Floor Sealing

June 2010

Three attachments describe unusually large and varied floor sealing opportunities in an attic floor. Closure is with tightly-fit GP Densarmor drywall, gun-applied polyurethane foam, and a pushing down of loose fiberglass into accessible outside walls. A late-discovered blower door measurement by a competitor in weatherization, was not helpful. As always, I fix whatever problems are visible. Access for inspection was hard-won, in the course of actual work. The report is an excellent example of misapplied investment in testing. The test personnel had no interest in doing difficult sealing repairs, and made no effort to find and mark leaks for others to repair. The blower door measured infiltration was 4220 CFM at minus-fifty Pascal house vacuum, for a single-floor house with 1400 sq ft heated area. If real, this is extremely large leakage, though at relatively small cost in energy inefficiency. My analysis shows that about $200 per year might be saved by stopping infiltration, to a Building Tightness Limit, BTL, of 1400 CFM50, where there is healthy fresh air exchange of 7.5 times house air volume, each hour. Other weatherization measures, adding insulation and simply keeping attic air out of walls below, will save five times as much, and should be the focus of incentives. Sealing only against infiltration, verifiable by blower door testing, is a grave disservice. The "Home Performance Test" merely wasted customer and public funds, and was a further cost to the consumer in conflict-of-interest sale of very expensive duct wrapping. The duct service did little good, and interfered with more-important weatherization. The arm-twisted sale was induced with a mark-down of the cost of the unproductive test.

The customer deserves a no-cost retest after my best effort of sealing, by the rebates organization, Energy Trust of Oregon/ Conservation Services Group.

One "Rule" of sealing is offered:

Where a floor pit is open to outside walls, the pit is best filled, not sealed.

July 2010

A floor pit over a basement stairwell is a very clear example of "sealing" opportunity that is unrelated to blower door testing. Pits amplify heat losses in an attic floor, by acting through extended wall and ceiling areas below. Amplification is typically by an area factor of ten. Here, in triangular shapes, the multiple is only five. Please study the simple math, in the attachment titled "Insulation Review With Floor Pit Over Stairwell.pdf", and in another blog posting, here.