Minimum R Values For Roof And Walls

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.

Minimum r values for roof and walls.

Basement walls require a minimum of either r 10 continuous or r 13 batted insulation. Roofs or ceilings need to be insulated to a minimum of r 38 in zone 3 or r 49 in zone 4. R value measures how well certain building insulation materials can resist heat. Recommended home insulation r values.

Insulation level are specified by r value. The higher the r value the greater the insulation performance. Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials. 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.

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

Note that there are many other requirements and exceptions to these figures depending on the state type of home and materials your home uses. You should of course see the manufacturer provided technical data sheet for the r value of specific products. See the department of energy s doe ranges for recommended levels of insulation below. R value is a measure of insulation s ability to resist heat traveling through it.

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. 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. Know exactly how much you need with our project calculators.

Required r values for walls roofs and floors.