Quick answer: To check your attic insulation R-value, look in from the hatch, identify the material, measure its depth with a ruler, and multiply the inches by the material’s R-value per inch. For example, 6 inches of blown cellulose at about R-3.5 per inch is about R-21. Do not touch loose grey-brown or gold pebbly fill (it could be vermiculite), and never step between the joists. Your result tells you which Ontario attic rebate tier you likely fall into, with up to $1,250 available and amounts that can change.
Updated November 2026
On this page
- Key takeaways
- Is it safe to check your own attic insulation?
- How do you check attic insulation R-value step by step?
- What type of insulation is in your attic?
- What is the R-value per inch of common insulation?
- How do you convert insulation depth to R-value?
- How many inches do you need for R-50 and R-60?
- Which rebate tier would you likely fall into?
- What if your measurement is uneven?
- Frequently asked questions
- Get a free attic assessment
Key takeaways
- Check from the hatch or a ladder. Do not walk into the attic unless there are boards to stand on.
- R-value is roughly depth in inches times the R-value per inch for your material.
- Loose, pebbly, grey-brown or gold fill may be vermiculite. Do not touch it.
- R-50 takes roughly 14 inches of cellulose or about 17–20 inches of blown fiberglass.
- Your starting R-value sets your rebate tier: R-12 or less, above R-12 to R-25, or above R-25 to R-35. See current rebates.
Is it safe to check your own attic insulation?
Yes, if you stay at the hatch and follow a few rules. Most attic injuries come from stepping through the ceiling, and most health risks come from disturbing the wrong material.
Safety rules before you start:
- Stay on the ladder or at the hatch. Ceiling drywall between the joists will not hold your weight. One wrong step can put your foot through the ceiling.
- Do not touch loose grey-brown or gold pebbly fill. It may be vermiculite. Some vermiculite, such as Zonolite Attic Insulation from the Libby mine in Montana, may contain asbestos. Health Canada advises not disturbing it and using qualified professionals for testing. Libby ore was used until 1990.
- Watch for wiring. Do not move or pull on wires, junction boxes or old knob-and-tube wiring. Keep the ruler away from them.
- Wear basic protection. A dust mask, gloves, long sleeves and eye protection are sensible for fiberglass or cellulose.
- Use a good light. A headlamp keeps both hands free on the ladder.
- Pick a mild day. Attics get very hot in summer and very cold in winter.
- Keep children and pets away from the open hatch.
If you see droppings, nests, mould or the pebbly fill described above, close the hatch and stop. Those need a professional look first. See vermiculite and asbestos removal and animal and insect feces removal.
How do you check attic insulation R-value step by step?
- Open the hatch and look. Let your eyes adjust and scan the whole area you can see.
- Identify the material. Use the guide below. If you cannot tell, take a clear photo.
- Find a typical spot. Pick an area near the hatch that looks like the rest of the attic, not a pile or a bare patch.
- Measure the depth. Push a ruler or tape measure straight down until it touches the ceiling drywall. Read the top of the insulation. Do not compress it.
- Check two or three spots you can reach from the hatch, and use the average.
- Look at the joists. If you can see the tops of the joists, write that down. It is a sign of low insulation.
- Note the edges. Look toward the eaves. Thin or bare areas there are common.
- Do the math using the table below.
- Write it down with photos. You will want this when you compare insulation quotes.
What type of insulation is in your attic?
| What you see | Likely material | Safe to measure? |
|---|---|---|
| Fluffy white, pink or yellow loose fibres | Blown fiberglass | Yes, gently |
| Grey, shredded-paper look, dense | Blown cellulose | Yes, gently |
| Rolls or blankets between joists, often with paper facing | Fiberglass batts | Yes, check the printed label if visible |
| Rigid foam layer sprayed on surfaces | Spray foam | Measure if exposed; do not cut |
| Loose, pebbly, grey-brown or gold granules | Possibly vermiculite | No. Do not touch |
What is the R-value per inch of common insulation?
These are general industry figures and actual values vary by product and installation.
| Material | Approximate R-value per inch |
|---|---|
| Blown fiberglass | about R-2.5 to R-3 |
| Blown cellulose | about R-3.5 |
| Open-cell spray foam | about R-3.5 to R-3.7 |
| Closed-cell spray foam | about R-6 to R-7 |
For fiberglass batts, the R-value is often printed on the facing or the original packaging. If you can read it without moving anything, use that number.
How do you convert insulation depth to R-value?
Multiply the depth in inches by the R-value per inch. If you have two layers of different materials, work out each layer and add them together.
Worked examples:
- 4 inches of blown fiberglass: 4 × 2.5 = R-10, up to 4 × 3 = R-12. Result: about R-10 to R-12.
- 6 inches of blown cellulose: 6 × 3.5 = about R-21.
- 8 inches of blown cellulose: 8 × 3.5 = about R-28.
