I have a customer wanting to save on her cooling costs. We live on Maui, on the dry, sunny (south) side of the island where many people use their a/c’s about 360 days a year. We pay 21 cents per kilowatthour. She’s got a hip roof, with what looks like a ridge vent and the usual intake vents in the frieze blocking of the eves. The house is about 8 years old. The attic has NO INSULATION.
My questions are:
Fiberglass vs. blown-in cellulose insulation?
Radiant Barriers. A brochure from our Maui Electric Company claims that the return on your investment for installing a radiant barrier is the same as that for attic insulation. Are radiant barriers really that effective? How easy do they go in?
Any thoughts on solar-powered roof fans or turbine vents (Whirlybirds)? We have strong tradewinds for most of the year, but suffer the real heat on the days that the winds stop blowing.
Replies
I'm in Florida and have been impressed with some of the better quality solar powered vent fans. They move a considerable amount of air and operate for free. They can make a substantial difference in attic temperatures. My only reservation about them is longevity. The good ones are not cheap. Will they last. These I suspect are best used where ridge and soffit vents are not possible. Some hip roofs leave areas closed in and difficult to ventilate. I'm less impressed with line powered vent fans because I have seen them run up power bills without returning any real savings. The cheaper of the line don't last and some leak.
The DOE studied attic ventilation in the late 70s and demonstrated that the turbine type were no better than the same sized non-rotating vent. Consistently balanced continuous ridge and soffit vert gave the best results long term.
JLC just had a big article on this.
If you can't find a copy, then you can get it online.
http://www.jlconline.com, Research.
A few artciles are free, the others are $5.