Wall insulation least effective?

home more comfortable.

The four-part study used new blow' er door testing technology to record data on identical one-story, 1,360-sq.ft. wood frame houses. The Phases: Part l: Effect of wet-blown cellulose & Kraft-faced fiberglas s insulation on air infiltration of a house

The first part of the test revealed minimal performance difference in ability to reduce air flow between R13 Kraft-faced fiberglass and wetblown cellulose fiber wall insulation.

Yuill said the test also showed that "air leakage through the walls is small compared to the overall leakage through the other comPonents of a house. The majority of a house's air leakage occurs in the floors, ceiling and ducts. The comPlete removal of the wall cavity insulation would only result in a l.S%o increase in air leakage throughout the entire house."

Most resistance to air flow through the wall system of a house is provided by the drywall (77V0), not wall cavity insulation (ll7o). Siding and sheathing provide the remaining l2%o.

P art 2: Effect of loose -fill fiberglass & Krafi-fac ed fib e rglas s insulation

Next, R-15 Kraft-faced fiberglass batts and loose-fill fiber glass insulation ("BIB" or "Blown in Blanket") were shown to have little effect on total air resistance. While fiberglass batts had tzEo $eater resistance to air infiltration than BIB insulation, the difference is minimal because wall cavity insulation has a verY small influence on the total air infiltration of a house (abott O.2Vo).

The majority of a house's air leakage occurs in the floors, ceilings and ducts.

Part 3: Effects of various wall system air tightening mnterials & techniques

Researchers used housewraP, insulating and fiberboard sheathing, vinyl and aluminum siding, and caulking and sealing during the third test. Installing a housewrap over untaped rigid foam sheathing Produced the most effective barrier, reducing whole house air infiltration bY l27o' Installing housewrap over fiberboard sheathing, taping rigid foam sheathing, or caulking and sealing the inside of the wall system each reduced infiltration by 9Vo. UntaPed rigid foam sheathing and untaped fiberboard sheathing offered little resistance.

Part 4: Effects of sealing components

Finally, caulking and sealing floors, ceilings, walls and duct systems reduced overall air leakage by 36Vo. Specifically, air flow was reduced by l|Vo by caulking and sealing the ceiling, l3%o bY the floor and basement, and9%o by the walls.