CONSTRUCTION OF GLASS ROOFS



PF2302 Construction Technology

AY 2008/2009 Semester 2

Skylights and Butterfly Roof System

Prepared By:

Chua Sen Yan Mervin U077844L

Cao Weitian Cindy U069270E

Koh Fei Shu Doreen U069292W

Lee Hui Boon U099216X

Lee Pei Yun U069187J

Lian Jingyun Christina U065433Y

Tan Chew Hoon Jacelyn U069274B

Tan Jac See U069189H

Teo Feng Ni U069291J

Teo Mun Ling U069185L

CONTENTS

|1. |Introduction |1 |

|2. |Case Study: Changi Airport Terminal 3 (T3) | |

| |2.1. Movable Perforated Sunshade Louvers |2 |

| |2.2. Skylights with Double-Glazed, Low E-Coating and Low Iron Glass |5 |

| |2.3. Parabolic Reflector |6 |

| |2.4. Daylight sensors, wind sensors and CCTV Camera |7 |

|3. |Construction Process Of T3 Skylight With Butterfly System | |

| |3.1. Design Stage |8 |

| |3.2. Construction Stage |9 |

| |3.3 Post-Construction Stage |11 |

|4. |Advantages Of Skylight With Butterfly System | |

| |4.1. Skylight |11 |

| |4.1.1 Aesthetics | |

| |4.1.2 Functionality | |

| |4.2. Butterfly Roof |12 |

| |4.2.1 Aesthetics | |

| |4.2.2 Functionality | |

|5. |Conclusion |14 |

|References | |

|Appendix | |

| | | |

| | | |

| | | |

| | | |

| | | |

1. INTRODUCTION

In the past, people often had a misconception of glass being unable to withstand heavy load due to its unpredictable nature. However, as science and technology undergoes massive progression through research and development (R&D), glass is becoming a widely used material in buildings. With the advancements made in glass technology, glass is not only used for windows, but is increasingly being used in façades and even on roofs as skylights, that make good use of daylighting and is beneficial to the environment as it aids in the conservation of energy.

The Singapore Changi Airport Terminal 3 (T3) is one good example of a building that makes use of glass in its roof structure. It is also the first large-scale building to use the skylights system. Hence, a case study on the Singapore Changi Airport T3 is done to illustrate the components and methodology used in the construction of skylight with butterfly roofs using silicon glass glazing technology. The benefits of using this system are also discussed in this report.

2. Case Study: Changi Airport Terminal 3

Changi Airport T3 commenced its operations on 9 January 2008, and is the largest of the 3 terminals in Singapore with 4 upper and has 3 basements levels, with a handling capacity of 22 million passengers a year. This S$1.75 billion terminal comprises 380000 square meter of space and is located directly opposite Terminal 2[1].

T3 is made of steel trusses supported by a cable-braced roof filled with glass skylights, which is commonly known as the daylighting system. This daylighting system, as shown in Figure 2.1 below, is first of its kind to be implemented in such a large-scale airport terminal building and consists of 4 main components, namely the movable perforated sunshade louvers; skylight with double-glazed, low e-coating and low iron glass; parabolic reflectors for glare control and daylight transmission and the various wind and light sensors used in the system.

[pic]

Figure 2.1 Model of Daylighting system

2.1. Movable Perforated Sunshade Louvers

The roof is T3 is covered by 919 movable sunshade louvers installed on the 300m by 200m main roof as shown in Figure 2.2 below.

[pic]

Figure 2.2 Layout of the movable sunshade louvers on main roof

These movable sunshade louvers are able to regulate the amount and flow of natural light entering the building as it moves according to the position of the sun and external lighting conditions. On sunny days, the louvers of the daylighting system will be adjusted to maintain the lighting condition at a level of 600 to 1000 lux. However, on a overcast day or during the night, the system will open up the louvers to allow more daylight into the building and artificial light from easily accessible sources near the ground level is reflected off the louvers to provide uniform illumination within the terminal building. This helps to reduce the use of artificial lighting during the day and hence, reduces energy consumption. Figure 2.3 below illustrates the movable sunshade louvers in a fully opened position.

