that, using the prevalent sources of energy, increases the overall carbon footprint of the Retrofit+Addition. Figure SEQ Figure \* ARABIC 27. Retrofit+Addition Emissions Results Figure SEQ Figure \* ARABIC 28. Retrofit+Addition RenderingThe Retrofit+Addition end result is a 1,875 square foot aesthetically and functionally modern home built around the bones of a 61 year old house. It is more livable, and adds more storage and convenience while outperforming the base case in every metric. The Base Retrofit offers the best combination of resource, emissions, and cost savings but may have limited appeal due to its size. The table below gives the summary for all three case studies.MonthlyMonthlyAnnualCase StudyElectricity (kWh)Gas (therms)Water (cu.ft.)Utility CostUtility CostBase Case9,9032074,400$207.95$2,495.37Base Retrofit2990.7162.513,080$86.61$1,039.21Retrofit+Addition3010.5162.933,100$90.07$1,080.84Figure SEQ Figure \* ARABIC 29. Summary of ResultsConclusions The need for sustainable solutions has been and continues to be well established, yet the United States lags far behind several other developed nations when it comes to implementing them. We are by every metric living unsustainably. The built environment, due to its thirst for energy and resources, is one area where changes can make major and immediate positive impacts in every sphere of sustainability. Commercial construction has been an early adopter of sustainable building practices in the U.S., but the residential sector has lagged behind. Perceptions of higher costs and lower returns are not always inaccurate, but they don’t have to be a universal truth. While some builders will charge $500,000 or more for a “green” home, that kind of investment is not necessary to sustainably retrofit a home. It could be argued if sustainability is unaffordable then it’s not really sustainable at all, yet the trend seems to be green living can only be had at a premium price. The graph below illustrates the differences between market prices and the construction costs determined in this study. Even tacking on an additional 10% for profit over what was already built in, the case studies still provide more value at affordable or close to affordable (on a median income) price tags.Figure SEQ Figure \* ARABIC 30. Green Housing Affordability in Southern ArizonaIt is very possible to retrofit a moderately sized existing home to reduce its energy consumption by fifty percent or more, substantially lower its water consumption, and do it all well within the price range of a median income earner. Additionally, with the simple layout and structural design of the older homes in southern Arizona, more square footage can easily be incorporated and still maintain close to the same energy and water efficiency performance as a basic retrofit while still costing significantly less than what is currently being offered on the market, in some cases hundreds of thousands of dollars less. Figure 29 reiterates the energy and environmental savings that this study found possible.Figure SEQ Figure \* ARABIC 31. Energy & Emissions: 3 Case Studies70612003543300Cost ComparisonsEconomically it may make more sense for some homeowners to spend a few thousand dollars upgrading insulation, replacing some windows, and sealing the building envelope and figuring out their electricity usage from there. Then going through a utility or purchasing or renting a PV system may be the more cost effective route rather than an intensive energy retrofit. On the other hand, developers may find that investing $50,000 to $150,000 into retrofitting the right properties may actually be more profitable than building new if they can keep the final cost closer to the median income affordability. The profitability would come from two factors, the first being that a more affordable price point would mean more potential buyers, and the second is the home’s green selling points, especially the ones that lower a prospective homeowner’s monthly bills. This is where more local, state, and federal tax breaks and incentives would go a long way.The lack of Federal and State incentives is a travesty. The environmental, social, and economic benefits of