Types of Insulation
Soft foam has two features. It is insulation, (approx. 4-R per inch of thickness) and it is classified as an air barrier. Technically it has no more thermal capacity than conventional insulation. Although, because foam does not allow air to pass through it the performance value is conservatively 3 to 4 times that of fiberglass and cellulose.
Hard foam has three features. It is insulation, (approx. 7-R per inch of thickness) an air barrier and a vapor retarder. It has more thermal capacity than conventional insulation. The vapor retarder feature stops liquid water from moving through the product. Applications where liquid water may come in contact with the foam or when extreme relative humidity levels are present hard foam is a good solution.
An example where foam differs from conventional insulation:
Can lights that are installed in a ceiling that come in contact with insulation must have an IC rating. This rating means that insulation can be installed in direct contact with the light. Loose fill fiberglass or cellulose insulation can be installed at any depth around the can without a problem, (except infiltrating into your home). But you can not install foam directly on the can because the heat generated by the light bulb does not disipate through the foam causing the light to overheat. A thermal overload is built into the light that turns it off when a predetermined temperature is reached and the light turns off. This feature should be very important to you. Check out the "Dare to Compare" display on the resources page for another example.
Why is air sealing so important?
According to the U.S. Department of Energy, up to 40% of the energy lose in a home is caused by air infiltration. The U.S. Environmental Protection Agency states that the most common sources for indoor air quality problems include chemicals from building materials and mold. The U.S. Green Building Council promotes the idea that environmental friendly green building practices help preserve the earth for future generations.