Below Grade Walls

This section discusses:

• Poured concrete basements and crawlspaces
  • whether it is better to insulate concrete foundation walls from the exterior or interior;
  • the difference between damproofing and waterproofing; and
  • how much insulation is enough.
• Manitoba Building Code
  • Foundation Walls
  • Depth of foundation wall insulation
  • Regional sensitivity

Poured concrete basements and crawlspaces

Interior vs. exterior insulation

Most new homes in Manitoba use a poured concrete basement or crawlspace foundation. The walls of these foundations are typically insulated from the interior with a wood frame wall and batt insulation covered with a polyethylene air-vapour barrier. However, insulating from the exterior with a rigid insulation has several advantages that potential homeowners often overlook.

Before deciding which method to use for your new home, compare both and weigh which advantages are the most important to you:

Interior insulation advantages

• lower material cost
• practical to achieve high insulation values
• a finished interior surface (e.g. drywall, paneling) can be easily added
• no thermal bridging with brick veneer

Exterior insulation advantages

• less labour to install
• easier to insulate and seal area where foundation wall and floor system meet
• thermal mass of the foundation wall is inside the house (an important consideration if you live in a remote area prone to extended power interruptions)
• reduced potential for soil freezing to the surface of the foundation and lifting it (called "adfreezing")
• less prone to hidden water seepage and mold problems
• foundation wall is kept warm reducing the risk of condensation problems
• less effort and expense to clean up and repair after a flood
• no loss of interior space