Masonry Magazine July 2003 Page. 17
By Pat Conway, AIA, CSI
Area Director of Technical Services
International Masonry Institute of Wisconsin
Depending on your perspective, new building codes can mean new obstacles or new opportunities. Newly adopted air barrier codes and recommendations are no exception.
Installation of the air barrier for Marquette University's new John P. Rayner S.J. Library was made easier by the omission of the brick ties, which were installed along with the brick veneer, after the air barrier and rigid installation. The membrane's self-healing properties eliminated concern about punctures.
So What does this Mean for Mason Contractors?
A FEW PROACTIVE mason contractors have jumped on the bandwagon to prepare themselves for upcoming new codes and recommendations. Hudson, who as president of The Waterproofing Company, Inc. in Boston is signatory with the International Union of Bricklayers and Allied Craftworkers (BAC), has seen his business increase more than fourfold in the past year or so.
Also, Bill Dentinger of Bill Dentinger Masonry, Inc., in Waukesha, Wis., was fortunate enough to retain the air barrier installation for his masons on the newly constructed 126,000 sq. ft., four-level Marquette University library.
Fred Kinateder, President of Fred Kinateder Masonry, Inc., (Waukesha) took it one big step further. He started a separate business unit, Waukesha Air & Vapor Barrier, Inc., that quickly found subcontracting opportunities outside the parent company. "Air barrier codes are so new around the country that now is the time for mason contractors to retain their work on the wall," says Kinateder. "If we don't convince architects that we have their best interests in mind, then others will slip into the back door, make a quick buck, and leave the client hanging."
In New Jersey, mason contractor Speranza Brickwork, Inc., followed the same path, creating a separate corporation called Building Barriers, Inc. Vice President of Operations David Jaye notes that, even without code requirements, architects in his state are showing a lot of interest. "Any sensible architect is going to be prepared," says Jaye. He notes that it's a particularly easy decision when specifications already include money for vapor barriers.
The Voice of the Mason Contractor
These pioneers get an assist from the International Masonry Institute (IMI). IMI's active role in the design, construction and public contracting communities helps get the word out and stresses proper use. "IMI gave us credibility," says Kinateder, "and got us further down the road that much sooner."
Why Install an Air Barrier?
THERE ARE TWO KEY REASONS why air barriers are catching on: energy efficiency in both cold and warm climates, and increased building envelope performance. According to the U.S. Department of Energy, up to 40 percent of the energy consumed to heat or cool a building is due to air leakage into and out of the structure.
Air barrier proponents also point to increasing concern with mold and mildew, and rising litigation costs - especially in metal stud and gypsum board backup construction. All these factors have shifted the cost-benefit calculation, and are steadily eroding the largely economic resistance to air barriers.
In Massachusetts, the primary impetus for the new code was energy savings.
In Wisconsin, the motivation was protecting the exterior building envelope from moisture-related damage. The state's newly adopted IBC version ("Wisconsin Enrolled Commercial Building Code - 2002") requires an "air barrier" in exterior walls, plus - in stud backup walls only a "water resistive barrier" and "vapor retarder." If properly designed and detailed, these requirements may be satisfied with one product at one location within the wall.
National air barrier expert Lynn Lauersdorf with Wisconsin's Bureau of Architecture and Project Management agrees with ABAA that the key is looking at it as a system. "You really have to cover the whole thing," he says.
It is critical to differentiate between "product" and "system" properties. While a vapor retarder slows down the transmission of water vapor by diffusion, an air barrier system stops moisture migration by air leakage. Vapor retarders and air barriers have different metrics. For example, in Wisconsin, an air barrier is defined as: "a material or combination of materials collectively having maximum air leakage rates of 0.06 cfm/ft2 at 0.30 inches H:O when tested in accordance with ASTM E783, installed to resist air leakage into the exterior envelope."
Designers need to address those points in the exterior building envelope, which may let an abundance of air infiltrate or exfiltrate. When air moves, it takes moisture with it, which is air leakage. But moisture can move without air movement, which is diffusion. Air barriers stop air leakage, while vapor retarders restrict moisture diffusion.
Which problem do you think will cause more problems for your building: moisture diffusion or air leakage? Hands down, the answer is air leakage. Many experts say the latter problem is at least one hundred times worse than the former.