R Value Of Attic Air Space

You can achieve better thermal performance in your attic by adding an additional layer of insulation.

R value of attic air space.

Fiberglass batt 3 14 fiberglass blown attic 2 20 1 fiberglass blown wall 3 20 rock wool batt 3 14 rock wool blown attic 3 10 rock wool blown wall 3 03 cellulose blown attic 3 13 cellulose blown wall 3 70 vermiculite 2 13 air entrained concrete 3 90 urea terpolymer foam 4 48 rigid fiberglass 4 lb ft3 4 00 expanded polystyrene bead board 4 00 extruded polystyrene 5 00 polyurethane. Existing 3 4 inches of insulation. Applications air space requirements. What i m talking about is a house with ducts in unconditioned space especially an unconditioned attic.

If we put ducts in unconditioned space they have to be insulated to either r 8 if they re in an unconditioned attic or r 6 in any other type of unconditioned space. It appears that a reflective surface in a very leaky air space provides little to no thermal benefit in comparison to an air space formed with non reflective surfaces astm c1363 testing example 1. Fibers from rock or recycled slag from blast furnaces. 1 and 6 the r value of a non reflective air space and vinyl siding provides an r value of about r 0 64.

Work out all the different materials and surfaces that make up the wall ceiling or surface you want to work out the r values and u values for. Add insulation to attic. The higher the r value the better the thermal performance of the insulation. The r value calculator is best used as follows.

Material r inch r thick ness insulation materials. Insulation is technically a solid with a lot of air in it therefore. Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work. The irc also prohibits a vapor retarder on the attic floor of conditioned attics so that any moisture that may build up in the attic can dissipate into the house.

The total insulation r value for the assembly will be an r 39 r 20 r 19 which complies with the prescriptive requirements of the 2009 iecc. Air gaps larger than this work well too they promote ventilation on the foil and help keep the air dry and the air temps lower. Doesn t insulation count as an air space. Achieving greater r values in exterior walls.

Our r value cognitive dissonance. R value of building materials. Recommended insulation levels for retrofitting existing wood framed buildings. The most common blown in material used but it can rot and grow moldy if exposed to moisture.

Remember the horizontal or vertical orientation of the material is important to get its insulation value correct. Fibers from recycled post consumer paper that are treated for insect and fire resistance.