R Value For Flat Roof Insulation

R value is calculated by more than just the insulation.

R value for flat roof insulation.

To convert the r value of a specific thickness of a material to rsi divide the r value by 5 67826. Recommended insulation levels for retrofitting existing wood framed buildings. To calculate the r value of a roof system your contractor will take into account the underlayment coverboards adhesives insulation and even the membrane. For example two inches of extruded polystyrene with an r value of 11 has an rsi of 1.

R value measures how well certain building insulation materials can resist heat. We recommend having at least 20 r value worth of material for optimal energy efficiency. While expensive the best insulation is polyiso rigid foam. To convert rsi to r value multiply the rsi by 5 67826.

Excellent lttr value compared to any other fm class 1 rated products of equivalent thickness. You can expect to pay about 55 100 sq ft. Minimum insulation r value requirements non residential above roof deck. You should of course see the manufacturer provided technical data sheet for the r value of specific products.

Know exactly how much you need with our project calculators. It is top quality and the most cost effective product for your flat roof. R value of various materials. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces.

Existing 3 4 inches of insulation. Add insulation to attic. For a very good introductory overview article on r value see r values over at the website of. R value is used in the united states.

For a 1 inch board equivalent of 6 r value. Flat expanded polystryene eps roof insulation provides high long term r value of eps and labor saving face laminates. Fm approved subject to the conditions of approval as a roof insulation when installed as shown in the current edition of the factory mutual research approvals guide. State applicable energy ashrae zone minimum r value state local ms mississippi ashrae 90 1 2010 2 r 20 3 r 20 state local mo missouri 2012 iecc 4 r 25 5 r 25 state only mt montana 2012 iecc 6 r 30.

See the department of energy s doe ranges for recommended levels of insulation below. The higher the r value the greater the insulation performance. The average r value for some common roof materials include. Rsi r value système international is the metric equivalent.

Flat expanded polystryene eps roof insulation is suitable for use with all roofing membrane materials flat eps roof insulation is compatible with loose laid and attached single ply membranes conventional built up roofing or modified bitumen systems.