Roof R Value Code

Recommended home insulation r values.

Roof r value code.

Both codes provide specific instructions for re roofing projects and both are clear that replacements must comply with insulation r value requirements if the roof system is part of the building thermal envelope and contains insulation entirely above the deck. Building and energy codes almost always specify a required minimum r value for exterior walls and roof assemblies with above deck insulation so the minimum required r value in your local jurisdiction is something that you need to take into account when planning a building project. Code official finds proposed design is satisfactory and complies. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation.

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. Insulation level are specified by r value. R value based method of section c402 1 3 u c and f factor based method of section c402 1 4. Please note that the r values for roof membranes shingles tiles air films and roof deck materials might or might not be permitted by your local code to be included when total roof assembly r value is being calculated for the purpose of satisfying energy code requirements.

R value is a measure of insulation s ability to resist heat traveling through it. These energy code r value requirements change from state to state and even city to city. For roofing replacements it is necessary to look at the ibc. Roof replacements shall comply with section c402 1 3 c402 1 4 c402 1 5 or c407 where the existing roof assembly is part of the building thermal envelope and contains insulation entirely above the roof deck.

Existing buildings requirements are sprinkled throughout the i codes. 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. Always check with your local code authority. 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.

To convert rsi to r value multiply the rsi by 5 67826. The higher the r value the better the thermal performance of the insulation. State applicable code ashrae zone minimum r value state local al alabama 2015 alabama commercial energy code 2 r 25 3 r 25 state local ak alaska 2012 alaska building energy efficiency standard. 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.

For example two inches of extruded polystyrene with an r value of 11 has an rsi of 1 93721.