Does not consider internal convection effects.
Roof insulation r value per inch.
The r 0 87 value for the first value in this air r value table subsection.
All these have r values ranging from r 3 2 to r 3 8 per inch.
To convert the r value of a specific thickness of a material to rsi divide the r value by 5 67826.
Does not consider presence absence of reflective barriers.
Closed cell spray foam has a far better r value per inch than other less effective insulations like cellulose fiberglass or even open cell foam.
When determining how much insulation you need don t guesstimate calculate.
To convert rsi to r value multiply the rsi by 5 67826.
R value measures how well certain building insulation materials can resist heat.
The r value of closed cell foam is r 6 5 7 per inch.
Contractors often use it to insulate under slabs ceilings walls and roofs.
For example two inches of extruded polystyrene with an r value of 11 has an rsi of 1 93721.