At the most basic level, insulation helps keep your building at a livable temperature. It keeps the air in your home from leaking outside and vice versa. The efficiency of insulation is determined by its ability to keep heat from moving through it. There are three ways that heat can move from one area to another:
- Conduction: This is the transfer of heat through a solid, like how your spoon gets hot when you leave it in a bowl of soup. Insulation serves to stop this heat transfer from occurring through the walls of your house. This is commonly known as the “R” value.
- Convection: When heat is transferred through air movement because of a difference in pressure, the process is called convection. Anytime air moves, heat can be transferred with it. When air leakage occurs through your insulation, heat is being lost through convection.
- Radiation: The final method is transfer of heat through light rays. The sun gives us warmth through radiation. ‘Radiant barriers’ can help block light rays and reduce heat generation in a building.
R-value, the measurement given to the conductive portion of the heat transfer equation, is not necessarily a good indicator of the overall performance. Therefore it DOES NOT follow that the higher the R-value, the more effective the insulation will be if the other 2 components of the heat transfer equation have poor values. Therefore, as these numbers are usually based on lab tests under optimal installation conditions they may be misleading when reflecting real-world situations.
A better comparison of how a specific insulation can be expected to perform would be to compare the BTU heat loss value per square foot or a measurement of “functional R value” (how the product performs in the real world) of the various insulations you are considering using. When this type of comparison is done, Walltite Eco spray foam will always outperform fiberglass (the most commonly used insulation) by a very large margin, resulting in very significant financial savings to you in the operating cost of any building and over the life span of the building.