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08/01/2014

Air Leakage Testing: A Hot Button or Hot Air?

Find out when and where pressurization is a valuable forensic tool

By Christopher Curtland
 

Find out when and where pressurization is a valuable forensic tool.

Blowing air into your building can prevent you from blowing your stack about its envelope performance.

Air leakage testing quantitatively measures air seeping through your enclosure. The process involves pressurizing a space with blower door fans to create a detectable differential across the envelope.

But it’s not always an appropriate method for problem detection. Pressure testing is necessary when problems have become particularly invasive or if quantitative analysis is desired to prove compliance, verify performance, or identify opportunities for upgrades.

Become an educated consumer of this service by building a rudimentary understanding of building science and enclosure performance. They say not to judge books by their covers – but the same can’t be said of buildings.

Contemplate the Clues

Looking for issues actually starts with listening. Heed occupant complaints as a source of valuable information. “If there are problems, your people will let you know,” says Dean Lewis, education and technical information manager at the American Architectural Manufacturers Association, which provides standards on testing methods for the industry.

Clues and Calamities

Develop a basic knowledge of building science and the physics of building enclosure performance before turning to expensive field testing, advises Daniel J. Lemieux, principal and unit manager at engineering firm Wiss, Janney, Elstner Associates.

Inappropriate or unnecessary testing can lead to false results and misguided repair efforts. These pitfalls can be avoided if you know what you’re looking for. Consider Lemieux’s warning signs and the potential problem resulting from them.

1. Water staining or moisture presence at interior drywall soffits, blind-pockets, lay-in ceiling tiles, and above windows and doors In clay brick and concrete masonry cavity wall construction, this could indicate defects in the through-wall flashing above the windows and doors rather than defects in the window and door products themselves, a common source of misdiagnosis.

 In architectural precast concrete and similar barrier-type exterior wall construction, this may reveal wintertime condensation on the inboard surfaces of the architectural precast concrete panels and anchors at floor-line spandrel conditions.

 This is also a potential indicator of breaches in perimeter joint sealants and gaskets often associated with improper design and installation, normal weathering and deterioration, or deferred maintenance.

2. Water staining or moisture presence on interior window and door frames, vertical mullions, inboard glass surfaces, and similar areas In addition to the situations above, this might point out defects in the installation of interior zone-dams, end-dams, and seals at frame joinery in exterior window and glazed aluminum curtainwall assemblies. Repair may require de-glazing or perhaps conversion of internally drained windows and curtainwall assemblies into barrier-type assemblies that rely on an additional exterior joint sealant to resist rainwater penetration.

3. Water staining, moisture presence, or formation of wintertime frost on interior window frame, sill, and inboard glass surfaces at insulating glass unit perimeters (IGUs)

In cold climates or regions that experience unexpectedly cold wintertime outdoor air temperatures, this could show thermal bridging at window anchors, sub-sill flashing and frame receptors, and aluminum or stainless steel spacer-bars used in the assembly of IGUs.

4. Wet carpet or water staining and related damage to interior floor finishes at exterior wall lines In addition to potential breaches in perimeter joint sealants and gaskets of exterior wall systems, this may also indicate wintertime condensation and thawing of frost on the inboard surfaces of the architectural precast concrete panels and anchors at floor-line spandrel conditions.

5. Discoloration on interior or exterior wall surfaces, either in the field of the wall or in-line with metal studs and fasteners This may indicate thermal bridging across the enclosure or improper design, placement, and installation of a continuous insulation layer, vapor retarder, and air barrier.

6. Inability to effectively maintain a consistent and comfortable indoor environment for occupants This could also reveal the lack of a properly installed continuous insulation layer, vapor retarder, and air barrier.

IAQ surveys may turn up comments on dust, mold, pests, and exterior noise, explains Lee Durston, senior building science consultant at engineering firm Morrison Hershfield. Although it may be easy to disregard their remarks, use occupants as your eyes and ears in the field.

Perhaps the most fickle and frustrating complaints concern thermal comfort. But drafts and stuffiness can be significant indicators.

“Pay attention to the presence of personal comfort devices like heaters or fans,” recommends Doug Phelps, director of business development at window and door supplier Pella EFCO Commercial Solutions. “Seeing those is a good clue that the space isn’t performing.”

Lastly, if moisture has penetrated the system, you can be certain that air has. “Relatively common clues include water staining or the presence of detectable moisture at various locations like wall surfaces, ceiling tiles, window and door frames, or carpet and flooring finishes,” explains Daniel J. Lemieux, principal and unit manager at engineering firm Wiss, Janney, Elstner Associates.

It can be helpful to make a few notes in cases of apparent water leakage failure. “Were leaks noticed during a severe storm? Did your local news outlet comment on particularly strong winds or wind-driven rain?” says Lewis. “That information can assist in evaluating whether the system actually failed to meet its ratings or if conditions exceeded the manufacturer’s design.”

Now that you know what evidence to look for, you can ascertain whether pressure testing can further your forensic investigation.

Mull Methodology and Motivation

If any combination of the aforementioned clues has been observed at your site, air leakage testing can help you identify the root causes. If a problem becomes invasive, you want to be sure to get the solution right the first time.

“Pressure testing is a troubleshooting tool in a lot of practices,” says Ned Lyon, staff consultant at engineering firm Simpson Gumpertz & Heger. “But it is also used as a way of quantifying or categorizing performance.”

