Proper Ventilation Part 3

Last time we covered a primitive but effective ventilation system in an older home. Today we will discuss a design of one in a newer type home. Since homes built since 1970 have been guided by energy efficiency codes they are "tighter" as far as allowing "free ventilation", so we have to work a little harder to get them to "breathe".
We will start with the attic. First we need intake air. Since we want the hot air that builds near the top of our roof to exit, we need cooler air to enter--lower in the attic. The most common way of doing this is vents in the eaves. However the most common mistake is to cover these openings with insulation. The best way to handle this is to create a duct from the opening to above the insulation level to allow free intake air.
The next step is to have an exit for our attic air and that would be as high as possible in the roof and an active rather than passive source. I recommend a solar attic fan. It will actively pull the air out with no energy consumption. This system has the potential of keeping the attic no higher than the ambient or outside temperature. Attics have gotten as high as 180 degrees on a 105 degree day if they are not ventilated.
On homes I have installed these systems on we have seen a minimum of a 10 degree drop inside of the home with no active air conditioning or indoor ventilation turned on. This has occurred no matter what the insulation value was in the attic.
Next time we will discuss insulation options.