ASHRAE Journal - February 2013 - 59

G) Install flashing tape at head; H) Fold housewrap down at head; tape in place with sheathing tape; I) Interior view prior to window installation; J) Interior view
after window installation; K) Air seal window around entire perimeter on interior with sealant and sealant backer rod.

lap.§ We have to thank the roofing industry for this technology. Nice job roofers.
Adhesives have come a long way in
my lifetime. We glue planes together,
cars together, bridges together and tissues together. And we have made them
resistant to heat and ultraviolet light and
compatible with almost anything. But
with all of the advances in materials science, we have still not figured out how to
get things to stick to mud, dirt and frozen
surfaces. Let me repeat this because as
good as things are there is no way to
stick stuff to muddy, dirty, cold, wet and
frozen surfaces. I should repeat it again,
but you folks should just stop here, reread
the previous sentence and think about it.
Reread it again. OK, now let’s move on.
Residentially, we now use tapes on
wood sheathings (Photo 8) and foam
sheathings (Photo 9) to provide water
management and air management. So
how well do these systems actually work?
Now? Real well. In the early days? Not
so good. The residential tape systems had
to go through the same learning curve
the commercial membrane systems went
through.#

Photo 8: Wood Sheathing. Residentially we now use tapes on wood sheathings that
have factory applied membranes factory bonded to them to provide water management and air management. Photo 9: Foam Sheathing. Foam plastic sheathing panels
are taped together creating a water-resistive barrier system. These systems are now
around 20 years old. This image dates back to a subdivision development in Chicago
in 1995. 3M was one of the first to develop acrylic based tape systems for housewraps
in the 1980s and they migrated to foam sheathings in the 1990s.
Tapes are typically a carrier sheet,
which provides strength, and the adhesive, which provides the “sticky.”
Carriers are often made of polyethylene
or polypropylene, but can be made of
aluminum foil or other materials. Flashing tape manufacturers are advancing the
technology by fine-tuning both the carrier
films (“facers”) and adhesives.

There are two basic groups of adhesives used in tapes: butyl and acrylic.
Most butyl tapes are typically called
“flashing” tapes and the acrylic tapes are
typically called “sheathing” tapes. The
butyl tapes are “thicker” and are “gooey”
on the back. The acrylic tapes are very
thin. The butyl tapes handle movement
better than the acrylic tapes. The acrylic

§A

pressure bar and a gasket? Wow. Why is something so “serious” needed in a commercial building? Well, when you are up 20 floors the “loads” are an order
of magnitude greater than when you are up 2 floors. And, with commercial buildings, the hygric buffering is significantly lower. “Hygric buffering?” Nice new
popular phrase that means storage and redistribution. I can store a great deal of incidental water in wood framing and wood sheathing. I can’t store squat in a
steel stud or gypsum sheathing. A tiny leak in a high rise made out of glass and steel and gypsum that “sees” big “loads” is a much bigger issue than a tiny leak
in a low rise made out of wood and wood products.

#And the same learning curve the residential and commercial housewrap and building wrap folks went through. How easy folks forget the problems with UV exposure and surfactants and blow off an incompatibility with sealants. Today’s systems are awesome, but 20 years ago they mostly sucked. Heck, even as recently
as 10 years ago wood sugars, tannins and other surfactants drove folks crazy.

February 2013

ASHRAE Journal

ASHRAE Journal - February 2013

Table of Contents for the Digital Edition of ASHRAE Journal - February 2013