Thermal Properties - Air Infiltration and Leaks

Uncontrolled leakage of air through exterior walls and ceilings of homes is almost as important as R-value in determining how much energy will be required to heat and cool your home.

Air sealing is important, not only because drafts are uncomfortable, but also because air leaks carry both moisture and energy, usually in the direction you don’t want. For example, air leaks can carry hot humid outdoor air into the house in the summer, or can carry warm moist air from a bathroom into the attic in the winter.

Most homeowners are aware that air leaks into and out of their houses through small openings around doors and window frames and through fireplaces and chimneys. Air also enters the living space from other unheated parts of the house, such as attics, basements, or crawlspaces.

Weathershield and ProCell insulation due to its ability to fill all gaps and its greater mass (density) inhibits air movement whereas tests have proven that air movement through and around light density insulating materials can reduce its effective insulating value by one half. That’s right, a loss of Rvalue equivalent to 50%.

Two independent studies by the University of Illinois and Oak Ridge National Laboratory documented this long standing claim that cellulose insulation outperforms loose-fill fiberglass insulation because of its higher density and lower air permeability. Weathershield and ProCell completely fill cavities and irregular surfaces thus eliminating gaps and voids which lead to air leakage and convection. In retrofit applications, where additional attic insulation is desired and where air leakage is occuring through other insulation types, a simple solution to fixing this R-value degradation is to add 2 to 3 inches of cellulose insulation on top of the existing insulation or remove and replace the insulation with cellulose insulation. This will substantially increase the overall insulation value of a home.

Based on air permeability, the Oak Ridge scientists have calculated that cellulose insulation will not lose R-value due to convective heat loss at temperatures as low as 40o F below zero. This means that cellulose insulation maintains its resistance to heat transfer under virtually all weather conditions that occur in North America. In another study conducted by the University of Colorado School of Architecture and Planning, air infiltration tests conducted on two buildings, one insulated with cellulose and the other with fiberglass, showed that cellulose insulation tightened the building by roughly 38% more than the glass insulated one.

In conclusion, cellulose has a better resistance to air flow and prevents the upward movement of air caused by temperature differences (the R-value of cellulose actually improves during cold Canadian weather).




 

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