Structural Deficiencies
Air Conditioning for an old Home
Pillar To Post Continuing Education Program
Table of Contents
• Chapter 1: Overview and Objectives
• Chapter 2: Introduction to Air Conditioning
• Chapter 3: Old Home Challenges
• Chapter 4: Air Conditioning Solutions
• Chapter 5: Houses with No Ducting
• Chapter 6: Interior Elements
• Chapter 7: CEP Quiz
• Chapter 8: Presentation Evaluation
Chapter
1
Chapter 1
Overview and Objectives
Chapter
1
Overview and Objectives
A
ir conditioning is a luxury for some and a necessity for others. Either way, many home buyers are looking for homes with air conditioning. If the home does not have air conditioning, no problem, just add central air onto the existing heating system. Unfortunately, it may not be so easy if the home is an older home. It can be a challenge to air condition an older home. The two main reasons are, the ducting systems were not designed to carry cold (heavy) air and there are still many old homes that don’t have air ducting systems at all because the heating system is forced hot water rather than forced air. Even though it is a challenge, there are still options for these older homes. Knowing these options could help clinch the deal with a client.
This course looks at air conditioning systems, how they work and how older homes can be retrofitted with air conditioning.
This course will teach you:
• the very basics of how air conditioning systems work.
• terms and definitions relating to air conditioning systems.
• the challenges of air conditioning an older home.
• modern solutions to the old home challenge.
By the end of this session you should be able to:
• identify the challenges an old house presents for air conditioning.
• list three ways to improve air conditioning with a forced air system.
• list two options for air conditioning a hot water heated house.
• list two downsides to window units.
• suggest an air conditioning solution for a particular old house challenge.
This knowledge will:
• help you serve your clients better.
• help you answer your client’s questions.
• show your clients that you are a knowledgeable professional.
Chapter
2
Chapter 2
Introduction to Air Conditioning
Chapter
2
Introduction to
Air Conditioning
Moving Heat
H
eat would normally like to flow from hot to cold. If your house is hot inside and it is cold outside, the house will cool all on its own. Unfortunately, most of us are not trying to cool our houses when it is cold outside. We want to cool the house when the outside temperature is even hotter than inside. This requires moving heat in the opposite direction than it wants to go. This requires sophisticated mechanical equipment – an air conditioner. An air conditioner can move heat “against the temperature gradient”.
A standard residential central air conditioner is called a split system because there are two separate parts of the system. One part is located in the house and is called the evaporator and the other part is located outside the house and is called the condenser. The two parts are connected together with pipes that contain refrigerant.
So how does it work? The system cools the house by collecting heat and moving it outside. More specifically –
1. The evaporator is a device that sits in the air stream inside the house. The household air blows through the evaporator and the evaporator removes heat from the air stream. By the time the air comes out the other side of the evaporator, the air may be about 20 degrees F cooler.
2. What does the evaporator do with the heat that it has collected? It sends it along with the refrigerant to the condenser outside. The condenser releases the heat to the outside air. The function of the condenser is exactly opposite to the job of the evaporator. The air stream flowing through the condenser heats up as the heat is added to it.
This picture shows a furnace with an air conditioning system added to it. At the top right of the picture, you can see the refrigerant lines entering the ducting. You can’t see it but the evaporator is located inside the ducting on top of the furnace. As air passes through the evaporator it gets cooled.
The pictures below show the outdoor part of the system, the condenser.
In summary, an air conditioning system works by moving heat from inside the house to outside the house. The result is, the air inside the house gets cooler and the air outside the house gets hotter.
Air Handler
In the last section we pointed out that the evaporator sits in the household air stream. In this section we look more specifically at how this happens.
The device that circulates air through your house is called the air handler. An air handler has a blower, a filter. The air conditioning components including the evaporator are added to the air handler.
If your house has a forced air furnace, you don’t need a separate air handler because the furnace already has an air handler. The air conditioning evaporator can simply be mounted in the furnace (more correctly in the furnace plenum). If your house does not have a furnace, the air handler is a separate device dedicated solely to the air conditioning system.
There are two reasons we are covering this small item in such detail –
1. Many people are confused when we talk about the air conditioning system in the furnace. What does the air conditioning system have to do with the furnace? They share an air handling system. The air conditioning system piggy-backs on the furnace.
2. As we will see, the air handling system is often the part of the system that is a problem in older homes.
|[pic] | |
| |Check Your Knowledge |
| |Answer the questions below in the spaces provided |
1. True or False? An air conditioning system moves heat against the temperature gradient.
2. The part of the central air conditioning system that is inside the house is called the …
_______________________________________________________
3. The part of the central air conditioning system that is outside the house is called the…
_______________________________________________________
4. If you have a forced air furnace for heating and you want to add air conditioning, you don’t need a separate air handler. Explain:
____________________________________________________________________________________________________________________________________________________________________________________________________________________________
Chapter
3
Chapter 3
Old Home Challenges
Chapter
3
Old Home Challenges
T
oday, air conditioning is common in many areas of the country. Years ago, almost nobody had air conditioning. Since nobody had air conditioning, the houses were not designed with air conditioning in mind. This poses some challenges when air conditioning is desired in an old home.
