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Building Codes

 
The University of Wisconsin-Madison's Grainger Hall suffered efflorescence in its first winter due to air leakage.

While air barrier systems are designed to save energy and lower energy bills, they also present very real business opportunities to mason contractors. Air barrier technology for exterior building envelopes is becoming better understood and appreciated in the United States, as evidenced by both design recommendations and changing building codes. With them comes the need to determine the best-prepared craftworkers for installing them.

Air barrier systems covering the entire building envelope have been required in Canada for nearly two decades. The first in the U.S. to pay attention was Wisconsin, which in 1985 laid out an air barrier requirement for state-owned projects. In 2001, Massachusetts became the first state to require them by code, which became effective July 2001. One year after that, Wisconsin amended its version of the International Building Code (IBC) to include air barriers.

Today, another 21 states are considering air barrier requirements for their respective building codes, according to the Air Barrier Association of America (ABAA). ABAA President John Hudson predicts a national code rule within five years.

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.

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.


Installation of the air barrier for Marquette University's new John P. Raynor 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.

 

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 H2O 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.

The success or failure of air barriers boils down to how the details are addressed: where products stop and start, where backup systems change, movement joints, penetrations, utilities, and more. According to the "Construction Waterproofing Handbook" (McGraw-Hill, 1999), "As much as 90 percent of all water intrusion problems occur within one percent of the total building or structure exterior surface area."

So, achieving an effective air barrier system means a lot more than spraying a typical below-grade waterproofing on a block backup wythe. It is particularly important for designers and installers to realize that those problematic points often occur above the ceiling and below the roof deck or floor above. Many case studies have demonstrated that moist air will rise through suspended ceiling tile and then exfiltrate into the exterior building envelope through the many clumsy details such as top of wall, penetrations and joist bearings, to name a few.

Wisconsin official Lauersdorf notes in "Minimum Requirements and Guidelines for the Exterior Building Envelope 2001" that "air leakage is usually much more destructive to the integrity of the exterior wall system than vapor transmission. In fact [it] may be the leading cause of wall problems (in Wisconsin)."

Just what wall problems are coming up? In climates with significant freeze/thaw periods, moisture can get into an exterior wall system, reach its dew point and create frost or condensation. Depending on where this occurs, negative effects may be stud corrosion, tie corrosion, reinforcement corrosion, mold, mildew, degradation of insulation R-value, brick efflorescence and/or spalling, water on interior finishes, and increased energy costs. Designers and constructors need to be particularly aware of projects that may have high interior relative humidity levels, such as hospitals, nursing homes, swimming pools, museums, libraries, food processing, printing centers, etc.

The next question is where to locate an air barrier in the exterior wall. The answer is: it depends, starting with regional guidelines. Wisconsin code puts it on the interior side of the wall insulation. In a brick and block cavity wall design with the rigid insulation in the cavity, the air barrier is often placed between the insulation and the block backup wythe.

Then there's selection of an air barrier system. While many products will meet air leakage requirements, the trickier part is finding a system to address all the problematic points. Air barrier attributes include: bridging capabilities, expected service life (durability), continuous coverage, and being secured (to a substrate).

Another important factor is environmental compatibility, which influences many a designer. Is the product recognized by environmental standard publications? Does the Volatile Organic Compound (VOC) count meet your local requirements? Does it include minimal manufacturing waste, benign over-spray, non-toxic run off? Is it worker-friendly?

Quality Assurance
The key considerations are to match a product and application method to specific project needs and to require certified installers. "This is a high quality assurance process," says ABAA's Hudson, who believes that if air barriers are designed into masonry wall systems, trained masons should apply them, giving exterior building envelopes a single source of responsibility.

A number of BAC signatory contractors (and some locals) have joined ABAA and many are now listed as licensed ABAA contractors after completing the required training. IMI New England Director Steve Bolognese sits on ABAA's Board of Directors.

In Boston, Local 3 of the International Union of Bricklayers and Allied Craftworkers (BAC) got an early jump, training its own ABAA-certified instructors and serving as an authorized training delivery agent. IMI training centers across the country are in the same process. "The union is ready to train upon need," says BAC Local 3 President Charles Raso.

Mason contractors need to be aware that air barrier systems may be mistakenly given to another trades, or worse, to installers who do not understand the intent of air barrier systems. That can easily lead to site coordination and performance issues.

Josh Babiasz, project field engineer on the Marquette Library project for Opus North Corporation (Milwaukee), credits a "perfect" installation to ease of application and Dentinger's experienced bricklayers. "It's a part of their training, and they do this a lot."

However, "It is important that someone goes back and looks at air barrier installations for gap bridging and other imperfections before the masons install their veneer," says lead exterior shell architect Kevin Anderson of Potter Lawson & Flad, LLC, the architects of record for Madison, Wisconsin's 400,000 sq.ft. Overture Center for the Arts, where the air barrier system was the equivalent of covering an entire city block.

Detailing and sequencing are equally important, says Mike Young, President of Waukesha Air & Vapor Barrier, Inc., which installed Overture's air barrier system. "Qualified applicators, like those that are ABAA certified, are key. People who know what it is supposed to accomplish provide real value."

Kinateder notes that since the air barrier adds another step to the wall assembly, "In order for us to maintain control of our productivity and to be sure that the wall is functioning as intended, we need to be involved in the installation."

It starts with scheduling, he says. "One of the reasons we started installing air barriers was because we were worried about coordination issues. We now install as a sub for other contractors, and we really give their scheduling needs the highest priority." Sharing scaffolds isn't a problem, because he has faith in his trained bricklayers. "We wouldn't let anyone on our scaffold without the proper training."

Whether driven by code or design, air barriers are creating good business opportunities for contractors, while giving their clients more watertight and energy efficient masonry structures. Practitioners and proponents say it is a matter of "when," not "if," air barriers become standard practice. "If it's going to be dictated — and it obviously is," says Bill Dentinger, "mason contractors better get it."


For more info contact Pat Conway, AIA, CSI at pconway@imiweb.org or (608) 437-6871. ABAA can be reached at www.airbarrier.org.



  • Building Codes: Past and Present
  • Free Guide for Masons


  • Side Storie:
  • Building Codes: Past and Present
  • Free Guide for Masons





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