building and living greener are countless, yet fossil fuel companies are receiving 78% more in government subsidies than sustainable initiatives CITATION Glo15 \l 1033 (Initiative, 2015). With homeowners saving more than $100 per month on utilities to be spent elsewhere, reducing annual water use by between 60-75 thousand gallons per household, and reducing energy consumption and the related emissions by two-thirds, it seems like a no brainer. If just ten percent of the homes nearly 84,000 homes built before 1970 in Tucson were to receive deep energy and water retrofits, regionally it would mean 630 million gallons of water saved per year, a 40,320 ton annual reduction in carbon emissions, and more than $12 million dollars a year savings for consumers. Sustainable retrofits will not be able to provide all of the housing needs for the growing population, but the environmental, economic, and social benefits that they have the potential to provide should make them serious consideration for homeowners, homebuyers, and policymakers. Southern Arizona is especially well situated to take advantage of abundant sunshine to reduce their reliance on water intensive thermoelectric power production, and to become a national leader in renewable energy use and raising home efficiency standards, but it has to start with affordability. The climate change and resource challenges the world faces require sustainable solutions, but if only a small fraction of the population have the solutions available to them then only a small fraction of the problem is going to be addressed. Sustainable retrofitting is one piece of the puzzle, and one that can be available to a greater percentage of the population. Limitations This is one home out of thousands of potential candidates for a sustainable retrofit, and each home is unique. The square footage, solar orientation, and existing upgrades will vary from house to house. Some older properties will need major plumbing and electrical renovations for any upgrades to be effective, others may require structural repairs or improvements before roofing, solar, or insulation can be considered. Any comparison of real estate has to factor in location. Some of the green home listings were in prime downtown or foothills locations and as such command a premium price. Still, some of the price tags far exceeded the value added by location.An energy audit was considered for the base case, but due to the fact that none of the suggested strategies could actually be implemented in time to be retested it was decided that time and effort would be better spent into designing and testing the retrofit strategies using 3D and energy modeling software.Energy-10 is a very powerful tool, and provided at a basic level everything this capstone required of it, however it is no longer supported by the Department of Energy and several features that would have generated deeper levels of information, produced helpful graphs, or saved hours of time manually calculating data either didn’t work at all or had glitches at various inopportune times.Energy-10 has a limited materials list. Every effort was made to create accurate inputs when there were no existing E-10 material profiles, but performance variables can vary widely between manufacturers. In those instances a median value was selected.Cost is still a limitation, despite the evidence showing that a basic sustainable retrofit can generally be accomplished within the budget of a median wage earner. The financial assumptions made to establish affordability for median wage earners were generous, possibly too much so. Hard numbers for median and average debt to income ratios were unavailable. Even with the best case median income financial scenario, sustainable techniques and strategies such as whole house energy monitoring and remote water tracking, graywater retrofits, and structural design changes to improve air flow and natural lighting will more than likely have to be left on the table. It may not be feasible in some cases to replace every fixture in the house with WaterSense labeled products, nor will every project have the budget to replace entire mechanical systems or appliance packages