Most people think about insulation as the answer to a cold, expensive house. It’s only half the answer.
The other half is air sealing — stopping the air that leaks in and out through hundreds of small gaps you can’t see. In a lot of Uxbridge homes, especially older and rural ones on expensive propane or oil, air leakage wastes as much energy as missing insulation does. You can add all the insulation you want, but if the house is still leaking air, you’re heating the outdoors.
If you’re serious about a comfortable, efficient home — not just a slightly-less-cold one — you have to think about the house as a system. Here’s how spray foam and whole-home air sealing fit together.
Insulation vs. air sealing: the difference that matters
They sound like the same thing. They’re not.
Insulation slows heat conduction — heat moving through a material. More insulation, slower heat loss through that surface.
Air sealing stops air movement — warm air physically leaking out through gaps, and cold air leaking in. This is a completely separate path for losing heat, and insulation does almost nothing to stop it.
A house can be well-insulated and still leak like a sieve. In fact many are — insulation was added over the years, but the hundreds of small air-leak points were never addressed. The result: high bills and drafts despite “having insulation.”
In an older or rural Uxbridge home, air leakage is often the bigger problem of the two. Which is why the efficiency-minded approach tackles both.
Where the air actually leaks
A typical home leaks air through:
- The attic ceiling — top plates, wiring, plumbing stacks, the chimney chase, exhaust fans, light fixtures, the hatch
- The rim joist around the top of the foundation
- Gaps around windows and doors
- Basement and crawlspace penetrations
- The many small gaps that decades of renovations leave behind
The higher and lower leaks are the worst, because of the stack effect: warm air rises and escapes high (attic), which pulls cold air in low (basement/crawlspace). The taller and leakier the house, the harder this pump runs — all winter.
The two tools: targeted foam and whole-home AeroBarrier
There are two ways to seal a house, and the best approach often uses both.
Targeted spray foam — sealing the big, known leaks
Closed-cell spray foam seals and insulates the specific high-leakage assemblies in one pass:
- Rim joists — a continuous leak around the whole foundation perimeter
- Crawlspace walls — common under rural Uxbridge homes and additions
- Cathedral and shallow roof assemblies — where there’s no room for anything else
- Cold floors over unheated spaces — additions, porches, bump-outs
This is hands-on sealing of the assemblies you can identify and reach. Closed-cell spray foam →
AeroBarrier — sealing the hundreds of leaks you can’t find
Here’s the one most people haven’t heard of. AeroBarrier is a whole-home air-sealing technology that seals the entire building envelope at once, from the inside.
The house is pressurized, and a fine aerosol sealant is dispersed into the air. As air rushes toward every leak, the sealant is carried to the gaps and seals them — hundreds of them simultaneously, including the ones no one could find by hand. The system measures the air-tightness in real time, so you get a verified result, not a guess.
Why it’s a fit for Uxbridge’s efficiency-minded homeowners:
- It seals leaks that hand-sealing simply can’t reach
- It gives a measured, verified air-tightness number
- It’s ideal for a comprehensive comfort-and-efficiency upgrade, and for deep energy retrofits
- It qualifies as an air-sealing measure under the rebate program
The right order: seal, insulate, ventilate
Doing this as a system means sequence matters.
1. Air seal first. Seal the big leaks (foam) and, for a comprehensive job, the whole envelope (AeroBarrier). Sealing before insulating means you’re not burying leaks under new insulation.
2. Insulate to full depth. With the leaks sealed, insulation can do its job — attic to R-60, walls via drill and fill where needed, foam where assemblies require it. Attic insulation → · Drill and fill →
3. Ventilate deliberately. This is the part DIY air-sealing gets dangerously wrong. A house sealed tight needs a planned way to bring in fresh air — otherwise you get humidity, stale air, and potential problems with combustion appliances (a propane furnace, oil furnace, or wood stove needs adequate combustion air and safe venting). Tightening a house with combustion appliances without addressing ventilation and combustion safety is a real hazard.
⚠️ This is exactly why whole-home air sealing is an assessment-first, professional job — not a weekend project. The sealing is straightforward. Getting the ventilation and combustion safety right is what keeps a tightened house healthy and safe. A carbon monoxide detector is essential in any home with combustion heating, and more so in a tightened one.
Where foam isn’t the answer
Your attic floor — a standard truss attic is best served by cost-effective blown-in, not foam. Foam’s premium isn’t needed on an accessible attic floor. Attic insulation →
Interior walls where you only want quiet — mineral wool for sound.
Over an unresolved moisture problem — fix water first, always.
As a substitute for ventilation — sealing without a fresh-air plan creates problems; it doesn’t solve them.
Practical questions
Is air sealing really as important as insulation? In many older and rural Uxbridge homes, yes — air leakage can waste as much energy as missing insulation. A comprehensive job addresses both.
What’s the difference between spray foam and AeroBarrier? Foam seals specific assemblies you can reach (rim joists, crawlspaces) and insulates them. AeroBarrier seals the whole envelope at once, including the countless small leaks you can’t find, and measures the result. They complement each other.
Will sealing my house too tight cause problems? Only if ventilation isn’t addressed. A properly tightened house includes a deliberate fresh-air strategy and combustion safety. That’s part of doing it right.
Do I need to leave during spray foam? We install Insulthane Extreme by Elastochem and residents can generally remain; we’ll discuss ventilation and re-entry for the sprayed area, and flag any respiratory sensitivities.
Does air sealing qualify for the rebate? Yes — air sealing is a measure under the Home Renovation Savings program (measured against a target in the energy assessment). AeroBarrier’s verified air-tightness result fits that framework well. Uxbridge rebate details →
⚠️ Program terms change — confirm at homerenovationsavings.ca.
Get a whole-home assessment, not just an insulation quote
If you want a genuinely efficient, comfortable home — especially an older or rural one on expensive fuel — the right starting point is looking at the whole house: where it leaks, where it’s under-insulated, and how to seal and insulate it safely as a system.
Pro Insulation Contracting has insulated Ontario homes for over 10 years and serves Uxbridge and the surrounding townships. We install spray foam, AeroBarrier, blown-in, drill and fill, and more — and we’ll tell you which combination your home actually needs.
📞 705-315-8118 · Book a free assessment →