The need for quantitative testing continues to increase as energy code requirements for airtightness become more stringent and designers include targets for specialty high-humidity buildings such as pools and museums, Lyon explains. The 2012 International Energy Conservation Code requires a dedicated air barrier for the enclosure and allows whole building air leakage testing to demonstrate compliance.

Similarly, pressure testing is used to prove the performance of certain construction projects and upgrades. After making improvements to glazing, storefronts, curtainwalls, or other envelope components, make sure the manufacturer measures and verifies their claims.

Regardless of your motivation for implementing pressure testing, having a basic understanding of how the process works will help you get the most out of it.

A calibrated fan about 30 inches in diameter can move up to 6,000 cfm of air, explains Lyon. A frame and cover mount up to three fans to a doorway. The fans then create a pressure differential across the building enclosure. Although some crafty FMs attempt to crudely mimic pressurization with makeshift methods, this intensive procedure necessitates outside expertise.

“We’ve received questions like, ‘My windows are leaking – how close should I be able to hold a cigarette lighter without it blowing out?’” adds Lewis. “Variations of do-it-yourself testing have involved leaf blowers and garden hoses, but there are no ‘kitchen drawer’ tests for air leakage or water penetration.”

The size of your building and scope of the test will determine where to go for help. “There are several small firms that can handle residential-size buildings and one- or two-story structures,” explains Lyon. “A local utility program may even perform blower door testing as part of an energy audit. When you start moving up in size, you run into trouble.”

Designing and setting up a test is an art, Lyon adds. Computer controls monitor multiple fans at once, and although the actual test may only take a couple hours, the planning can take several days.
A simpler and perhaps less costly approach is to shirk measuring leakage and instead utilize tracer smoke to visually identify problem spots. “Looking around outside for the smoke can help you find leakage locations,” says Lyon. “It’s a more qualitative method.”

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Ponder Problems and Realize Remedies

The solutions you need can be many, ranging from the simple, such as sealant or gasket replacement, to the drastic, like recladding, explains Matt Williams, associate principal at engineering firm Arup.

“Testing can open a can of worms,” he adds. “There is a question about expectations and a discussion about useful life. When is remedial work appropriate and when is there a need for recladding? A quick fix may last 10 years, but what could a replacement do? You can keep investing in patchwork every year, but at some point you start to think about more fundamental changes.”

Identifying air leakage helps you set the baseline condition for your facility. From there you can assess the bare minimum to be done to keep your building relevant in the current market, says Williams. Progressive owners and FMs may use the quantitative analysis as selling points for significant strides.

Sprinker Recreation Center

Background
    Despite its popularity as the only ice rink in the county, Sprinker Recreation Center was in poor condition. Pierce County Parks and Recreation, the arena’s owner, determined the facility would require complete replacement at a cost of $35 million.
    With lack of funding for a project this size, the building was scheduled for closure. Public outcry led the county to seek alternative ideas.

Problem and Testing
    With large fans, an engineering firm pressure tested the building and found an abnormally high air leakage rate at roughly 0.8 cfm/sf at 75Pa. Most of this was occurring at roof-to-wall connections.
    Leakage was also allowing vapor-laden air to infiltrate the space and condense on the bottom side of the cold metal roof deck. These condensation droplets were dripping onto the ice, creating a safety hazard. Conditions were also resulting in poor air and ice quality and rusty roof components.
    Because of the excess humidity, the existing mechanical systems were being asked to work so hard that additional dehumidification machines were brought in, producing associated energy costs. It only exacerbated the problem by sucking in more vapor-laden air at the roof-to-wall joint.

Solution and Remedies
     Low-emissivity ceilings in ice arenas are typically made of suspended fabric. This method wouldn’t work at Sprinker, because there were potential conflicts with lights, fire sprinkler heads, and potential damage from hockey pucks.
     The team tested special low-emissivity paint that helps minimize heat transfer by radiation from the ice to the roof, keeping the roof warmer and the ice cooler. The paint is normally used on large oil tanks to keep the oil from getting too hot from solar radiation. At Sprinker, it slows down ice melt by reducing the flow of radiant heat to the roof.
    Air leakage was reduced to roughly 0.26 cfm/sf at 75Pa. The mechanical system was converted to natural gas and lighting was improved. The project also entailed aesthetic improvements to the counter, ticketing office, restrooms, and waiting areas. All improvements were made with a $6 million budget.

 

“There are buildings and districts in Los Angeles where they’re aiming to reduce energy consumption by 70-80% over the next two decades,” Williams explains. “They first look at existing stock and identify easy, short-term, low-hanging fruit items and then go to longer payback, capital expenditure projects. So testing is certainly very relevant to buildings that are in desperate need of attention.”

The firms that provide this analysis should be able to help FMs provide that TLC. Just perform your due diligence before enlisting them.

Vet the Vested Factions

Be sure to perform a thorough background check on the firm that offers pressurization testing. Ensure that they are performing tests in accordance with industry standards.

Beyond that, find a firm that can help you implement actionable items that arise out of the testing. “Don’t just go for the company that comes in with the fans and gives you a number and a report,” warns Lyon. “Make sure they can consider the problem you need to deal with and figure out the best way to solve it.”

Some of the symptoms outlined above can be confusing. They make it difficult to distinguish if you’re having air barrier or HVAC problems. Call upon experts that can help digest this muck.

“Use someone with knowledge about envelopes as well as testing. They know where to look and have X-ray eyes for this stuff,” says Lyon. “The FM is stuck with the calls of ‘I’m uncomfortable’ and ‘Go fix this’ or ‘Adjust that.’ He’s juggling a lot of things and can’t always look at the big picture.”