with Energy Star rated units. Another major assumption, and one of the largest variables found during Energy-10 testing, was user loads, in particular thermal comfort. The willingness of homeowners to adapt to a wider range of thermal comfort and reduce the use of heating and cooling, as well as appliance use and other user controlled variables, have a major effect on overall energy use. Behavioral modifications were assumed in this study, but were not weighted too heavily and the effects they had on the outcomes were indicated.RecommendationsFurther study into the water-energy nexus focusing on quantifying the reciprocal effects saving energy has on water supplies and vice versa would be a powerful tool in considering the greater impact sustainable retrofits can have at local and regional levels;A study of residential vs. commercial retrofits from a business model perspective might shed some light on why the commercial sector has seen far greater growth in green retrofits, and what lessons could be applied to residential;Investigate incorporating city planning with large scale neighborhood retrofit projects;Investigate more detailed life cycle analyses of retrofits vs. new construction;A social comparison of developed nations with differing degrees of investment into sustainable infrastructure, taking a look at health, happiness, education, wealth, crime, and other statistics to determine if and to what degree a society experiences an improved quality of life with a higher level of commitment to sustainability;Incorporating interviews with homeowners, prospective homebuyers, and construction companies into a study of sustainable retrofitting would be useful.AppendixTable 1. American Housing Survey: TucsonTable 2. Green Listings in Southern ArizonaTable 2. Green Listings in Southern Arizona (continued)Table 3. Base Case Actual Electric and Gas Consumption vs. Energy-10 Outputs1 kWh = 3412.142 Btu1 therm = 99976.1 BtuEnergy-10 Base Case Annual Energy Consumption = 43.7 kBtu/ft?Base Case square footage = 1,344 Energy-10 Base Case Total Btu = 43.7 kBtu/ft? x 1,000 x 1,344 ft? = 58,732,800 BtuActual Base Case = 9,903 kWh + 207 therms = (9,903 kWh x 3412.142 Btu/kWh) + (207 therms x 99,976.1 therms/Btu) = 33,790,442.23 Btu + 20,695,052.70 Btu = 54,485,494.93 BtuActual Base Case kBtu/ ft?= 54,485,494.93 Btu/1,344 ft?/ 1000 = 40.5 kBtu/ ft?Actual vs. Energy-10 = 40.5 kBtu/ ft? / 43.7 kBtu/ ft? = 92.7% accurateMonthElectric (kWh)Gas (therms)Jan553 63 Feb470 36 Mar466 21 Apr515 10 May669 8 Jun1,242 7 Jul1,457 6 Aug1,350 8 Sep1,122 6 Oct891 7 Nov573 10 Dec595 25 Annual Total9,903 207 Monthly Total825.25 17.25Annual Btu's33,790,442.22620,695,052.70Annual Electric + Gas Btu's54,485,494.93Table 4. Utility Costs Base CaseTEP Average Monthly Rate (including taxes and service charges): $0.132/kWh Southwest Gas Average Monthly Rate (including taxes and service charges): $2.278/therm?Electricity Usage (kWh)?Gas Usage (therms)?MonthMonthly BillMonthly BillWater Usage (ft?)Monthly BillJan553$73.0063$143.51200$52.98Feb470$62.0436$82.01300$58.67Mar466$61.5121$47.84400$60.84Apr515$67.9810$22.78300$58.67May669$88.318$18.22400$60.84Jun1,242$163.947$15.95600$65.19Jul1,457$192.326$13.67500$61.81Aug1,350$178.208$18.22500$62.94Sep1,122$148.106$13.67300$58.67Oct891$117.617$15.95300$58.67Nov573$75.6410$22.78300$58.67Dec595$78.5425$56.95300$58.67Annual Usage9,903$1,307.20207$471.554,400$716.62Monthly Average825.25$108.9317.25$39.30366.67$59.72Base Case Energy Cost/ ft? = ($1,307.20 + $471.55)/1,344 ft? = $1.323/ ft?Water Conversion: Cubic feet to gallons:1 cubic foot = 7.48052 gallons, Base Case = 32,914 gallons/yearTucson Average Water Consumption: 10,970 cubic feet x 7.48052 gallons = 82,016 gallons/yearRetrofit CaseBase Case Annual Energy Use (E-10 results)= 43.7 kBtu/ft?Base Retrofit Annual Energy Use (E-10 results) = 13.2 kBtu/ft?Percent Decrease in Energy Use = 1 - Base Case Annual Energy Use/Retrofit Annual Energy Use = 1 – (13.2 kBtu/ft? / 43.7 kBtu/ft?) = 69.8%Base Retrofit Electricity Costs = ((1 - 0.698) x 9,903 kWh)($0.132/kWh) = (2990.71 kWh)($0.132/kWh) = $394.77Table 4. Utility Costs (continued)Base Retrofit Natural Gas Costs = ((1- 0.698) x 207 