Minimum R Values For Roof And Walls

When determining how much insulation you need don t guesstimate calculate.

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. 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. Insulation level are specified by r value.

Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials. Recommended home insulation r values. Know exactly how much you need with our project calculators. R value is a measure of insulation s ability to resist heat traveling through it.

Required r values for walls roofs and floors. 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. 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.

The higher the r value the greater the insulation performance. Below is a table outlining the basic r value requirements for walls roofs and floors. 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. Note that there are many other requirements and exceptions to these figures depending on the state type of home and materials your home uses.

The higher the r value the better the thermal performance of the insulation. R value measures how well certain building insulation materials can resist heat. Roofs or ceilings need to be insulated to a minimum of r 38 in zone 3 or r 49 in zone 4. 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.

See the department of energy s doe ranges for recommended levels of insulation below.