Minimum R Values For Roof And Walls

Roofs or ceilings need to be insulated to a minimum of r 38 in zone 3 or r 49 in zone 4.

Minimum r values for roof and walls.

If structural sheathing covers 40 or less of the exterior continuous insulation r value shall be permitted to be reduced by no more than r 3 in the locations where structural sheathing is used to maintain a consistent total sheathing thickness. 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 7 r 35 8 r 35. Walls need to be insulated to a minimum of r 20 if the insulation is between the studs or r 15 r 5 if the insulation is a combination of insulation between the studs and a continuous layer of exterior insulation in zones 3 or 4. With an r value of 4 0 to 5 1 per inch depending on the manufacturer pre expanded injection foam provides a higher r value than fiberglass or cellulose and it seals the building from air leakage at the same time.

Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials. See the department of energy s doe ranges for recommended levels of insulation below. When determining how much insulation you need don t guesstimate calculate. 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.

Insulation level are specified by r value. R value is a measure of insulation s ability to resist heat traveling through it. 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. Required r values for walls roofs and floors.

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. Basement walls require a minimum of either r 10 continuous or r 13 batted insulation. Below is a table outlining the basic r value requirements for walls roofs and floors. R value of various materials.

For a very good introductory overview article on r value see r values over at the website of. Know exactly how much you need with our project calculators. Recommended home insulation r values. The higher the r value the better the thermal performance of the insulation.

You should of course see the manufacturer provided technical data sheet for the r value of specific products.