[pic]

Figure 2.3 Movable sunshade louvers in fully open position during an overcast sky

In addition, the butterfly system is also dependent on the external luminance. Figures 2.4 and 2.5 below show how the system works in relation to the time of the day. For example, if the sun is at 90( to the horizon (i.e. at noon), the butterfly system will move to the position where both butterfly flaps will block the sunlight into the terminal building.

[pic]

Figure 2.4 Rotational steps for butterfly system in relation to external luminance

[pic]

Figure 2.5 Mechanism of the movable sunshade louvers from morning to sunset.

2.2. Skylights with Double-Glazed, Low E-Coating and Low Iron Glass

The other major component of the daylighting system is the skylights. The type of glass used on roofs is important due to safety considerations. Hence, a laminated insulated double-glazed glass of 10mm and 8mm (heat strengthened glass) with the interlayer of 1.52mm thick of PVB, imported from Belgium is used in T3. Laminated glass is a type of safety glass that will produce a “spider web” cracking pattern instead of big sharp pieces of debris when broken.

The laminated glass used in T3 is a low-iron glass that is clear and allows high light transmission and minimal green cast. Since it has an interlayer of PVB, it permits approximately 70% of sunlight to enter, while rejecting about 65% of the radiant heat, maximizing both thermal comfort and natural lighting into the terminal building. It is also designed to withstand wind pressure of -0.36 kPa (Typical Area), -1.59 kPa (Edge Zones) as well as apositive design load of 0.75 kPa (Live Load), with water infiltration wind pressure of about +0.57 kPa.

It is also important to note that prior to the installation of the skylight, the glass is also checked to see if it complies with BS 6262: Code of practice for glazing for buildings as well as the GANA Glazing Manual.

2.3. Parabolic Reflector

Aluminum parabolic reflectors are used to redirect daylight to other parts of the terminal building at a degree of about 450 to prevent the sunlight’s glare from causing any visual discomfort to the terminal users. Figure 2.6 below illustrates the path of sunlight entering the parabolic reflector system.

[pic]

Figure 2.6 Path of sunlight entering into the parabolic reflector system

2.4. Daylight sensors, wind sensors and CCTV Camera

There are safety features incorporated into the daylighting system too. They are the wind sensors and the single CCTV camera installed on the terminal roof as depicted in Figure 2.7 below.

[pic]

Figure 2.7 Location of the installation of daylight sensors, wind sensors and CCTV on main roof

Wind sensors are used to track wind speeds and a computerized control system will automatically shut the sunshade louvers in exceptionally strong winds to prevent the damage of the glass. The CCTV camera on the roof enables operators to monitor real time physical condition of the sunshade louvers. Figure 2.8 below shows the actual installation of the wind and photo sensors on the roof of T3.

[pic]

Figure 2.8 Actual site installation of wind sensor and photo sensor

3. CONSTRUCTION PROCESS OF T3 SKYLIGHT WIth Butterfly system

Concrete is used for the construction of the roof in T3. Silicon glass glazing is applied on the roof to allow the installation of skylights at the allocated points. The butterfly system, an intelligent building system, is also fixed to regulate the amount of light entering the terminal. This butterfly system works almost like the movable sunshade louvers installed internally in T3, as mentioned earlier.

The construction of this T3 skylight with butterfly system roof is carried out in the following processes:

3.1. Design Stage

In the design stage, other than the conceptualization of ideas, mock-ups were also conducted to ensure that projects are feasible. Figure 3.1 below illustrates a mock-up carried out offsite to review the roof skylight design. A water test, shown in Figure 3.2 below, was also conducted to ensure water tightness of proposed skylight details, using the same mock-up.

