There are many considerations when building a desert home that might not be obvious to non-desert dwellers. One of those has to do with what kind of cooling system to install. I received the following email:
I am planning a move to the Phoenix area. Can you answer these questions for me? Some houses have evaporative cooling. What is it? Will it cool a house as well as a central air system? Regarding really high ceilings....are high ceilings better than lower ceilings when trying to cool a house down?
An evaporative cooler, also known as a swamp cooler, pulls in air from outside and uses water run through soaked pads in the cooler to lower the temperature of the air and flow that air through your home. It can be used as the sole cooling source for a home, but it is not effective during our humid monsoon months when the humidity rises. Of course, two of those are our hottest months. One disadvantage of a swamp cooler is that it uses more water (that cost depends on where your home is located) and requires regular maintenance.
Of course, air conditioners should be regularly maintained, but when your A/C is working properly there are no pads to replace, and when it isn't there's no risk of water leaking into your home, both of which are the case with evaporative cooling. I speak from experience about water leakage from a cooler!
If you are starting from scratch building a home, you can:
- build with only evaporative cooling. This is only advisable if you (a) don't live in the home in the summer, and (b) don't expect to ever sell the home.
- build the home with A/C only. This is what most people do. I imagine the basic reasons are that there are fewer large pieces of equipment to maintain and repair, and that if you can't use a swamp cooler for the worst part of the summer the savings aren't that great.
- build the home with both. For the best efficiency, this would be your option since you can plan the placement of the units and the duct work properly from the start. That doesn't mean, however, that it will save you a lot of money. You'll have to do some math -- how many years will it take to offset the cost of the extra unit and the increased water bill? Will you live in the home that long?
Swamp coolers were much more popular here before central air conditioning became more efficient. Whichever way you decide to go, don't forget to take that aspect into account. Also, be aware that both electric companies here have plans that allow you to manage peak and off-peak electricity usage to save money on your electric bill, and using a programmable thermostat will definitely help, too.
If you intend to buy an older home, make sure you know what kind of cooling system it has, how old it is and how well-maintained it has been.
The Consumer Energy Center provides a detailed description of evaporative cooling. This article about evaporative cooling from the University of Arizona in Tucson explains local usages and issues to consider.
With respect to the high or vaulted ceilings question, clearly when you have vaulted ceilings you are heating and cooling more area of your livable space than is necessary. Vaulted ceilings are common here—they are probably cheaper to build—and are viewed as beneficial by many buyers since the home has a larger, more open feel and often more interior light (which could mean more heat in the summer). The good news about vaulted ceilings is that they allow you to comfortably install ceiling fans without the worry of tall people being decapitated!
Ceiling fans also come with light kits so they can do double duty in a room (the room has to be wired for it). You will have to determine for yourself if the degree to which the ceilings are vaulted are worth an extra cooling/heating expense.
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