Chances are, if your house get’s blazing hot on the upper levels during the summer time, it’s because your roof and attic space are working together like an oven. They do this through two obvious measures: 1) by providing heat – in this case absorbing sun’s radiant energy, and 2) by sealing relatively tightly to maintain that temperature – your attic walls and roof. If the space in your attic builds up heat there are equally only two means by which to abate the heat in your living spaces without relying on costly air conditioning. 1) Shield yourself from the heat with good insulation 2) remove the heat from the attic space. Believe it or not, in most cases with an unconditioned attic, this is easy and cost-effective. I know from experience; my house doesn’t get hot.
The obvious measure of insulation is to separate the indoors of your home from the unwanted outdoors climate that also can inhabit your attic. If you have an unconditioned attic like mine, adding high quality insulation like paper cellulose to seal the deck (joists included) above your attic will do the most of the work in abating the summer time heat. The insulation, however, only protects your from the heat; it doesn’t outright remove it. The next step is to install a system to remove that air. Now, most homes (not all) have some sort of passive ventilation in their attic such as a ridge vent or soffit vents. While these prevent the attic from slowly crumbling from the heat, the only do enough to protect the life of the material up there from moisture build up. While they are also designed to remove hot air that function tends to be minimal. After all, hot air travels in the direction of cooler air. If the air outside is hot the hot air inside has less encouragement to naturally move outside. Some of this will happen because your attic will definitely be hotter than the outdoor temperature, but the heat outside will slow this process. The best option is to use mechanical ventilation. That’s why I encourage people to install as Solar Star solar-powered attic fan. http://www.seacoastgreenovations.com/products/solartube.aspx
These nifty devices work exactly when you need them and cost nothing to run. And while they cost slightly more than an electric attic fan, you’ll more than make up that money by saving on installation costs because there is no need to hire and electrician. Also, it’s easy to install. I love products like this because not only do they serve their original purpose, they do so in a sustainable manner.
(*Note: Solar Star fans need to be properly located, especially in roofs with ridge vents.)