I calculate insulation resistance to heat loss or r percentage improvement always as relative to the original number.
15 roofing felt r value.
Organic dry felt is made from 100 post consumer recycled material.
If the slope is between 3 12 and 4 12 use two layers of 15 felt for asphalt shingles.
The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process.
0 87 wood drop 1in.
The type and amount of roofing felt to apply varies according to roof slope.
15 pounds per hundred square feet and 30 pounds per hundred square feet.
0 05 wood 0 94 metal any 0 00 ceramic tile in.
R3 r18 r21 total roof r value.
For many years roofers used asphalt saturated felt under roofing shingles and it was historically available in two standard weights.
The 15 pound was for lighter weight projects while the 30 offered more heavy duty protection.
The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.
Calculate percent improvement in r value.
15 astm 4869 type i is an authentic 15 astm 4869 type i is an authentic asphalt saturated organic felt underlayment is used as a breathable secondary weather resistant barrier when applied over the roof deck prior to the installation of the primary roofing product.
0 20 siding r value per inch r v per unit wood shingles 16in.