Roof R Value Code

Always check with your local code authority.

Roof r value code.

Existing buildings requirements are sprinkled throughout the i codes. Average wall and roof u factor 0 200 in climate zones. Recommended home insulation r values. 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.

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. 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. For example two inches of extruded polystyrene with an r value of 11 has an rsi of 1 93721. R value based method of section c402 1 3 u c and f factor based method of section c402 1 4.

Code official finds proposed design is satisfactory and complies. To convert rsi to r value multiply the rsi by 5 67826. 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. 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 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. 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. 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. Insulation level are specified by r value.

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. These energy code r value requirements change from state to state and even city to city. 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. The higher the r value the better the thermal performance of the insulation.

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.