R Value Of Attic Air Space

Doesn t insulation count as an air space.

R value of attic air space.

Fibers from rock or recycled slag from blast furnaces. The higher the r value the better the thermal performance of the insulation. What i m talking about is a house with ducts in unconditioned space especially an unconditioned attic. Material r inch r thick ness insulation materials.

Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work. The r value calculator is best used as follows. Applications air space requirements. Recommended insulation levels for retrofitting existing wood framed buildings.

You can achieve better thermal performance in your attic by adding an additional layer of insulation. I m in georgia iecc climate zone 3 where our current state code requires r 13 in exterior walls r 18 in attic kneewalls r 19 in floors and r 30 in ceilings. Installed on bottom of rafters or directly to inside of roof deck. Insulation is technically a solid with a lot of air in it therefore.

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. R value of building materials. Existing 3 4 inches of insulation. 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.

Fibers from recycled post consumer paper that are treated for insect and fire resistance. 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. 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. 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 most common blown in material used but it can rot and grow moldy if exposed to moisture. 1 and 6 the r value of a non reflective air space and vinyl siding provides an r value of about r 0 64. Achieving greater r values in exterior walls.

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. Our r value cognitive dissonance.