A lot of people run expensive air conditioning when it is actually pretty cool out- after the sun has been baking a California house all day it can be cool in the evening but the house is still holding a couple of hundred thousand BTUs of heat. In more temperate parts of the country, just moving the air and having good ventilation could eliminate the need for AC much of the time.
What would keep a lot of people cool and comfy is a good attic fan, but they have usually been noisy and a big leaky hole in the ceiling come winter. Until this little thing, the Airscape, came along.
sorry Kim for the fuzzy picture.
It can move up to 1700 cubic feet per minute quietly (it uses fans designed for computer rooms instead of the old big blades) and has a motorized insulated damper built in, instead of the usual crappy leaky louvres. 1700 CFM didn't seem like much to me, but they note on the website:
While on the surface it may seem like more CFM equals better cooling, it turns out that old-style fans, with their enormous flow rates, were unnecessary overkill. The main function of a whole house fan is not simply to replace hot air with cooler air – it is to cool down the entire structure by drawing off the heat. And this takes time. Even with very high air flow – say 5000 CFM - your house can only shed pent-up heat at a limited rate. So there is a point of diminishing returns that needs to be considered against noise. You reach a point where you could double the airflow, which would quadruple the noise, yet only speed up the cooling process by 20 or 30%. So what’s really effective is slower flow over a longer period with quiet operation.
it isn't as sexy as a 2Kw photovoltaic system, but it is a whole lot cheaper and and saves a lot more CO2. It is another interesting comparison of why we should be going after the low hanging fruit first.
More on energy saving at lower cost:
Solar Hot Water First. Then Photovoltaics.