R-value converter
Convert US R-values to metric RSI and back, plus the tog on your duvet and the U-value on your windows.
That's 1.41× as insulating as an insulated wall, while loft insulation is 1.7× better. That is a U-value of about 0.2839 W/m²·K.
What it means
How well does it insulate?
R-values here are for the material alone. Real walls lose extra heat through studs, gaps and joints.
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Three things worth knowing
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US R is 5.68 × RSI
R-30 loft insulation is RSI 5.3. If a number looks surprisingly big, it is almost certainly US R-value.
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Tog came from a suit
British researchers coined "tog" in the 1940s from togs, slang for clothes: one tog was roughly the insulation of a light suit.
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R and U run opposite ways
A high R-value is good insulation; a high U-value is bad. They are reciprocals, so RSI 5 is U 0.2.
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Background
About insulation units
R-value measures resistance to heat flow. The US R and metric RSI measure the same thing in different units, so R-19 is RSI 3.35. Bedding uses tog, clothing uses clo, and windows are rated by U-value, which is simply one divided by RSI.