3.2. Construction Stage

During the construction stage, skylights were installed on reinforced concrete upstanding parapets. The cast in-situ method was used for the concrete used in the reinforced concrete roof whereas the pre-cast method, shown in Figure 3.3 below, was used for the upstanding parapets.

After the completion of the roof structure, the installation of the skylight glass panels was carried out. During this process, tower cranes were used to hoist glass panels to the roof and delivered to the various skylight locations. These skylight locations could be easily identified by the openings left in the slabs on both intermediate and roof levels. Openings would later be sealed with concrete after glass panels have been installed and tower cranes dismantled.

Glass panels were installed using silicone-sealed glazing, shown in Figure 3.4 below. The silicone seal between glass panels is set flush with the surface of the glass, which allows a smooth and continuous finish. Each glass panel is also clamped in place by short lengths of pressure plates with screws, which are secured to an aluminum channel. The gap between the glazed units is sealed with silicone and supported by a backing rod behind it to form a back edge.

Following the installation of glass panels, secondary roof works to fix the butterfly system were carried out. Aluminum copings were fixed around skylight glass panels as shown in Figure 3.4 above. Aluminum copings are construction units placed at the top of the parapet wall and serve as covers for the wall. They are fixed to protect all parts and fittings around the glass panels to improve water tightness and also allow rainwater to be drained off smoothly from the skylights.

3.3 Post-Construction Stage

After the entire skylight with butterfly system had been fully installed, testing and commissioning took place. The full details of the main roof skylight fixings are provided in the Appendix.

4. Advantages of Using SKYLIGHT WITH BUTTERFLY SYSTEM

Compared to the common modular conservatory systems, skylight with butterfly system constructions offer many advantages with regard to both aesthetics and functionality.

4.1. Skylight

4.1.1. Aesthetics

Aesthetically, skylights, also known as glass roofs, give a sense of openness, and with the use of glass, designers are permitted to create more and better designs. However, glass is often said to give less security due to its transparency. In spite of this, glass roofs are still increasingly being used in buildings that require first-class security like the British Musuem in London, Changi Aiport Terminal 3 in Singapore and the Massachusetts State House in Boston.

4.1.2. Functionality

Functionally, glass being transparent to visible light, allows designers to make good use of daylighting. Daylighting allows the substantial decrease in energy consumption for buildings since lighting is 8.8% of electricity use in US residential buildings and 23.1 % of total electricity use in US commercial buildings, according to the Department of Energy (DOE) end-use survey from 2001 and 1999 respectively[2]. In spite of being argued as an expensive material for the construction of roofs and also raises the maintenance cost of the building due to the dust, stains, dirt, impurities, contamination that may significantly affect the transparency of glass, the cost savings from the reduction of energy usage by using natural lighting is definitely outweighed in the long run. In addition, daylighting is also known to have a profound effect on the stimulation and regulation of the human body. In a study conducted in a Swedish elementary school, 4 classrooms with 4 different levels of daylighting were observed, where students were monitored for behavior, health, and the stress hormone, cortisol. The study suggested that the lack of daylight interrupted hormone patterns, leading to less concentration and cooperation, affecting growth and absenteeism[3].

Other than daylighting, glass is resistant to the effects of weathering. Hence, using glass as a material for roofs is a good idea since it does not deteriorate, corrode, stain or fade and is durable. Studies have also indicated that the use of glass in roofs is able to reduce the overall noise level by 6 dB[4]. This might be essential for Singapore’s Changi Airport, T3, since aeroplanes generate huge amounts of noise, which should be masked off effectively from the terminal. However, it is important to note that glass is sensitive to surface imperfections. Hence, specific design principles need to be followed as according to the various standards implemented by the various countries and the appropriate factors of safety should also be applied.

