Minimum R Values For Roof And Walls

R value of various materials.

Minimum r values for roof and walls.

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

Roofs or ceilings need to be insulated to a minimum of r 38 in zone 3 or r 49 in zone 4. Below is a table outlining the basic r value requirements for walls roofs and floors. Recommended home insulation r values. 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.

Insulation level are specified by r value. See the department of energy s doe ranges for recommended levels of insulation below. Note that there are many other requirements and exceptions to these figures depending on the state type of home and materials your home uses. 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.

When determining how much insulation you need don t guesstimate calculate. Basement walls require a minimum of either r 10 continuous or r 13 batted insulation. The higher the r value the greater the insulation performance. 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. R value measures how well certain building insulation materials can resist heat. Required r values for walls roofs and floors. 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.

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.