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FAQ
Quick answer: Most insulation questions come down to four things: how much R you need for your climate, how much you already have, which material suits the space, and whether to do it yourself. Start with the ENERGY STAR or Natural Resources Canada guidance, measure what you have, then use our calculators and guides to plan.
Guides
How much insulation do I need?
How much insulation should be in my attic?
ENERGY STAR's retrofit table recommends totals from R30 to R60 by U.S. zone; in Canada check your provincial code. See recommended R-value by zone and Canada R-value requirements.
How do I find my current R-value?
Measure depth in several spots, identify the material and multiply by a typical R per inch. Use the attic insulation calculator.
How much insulation for a 10×12 shed?
Use the shed calculator with your wall height and openings.
How many bags of blown-in do I need?
Use the bag chart and the blown-in calculator.
Materials
What is the R-value of spray foam?
Typical: open-cell about R3.5–3.7/in, closed-cell about R6–7/in; your product label governs.
Blown-in or batts?
See blown-in vs batt.
Fiberglass or cellulose?
What is an R-value chart?
A table of typical R per inch; see the R-value chart.
Cost, rebates and hiring
What does attic insulation cost?
It varies; use your own prices in the cost calculator.
Are there rebates?
Sometimes; see insulation rebates. We never quote amounts.
Should I hire a contractor?
See DIY vs hire.
Can I rent a blowing machine?
Yes, often; see machine rental.
Safety
What if my attic has vermiculite?
Do not disturb it. Health Canada and the EPA advise leaving it alone and hiring trained professionals. See attic insulation removal.
What should I wear?
A fitted particulate respirator, eye protection, gloves and long sleeves; see tools and PPE.
Can insulation touch recessed lights?
Only fixtures rated for insulation contact; follow labels and code.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: Zone 6 home, attic 1,100 sq ft with 3 in of old fiberglass batts (assumed R3.2/in = R9.6). ENERGY STAR's target with 3–4 in existing is R49. Add R39.4; with loose-fill at an assumed R2.5/in that is about 15.8 in. With an assumed 40 sq ft per bag at that level and 10% waste: 1,100 ÷ 40 × 1.1 = 30.25, so 31 bags.
Planning and process
Should I air seal before insulating?
Yes; see air sealing first.
Do I need baffles?
If you have soffit vents, yes; see attic ventilation baffles.
What are depth markers?
Rulers in the attic showing installed depth; see depth markers.
When should old insulation be removed?
When wet, mouldy, contaminated or a hazard; see removal.
Can I insulate over old insulation?
Usually yes, if it is dry, clean and not vermiculite.
Savings and comfort
How much will I save?
It depends on climate, existing R, leaks and fuel; try the savings calculator.
Why is my upstairs still hot?
Air leaks, ducts in the attic, and sun on windows all matter.
Does more insulation help in summer?
Yes, it slows heat from a hot attic into the house.
Other spaces
How do I insulate a shed?
See the shed calculator.
What about basement walls?
ENERGY STAR lists targets; rigid foam or batts are common. See compare.
What about rim joists?
Rigid foam or closed-cell spray foam; see the spray foam calculator.
Do I need a permit?
Sometimes; ask your local building department.
Are RSI and R the same?
No; RSI is metric. R ≈ RSI × 5.678.
Safety
Is fiberglass dangerous?
It irritates skin and lungs; wear PPE. See tools and PPE.
What should I do about vermiculite?
Do not disturb it; follow Health Canada or EPA guidance and get professional advice.
Can insulation touch light fixtures?
Only fixtures rated IC; keep clearance from others and from flues.
Is it safe to work in a hot attic?
Plan for cooler hours, take breaks, hydrate, and work with a helper.
Costs and incentives
How much does insulation cost?
Prices vary; we give illustrative examples only. See attic insulation cost.
Are there rebates?
Programs vary and change; see insulation rebates. We list no amounts.
Is DIY cheaper?
Often in labour, but not always overall; see DIY vs hire.
Should I rent a machine?
For loose-fill top-ups, often; see machine rental.
Why is my quote different from the calculator?
Calculators use your inputs; quotes add labour, prep and local factors.
Measuring and calculating
How do I measure attic area?
Measure the floor area of the house below the attic, length × width for each rectangle.
How deep should loose-fill be?
Use the manufacturer's bag chart for your target R; see the blown-in calculator.
How do I add up layers?
Add R-values of each layer; use the R-value calculator.
What is installed vs settled depth?
Installed is right after blowing; settled is after time. Bag charts list both.
How many batts do I need?
Use the batt calculator with coverage per bag.
Codes and climate
Which R-value do I need?
See recommended R-value by zone.
What about Canada?
See Canada R-value requirements.
Does insulation need a vapour barrier?
It depends on climate and location in the house; ask local officials.
About this site
Who writes these guides?
An independent team; we follow official sources and label all examples.
Do you sell insulation?
No. We have no affiliate links or sponsored products.
Can I trust the calculator results?
They are estimates based on your inputs and stated assumptions; verify with labels and professionals.
How do I report an error?
Use the contact page.