Foam vs Fiberglass Insulation

The filter medium for most furnace filters is fiberglass -- the same spun fiberglass used as insulation. Fiberglass is used for an air filter because it has less impedance to the air flow, and it is cheap. In other words, the air flows through it very readily. It is ironic how we wrap our house in a furnace filter that will strain the bugs out of the wind as it blows through the house. There are tremendous air currents that blow through the walls of a typical home. As a demonstration, hold a lit candle near an electrical outlet on an outside wall when the wind is blowing.

The average home with all its doors and windows closed has a combination of air leaks equal to the size of an open door. Even if we do a perfect job of installing the fiber insulation in our house and bring the air infiltration very close to zero from one side of the wall to the other, we still do not stop the air from moving through the insulation itself vertically both in the ceiling and the walls.

We spend thousands of dollars on energy efficient windows, doors, and HVAC equipment and then we install non-energy efficient insulation to save money. There is only one insulation product in todays market that leads the pack in energy efficiency, that product is sprayed expanding foam. When installed, the expanding foam gets into every nook and cranny, sealing all air penetrations.

Some advantages of foam insulation are: