Licking the Envelope Problem

Education can improve building envelope construction

The building envelope is more than just a pretty façade. Functioning as the skin of the building, the envelope is responsible for thermal comfort, air quality, and structural support. It's also the largest factor in energy expenditures, determining how much fuel the building consumes and how much of the owner's budget will go up the chimney. When the envelope fails, owners and users face the possibility of serious health issues, large energy bills, and costly remediation.

Tang Lee, professor of architecture, University of Calgary, likes to compare humans with buildings to illustrate the importance of building envelopes in thermal control. "The analogy that I give is there's this naked guy walking down the street wrapped in two pieces of paper in the winter," Lee explains. "That's absurd. We'll put him in the mental hospital. But that's what we do with our buildings."

Lee makes reference to R2, the insulation value of the glass-curtain walls popular in downtown Calgary. Due to its aesthetic qualities, large installations of glass are rapidly becoming a must-have architectural feature in commercial towers. While glass curtain wall can be made to work in Alberta's climate, Lee claims that the impact in fossil fuel costs must be considered.

"Buildings consume one-third of all the fossil fuel," he says. "We can have a huge impact by building buildings that are more energy conserving than insulating with two pieces of paper."

Lee advocates a "made-in-Alberta"solution to building envelope design, using materials that are readily available and work with the climate, as well as with the skills of the provincial labour force. The province's extreme temperature ranges of -30 to 30° Celsius, with temperatures in sheltered southern exposures reaching 60° Celsius, calls for designs and materials that take thermal expansion and contraction into account and can adjust to the province's fluctuating temperatures without using unnecessary amounts of natural resources.

For Lee, continuity is the operative word when it comes to minimizing heat loss in buildings. The accepted practice of insulating between steel studs, for example, is a mistake in his estimation. "Between the steel studs you've got lots of good insulation, but the steel studs conduct the heat out and that's considered a thermal bridge,"he explains.

He adds that this doesn't mean an end to using steel in Alberta construction. "We can use steel, but then we have to wrap it up on the outside with thermal insulation. By wrapping the steel, we [have] a thermal brig rather than a thermal bridge."

A couple of inches of Styrofoam around the steel stud prevents the steel from transferring heat to the exterior of the building. Lee points out that the concept is simple, akin to dressing oneself to go out in the winter.

The idea of wrapping the exterior of building envelopes with insulation to improve thermal control and lower energy costs was developed in post-war Germany. Peter Culyer, marketing and technical services manager, Dryvit Systems, explains why the exterior insulating technology his company imported from Germany and manufactures and installs in North America works well in Alberta construction.

"When you see a bag of bat type insulation [labeled] R12, that [means] R12 when the insulation is not in contact with anything else,"says Culyer. "Once it's put into a wall in between metal studs, there's a temperature gradient from the exterior to the interior. The effective R-value is diminished."

In contrast, the exterior insulation and finish systems (EIFS) provided by Dryvit move thermal resistance to the exterior of the building, where thermal bridges, joints or other interfaces can't interfere. The system is used on new construction and can be installed over the current envelope, making it an easy solution for retrofits.

Studies appear to back up Dryvit's claims of superior thermal control. "In the studies we've conducted along with the Department of Energy in the United States, it was found that, in whole wall comparisons, [Dryvit technology] is 84% more effective than it's closest rival, concrete,"says Culyer.

Chateau Lake Louise was one of the company's early projects, completed in the mid-1980s. "Chateau Lake Louise was originally a summer-only resort,"explains Culyer. "They couldn't afford to heat the darn place in the winter!"The Dryvit system was placed over the original cladding and, along with other upgrades, allowed the hotel to stay open year-round.

Recent renovations at the Chateau produced some good news for Dryvit. When a portion of the cladding was removed, it was discovered that the underlying sheathing showed no sign of moisture leakage, backing up the company's claim that EIFS are building envelope solutions, not just attractive claddings.

Using designs and materials that work with the climate is only a piece of the building envelope puzzle. Bob Passmore, principal, Building Science + Architecture, expresses frustration at the lack of knowledge exhibited by some involved in building envelope construction.

"We have more problems than we have solutions right now,"says Bob Passmore, principal, Building Science + Architecture. A registered architect, Passmore isn't pleased with the state of Alberta's residential building envelopes. Investigations of leaking structures produce evidence of ignorance, cost cutting, and plain, old, lack of concern.

"What's happening is that the envelopes are not being detailed to keep water out,"Passmore explains. He cites a recent example of a $1.5 million home that lacked damp proofing and did not have pressure-treated wood in certain areas, even though the building code clearly states that pressure-treated wood must be installed in those areas.

Education regarding the importance of following building code requirements in envelope construction could lessen occurrences of such instances, saving owners money and protecting the health of occupants.

Passmore also wants to see every sub-trade educated in the compatibility of materials. Products that degrade when wet must be used properly, but often aren't. Making matters worse, product manufacturers tend to develop new products without considering the role of each product in relation to the other components of the envelope.

One such product is a hard plastic waterproof barrier designed to go under stucco. Passmore has heard from stucco installers who've tried the product that each time a staple is shot into the wire, the plastic barrier is shattered. "We're seeing a lack of thought,"he states. "And I don't know how people think these things are going to work."

Lee agrees. "It is imperative for the building industry in Alberta to spend the time and effort and have the understanding to design and build better building envelopes,"he says, adding that the province's climate may make education a bigger requirement in Alberta than elsewhere.

Building owners also have a responsibility to educate themselves in order to protect their investments. Lee proposes building maintenance manuals. "We have a maintenance manual for our toaster and yet we don't have one for something as complicated—and custom built—as a building,"he says with amazement.

Indeed a maintenance manual would take the pressure off architects, who are currently liable for water and mould damage for up to 10 years after construction, regardless of the amount of maintenance performed.

Education and a willingness to work within the confines of the province's climate, labour skill sets and accessible materials will improve the performance of building envelopes, but what will these new and improved skins look like?

The U.S. Department of Energy funded the development of a 20-year plan for residential building envelopes. Members of industry worked together to set goals for building envelope construction in the year 2020. The goals are at once lofty and common sense.

Ultimately, the building envelope of the future is made up of modular components that allow for flexibility and change, adapting to the evolving needs of the users and technological advances. It is affordable, durable, and sustainable, and it uses technology to provide comfortable, healthy internal environments.

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