Rim Joist Spray Foam Insulation In Woodstock, Ontario

Cold Air Leaks In Where The House Meets The Foundation

We seal it. The rim joist sits right at grade, where wind pushes cold air through the gap between the concrete and the sill plate, and between the sill plate and the floor above. Most basements in Woodstock still have a piece of fibreglass batt pushed into each joist bay, and a batt does almost nothing to stop moving air.

The result is a cold floor along the outside walls, a draft at the baseboards on the main floor, and in January, frost on the wood behind the batt. When that frost melts, the wood stays damp, and damp wood is where mould starts.

Why Closed-Cell Spray Foam Works Best On Rim Joists

Closed-cell spray foam sticks to wood and concrete, fills every odd-shaped joist bay, and seals around the pipes, wires and vents that pass through the rim. At about two inches thick it is also a vapour barrier. Warm, humid basement air never reaches the cold wood, so condensation has nowhere to form.

Rigid foam boards cut to fit each bay can also work, but every edge has to be sealed with canned foam. Those edges are where most rim joist work done by hand leaks again within a few years.

Rim Joist Insulation Is Often The Best Value Upgrade In A Home

A rim joist job is small, and the change in comfort is easy to feel. The full perimeter of a typical Woodstock house is done in a few hours, and the floors above feel warmer that same winter. It pairs well with basement insulation or crawl space insulation, and it is worth doing before a basement is finished, while the joists are still easy to reach.

What Does Rim Joist Spray Foam Insulation Cost?

Most rim joist spray foam insulation jobs in Woodstock cost between about $800 and $2,000 for a whole house. The price depends on the length of the perimeter, the depth of the joists, and how much ductwork, plumbing or finished ceiling is in the way. Your written estimate lists all of it. Answers to other common questions are on our spray foam insulation FAQ.