Want to cut your air conditioning and heating costs? Look up, and think green.
A green roof in Montreal dramatically cut air conditioning and heating costs in a 100-year-old duplex in Plateau Mont Royal, a new study has found.
Air conditioning requirements were cut by at least 91 per cent, and the energy needed for heating dropped at least 27.4 per cent, the study found.
Over 10 years, a green roof could save $2,320 to $2,904 in heating and air conditioning costs, it concluded.
"Those are significant savings," said Sébastien Jacquet, who did the study as part of a master's degree at Montreal's École de Technologie Supérieure.
The Montreal Urban Ecology Centre built the green roof in 2005 to compare its performance to a conventional roof, said president Owen Rose.
There were two sections, one with irrigation, one without. Special instruments were installed in the green roof to collect data used in the study.
Rose said green roofs offer many benefits in urban centres, by absorbing storm runoff, filtering air and noise pollution, and reducing heatisland effect, where large concrete or paved areas absorb heat, increasing the temperature in the surrounding area.
The costliest part of the MUEC's $80,000 green roof was building a structure on the 100-year-old building to support the new roof, Rose said.
"In new construction, it costs very, very little to put in place the structure to support a green roof," Rose said. "Once that structural capacity is there, even if you don't have the budget for a green roof right away, you could put one on five, 10 or 15 years later without any trouble."
Because of their many benefits, green roofs are welcome in Montreal, said Alan DeSousa, the city's executive committee member in charge of sustainable development.ÿ
The city of Montreal is harmonizing the building codes of its 19 boroughs, and once it is adopted by city council, city employees will look at implementing sustainable technologies such as green roofs, DeSousa said.
About 100 green roofs are in place or being built in Montreal, Rose said. They include sites at the city's four universities, the Palais des congrès and Jean Talon Market.
Several new municipal buildings, including park chalets, libraries and fire stations, have green roofs.
Rose said people living in existing buildings where the cost of installing a green roof could be prohibitive can take steps to combat heat-island effect by removing concrete, planting vines along building walls, and planting trees, which provide natural air conditioning and beautify the surrounding area.
The study (in French only) is on The Gazette's Green Life blog at www.montrealgazette.com/greenlife
WHAT'S IN A GREEN ROOF;
Green roofs include several layers of material between the building and the vegeatation