The Prescriptive approach to compliance.

- Convert exterior frame from 2 x 4 to 2 x 6
- Change cavity insulation products
- Use urethane foam
- Change the above grade wall assembly
- Install foam as exterior wall sheathing
- Upgrade window performance values
- Increase ceiling insulation value
- Install foundation insulation


The Prescriptive approach will require builders to change exterior above grade walls from 2 x 4 to 2 x 6 or change the cavity insulation and or the wall sheathing product to increase the R-Value of the assembly.
Additional changes will be required as increasing the U-Value of the windows, installing additional ceiling insulation and adding foundation insulation to the exterior or interior of the foundation wall.


From a building science perspective this is a good start to building an energy efficient home: The foundation insulation is a significant player for reducing the building-heating load (See Note). Increasing the window performance does substantially reduce the heating and cooling demand, especially with a large wall of windows having northern exposure. Increasing the R-value of insulation will slow down heat transfer. However, the Prescriptive approach does not take into account the true infiltration rate of the building envelope. It is based on a default number that may only be close.

The only way to know the true rate of infiltration is to test the building with a diagnostic tool called a Blower Door.



For information on how a Blower Door works click here.

Note: Be very cautious when choosing the materials and the approach that you will be using to insulate foundation walls. The following information is provided to benefit from the lessons learned when using vapor barriers and fiberglass insulation. Please read this information before choosing your materials and installation methods.
Click Here for basement insulation systems document (608KB pdf).

The System Approach to Compliance>