Insulation levels are specified by R-Values, a measure of insulation’s ability to resist heat traveling through it. The higher the R-Value, the better the thermal performance of the insulation. The table below shows what levels of insulation are cost-effective for different climates and locations in your home.
To convert from one to the other use the following formulas:
1/R-value = U-value or 1/U-value = R-value
Example: R-19 (common for walls) = 1/19 = U-Value of .053
HRVs/ERVs are typically sized to ventilate the whole house at a minimum of .35 air changes per hour. To calculate minimum CFM requirements, simply take the square footage of the house (including basement) and multiply by the height of the ceiling to get cubic volume. Then divide by 60 and multiply by .35