Inadequate Ducting
There are a number of ways that ducting in an old house may not be adequate for air conditioning:
• Hot air rises and cold air does not. An old home will have ducts designed for hot air handling. During the heating season, all is well because the hot air tends to move up through the ducts and up through the house naturally. During the cooling season, the top floor will not cool properly and, if there is a basement, it will be too cold.
• Cold air is heavier than hot air so it is harder to move through the ducting. Ducting designed for air conditioning will be larger.
• Old home usually don’t have adequate return air ducting, often only a single return air duct on the main floor. This is not a good layout for air conditioning.
No Ducting
The other issue with many older homes is that they don’t have any ducting at all. Many older homes in North America are heated with hot water. Instead of ducting and air registers, these homes have hot water piping and radiators or convectors. In these homes you don’t have an air handling system to piggy-back onto.
Homes with electric baseboard heating have the same issue.
Chapter
4
Chapter 4
Air Conditioning Solutions
Chapter
4
Air Conditioning Solutions
S
ome home buyers may not buy an old home because of the belief that it can’t be air conditioned effectively. If the lack of air conditioning is the only thing holding someone back from buying a home, it would be a shame to have them miss out because of this small item. There are tricks and solutions that will work for almost any home. Now that we have an understanding of central air conditioning and the problems with air conditioning older homes, let’s have a look at the solutions.
Balance the Air Registers
This section is relevant to:
1. Old homes with central air conditioning, where the cold air distribution is not optimal.
2. Old homes without central air but with the possibility of adding central air as a piggy-back onto the furnace.
We now know that central air conditioning with ducting designed for hot air will not perform as well as a ducting system that was designed for air conditioning. On the other hand, most old homes can be cooled reasonably well by adjusting the air registers.
Here is how it works. If you want more cooling in an area, open the registers more. If you want less cooling, close the registers a little. Let’s take this a little further. If you want more cooling in an area and the registers are already fully open, you have to close them down in another area.
This picture shows an air register. You can see the adjustment dial on the left. This register is closed.
Most people don’t know that they need to change the balance seasonally. During heating season, you adjust the registers to favor the main floor slightly since the hot air will tend to make its way up through the house naturally. In the cooling season, adjust the registers to favor the top floor. This will give more air flow to the top floor and the cold air will fall down through the house. For best results, some experimentation is required.
It’s not uncommon to find homes where the air conditioning levels on the main floor are extremely cold just so they can get enough cooling for the bedrooms on the second floor. If the registers were adjusted properly, you could probably achieve much more uniform and energy efficient cooling throughout house.
Duct Booster Fan: Most two story houses can be air conditioned sufficiently by balancing the air registers seasonally. Three story houses are more of a challenge. Even if you close down the main floor registers and open the third floor registers fully, you probably won’t get enough air flow on the third floor to get adequate cooling. There is a trick worth trying, a duct booster fan. This is a simple fan the mounts over the air register or in the register. The fan creates a suction that sucks more air to the register. There is only so much you can do with a booster fan but it may make the difference between a comfortable room and a room that is too hot.
Two-Speed Fan (blower)
The blower circulates air thorough the house. Many blower fans, even older ones, are capable of operating at more than one speed. A standard set-up for air conditioning and heating is to have the blower operate at a higher speed for air conditioning than for heating. The higher speed will handle the heavy cold air while the lower speed is ideal for hot air.
A technician may be able to adjust the speed settings to give you better air flow. There are limitations to this approach –
• There is only so much you can increase the blower fan speed before the air starts whistling in the ducting.
• The evaporator is designed to have a particular air volume flow rate through it (cubic feet per minute). The system will operate efficiently within a particular range. If you increase the blower speed too high, you may not get efficient operation of the system.
An experience technician can identify if anything can be done with respect to blower speed and whether it is advisable for your system.
Add Return Air Registers
The two suggestions we have covered so far are quick and inexpensive solutions. They may or may not work depending on the situation but they are worth considering before you spend a significant amount of money. Adding return air registers is more expensive and invasive.
What’s return air? The air handler circulates air through the house. This means that air is drawn into the air handler; the air is conditioned and then pushed out through the air supply ducting system. The air drawn into the system is the return air.
Supply registers versus return registers. Air supply registers are readily apparent because there is conditioned air blowing out of them and there is at least one in every room. Return air registers are a little less obvious because air flows into them and every room does not have a return register.
