Roof Batt Insulation R Value

R value of roofing materials and building insulation.

Roof batt insulation r value.

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. R value per inch ft f hr btu rsi per millimeter k m w r value for typical installed thickness not per inch source. 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. R value measures how well certain building insulation materials can resist heat.

The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. Step 1 determine the r values of all the materials you have used and then add them together. Closed cell spray foam insulation. The increase r21 r3 exactly 18 the value by which you are increasing the r value.

Minimum insulation r value requirements non residential above roof deck. The greater the r value the greater the resistance to heat transfer and the greater the insulating effect and subsequent energy savings. The percentage increase increase increase original number 100. 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.

R3 r18 r21 total roof r value. The stud wall plus the insulation has an r value of 16 5 11 16. National roofing contractors association. When determining how much insulation you need don t guesstimate calculate.

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. 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. Existing 3 4 inches of insulation. Built up roof membrane gravel surfaced membrane and gravel only 0 33.

Know exactly how much you need with our project calculators. As a benchmark one inch of solid wood has an r value of 1. Recommended insulation levels for retrofitting existing wood framed buildings. It has a lower r value per inch than closed cell foam and is vapor permeable.

Add insulation to attic. I calculate insulation resistance to heat loss or r percentage improvement always as relative to the original number. 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.