R Value For Flat Roof Insulation

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.

R value for flat roof insulation.

Minimum insulation r value requirements non residential above roof deck. The higher the r value the greater the insulation performance. You can expect to pay about 55 100 sq ft. 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. Flat expanded polystryene eps roof insulation provides high long term r value of eps and labor saving face laminates. For a very good introductory overview article on r value see r values over at the website of. Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials.

Know exactly how much you need with our project calculators. To calculate the r value of a roof system your contractor will take into account the underlayment coverboards adhesives insulation and even the membrane. When determining how much insulation you need don t guesstimate calculate. For example two inches of extruded polystyrene with an r value of 11 has an rsi of 1.

To convert the r value of a specific thickness of a material to rsi divide the r value by 5 67826. Rsi r value système international is the metric equivalent. You should of course see the manufacturer provided technical data sheet for the r value of specific products. R value of various materials.

The average r value for some common roof materials include. Recommended insulation levels for retrofitting existing wood framed buildings. 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. See the department of energy s doe ranges for recommended levels of insulation below.

R value is used in the united states. Add insulation to attic. For a 1 inch board equivalent of 6 r value. 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.

Excellent lttr value compared to any other fm class 1 rated products of equivalent thickness. R value is calculated by more than just the insulation. Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value. To convert rsi to r value multiply the rsi by 5 67826.

While expensive the best insulation is polyiso rigid foam.