Rim Joists, also referred to as Joist Headers or Joist Ends are a very critical area to focus on in regards to proper insulation. This space is located between the top of the basement wall, and the start of the first floor. This floor/wall interface is a major source of heat loss and infiltration.
The old way of insulating rim joists was to use fiberglass batts. Fiberglass is a poor choice of insulation and should never be used in rim joists because it's nearly impossible to install a proper vapor barrier. Fiberglass will also allow for a lot of air leakage. Without a air/vapour barrier warm air passes through the fiberglass causing condensation. This can cause mould or rotting.
SPF is better suited than fiberglass to insulate rim joists, because it insulates and seals air leaks, and prevents water intrusion. As SPF is applied, it expands to seal cracks and gaps, preventing condensation from forming on the rim joist and protecting the home from mould and rot that can result from condensation.
In Manitoba, building codes require an approved fire barrier material to be installed between the SPF and the interior occupied space. If drywall is installed on the ceiling then no farther fireproofing is required. Ask us about fireproofing options we offer.
