Insulating Your House from CMHC Series 3-10

Insulation Effectiveness

R values and their metric equivalent, RSI values, are a way of labelling the effectiveness of insulating materials. The higher the R value or RSI value, the more resistance the material has to the movement of heat. Insulation products sold in Canada are labelled with R and RSI values. Provincial building codes specify minimum R (or RSI) values for new construction, with different values for different applications. It is important to know what your local building code requires when planning new construction.
Note: The way the insulation is installed plays a large role in its effectiveness. Compressing the insulation, leaving air spaces around the insulation and allowing air movement in the insulation all reduce the actual R value of the insulation.