white papers

Outboard Insulation: Basement and Wall Strategies for Southern Ontario

With the popularity of brick and stone veneer claddings in the Southern Ontario new construction housing market, the code-driven trend of outboard insulation strategies creates some challenges for builders. Builders have grown accustomed to the ease of construction and costs associated with 8” cast-in-place foundation walls. Outboard insulation strategies, while efficient from a thermal perspective in our climate zone, can create foundation wall depth issues, e.g. maintaining bearing for heavyweight veneers, and the 1” drainage gap required by these wall types to vent bulk water. Through a series of residential design workshops sponsored by the Enbridge Gas Distribution’s Savings By Design program, a clear link to cost as a primary objection has surfaced amongst most (80%) of builder proponents questioned. This paper describes seven above ground and basement wall strategies, options which rely on a typical 8” foundation pour (some requiring enhanced rebar schedules) and which utilize outboard insulation between 2” to 4” thickness with masonry veneer claddings. This outboard insulation strategy, along with balanced interstitial insulation levels, meets the standard for net zero ready housing and will likely be code compliant construction by 2030 in Ontario. Criteria for applying these building strategies included ease of construction, durability of wall systems, and thermal and structural performance. Order-of-magnitude pricing, including local labour factors, have been included for each system and may be compared and contrasted with the more typical 10” foundation strategy to determine which approach makes greater holistic sense.

Authored by Dave Petersen & Miyoko Oikawa