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R Value Chart

What R-value means

R-value is a material's resistance to conductive heat flow. A higher number means heat moves through more slowly. For a single, uniform material, R-value grows with thickness: double the inches of the same uncompressed product and you roughly double the R. When layers are stacked, their R-values add, which is what our R-value calculator does. R-value is measured under standard laboratory conditions, so real performance in a home depends on installation quality, air movement, moisture and framing.

Typical R per inch by material

The ranges below are commonly cited typical figures, rounded. Individual products differ, sometimes a lot. The label on the bag, batt or kit is the number that counts for code, for bag charts and for our calculators.

Why R per inch is a range

Density, fibre type, binders, facers and manufacturing all change the number. Loose-fill also depends on how it was blown: blown too fluffy and it settles; blown too dense and you use more material for the same R. Polyiso can lose some R-value at low temperatures. Old insulation that has been compressed, wet or contaminated with dust may perform below its original rating. That is why our calculators let you enter your own R per inch.

Nominal vs whole-assembly R

The R printed on a batt is for the insulation alone. A wall also has studs, plates, sheathing, drywall and air films. Wood framing has a much lower R per inch than insulation, so heat bypasses the insulation through the studs, a process called thermal bridging. Whole-wall R is usually lower than the cavity insulation's R. Continuous insulation over the framing, such as rigid foam sheathing, reduces thermal bridging. In attics, a deep, continuous layer over the ceiling joists avoids most bridging, which is one reason attics are an efficient place to add R.

Compression

Squeezing a batt into a thinner space reduces its total R-value, even though R per inch may rise slightly. Do not stuff thick batts into shallow cavities. If your cavity is 3.5 in deep, use a batt made for that depth. In attics, avoid walking on or storing items over insulation.

Air movement

R-value only describes conduction. Air leaking through or around insulation carries heat and can make a high-R layer perform poorly. Fibrous insulation like fiberglass does not stop air flow on its own. That is why air sealing first is a common recommendation from ENERGY STAR and Natural Resources Canada.

Moisture

Wet insulation conducts heat better and can promote mould and rot. Fix roof leaks, vent bathroom fans outdoors, and control vapour according to your climate and code. Closed-cell foam resists moisture; fibrous products need to dry.

How much R do you need?

That depends on climate and where the insulation goes. ENERGY STAR publishes recommended levels by U.S. climate zone, and in Canada the building code in your province or territory sets requirements, with guidance from Natural Resources Canada. See recommended R-value by zone and Canada R-value requirements.

Worked example

Figures below are illustrative examples (2026-10-29), not quotes or guarantees.

Assumptions: you want R49 in an attic. With loose-fill at an assumed R2.5/in, you need 49 ÷ 2.5 = 19.6 in settled. With cellulose at an assumed R3.5/in, 49 ÷ 3.5 = 14 in. With closed-cell foam at an assumed R6.5/in, 49 ÷ 6.5 = about 7.5 in, though foam this deep is unusual and costly in attics. The product with the lower R per inch needs more depth, not necessarily more cost.

Converting between systems

Canada and the U.S. use imperial R (ft²·°F·h/BTU) on most residential products. Metric RSI uses m²·K/W. To convert, RSI ≈ R ÷ 5.678, so R49 is about RSI 8.6. Canadian codes often list both.

Reading a product label

Product labels and data sheets list the R-value for a stated thickness, and loose-fill bags carry a coverage chart. Look for the R-value, thickness, and the test standard. In Canada you may see RSI next to R. Use those numbers in our calculators rather than the typical ranges above. For older insulation already in your attic, typical ranges give a reasonable estimate, but treat the result as approximate.

Why this chart is approximate

Real performance depends on installation quality, density, moisture, and air movement. A gap of a few percent in coverage can reduce effective R noticeably. Air leaks bypass insulation entirely. So treat the chart as a planning tool, and rely on air sealing and careful installation to get close to labelled performance.

Quick tip

Always prefer the label R over a typical range.

FAQ

Is higher R-value always better?

Higher R slows heat flow, but each extra inch saves less than the one before. Follow recommended levels for your climate.

Do R-values add when layered?

Yes, for layers in series. Use the R-value calculator.

Why does my product's R differ from this chart?

Charts show typical ranges. The label is what counts.

Does vermiculite insulate well?

It has a modest R per inch, and older vermiculite may contain asbestos. Do not disturb it; see attic insulation removal.

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