therms)($2.278/therm) = (62.51 therms)($2.278/therm) = $142.40Base Retrofit Water Costs = (base case –( base case x 30% est. savings))($0.163/cubic foot) = (4,400 cu.ft. – (4,400 cu.ft. x 0.30)($0.163/cu.ft.) = (3,080 cu.ft. x $0.163) Cost = $502.04 Total Gallons = 23,040/yearBase Retrofit Total Utility Costs = $394.77 + $142.40 + $502.04 = $1,039.21Retrofit+Addition CaseBase Case Annual Energy Use (E-10 results)= 43.7 kBtu/ft?Retrofit+Addition Annual Energy Use (E-10 results) = 13.3 kBtu/ft?Percent Decrease in Energy Use = 1 - Base Case Annual Energy Use/Retrofit+Addition AEU = 1 – (13.3 kBtu/ft? / 43.7 kBtu/ft?) = 69.6%Retrofit Electricity Costs = (1 - 0.696 x 9,903 kWh)($0.132/kWh) = (3010.51 kWh)($0.132/kWh) = $397.39Retrofit+Addition Natural Gas Costs = ((1- 0.696) x 207 therms)($2.278/therm) = (62.93 therms)($2.278/therm) = $143.35Retrofit+Addition Water Costs = (base case –( base case x 30% est. savings))($0.163/cubic foot) = (4,400 cu.ft. – (4,400 cu.ft. x 0.30)($0.163/cu.ft.) = (3,080 cu.ft. x $0.163) = $502.04 Total Gallons = 23,040/gallons per yearRetrofit+Addition Total Utility Costs = $397.39 + $143.35 = $1,042.78Table 5. Converting Therms to kWh for Solar Sizing1 kWh = 3412.142 Btu1 therm = 99976.100 Btu1 kWh/1 therm = (3412.142 Btu/1 kWh)/(99976.1 Btu/1 therm) = 0.034129 kWh/thermBase Case207 therms / 0.034129 kWh/therm = 6,065.22 kWhBase Retrofit62.51 therms / 0.034129 kWh/therm = 1,831.58 kWhRetrofit+Addition62.93 therms / 0.034129 kWh/therm = 1843.89 kWhBibliography BIBLIOGRAPHY 2013 Housing Profile: Tucson, AZ. (2015, May). Retrieved from : . (2015, 11 7). Retrieved from : Griffiths-Sattenspiel, W. W. (2009). The Carbon Footprint of Water. Portland, OR: River Network.Buildings and their Impact on the Environment: A Statistical Summary. (2009, April 22). Retrieved March 15, 2015, from : for Climate and Energy Solutions. (2015, 11 1). Residential End-Use Efficiency. Retrieved from Center for Climate and Energy Solutions: , S. E. (2009). Roofing Materials’ Contributions to Storm-Water. Reston, Virginia: American Society of Civil Engineers.Cynthia Robertson, R. E. (2011). 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(2014, April 25). CNN Money. Retrieved from : , G. R. (2012). Use of Raw Materials in the United States From 1900 Through 2010. Reston, VA: U.S. Geological Survey.McGraw-Hill: Analytics, D. D. (2012). Green Building Outlook Strong for Both Non-Residential & Residential Sectors. New York, NY: McGraw-Hill.P. Torcellini, N. L. (2003). Consumptive Water Use for U.S. Power Production. Golden, CO: U.S. Department of Energy: National Energy Renewable Energy Laboratory.Penafiel, K. (2006, 12 08). Reducing Off-Gassing for Better IAQ. Retrieved from : , B. (2012). One Planet, How Many People? . New York City: United Nations Environmental Programme.Pollin, R. H.-P. (2009). The Economic Benefits of Investing in Clean Energy. Amherst: University of Massachusetts.RESNET. (2015, 11 10). Learn About the HERS Index. Retrieved from Residential Energy Services Network: , T. (2007, January). Historic Preservation and Green Building: A Lasting Relationship. Retrieved from Building Green: , K. (2013, May 26). Architecture and Urban Ecosystems: From Segregation to Integration. Retrieved from The Nature of Cities: , R. (2005). Sick of Poverty. Scientific American, 92-99.Smith, W. B. (2009). Forest Resources of the United States. Washington, D.C.: U.S. Department of Agriculture, U.S. Forest Service.Sustainable Buildings and Climate Initiative. (n.d.). Retrieved March 12, 2015, from United Nations Environment Programme: . Dep't of Energy. (2012, March). Chapter 1: Buildings Sector. Retrieved from Buildings Energy Data Book: . (2015, February 23). Green Building Facts. Retrieved from US Green Building COuncil: Articles: , M., Gottschalk, A., & Smith, a. A. (2011). Household Debt in the U.S.: 2000-2011. Retrieved from : - Non-Hazardous Waste - Municipal Solid Waste. (2015, June 25). Retrieved from : Use in the United States. (2015, June 18). Retrieved from USGS: Use Statistics. (2015, 11 10). Retrieved from : , R. (2006, August). Homeownership and Wealth Accumulation. 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