4.2. Butterfly System

The design of a butterfly roof resembles the lines, angles and wingspan of a butterfly when they are flapping in an upward motion. A butterfly roof has 2 adjacent gables sloping both inward and downward towards the middle to create a central valley. Butterfly roofs can be of varied angle gradations and may not be of identical length or angle on each glade. Hence, it is possible to have a butterfly roof where only one gable slopes in either direction.

4.2.1 Aesthetics

Butterfly roofs have many aesthetic design benefits since nature can be introduced to become part of the interior. Butterfly roofs also allow for improvements and advancements in exterior design, such as window placement. Butterfly roofs are also good alternatives to flat glass roofs since they give more design to the architectural features of a building.

4.2.2 Functionality

In general, people usually use butterfly roofs to accommodate solar applications and/or rain catchment. Solar panels can be installed on the butterfly roofs to collect photovoltaic energy for conversion to electricity, or as a method for heating water.

Butterfly roofs allow the capture of rainwater in the central valley of the roof between the inward and downward facing slopes. The owner can utilize the water for many purposes such as watering of plants and flushing of toilets.

Gallery windows used in butterfly roofs on the seams of the house can be lengthened because of the height of the outer walls, which can provide plenty of light into the house. There are many benefits to having natural daylighting and one example is the decrease in energy consumption, which leads to a lower utility bill, as mentioned earlier.

5. CONCLUSION

In conclusion, the innovative daylighting system implemented in the Singapore Changi Airport T3 had proven to be very successful. As the world increasing emphasizes on the sustainability of the Earth, green technologies are increasingly being valued as well.

This skylight with butterfly roof system is proven to be advantageous as it not only allows natural light to be brought indoors in a soft and diffused manner without the tropical heat, but also introduces significant landscaping within the building. High initial costs are also essentially converted to energy savings since buildings are able to better utilize the consistent equatorial sun to limit the amount of energy required for lighting and minimize the building’s cooling load. In addition, since almost every component of the daylighting system is prefabricated, quality and productivity can also be ensured as quality and productivity of the construction industry are increasingly being emphasized as well.

Hence, the implementation of this sustainable strategy into roofs is definitely feasible and should be encouraged.

References

Birdair, Inc., “Birdair, Inc. to Construct Glass Roof for Green Point Stadium.” Web report by PR Log Free Press Release, 2008. Available at:

CAAS, 2007. Changi Aiport T3. Available at: )

Department of Energy. "End-Use Consumption of Electricity 2001." Web report by the Department of Energy, 2001. Available at:

Downer, J.. What is a Butterfly Roof?. Online. USA: eHow, Inc. Available at: .

Kiiller, R., C. Lindsten. "Health and Behavior of Children in Classrooms with andcwithout Windows." Journal of Environmental Psychology, Vol 12, pp.305-317, 1992

Watts, A., 2005. Modern Construction Roofs. Austria. Springer-Verlag/Wien.

APPENDIX

Main Roof Skylight Fixing Details (Part 1)

Main Roof Skylight Fixing Details (Part 2)

-----------------------

[1] CAAS, 2007. Changi Aiport T3. (Source: )

[2] Department of Energy. "End-Use Consumption of Electricity 2001." Web report by the Department of Energy, 2001. Available at:

[3] Kiiller, R., C. Lindsten. "Health and Behavior of Children in Classrooms with andcwithout Windows." Journal of Environmental Psychology, Vol 12, pp.305-317, 1992

[4] Birdair, Inc., “Birdair, Inc. to Construct Glass Roof for Green Point Stadium.” Web report by PR Log Free Press Release, 2008. Available at:

-----------------------

Fall

08

Reinforced Concrete Upstanding Parapet

Skylight Glass Panel

Aluminium Coping

Silicone Weather Sealant with Backing Rod

Figure 3.4 Cross-section of main roof skylight

Figure 3.1 Skylight Mock-up

Figure 3.2 Mock-Up Water Test

Figure 3.3 Pre-cast mould for upstanding parapets

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download