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Q. I bought a Ryan Home (colonial) three years ago which was built new. I was told that an attic fan would not be necessary. With the price of air conditioning “going through the roof”, does it make sense to add the attic fan?
A. I have received more questions about attic fans in the last month than I have in the last five years. I’m sure the one fact that’s propelling the interest is the cost of electricity. Although you would think it makes common sense to somehow augment the ventilation of your attic space and that adding a fan-- powered by electricity-- would do the trick, I can think of a number of reasons not to.
The whole notion of getting hot air out of the attic space above our heads in summer is not a new idea and it even predates the use of insulation. As soon a folks were able to get electricity to their homes they bought cooling fans and sticking one up in the attic to vent hot air from there made sense and they helped cool things a lot.
The best types are gas tankless water heaters that many people see while traveling overseas in Europe or Japan. But keep in mind, these models tend to be point-of-use water heaters and the plumbing set up in your home is rigged for remote water heating that is directed through a series of pipes to each individual point of use.
Whole house fans that sit horizontally in the ceiling of the uppermost floor of the house and are about two feet across and pull hot air from the house forcing it up into the attic and out the gable vents were popular up through the 70s and are still a good idea. When the AC isn’t being used and windows are open they create an interior breeze that delays the temptation to turn the air on much longer than not moving any air. That’s all we had when I was young and we got by pretty well.
But in the recent generations of home building, especially since the 1970s and the sensitivities generated by fuel shortages and skyrocketing energy costs, houses began to be built differently. The key now is that houses are insulated so much more than ever before and the houses themselves are tighter than ever before.
The attic you have in your three year old house is outside of what is called the building envelope-- the space that’s insulated, heated or cooled-- and the way designers ventilate that space is by a combination of ridge venting along the very top of the roof at the peak and soffit venting located at the lowest part of the eaves. It’s a convective system that uses the energy of the sun to do the venting work. As the roof shingles and wood heat up it heats the air just under the roof and the hot air begins to rise. As it does it washes the underside of the roof with air and vents heated air out at the very top.
Adding a fan to that mix will initially interrupt that venting mechanism but it gets worse. What a powered vent fan does is depressurizes the space it’s in and then it will want to pull air from wherever it can and some of that power will drain air from the house itself. Now you are pulling air leaked from the house that you paid good money to cool plus you’re paying for the electricity to run the fan.
The thing that really bothers me about attic fans is that they operate out of sight and out of mind and when they get old up in that basically exterior environment they wear out and can burn up-- taking the house with them. I have been up in attics and discovered attic fans about to burst into flames and know folks who have lost homes from them.
The independent studies I've seen show an annual dollar savings with its use of $179.00 in the test areas out West. It'll be less around here--about $50. a year if you are on both municipal water and sewer-- but what you want is the convenience. Some Home Depots carry them and I'm sure they could order one in for you if you asked. You can find out more about them at www.gothotwater.com
Your state of the art passive attic ventilation system is as good as it gets and whoever told you when you bought the house that an attic fan was unnecessary was right.