Quick answer
Air sealing closes gaps and cracks in a home’s envelope to stop uncontrolled air movement. Spray Foam Kings uses open‑cell or closed‑cell spray foam to create a durable, airtight barrier throughout the house.
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Why air sealing matters in Ontario
Ontario’s climate swings from hot, humid summers to cold, windy winters. Unsealed homes lose heat in winter and gain heat in summer, driving up heating‑and‑cooling bills and creating uncomfortable drafts. Air leaks also allow moisture‑laden air to enter wall cavities, increasing the risk of mould, rot and reduced indoor‑air quality. By sealing the building envelope, you:
- Reduce energy consumption and lower utility costs.
- Improve comfort with consistent indoor temperatures.
- Enhance the performance of existing insulation.
- Decrease wear on HVAC equipment, extending its lifespan.
- Minimise moisture intrusion that can lead to mould growth.
How spray foam creates an airtight envelope
Spray foam expands on contact, filling gaps as small as a pinhole and adhering to wood, metal, concrete and drywall. Two types are available:
- Open‑cell spray foam expands quickly, creating a soft, breathable barrier that is ideal for interior wall cavities and attic floors. It provides an R‑value of about R‑3.7 per inch and costs $1.50–$3.50 per sq ft installed.
- Closed‑cell spray foam is denser, acts as a class‑II vapour retarder at 2 inches or more, and delivers an R‑value of roughly R‑6 per inch. It is the preferred choice for rim joists, crawl spaces, basements and any area where moisture control is critical. Installation costs $2.50–$5.00 per sq ft installed.
Both products are applied by CUFCA‑trained technicians who are NFCA‑certified for fire‑resistive applications. The foam cures in minutes, forming a seamless seal that lasts 25‑30 years under normal conditions.
Open‑cell vs closed‑cell for air sealing
| Feature | Open‑cell spray foam | Closed‑cell spray foam |
|---|---|---|
| R‑value per inch | ~R‑3.7 | ~R‑6 |
| Air‑sealing ability | Good for interior cavities | Excellent for structural gaps, rim joists, crawl spaces |
| Moisture resistance | Breathable, allows some vapour diffusion | Acts as a vapour barrier at 2 inches+ |
| Typical cost (installed) | $1.50–$3.50 / sq ft | $2.50–$5.00 / sq ft |
| Best use for air sealing | Attic floors, interior walls | Basement walls, rim joists, crawl spaces, flat roofs |
Choosing the right foam depends on the location of the leaks and whether vapour control is also required.
Cost considerations for air sealing a whole house
Spray Foam Kings provides a free, written, itemised quote before any work begins. Prices vary with the type of foam, the size of the area, and the difficulty of access. Below are the main cost drivers:
| Cost factor | Why it matters | Price (if listed) |
|---|---|---|
| Type of foam (open‑cell vs closed‑cell) | Determines R‑value, moisture control and material cost | $1.50–$3.50 / sq ft (open‑cell) ; $2.50–$5.00 / sq ft (closed‑cell) |
| Square footage of area to be sealed | Larger areas require more material and labour | Example: 1,200 sq ft attic at R‑20 – $2,800–$4,200 (open‑cell) ; $6,000–$8,400 (closed‑cell) |
| Accessibility of cavities | Tight or hard‑to‑reach spaces increase labour time | No specific price; quoted after inspection |
| Rim‑joist size and condition | Rim joists are a common source of air leaks; closed‑cell is recommended | $800–$1,500 per rim‑joist area |
| Rebate eligibility | HER+ and Greener Homes rebates can offset up to $10,600 | Handled by Spray Foam Kings; reduces net cost |
Typical process for air sealing a home
Inspection > Preparation & safety set‑up > Foam application > Curing & inspection > Clean‑up & final walkthrough
Key factors to evaluate before starting
- Age of the home — older homes often have more gaps and may need extensive sealing.
- Location of leaks — attic, rim joist, crawl space or interior walls each have preferred foam types.
- Moisture risk — areas prone to water intrusion benefit from closed‑cell foam’s vapour barrier.
- Rebate eligibility — confirming HER+ or Greener Homes qualification can lower out‑of‑pocket cost.
- Occupancy requirements — whole‑home projects need 24–48 hours of ventilation before re‑occupancy.
Frequently asked questions
What is air sealing and how does it differ from insulation?
Air sealing stops uncontrolled airflow through gaps, cracks and penetrations in the building envelope. Insulation slows heat transfer but does not block air movement. Combining both provides the greatest energy‑efficiency gains.
Why should I choose spray foam for air sealing in Ontario?
Spray foam expands to fill irregular gaps, creates a continuous barrier, and, in the case of closed‑cell foam, adds structural strength and vapour resistance—important for Ontario’s cold winters and humid summers.
How much does a full‑home air sealing project cost?
Costs depend on the foam type, total square footage and specific areas addressed. A typical 1,200 sq ft attic sealed with open‑cell foam runs $2,800–$4,200, while closed‑cell foam for the same area costs $6,000–$8,400. Rim‑joist sealing alone ranges from $800 to $1,500. A written, itemised quote is provided free of charge.
Can I stay in my house while the foam is being applied?
For small, isolated jobs (e.g., rim‑joist sealing) occupants can remain with proper ventilation. Whole‑home installations require a minimum of 24 hours of ventilation, and full re‑occupancy is recommended after 24–48 hours once the foam has cured.
Are there rebates or incentives for air sealing my home?
Yes. Spray Foam Kings is a registered Enbridge HER+ partner, offering up to $10,600 in rebates. The home may also qualify for the Canada Greener Homes program. Spray Foam Kings handles all paperwork, but you should confirm eligibility with your municipality.
How long will the air‑sealing work last?
When installed according to Ontario Building Code SB‑12 standards, the spray foam remains effective for 25–30 years under normal conditions. The workmanship warranty covers delamination, shrinkage or adhesion failures at no charge.
For more information on related topics, see our pages on basement insulation, signs of under‑insulation, and the smart way to cut energy bills with closed‑cell spray foam.
Get a free written quote from Spray Foam Kings.
Last updated October 31, 2026.