- 10 inches of blown fiberglass: 10 × 2.5 = R-25, up to 10 × 3 = R-30. Result: about R-25 to R-30.
- Two layers, 3 inches of old fiberglass plus 4 inches of cellulose on top: (3 × 2.5 = R-7.5 to 3 × 3 = R-9) + (4 × 3.5 = R-14) = about R-21.5 to R-23.
How many inches do you need for R-50 and R-60?
Divide the target R-value by the R-value per inch.
| Material | Inches for R-50 | Inches for R-60 |
|---|---|---|
| Blown fiberglass (R-2.5 to R-3) | 50 ÷ 3 to 50 ÷ 2.5 = about 17 to 20 | 60 ÷ 3 to 60 ÷ 2.5 = about 20 to 24 |
| Blown cellulose (R-3.5) | 50 ÷ 3.5 = about 14.3 | 60 ÷ 3.5 = about 17.1 |
| Open-cell spray foam (R-3.5 to R-3.7) | about 13.5 to 14.3 | about 16.2 to 17.1 |
| Closed-cell spray foam (R-6 to R-7) | about 7.1 to 8.3 | about 8.6 to 10 |
The Ontario Building Code targets about R-60 for attic ceilings in new homes in most of Ontario. The standalone attic rebate needs at least R-50. For a deeper look at materials, read cellulose vs fiberglass vs spray foam.
Which rebate tier would you likely fall into?
Your measured starting R-value points to your likely tier on the Home Renovation Savings Program standalone attic path. Your contractor confirms the final number. The rebate is 50% of your after-tax insulation cost, up to the tier maximum. Amounts can change, and the program is currently scheduled to run until March 31, 2027.
| Your measured R-value | Likely tier | Upgrade to at least | Maximum rebate |
|---|---|---|---|
| R-12 or less | R-12 or less | R-50 | up to $1,250 |
| Above R-12 to R-25 | Above R-12 to R-25 | R-50 | up to $1,000 |
| Above R-25 to R-35 | Above R-25 to R-35 | R-50 | up to $800 |
| Above R-35 | No standalone attic tier listed | — | — |
| Cathedral/flat roof, R-12 or less | Cathedral/flat | R-20 | up to $650 |
| Cathedral/flat roof, R-25 or less | Cathedral/flat | R-28 | up to $750 |
Applying this to the worked examples above:
- About R-10 to R-12 (4 inches of fiberglass): likely the R-12 or less tier, up to $1,250.
- About R-21 (6 inches of cellulose): likely the above R-12 to R-25 tier, up to $1,000.
- About R-28 (8 inches of cellulose): likely the above R-25 to R-35 tier, up to $800.
- About R-25 to R-30 (10 inches of fiberglass): right on the line between two tiers. A contractor’s measurement decides it.
The work must be done by a participating contractor, and homes that already received an attic rebate from Enbridge, Save on Energy or the program may not qualify again. Full details are on the Ontario attic insulation rebate page, and our rebate study walks through more scenarios.
What if your measurement is uneven?
Uneven depth is very common. Eaves are often thin, and the area near the hatch is often crushed from foot traffic. Use the depth that looks most typical, and note the low spots. An installer will level everything out to the target depth. If the old material is damp, dirty or compressed, insulation removal may come first.
Frequently asked questions
Can I measure attic insulation without going into the attic?
Yes. In most homes you can measure from the hatch while standing on a ladder. Reach in with a ruler or tape measure and check two or three nearby spots. If you cannot reach a typical area, a professional assessment is the safer option.
What does it mean if I can see the ceiling joists?
It usually means the insulation is only a few inches deep and well below R-50. Many homes in this situation fall into the R-12 or less or the above R-12 to R-25 rebate tier. Measure to confirm.
How do I know if my attic has vermiculite?
Vermiculite is loose and pebbly, usually grey-brown or gold, and looks like small shiny granules. If you see it, do not touch it. Health Canada advises treating it as if it contains asbestos until it is tested by qualified professionals.
Is R-value the same as inches of insulation?
No. R-value measures resistance to heat flow, and inches only tell you the thickness. Different materials give different R-values per inch, so 10 inches of fiberglass and 10 inches of cellulose are not the same.
Does settled insulation lose R-value?
Yes. When loose fill settles or gets crushed, the depth drops and so does its R-value. Measure what is there now, not what was installed years ago.
Who confirms my starting R-value for the rebate?
Your participating contractor measures and documents the starting and final levels for the rebate submission. Your own measurement is a good estimate for planning and for checking that quotes make sense. See how to claim the attic insulation rebate.
Get a free attic assessment
Not sure what you are looking at, or found something you should not touch? Pro Home Insulation can measure your attic, identify the material and explain your likely rebate tier. We serve Toronto, the GTA and nearby Southern Ontario. Call (647) 250-0606 or Book online.