Ontario · figures verified Aug 2026 · Independent guide
Blown-In Insulation — Cellulose vs Fibreglass, With the Numbers That Decide It
Blown-in is how Ontario attics actually get insulated. The decision is not the brand on the bag — it is the material, the finished R-value, and a price you can compare. Here are all three, sourced.
The two materials, side by side
| Blown-in cellulose | Blown-in fibreglass | |
|---|---|---|
| R per inch (NRCan design value) | R-3.6 | R-2.9 |
| Installed price (market est.) | $1.50–$3.00/sq ft | $1.75–$3.50/sq ft |
| Typical 1,000–1,200 sq ft attic | $1,800–$3,200 | $2,000–$3,600 |
| Worth knowing | Denser, better at slowing air movement through the blanket; settles over time — a good quote states the SETTLED depth, not just the fluffed one. | Lighter and settles less, but needs MORE inches for the same R — compare quotes by finished R-value, never by depth. |
R values: NRCan “Keeping the Heat In” design values (federal source). Prices: Ontario market estimates from two independent published guides, verified 2026-08-29 — not quotes.
Compare quotes by finished R-value — never by inches
The same upgrade — say a ~R-12 attic to the R-50 program target (adding ~R-38) — takes about 11″ of cellulose but 13.5″ of blown fibreglass. Two honest quotes can name very different depths for identical performance. A quote that sells “18 inches” without a finished R (and, for cellulose, the settled depth) is not comparable to anything.
Program note: HRS pays by your starting R and caps at 50% of cost — beyond R-50 the program pays nothing extra. R-60, which market pages often sell, is common practice, not the program spec — a comfort choice you can make with open eyes.
Blown-in is the right tool
- Attic top-ups — NRCan calls loose-fill "excellent in attics"
- Irregular joists, clutter, tight corners a batt can’t fill
- Fast install: most top-ups are done in hours
- Adding R over existing dry insulation (the usual Ontario job)
Not the tool for
- Finished walls — loose fill settles and leaves gaps at the top (NRCan); walls are dense-pack or injection work
- Cathedral and flat roofs — a different assembly with its own rebate tiers
- A wet, mouldy or pest-contaminated attic — fix the problem first; removal may come before anything new
- Vermiculite present — lab test FIRST, before anyone touches it
Removal territory? The removal guide covers when it's warranted and what it costs.
DIY blower rental vs pro — the rebate changes the math
Rental blowers and bagged material are real: DIY materials for a typical attic run a few hundred dollars (market estimate). But the HRS attic rebate requires the work to be done by a participating insulation contractor — DIY work earns no rebate at all. Run both columns before deciding:
DIY cellulose top-up
$400–$800
materials + rental (market est.) · your weekend · no rebate · air sealing and baffles still on you
Pro cellulose, after rebate
$900–$1,950 net
$1,800–$3,200 installed − $900–$1,250 HRS (from below R-12; 50% cap applied)
The honest read: for a simple dry top-up with no rebate eligibility left (one attic-stream rebate per property), DIY can win on dollars. If your starting attic is thin and the rebate is live, the pro gap narrows to hundreds — and includes the air sealing that decides real-world performance.
Rebate rules: tiers by starting R, 50%-of-cost cap, completed by Nov 30, 2026, one attic-stream rebate per property — full attic cost + rebate math here.
Make every blown-in quote state
- Finished R-value (and for cellulose: SETTLED depth, not just blown depth)
- Material and coverage — bags used per the manufacturer’s coverage chart
- Air sealing FIRST, as its own line (top plates, penetrations, hatch)
- Baffles / soffit ventilation kept clear, hatch insulated and weatherstripped
- Any removal as a separate line — never blended into the insulation price
- HRS participating status, if you want the rebate
Ready to price your attic?
Tell us about your home once — we route it as a structured project, and the quote conversation starts informed. Typical attic top-up in Ontario: $1,500–$3,500 before the rebate.
Frequently asked questions
Blown-in cellulose or blown-in fibreglass — which is better for an Ontario attic?
For most attic top-ups, either does the job — the honest answer is to compare quotes by FINISHED R-VALUE and price, not by material or inches. Cellulose insulates more per inch (R-3.6/in vs R-2.9/in, NRCan design values) and usually prices lower ($1.50–$3.00/sq ft vs $1.75–$3.50/sq ft installed, Ontario market estimates); fibreglass is lighter and settles less. A contractor pushing one material without stating the finished R is selling, not advising.
How much does blown-in attic insulation cost in Ontario?
Market estimates (verified Aug 2026, two independent Ontario guides): blown-in cellulose $1.50–$3.00/sq ft installed — typically $1,800–$3,200 for a 1,000–1,200 sq ft attic; blown-in fibreglass $1.75–$3.50/sq ft — typically $2,000–$3,600. Access, air sealing, baffles and hatch work move the price; removal (if needed) is a separate line.
How many inches of blown-in insulation do I need?
Depth depends on the material, which is exactly why quotes should state the finished R-value instead. Example: taking a ~R-12 attic to the R-50 program target means adding about R-38 — roughly 11" of cellulose or 13.5" of blown fibreglass (NRCan design values of R-3.6/in and R-2.9/in). Same R, different inches — comparing two quotes by depth alone compares nothing.
Does blown-in insulation qualify for the Ontario rebate?
Yes — the HRS standalone attic stream pays by your STARTING insulation level (up to $1,250 below R-12), capped at 50% of the qualifying insulation cost, for work by a participating insulation contractor completed by Nov 30, 2026. The material (cellulose or fibreglass) doesn't change the tiers — the finished R does. DIY work does NOT qualify: no participating contractor, no rebate.
R-per-inch values are NRCan “Keeping the Heat In” design values; cost figures are market estimates from 2 independent published Ontario guides (verified 2026-08-29) — your quote sets the real number. Rebate rules from the official program site. ClaimRebate.ca is an independent homeowner guide — not a contractor, not a government service.