Energy efficiency is a major concern of the 21st Century. Many homeowners have a hard time paying for increasing energy bills, and many fear that this increase will continue indefinitely. In E:zero's opinion, except for normal up and down swings, energy costs will stabilize once major portions of our energy supplies have been converted to renewable sources, such as wind or solar. This indicates that current energy costs can be expected to triple in amount. Nobody knows how long this will take; however, the price of natural gas in Cleveland, Ohio has already doubled during the last two years!
The good news is that it is easy and affordable to improve the energy efficiency of your home. The key factor is the building's air-tightness. The general public has been misled for a long time by claims that R-value is useful as a standard to determine energy efficiency. Now we know that ACH - Air Changes per Hour -- are a much better indicator of insulation performance.
Heat Transfer and Air Control
R-value measures the resistance of a material to heat transfer in laboratory settings. The only thing measured here is conduction, which is comparable to the transfer of heat through the metal of a frying pan to the food in the pan. Houses, obviously are not frying pans, and are in-turn a far more important factor when considering energy savings. The energy lost by convection is when air is released through the walls and ceilings of a home, and is measured by an indicator called ACH.
Houses insulated with spray foam perform drastically better than conventionally insulated homes, since they are much more airtight. It has been shown in numerous studies that comparable homes insulated to the same R-value use up to 50% less energy when they are insulated with spray foam rather than fiberglass.
Air changes per hour (ACH)
(Involuntary) Air Changes per Hour = ACH. This is a measurement of air infiltration, which is the total amount of air lost through the building envelope. The analysis is done with all windows and doors closed. Very tightly constructed homes with spray foam insulation may achieve an ACH of 0.1, while properly constructed homes insulated with fiberglass may reach values between 0.7 and 1.0. The ACH of older, poorly maintained homes may be higher than 2.5. What this means is that homes insulated with foam lose their air 2.5 times per day compared with 17 times for homes insulated with fiberglass, and up to 60 times a day for old homes without insulation.
R-value is a measure of thermal conductivity expressed in kelvin square meters per watt (K*m2/W). The test method is defined by ASTM C518. In short, the conductive resistance of the insulation material is measured at 75oF (24oC) in an environment without wind. The problem with this method is that it is not very relevant to real-life situations. In particular, fiberglass shows peak performance at 75oF (24oC), while its performance is seriously diminished at 35oF (2oC) or 105oF (40oC), while foam shows hardly any deterioration. Likewise, homes are not in wind-still environments, and are often subjected to pressure differentials between indoors and outdoors due to temperature differences, forced air heating and cooling systems, etc. As such, we feel that ACH is far more relevant than R-value in determining insulation performance.
Spray Foam does not emit anything, good or bad. It does not disintegrate, unlike fiberglass, nor does it shrink, settle, or crack. Spray polyurethane foam simply performs for the lifetime of the building without needing maintenance or upgrading.