The photo on the right shows a return air register in an old home. You can see the floor joist passing through the middle. The floor joist space is used for channeling return air. The photo below shows a return air register in a wall. In this case, the wall cavity between walls studs is used for channeling return air. The fact that you can use wall and floor cavities for return air means that return air registers are often easier to install than supply register.
Most old homes only have a single return air register, often on the main floor in the front hall. This works reasonably well for heating but very poorly for cooling. Generally for both heating and cooling, more return air registers is better.
If you have an area that is not cooling well, one good solution is to add a return air register. What this does is create a “push-pull” effect. Cool air is forced into the room while hot air is sucked out. With the push-pull effect, not only is hot air removed but also the flow-rate of the supply register is increased.
Adding ducting is invasive but return air registers are often easier than supply registers because you can use the existing wall and floor cavities such as the space between wall studs or floor joists.
Add Supply Air Registers
Adding supply air registers is usually only considered as part of a major renovation. It is very invasive as it involves removing drywall.
Chapter
5
Chapter 5
Houses with No Ducting
Chapter
5
Houses with No Ducting
T
here are many homes that are heated with hot water or electric baseboard heaters. This means there is no ducting system in place for air conditioning. For some buyers, the ones that prefer air conditioning, this is a big negative. Today there are several very interesting options for these homes beyond tearing the walls apart to add standard ducting.
High Velocity Ducting
A high velocity ducting system is a ducting system of flexible mini-ducts. The size of these ducts is small enough that they can be fished through the walls with minimal plaster damage.
Since the cross-sectional area of the duct is so small, the air has to move at a very high velocity to give the same volume flow rate. This is why these systems are called high-velocity systems.
The photo on the right shows a high velocity duct system. There is a main trunk line (large part on top) with small diameter flexible ducting that can be easily fished through wall cavities. The photo below is a close-up of the air jet.
Ductless System
What’s wrong with window air conditioners? First, you lose a window. They are noisy because the compressor is located inside the unit. They only cool the immediate area. The bottom line is, window units are not a desirable solution to air condition a house that has no ducting.
There is a new system that is becoming more and more popular for homes without ducting. It’s called a ductless system. It is a point source cooling system like a window unit but with a number of benefits –
• You don’t mount it in a window
• It’s not loud because the compressor is separate from the point source cooling unit. The compressor is located outside just like in a standard central air unit.
• You are not limited in the cooling capacity
• You can locate it in an effective location like at the top of the stairs on the second floor. This will cool the second floor and the cool air will make its way down to the main floor as well.
The photo on the right shows the cooling unit of a ductless system. This would be mounted at the top of the staircase on the second floor. There is usually a remote control for operating the system.
These systems are ideal for homes that are not too sprawling. This is just a point source of cooling so some house configurations may not be ideal. You can have multiple point sources for larger homes.
The big benefit here is that you don’t have to add any ducting to the home so the installation is quick and easy. The downside is that the cooling just won’t be as even as a home that is ducted with standard or high velocity ducting.
|[pic] | |
| |Check Your Knowledge |
| |Answer the questions below in the spaces provided |
1. Which is heavier, hot air or cold air?
_______________________________________________________
2. True or false? Ducting in old homes is usually ideal for air conditioning.
3. True or false? If the home has no ducting, there are no options for central air conditioning. The only option is window units.
4. Describe how to balance the air registers for air conditioning.
____________________________________________________________________________________________________________________________________________________________________________________________________________________________
5. The device that adds suction to an air register to give more air flow is called a __________________________.
6. True or false? A two speed fan will operate on high speed for air conditioning and low speed for heating.
Chapter
7
Chapter 7
CEP Quiz
CEP Quiz – Air Conditioning for an Old Home
Name__________________
1. Why is a “split system” air conditioning system called a split system?
_________________________________________________________
_________________________________________________________
2. What is the indoor cooling coil called?
_________________________________________________________
3. What is the outdoor part of the split system called?
_________________________________________________________
4. List two systems you could recommend to air condition a home that does not have any existing air ducting.
_________________________________________________________
_________________________________________________________
5. What is the easiest fix for a forced air cooling system that is not cooling the third floor of the home adequately?
__________________________________________________________
__________________________________________________________
6. Which is the cheaper fix, adding return air registers or supply air registers?
__________________________________________________________
7. List two advantages of a ductless system over window air conditioners:
__________________________________________________________
__________________________________________________________
8. List two disadvantages of window units:
__________________________________________________________
__________________________________________________________
Chapter
8
Chapter 8
Presentation Evaluation
Presentation Evaluation – Air Conditioning for an Old Home
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Location: ___________________________________ Date: ________________________
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Pillar To Post
( Pillar To Post
14502 N. Dale Mabry Hwy., Suite 200,
Tampa, FL 33618
5805 Whittle Road, Suite 211
Mississauga, Ontario
L4Z 2J1
01/20/2008
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