Insulation
Spray Foam Insulation Calculator
Spray foam depth and cost for a target R-value, for open and closed cell.
Result
Closed cell foam is roughly twice the R-value per inch of open cell and also acts as a vapour retarder and an air barrier, which is why it costs several times as much. Spray foam is installed by licensed applicators and has curing and ventilation requirements that are not optional. Required R-values are set by climate zone and by local energy code, and they differ for attics, walls and floors. The figures offered here are common code minimums rather than recommendations, and a minimum is a floor, not a target.
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About this calculator
Open or closed cell?
Closed cell where space is tight, where you need a vapour retarder, or below grade. Open cell where you have depth to fill and want the lower cost per R.
Why is it sold in board feet?
One board foot is one square foot at one inch deep. Quotes are usually per board foot, so the depth matters as much as the area.
The formula
thickness = (target R - existing R) / R-value per inch
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