Built to last
Glass towers are an excellent long-term investment.
December 16, 2011 By James Lischkoff and Brian Burton
The fenestration industry has been hearing a lot recently about
durability and energy performance focused on new condominium
construction in downtown Toronto.
The fenestration industry has been hearing a lot recently about durability and energy performance focused on new condominium construction in downtown Toronto. Some industry insiders quoted in a recent CBC feature [“Throw-away buildings: Toronto’s glass condos,” CBC News, Nov. 14] suggested that these glass condominium towers are “throw-away buildings.”
These views typify the one-dimensional view of some engineers: if something cannot be easily measured and analyzed in mathematical terms then it is of no benefit to society.
It is surprising to read in this story that “building scientists have known for a long time that glass wall structures are less energy efficient than the stone and concrete buildings that were put up 40 or 50 years ago.” In fact, stone and concrete buildings from that era use far more energy per square metre than any other form of housing. Because they were constructed without insulation, using single-glazed aluminum windows, the suggestion that their energy performance is superior to glass towers cannot be supported.
If energy efficiency were the only concern, we would not be building high-rise towers with glass. We would be living in caves. Caves are the most energy-efficient structures ever used by mankind. It is our good fortune indeed that engineers do not rule the world.
| England’s Crystal Palace stood from 1851 to 1936 before being destroyed by fire. Clearly, glass buildings can last. But inadequate design, poor contract language, faulty materials and workmanship, compressed construction schedules, and lack of quality control, can contribute to an early decline.
What we do know for certain is that natural light is one of the most fundamental, positive, life-enhancing aspects of our environment. It is critical to all human endeavors and vital to our health. Despite the decades of research on the subject, we are often unaware that poorly designed interior environments may cause anxiety, stress, visual disorders and a host of other problems. The nurturing aspects of natural light are receiving more and more attention and it is well known that this attention to natural daylighting is front-and-centre in the design of health-care facilities. In these buildings the designers are clearly focused on the efficient use of glass and fenestration components. If glass and natural light are beneficial to humans in wellness and health centres, surely the occupants of office and residential buildings would also benefit from glass and natural light. A discussion of building envelope design cannot be based solely on energy efficiency without considering the positive attributes of the design itself.
Society would be better served if the discussion focused on how we can make better use of glass.
So what about glass itself? As a building material, glass is just as durable as any other common building material. Some of the oldest, 30-year-old, glass high-rise towers are being re-clad for a host of reasons other than energy efficiency. However, it is worth noting that they are not being re-clad because the glass has deteriorated. Glass, unlike some building materials, does not rot, corrode, suffer from the effects of moisture or deteriorate due to natural causes including exposure to the external environment. Considering the main ingredients in glass, glass should rank quite favourably as a sustainable building product. Unlike other traditional building components, such as masonry, glass is currently receiving a great deal of research and development attention that has resulted in dramatic improvements in energy efficiency without destroying its ability to effectively transmit natural light.
Paying attention to history
Decade-old published data on premature failures of building envelopes can give us some perspective that news reports lack. Keep in mind these reports came out long before the present increase in glass construction. In a report published by the Canadian Mortgage and Housing Corporation entitled 2001 Building Failures Study: CMHC Technical Series 01-140, prepared by R.J. Burnside and Associates, Robert Marshall reported: “In Canada, rehabilitation for roofing and wall system repairs costs an estimated $7.5 billion annually. An estimate of the premature failure rate is three to five per cent, or $225 to $375 million per year. Exposure to costly failures is significant for building owners, home warranty programs, insurance companies and builders.
For example, high-rise condominium claims were estimated to be about $20 million in 1990 for Ontario. A 2000 report for the GTA found that claims are common in the first few years of a building’s life, with the majority occurring in the first five years.” The plain fact evident here is that issues relating to quality control and costs of future repairs are by no means limited to glass towers.
What we do know for certain is that over the past 20 years, a period during which window wall construction was relatively rare, we have seen the percentage of claims for operational deficiencies of the building envelope increase dramatically. At the present time these deficiencies now comprise approximately 70 per cent of all identified defects and the expenditures required for remediation and repairs are astronomical.
Durability and quality in perspective
Remarkably, Canada has had a national model building code since 1941. For the most part, the tremendous benefits of the code are taken for granted by the general public. Our model building code approach has been supported by the International Residential Code, the Canadian Construction Materials Commission and the CMHC. Canada is internationally recognized as a leader in cold-weather building science. We also invest more money per capita in buildings than most industrialized countries. As a result, our building stock is second to none, with a total value of over $5 trillion.
