High-point thickness Low-point thickness R-value per unit Additional R-value Total roof area
check (value of 0 means no problem)
Total R-value at low point must be > 0
Total R-value at intermed point must be > low point n/a n/a n/a n/a
Total R-value at high point must be > int and low pt
R-value must be positive
Ratio of trap. Sides must be > 1 n/a n/a n/a n/a
Roof area must be > 0
Number of roof components must be >= 0
 
Conversions (Imperial to SI):
inches to mm
sq ft to sq meters
R-value to RSI-value
R-value/inch to RSI-value/mm
Btu/hr to watts
temp differential in deg F to deg C
Conversions (SI to Imperial):
mm to inches
sq meters to sq ft
RSI-value to R-value
RSI-value/mm to R-value/inch 0.0416866
Watts to Btu/hr
temp differential in deg C to deg F