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Comparison Of Insulation Materials

Homes should be well insulated in the attics, walls and underfloors to avoid heat loss in winter and to keep heat out in summer. The effectiveness of insulation material is measured in R value. The higher the R value, the more effective it is. Building codes in most mild climate jurisdictions require attic insulation to be R-30 or better and exterial wall to be R-13 or higher. After air-sealing the house, adding or installing insulation in a very cost effective way to improve comfort and save energy in the home. One of the best sources for insulation information is from the Oak Ridge National Laboratory.

Insulation MaterialR value / inchSource MaterialBest ApplicationPros and Cons
Fiberglass Batt3.14 – 4.30Strands of molten glassUnfinished walls, floor, ceiling; additions to atticFire and mold resistant; installation needs to fit the cavity exactly.
Fiberglass Blown2.20 – 4.30Strands of molten glassEnclosed existing walls or open new wall cavities; unfinished attic floor.Good for hard to reach places and filingl cavities completely. R-value is lower in attic application
Rock Wool Batt3.14 – 4.00Molten rock or slagUnfinished walls, floor, ceiling; additions to atticFire and mold resistant; installation needs to fit the cavity exactly.
Rock Wool Blown3.10 – 4.00Molten rock or slagEnclosed existing walls or open new wall cavities; unfinished attic floor.Good for hard to reach places and filing cavities completely. Fire and mold resistant.
Cellulose Blown3.60 – 3.9Ground paper or woodEnclosed existing walls or open new wall cavities; unfinished attic floor.Good for hard to reach places and filingl cavities completely. Recyled and sustainable material; absorbs moisture. May settle a little over time. Some products have additives to retard fire or mold development.
Cotton Batts3.7CottonUnfinished walls, floor, ceiling; additions to atticTypically made from recycled denim or waste denim material. Susceptible to moisture. Requires exact fit during installation. Some products have additives to retard fire or mold development.
Wool Batt3SheepUnfinished walls, floor, ceiling; additions to atticMaterial is natural and sustainable, moisture resistant and retains lift. Costs somewhere between fiber glass batts and cellulose.
Wool Blown3SheepEnclosed existing walls or open new wall cavities; unfinished attic floor.Material is natural and sustainable, moisture and fire resistant, and retains lift. Costs somewhere between fiber glass batts and cellulose.
Straw bale[24] 1.45StrawWall additions.Material is natural and sustainable. Provides structural strength for exterior walls. Need to keep moisture away.
Polyurethane closed-cell spray foam5.5 to 6.5PetrochemicalUnfinished walls, floor, ceiling; additions to attic.Easy to fill up crevices for great air sealing. Source material is not ideal. Requires professional installation.
Polyurethane open-cell spray foam3.6PetrochemicalUnfinished walls, floor, ceiling; additions to atticEasy to fill up crevices for great air sealing. Moisture resistant. Source material is not ideal. Most expensive than open cell but better insulation. Also requires professional installation.


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