In addition to climate challenges, over time buildings have become more and more complex while our expectations of the indoor environment are extremely high and continue to rise. This is to be expected in a country where the citizens are 80 per cent urbanized and spend over 90 per cent of their time indoors. Even a relatively small building can contain more components than a jet aircraft and most buildings are essentially one-off prototypes. Buildings are not manufactured on assembly lines and as a result the industry has suffered from what marketing people call “immobility” in the finished product. The industry is highly resistant to innovation and relative to its size we invest a negligible amount on R&D (less than 0.1 per cent of revenues). We have also been extremely slow in incorporating computer technologies. So while it is generally accepted that, although we possess the expertise in building science to improve quality and building performance, we typically fail to systematically apply the knowledge.
Most buildings are not properly commissioned to verify and document that they meet acceptable performance standards prior to occupancy. Most designs for new buildings are not clear enough in detailing the manner in which materials and systems interface with one another and how they should be assembled on site. On-site quality control measures and quality management in most aspects of the industry are inadequate. This is particularly true of on-site inspections and proper mock-up testing. “Face-seal” construction technology (generally recognized by building scientists as outdated) is still used on most buildings in spite of the fact that it is virtually impossible to effectively seal all building joints. In addition, the various components of the building envelope have different levels of durability, which means they wear out at different rates.
We continue to construct buildings without the input of building scientists who assess building systems to ensure maximum compatibility between subsystems and review component interface detailing to achieve viable long-term performance. So while we can build quality glass buildings that meet all reasonable expectations for longevity and energy efficiency, we often simply fail to do so.
The high cost of repairs
The insurance industry in Australia, a country with a building stock very similar to Canada, commissioned a formal study that found the cost of repairing damage to structures is actually greater than the five per cent estimate of the annual investment cost of new construction put forward in the Canadian study in 2001. The Australia report suggests that indirect costs add an additional five per cent, bringing the total closer to 10 per cent. Here in Canada we invest approximately $307 billion in construction every year, or approximately $8,000 for each citizen. Applying the 10 per cent formula across the board to include all aspects of construction activity, we would be looking at somewhere in the vicinity of $20 billion annually to repair the damage caused by defects, or approximately $1,600 a year for every Canadian. The report highlighted the fact that a very large percentage of defects are either unnoticed or overlooked, or repairs are deferred. It is not hard to see how the high cost of repairs contributes to lax maintenance, which can result in the kind of catastrophic failures that have made the news lately.
Why is good QC a challenge?
When it comes to addressing quality issues, several reports have identified the primary reasons the industry has struggled for decades. Lack of expertise and resources to improve quality tops the list. A rigid attitude in executive management, or lack of top-management, and employee commitment to quality can contribute. Poor education and a lack of training make it hard for companies to implement improvements. The ever-increasing compression of construction schedules coupled with an emphasis on short-term objectives can be corrosive to good quality.
More generally, a tendency to cure symptoms rather than determine causes afflicts some projects. And most business owners agree that too many documents are required for building projects, or at least that they lack the ability to easily meet their documentation responsibilities. Finally, the current, high-pressure tendering and bidding climate is often cited as a reason for degraded quality.
Canada should substantially increase its investment in R&D focused on construction and quality issues in the sector. There should be a radical improvement in our approach to education, training, apprenticeship and certification of construction professionals. National and provincial building codes should be modified to ensure that design reviews by building scientists are mandatory.
The industry requires some form of incentive to encourage high-performing design and construction and to replace the current system where the lowest bid gets the work.
The current levels for on-site testing, inspection and mock-up testing should be increased by a substantial degree. A requirement for mandatory building commissioning should be included in the local and provincial codes and standards. Local building departments should be more vigilant in determining that structures meet minimum code requirements, including those for durability.
Given the size and importance of the industry the federal government should take the necessary steps to appoint a Minister of Construction and Housing, as is the case in many other nations.
Setting the record straight
If the general public comprehended the extent of the revenue and resources consumed by buildings and realized the cost and consequences of defective construction, current practices would not be tolerated. If we treated the construction sector in a similar fashion to the automobile industry, we would be forced to recall most of the buildings.
Considering that the construction sector is the nation’s largest industry and largest employer it almost certainly makes more economic and cultural sense to facilitate positive improvements rather than complain about the diminishing quality of our new construction starts after the fact.
Everyone in this industry knows there is nothing fundamentally wrong with glass building designs. But without a renewed emphasis on quality, we run the risk that the general public will lose sight of this fact.
James Lischkoff, P.Eng., is senior vice-president of building science for Exp (the new identity of Trow Associates) He can be reached at email@example.com.
Brian Burton is serving on CSA’s Fenestration Installation Technician Certification Committee. Brian is a research and development specialist for Exp and a regular columnist for Glass Canada magazine. He can be reached at firstname.lastname@example.org or by visiting www.exp.com.
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