Building InsulationAug 17th, 2009 | By builder | Category: Building Materials, Energy Efficiency, Things I wish I knew
Much like the building envelope, insulation is something that we all take for granted. It is not sexy, but it is something that is needed if you want your house to stay warm in the winter and cool in the summer. So we can put R-20 in the walls and R-40 in the attic and call it a day, right. Not quite as R-value rating is very deceptive. It is a laboratory controlled test that determines the R-value and once the products are out of the laboratory all bets are off so to speak. Batt and cellulose and ½ lb spray foam require a vapor barrier as air does flow through them while 2 lb spray foam does not allow air to flow through once it has reached a certain thickness.
It has been proven that as air moves through insulation it decreases its’ R-value as the temperature drops which is when you need it most. Installation also plays a major role in how efficient the insulation is. One of the biggest problems with batt insulation is not the efficiency of the product itself, but the loss of R-value due to improper installation. That is not to say that they are not efficient, only that they are less efficient certain types of insulation should be avoided, only that they need to be installed correctly. Now a days there are a couple of different option when it comes to insulation. It might even come down to where you live in the country as to what is available. Each type comes with its own pros and cons and can be broken down into three main groups. Batt, blown in or spayed insulation. Most houses have a combination insulation types. Most common is the batt insulation for the walls, but it can also be used in the attic or crawl space. Blown in insulation while mostly used in the attic can also be blown into the wall cavity as is done in most net zero homes. Last but not least is the spray category which includes both sprayed in cellulose and foam. As the ICF uses foam for blocks, I decided that I would have my attic sprayed. As sprayed cellulose is not common in my area, I focused on researching the different types of spray foams.