Two years ago, respected green architect Sheena Sharp made a presentation at the Buildings Show in Toronto, describing renovations underway on her home. Sharp’s house is unremarkable — a 1920’s semi-detached in mid-town Toronto, similar in appearance and construction to over 70,000 other homes in the city.
However, that was the point of Sharp’s presentation — the existing inventory of urban housing should be renovated, not demolished. Sharp’s house was proof. By insulating and renovating to Passive House standards instead of demolishing and rebuilding, she was on track to achieving a Net Zero Carbon result.
Sharp explained that the carbon created when the house was originally built was, in fact, “embodied” in the existing structure. Careful material selection and the building’s projected low-carbon post-renovation performance would offset any new carbon created during the renovation process.
Talk of Net Zero Carbon seemed almost radical at the time. However, public understanding of carbon, the best known of the various GHGs, has changed over the past two years. Today, the concept of retaining the carbon embodied in existing structures, rather than creating new carbon through demolition and reconstruction, is being embraced in projects well beyond the scale of Sharp’s modest home.
This is particularly true in large urban areas of Canada, home to hundreds of high-rise buildings built 50 years ago or more. Many are no longer energy-efficient by today’s standards. In some cases, the interior environments are becoming a health hazard for occupants. In other words, these buildings are failing.
“Deep Energy Retrofits”, as they are sometimes referred to, are finding traction in these large-scale situations, with leadership coming from municipal governments such as the City of Toronto. Under the City’s Green Will Initiative, over 300 million square feet of existing building space will be targeted for energy efficiency and interior air quality improvements, and carbon footprint reductions.
One notable example already underway is the Ken Soble Tower just down the road from Toronto. This 146-unit, 18-storey affordable seniors’ residence, built in the 1960’s and owned by the City of Hamilton, will undergo one of the largest EnerPhit/Passive House retrofits in the world. Using climate predictions for the year 2050, performance modelling for the renovated structure anticipates an operational GHG reduction of 94 per cent. Furthermore, by renovating rather than tearing down and rebuilding, an estimated 6,000 tonnes of carbon created in the ‘60’s will remain embodied in the original structure. That’s more attractive than sending thousands of tons of carbon into the atmosphere through new construction.
Projects like the Ken Soble Tower, an older building being saved instead of being replaced, is drawing attention to claims being made by some environmentalists. New construction, even when built to the highest standards of energy efficiency, is counterproductive, they say. No building can hope to save enough operational GHGs during its expected lifespan to overcome the high GHG price tag of the building process itself.
That argument, however, opens the discussion concerning building lifespan expectations. “In North America, people consider buildings in terms of a 30 or 40 year life span,” says Deborah Byrne, COO of Toronto architecture firm Kearns Mancini. “Why is it only 40 years? Why not longer? Why is it that I can walk into a 400-year old wood building in Europe and it’s totally structurally safe?” Byrne believes today’s disposable culture has contributed to these short lifespan outlooks. Short lifespan expectations can also distort the calculations related to a building’s projected GHG emissions savings over time. In other words, buildings need to be built better.
Are deep energy retrofits of older buildings the answer to construction’s GHG dilemma?
“I don’t think there’s one answer for every building,” says Byrne, citing structural variances that can occur. “And if you’re looking from the viewpoint that the lifespan of a building is only 30 or 40 years, it’s not going to work. Of course, if we do nothing, that’s not the answer, either.”
John Bleasby is a Coldwater, Ont. based freelance writer. Send comments and Inside Innovation column ideas to firstname.lastname@example.org.