Rated R Value For 2x8 Roof Joist

The thicker the insulation the higher the r value.

Rated r value for 2x8 roof joist. Solid panel insulation has amazing r values. Know exactly how much you need with our project calculators. Add r3 1 for each inch of new cellulose you blow in 1. Also i believe the overlooked benefit of covering the studs and creating a solid barrier with very few areas for air penetration can be well worth the cost.

Install it then have mark get out his caulking gun and seal all the corners. When determining how much insulation you need don t guesstimate calculate. Most common r value upgrades. Thanks 01 03 2008 05 37 pm 8.

The higher the r value the greater the insulation performance. 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. R value measures how well certain building insulation materials can resist heat. Are your rafters rough.

2009 ibc from table 720 1 3 minimum protection for floor and roof systems the floor construction of item 21 1 1 is wood joists wood i joists floor trusses and flat or pitched roof trusses spaced a maximum 24 o c. With 1 2 wood structural panels with exterior glue applied at right angles to top of joist or top chord of trusses with 8d nails. Sheetrock only has a r value or about 0 5. 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.

If you are starting with an un insulated space it is very important to read the section below titled estimating r values for un insulated spaces note. Substrate roof floor ceiling time assembly ff file no. 4 5 rigid will work in rafters as small as 2x6 and will get an r 30 and some change rating. This is very important in situations where your code requires an r 21 for the wall but you only have a 2 4 stud because closed cell spray foam is the only way you would achieve the required r value to meet code.

2 x 8 f d joists 16 o c 1 layer 3 4 bead board ceiling span 17 18 live load 40 lbs. If they are you can get cathederal ceiling batts. Add blown in cellulose to attic. I believe 8 1 4 is the thickness on an r 30.

Insulation rated on its ability to reduce thermal transfer or r value comes in rolls and batts that fit between joists. What r value do i need. To convert to si r values multiply by 0 176. In my brand you get an r 31 in a 2x8 at 2 5 pounds per cubic foot.