In warm weather, the roof gets sizzling hot during the day and radiates the heat into our living spaces at night. We spent many summer nights falling asleep with our heads lolling out the window to catch a breeze, listening to the Northern Katydid song for comfort. Unlike a lot of kids, my parents were EDUCATORS! So - I learned - the reason I woke up sweltering, brown bangs plastered to my forehead in clumps, was because of the magic of 'radiant heat' and 'thermal gain'. ISN'T SCIENCE INTERESTING?
The magic of science is happening in our house.
There are two steps to the insulation process. First, air sealing. Second, actual insulation. We're 1/2 through insulation and about 3/4 of the way done with air sealing. I am my parents' daughter, so you know what's coming, right? EDUCATION about AIR SEALING!
All air has moisture in it, and moisture has a dew point. The dew point is the condition below which water droplets begin to condense and dew forms. Think of the back of your toilet on a hot day: hot air hits cold porcelain surface. Voila. Dew.
So, if you've got 50% humidity at 70 degrees, that same volume of air, when cooled to 40 degrees will condensate. In an attic space in the winter, you have a cold roof. If any moist air hits that cold surface, the moisture will condensate. Why do you care of condensation? You care because it can lead to mold. If no moist air gets into that interstitial space, you don't have a problem because there's nothing to condensate. If you air seal perfectly. Air sealing also stops the movement of air that you've spent good money to heat or cool. If you can stop air from moving, it's not going to take the warmth (or cool) out with it.
To save money, Mr. Man is air-sealing our attic himself. The back half of the house was easy - BECAUSE WE TORE DOWN ALL THE CEILINGS in the back half of the house.