Roof R Value Code

The higher the r value the better the thermal performance of the insulation.

Roof r value code.

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. Recommended home insulation r values. These energy code r value requirements change from state to state and even city to city. For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3.

These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. Insulation level are specified by r value. Always check with your local code authority. 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.

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

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. For roofing replacements it is necessary to look at the ibc. R value is a measure of insulation s ability to resist heat traveling through it. To convert rsi to r value multiply the rsi by 5 67826.

Existing buildings requirements are sprinkled throughout the i codes. 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. 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. Code official finds proposed design is satisfactory and complies.

R value based method of section c402 1 3 u c and f factor based method of section c402 1 4.