To understand how insulation works, it helps to understand the three types of energy transfer-conduction, convection and radiation -which helps explain how a house will loose heat in the winter and allow heat in during the summer.

First, it's important to point out that heat (Thermal Energy) always flows from the warmer object to the colder object. That's conductive energy transfer. In the winter, the heat in your cozy living room makes its way to any space that isn't heated - the basement, the attic, the garage - and outside. In the summer, the heat outside is attracted to your cool walls, floors and ceilings.

Conduction is the process by which heat transfer takes place in solid matter, like your walls, while convection is the flow of heat through moving air. In the wintertime, heated air expands and rises to the ceiling. This is why most people choose attic insulation with greater R-value, or thermal resistance. In the winter, insulation should prevent heat from penetrating the ceiling and going right through the attic and outside the house. Because blown-in fiberglass has a lot of airspace, airflows can carry heat right through the attic and outside the house. If you have ever been driving around after it has snowed and seen roofs with no snow on them, you know that's exactly what happens. In contrast, Cellulose's density and it's superior performance in cold temperatures means it doesn't allow that convective degradation.

The third way energy is transferred is through radiation, or the way the sun warms the surface of the earth, which involves the transfer of heat through electromagnetic waves and absorption of that energy by a surface. Inside a home, surfaces may exchange heat with other surfaces through radiation, which can have some impact on indoor ambient temperature. But radioactive energy transfer is most relevant to home comfort in the summertime, when your roof and exterior walls absorb heat from the sun. That heat can enter the interior space through conduction and convection. And, again, it points out the importance of both the density of your insulation and a tightly constructed home with no air leaks