Minimum R Values For Roof And Walls

Minimum insulation r value requirements by state.

Minimum r values for roof and walls.

R value of various materials. Roofs or ceilings need to be insulated to a minimum of r 38 in zone 3 or r 49 in zone 4. The values in this table can also be used as a guide when installing insulation into alterations and additions or retrofitting existing homes with no insulation. Some of the possible material combinations may not be suitable for actual constructions i e.

It should be noted that these are minimum values only and that upgrading your insulation to a higher material r value can provide a better level of the resistance to heat in your home. 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 branz house insulation guide provides construction r values for common construction types.

You can find some of the examples here. See the department of energy s doe ranges for recommended levels of insulation. Non residential above roof deck this matrix provides the minimum insulation r values required by local and state municipalities. As the percentage of window increases the results become even more dramatic.

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. You should of course see the manufacturer provided technical data sheet for the r value of specific products. It uses the iso thermal planes method the same method as used in nzs4214 2006. For a very good introductory overview article on r value see r values over at the website of.

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. 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. In an uninsulated house more heat is lost through the ceiling and roof than any other part of the house making the roof the top priority for insulation. Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials.