Minimum R Values For Roof And Walls

Required r values for walls roofs and floors.

Minimum r values for roof and walls.

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. For a very good introductory overview article on r value see r values over at the website of. 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. The higher the r value the better the thermal performance of the 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. When determining how much insulation you need don t guesstimate calculate. 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.

Basement walls require a minimum of either r 10 continuous or r 13 batted insulation. R value measures how well certain building insulation materials can resist heat. Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials. 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.

Know exactly how much you need with our project calculators. 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. R value of various materials. Recommended home insulation r values.

You should of course see the manufacturer provided technical data sheet for the r value of specific products. Below is a table outlining the basic r value requirements for walls roofs and floors. The higher the r value the greater the insulation performance. 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.

Note that there are many other requirements and exceptions to these figures depending on the state type of home and materials your home uses.