Roof Batt Insulation R Value

Existing 3 4 inches of insulation.

Roof batt insulation 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. 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 4 r 25 5 r 25 state only mt montana 2012 iecc 6 r 30. The r value is a measure of the insulation batt s resistance to heat flow also known as thermal resistance. As a benchmark one inch of solid wood has an r value of 1.

The percentage increase increase increase original number 100. Closed cell spray foam insulation. The greater the r value the greater the resistance to heat transfer and the greater the insulating effect and subsequent energy savings. Recommended insulation levels for retrofitting existing wood framed buildings.

The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. In comparison an inch of blown fiberglass insulation has an r value of 3 1 3 4 and an inch of blown cellulose in an attic has an r value of 3 2 3 7 along with knowing the r value of a particular insulation it is also important to calculate the r value of a total system. It has a lower r value per inch than closed cell foam and is vapor permeable. Know exactly how much you need with our project calculators.

The stud wall plus the insulation has an r value of 16 5 11 16. See the department of energy s doe ranges for recommended levels of insulation below. R3 r18 r21 total roof r value. For example a 2 by 4 inch stud wall has an r value of 5 and a layer of 3 inch batt insulation has an r value of 11.

Built up roof membrane gravel surfaced membrane and gravel only 0 33. When it comes to choosing the right installation for your home it is not the thickness of the product or the type of material that counts but the r value. Step 1 determine the r values of all the materials you have used and then add them together. The increase r21 r3 exactly 18 the value by which you are increasing the r value.

R value measures how well certain building insulation materials can resist heat. The higher the r value the greater the insulation performance. 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. Minimum insulation r value requirements non residential above roof deck.

Closed cell spray foam has a far better r value per inch than other less effective insulations like cellulose fiberglass or even open cell foam. R value of roofing materials and building insulation. When determining how much insulation you need don t guesstimate calculate. National roofing contractors association.