Bello Haus — insulation R-values | bellohaus.net
The measured comparison of R per inch for the main insulation materials, with units, so you can pick a material before you calculate thickness.
The table below lists measured R-value per inch for the materials compared across this reference. Closed-cell polyurethane spray foam measures R-5.5 to R-6.5 per inch (RSI 38–45 per metre), which places it at the top of the measured range, and polyisocyanurate spray foam spans R-4.3 to R-8.3 per inch, the widest band among the spray-applied products.
Phenolic spray foam measures R-4.8 to R-7 per inch, overlapping the polyisocyanurate spray range at both ends, so the choice between the two spray products is decided by the cavity depth and the assembly target rather than by a clear per-inch winner.
On the board side, foil-faced polyisocyanurate rigid panel aged 5–10 years measures R-5.5 per inch. This is the documented exception whose R per inch increases with thickness; for every other material here, R-value per inch generally decreases as thickness increases, so a deeper layer buys proportionally less R.
On narrow screens, swipe or scroll the plate sideways.
Thinsulate clothing insulation measures R-1.6 to R-2.9 per inch, which is roughly a quarter of the closed-cell foam figure and shows how far a low-density textile sits from a foam when both are quoted per inch. The comparison is only valid in the same units.
US customary R-values are approximately 5.68 times as large as metric RSI values, so an RSI figure divided by 5.68 gives the US R, and a US R multiplied by 5.68 gives RSI. Convert before you compare a spec sheet in one system with a target written in the other.
A faced fiberglass batt is documented with its rated R-21 visible on the facing. Divide that rated R by the batt's thickness to recover the implied R per inch, then check it against the measured rows above to confirm the product line matches the assumption in your assembly calculation.
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