Minimum R Values For Roof And Walls

For a very good introductory overview article on r value see r values over at the website of.

Minimum r values for roof and walls.

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. 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. R value measures how well certain building insulation materials can resist heat. 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.

Basement walls require a minimum of either r 10 continuous or r 13 batted insulation. 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. Insulation level are specified by r value. Roofs or ceilings need to be insulated to a minimum of r 38 in zone 3 or r 49 in zone 4.

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. Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials. 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.

Note that there are many other requirements and exceptions to these figures depending on the state type of home and materials your home uses. 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. Below is a table outlining the basic r value requirements for walls roofs and floors. R value is a measure of insulation s ability to resist heat traveling through it.

Know exactly how much you need with our project calculators. When determining how much insulation you need don t guesstimate calculate. You should of course see the manufacturer provided technical data sheet for the r value of specific products. Recommended home insulation r values.

The higher the r value the greater the insulation performance.