Quote:
Originally Posted by villagetinker
I would ask about the CFM (cubic feet per minute) rating of the SOLAR fan versus an 120 volt AC powered fan. There will be a cost for the new AC supply, if you are lucky the supply for the attic light can be tapped for the new fan. There will be a cost to cut the hole in the roof for the vent (should be the same for either type of installation). I would opt for a thermostatic control on the AC powered fan this will allow it to turn on when needed and run until the attic is cooled off. Finally, look at the costs, installed and running, unless you put in a really big AC powered fan, the cost will probably be 10 to 20 cents per day, while the solar is free, however the installed costs between the 2 options maybe significant.
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The Solar Guys install two models. RM1500 and RM2400. There is a chart on their web site used to determine how many of each fan you need depending on the square footage of your home. AC powered fans will give you more CFM but the solar fans produce more than enough air flow. Initially, I had them install two RM2400s but it was too much for my 2600 sqft home. At peak times I could head the RM2400 in my living room if it was quiet so I had them replace one RM2400 with a RM1500 and that solved the problem. Now my attic never gets more than 10 degrees hotter than the outside air. I have temperature sensors in my attic with the data that shows this. Before the attic fans, my attic would superheat to around 150 degrees on a 90 degree+ day here in the Villages. The typical thought is that you need a huge attic fan to evacuate the hot air but assuming your soffit vents are not clogged and you have adequate air circulation in your attic, all you need is a fan with a moderate CFM to move the hot air out of the attic. A fan that's too large will start sucking air from the living space and you don't want that either.