Why Winter Is the Honest Season
A house hides its energy problems for eight months of the year. In summer, a poorly insulated wall and a well-insulated wall feel the same. In winter, the temperature difference across the envelope is at its maximum — which is exactly when thermal imaging, air leakage testing, and moisture readings reveal what's actually happening.
That makes late fall and winter the best time to assess a building envelope. If you're planning a renovation, an addition, or a basement finish, the assessment you do now shapes the design you build in spring.
What an Assessment Actually Examines
Thermal imaging of the envelope
Infrared imaging shows surface temperature differences across walls, ceilings, and floors. Cold spots reveal missing or settled insulation, gaps around windows and doors, and thermal bridging at studs, headers, and slab edges.
Air leakage paths
Air leaking out of a house carries far more heat than conduction through the same area. Common paths are at the rim joist, around penetrations, at the attic hatch, and where interior finishes meet exterior walls. Sealing these is usually the highest-return work available.
Moisture and condensation risk
Where warm moist air meets a cold surface, you get condensation — and eventually mould and rot. This is why adding insulation without addressing air sealing and ventilation can make a problem worse rather than better.
Insulation continuity and R-value
What insulation exists, where it is, and whether it is continuous. Compressed or settled insulation performs well below its rated value, and a gap in coverage defeats the assembly.
“Air sealing usually beats adding insulation. Tightening a leaky house is cheaper than re-insulating it, and it fixes the condensation problems insulation alone can worsen.”
The Ice Dam Connection
Ice damming — the ice that builds at your eaves and drives water under the shingles — is an energy problem wearing a roofing disguise. Warm air escaping into the attic melts snow on the upper roof; meltwater refreezes at the cold eave and backs up into the building.
So when you see large icicles or ice dams, you're looking at an air-sealing and insulation deficiency. The energy assessment identifies where that air is actually coming from, which is the information you need before anyone touches the attic.
The structural consequence is real: the water ice damming drives into the roof deck causes rot, and rot takes capacity out of the structure. Our post on snow load and roof structure in Ontario covers that side of it.
Where This Meets Your Permit
Energy performance isn't optional in Ontario. Permit submissions require energy compliance documentation — SB-12 for residential — demonstrating the project meets minimum performance. That means your renovation, addition, or new build has to be designed to a performance standard, and the compliance form must show project-specific inputs.
An envelope assessment feeds directly into that. Knowing where the insulation and air barrier actually are — and where they aren't — lets you design additions and renovations that meet the standard without over-specifying. It also prevents the common mistake of adding an insulated addition to a house whose existing walls won't come close, which creates a performance mismatch and often a condensation problem at the junction.
The current requirements are set out in the 2024 Ontario Building Code, which tightened insulation values and window performance relative to the previous edition.
Why Do This Before a Renovation, Not After
If you're planning work that opens walls — an addition, a basement finish, a kitchen renovation, a second-storey addition — you have a brief window when the envelope is accessible. That's when air sealing and insulation upgrades are cheapest, because the wall is already open.
Assessing the envelope before design means those upgrades can be specified into the drawings and priced into the project, rather than discovered mid-construction as a change order. It also means the energy compliance documentation reflects what's actually being built.
Envelope and Energy Assessment Across the GTA
Building stock and local conditions vary widely across the region. Find your city:
May Engineering Inc: Energy Compliance and Envelope Design
May Engineering Inc prepares energy compliance documentation for permit submissions and designs envelope assemblies that actually perform — air barrier continuity, insulation placement, and moisture management detailed at the drawing stage so the assembly works in an Ontario winter.
Planning a renovation or addition that will open up your walls? Talk to us before the design is fixed — that's when envelope improvements cost the least.
Renovating this winter?
Free initial consultation. Energy compliance documentation and envelope design for Ontario permits.