R Value Of Attic Air Space

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.

R value of attic air space.

Installed on bottom of rafters or directly to inside of roof deck. 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. 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.

The higher the r value the better the thermal performance of the insulation. Fibers from rock or recycled slag from blast furnaces. Our r value cognitive dissonance. 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.

Existing 3 4 inches of insulation. Add insulation to attic. Insulation is technically a solid with a lot of air in it therefore. Doesn t insulation count as an air space.

Applications air space requirements. Remember the horizontal or vertical orientation of the material is important to get its insulation value correct. 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. Material r inch r thick ness insulation materials.

What i m talking about is a house with ducts in unconditioned space especially an unconditioned attic. 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. You can achieve better thermal performance in your attic by adding an additional layer of insulation. Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work.

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. The most common blown in material used but it can rot and grow moldy if exposed to moisture. The r value calculator is best used as follows. 1 and 6 the r value of a non reflective air space and vinyl siding provides an r value of about r 0 64.

R value of building materials. Achieving greater r values in exterior walls.