You might also think that increasing insulation R-Value provides a proportionate increase in its ability to control energy loss. In reality, an R-8 insulation already controls 90 percent of potential energy loss through a material (Source: Fouriers Law of Thermodynamics). Upgrading from R-8 insulation to R-32 insulation, for example, would reduce conductive heat flow by only another seven percent (assuming no air can move through the insulation).
The real problem is heat loss through convection (or air leakage), which accounts for as much as 40 percent of the total energy lost by your home (Source: U.S. Department of Energy). And even the best conventional insulation on the market wont control air leakage - regardless of R-Value.
So, if R-Value doesnt provide the help wed like in comparing insulation, what will? The best strategy is to make a well-informed choice, by knowing the factors that will affect how well insulation performs in your home. If you are building, remodeling or just thinking about adding insulation, ask a builder, contractor or anyone providing information about insulation products the following questions:
How well does the insulation control air leakage that can account for up to 40% of a homes energy loss? (spray foam insulation such as Icynene is particularly effective at creating a continuous air barrier)
How quickly will the insulation pay for itself? (are the monthly energy savings greater than the monthly cost of financing the insulation purchase?)
How well does the insulation reduce air leakage in hard-to-insulate areas such as rim joists, cathedral ceilings, crawlspaces, garages, etc?
Can the insulation help reduce heating and cooling loads (and costs) while removing the need for larger/costlier mechanical equipment?
Will the insulation help keep out allergens, dust and other pollutants?
Will the insulation shift with the home over time as it settles? Will it leave spaces, gaps?
What happens if the insulation gets wet? Will it keep its insulating properties? Can it grow mold?
Does the insulation contribute to poor indoor air quality?
Can the insulation help control sound (around plumbing, between rooms, from outside)?
Does the insulation require a number of finishing materials (plastic wrap, gaskets, tape) to eliminate gaps or cracks?
A builder/contractor/sales person should be able to answer most of these questions and provide insulation options that can help your home become more energy efficient, healthier, quieter and comfortable.