Lawrence Solomon
National Post
April 17, 2009

To some, green roofs are wonderful. They absorb rainwater, reducing strain on sewer systems. They insulate buildings from the cold in winter and the heat in summer, and from noise all year long. They provide greenery that building occupants and building neighbours can sometimes view. Some green roofs even provide food.

To others, green roofs are terrible. They add to the capital costs of buildings. They need continual maintenance. They add to the insurance and warranty costs that building owners face. They may even harm the environment.

In the fantasy world of urban planners, green roofs that meet city cost-benefit tests always make economic sense. These tests assign dollar values to mostly intangible benefits such as improved aesthetics and a reduction in noise (at 1.3% of a building’s value for each of the four decibels of sound avoided, for example, one group of planners estimated a mammoth $100-per-square-foot benefit for New York properties).

Planners then subtract the tangible costs of green roofs, such as the extra expense of constructing what is, in effect, a very heavy second roof suspended above the real roof, and ignore the intangible environmental costs associated with this second roof: the additional noise during construction, the additional emissions associated with the extra steel and concrete required in construction. Because the mostly intangible benefits exceed the tangible costs, the planners endorse green roofs.

In the real world of property owners, green roofs suit a determined minority and – given the state of the art – repel the wary majority. Green roofs not only cost a fortune to build, they must be continually planted and weeded – not always easy or convenient given the need to bring men and material to a level above the real roof. Green roofs must be watched over vigilantly to make sure the drainage system that suspends tons of water-soaked soil inches above the real roof doesn’t threaten the occupants below. Weighed against such costs and risks, the benefits of aesthetics and better insulation are too meagre for most.

Toronto doesn’t inhabit the real world. Its lawmakers, impressed by fantasy cost-benefit calculations, are about to make mandatory the installation of green roofs in new construction of large condominium and commercial buildings. The upshot: More expensive housing and higher maintenance fees for Toronto residents, more expensive occupancy costs for businesses, more of the middle class and more businesses leaving an ever-less affordable Toronto, less tax revenue to support city services, more suburban sprawl.

One other upshot: a vulnerable building stock. Green roofs are a largely untried technology about to be introduced for the first time on a large scale in Toronto’s winter environment. If a common problem emerges in future, the city would have victimized thousands, perhaps tens of thousands, of hapless condominium owners.

This eventuality – too remote to even cross the minds of Toronto’s political establishment – is top of mind in British Columbia, which is still seared by the experience of its “Leaky Condo” scandal of the 1990s. In the booming housing market of the 1970s and 1980s, B.C. developers aggressively built California-style condo units, often relying on construction techniques suitable to California’s much dryer climate. Then the B.C. government, to promote energy conservation, required buildings to be airtight, inadvertently dooming much of the B.C. housing stock: Buildings – built in B.C.’s wet environment by developers who didn’t anticipate the new government standards – rotted en masse.

The cost of this unanticipated vulnerability in the B.C. housing stock? Between $1.5-billion and $2-billion to B.C. society, including hundreds of millions of dollars in destroyed property values for some 72,000 households. The citizenry still suffers from the anguish of seeing their homes destroyed.

Because of B.C.’s experience with this systemic failure, the province balked at the Brave New World of green roofs: Its Homeowner Protection Office stepped in to stop local municipalities that were planning to mandate green roof programs, especially after it discovered that three of the province’s four home warranty insurance providers wanted no part of the green roofs and that the fourth would only countenance green roofs “under very special circumstances – the right project, the right site, the right designer, the right installer and plenty of financial security for the insurer.”

While a Homeowner Protection Office study acknowledged that, in theory, “it is technically feasible to design, install and maintain a green roof such that it performs as well as a conventional roof or better,” it also balanced the theory with real-world practice: “The issues surrounding green roofs centre on the cost benefit of green roofs, the probability that such roofs will be designed, installed and maintained properly and the risks that may arise if they are not.”

Its bottom line: Experience in Germany and other countries shows that the learning process for green roofs can take time and that “an evolutionary approach that allows costs, benefits and risks to be assessed in each case is preferable to more directive, mandatory approaches.”

Toronto and other governments can best help their citizens, and best promote the healthy development of green roofs, by scrapping mandatory requirement for green roofs and also scrapping the many regulations that discourage green roofs, including myriad building code requirements and zoning that prevent unencumbered use of roofs for food production. Green roofs will then get built when people, not planners, judge them to be of benefit, and without systemic risk to society.

Lawrence Solomon is executive director of Energy Probe and Urban Renaissance Institute, and author of The Deniers: The world-renowned scientists who stood up against global warming hysteria, political persecution, and fraud.