Mot-clé : Lifecycle
Thème : Intro
18 February 2011
Par : Saga Cité
In Quebec, residential, commercial and institutional buildings’ operation and maintenance is responsible for a significant share of the GHG emissions: 10.3 billion tons CO2 equivalent in 2007, accounting for 12.5% of overall emissions. 41% of these emissions come from the residential sector, mainly due to the use of fossil fuels for heating. The good news is that those emissions have been steadily declining since 1990, thanks to improvements in buildings’ energy efficiency and the transfer from fossil fuels to cleaner energy sources. Although gains from further improvements in energy efficiency are still possible, we now need to capitalize on the high potential offered by the communities’ development and patterns.
The efficiency of urban form
The current development pattern based mainly on single-family detached houses leads to enormous energy losses, as far as heating is concerned in particular. The type and characteristics of a housing unit can vastly impact its heating energy needs.
Average energy consumption for heating by housing unit category
|Housing unit category||Consumption (kWh/yr)||Floor space (m2)||Consumption by m2 (kWh/yr/m2)|
|Single detached||24 903||138||181|
|Single attached||15 375||113||136|
2008 data collection for Quebec, Office of Energy Efficiency of Canada
In fact, heating a single-family detached house requires on average 2.3 times more energy than an apartment, and 1.6 times more than a single-family attached house. There are two main reasons that explain these variations:
- Size: On average, a single-family detached house is 1.5 times the size of a typical apartment and 1.2 times the size of a single-family attached house.
- Energy efficiency of the housing unit pattern: due to its shape and location, a single-family detached house is more vulnerable to the elements than a single-family attached house or an apartment. Indeed, the latter benefit from the protection and the heat from adjacent units. This explains why a single-family detached house requires 1.5 times more energy than a similarly-sized apartment and 1.3 times more than a single-family attached house.
These differences cause higher GHG emissions for single-family detached houses that rely on fossil fuels for heating (hydro-electricity is very common in Quebec and emits very little GHG). In this case, emissions of a single-detached house are 3.84 tons of CO2 equivalent/unit/yr. This number falls down to 2.87 tons/unit/yr in a single-attached house and an apartment only accounts for 2.45 tons/unit/yr.
Besides, units tend to be underused as they always get bigger while households slowly shrink. This results in unnecessary heating of mostly unoccupied rooms.
Lifecycle, materials and construction
Operations and maintenance are not the only aspects of a building accountable for GHG emissions. Indeed, when we look at the ecological footprint of a building, we must consider its whole liftecycle from design to operation and maintenance, and even the way it might be reused or recycled. Construction of buildings and infrastructure is responsible for about 20% of neighborhood energy consumption and greenhouse gas emissions over a 50-year assumed lifespan. Buildings must be designed in order to capitalize on the characteristics of the site in which they will be set, considering for instance orientation, shade and insulation. This practice is called bioclimatic architecture, and it materializes through passive solar building design. Building materials choices (local when available, non-toxic, easily recyclable…) and construction wastes management must also be addressed. Taken all together these considerations can have an important impact on the GHG emissions of buildings.
Healthier and more comfortable buildings
Energy efficiency and GHG emissions are not the only factors to take into account: greater comfort through better building design, for example, is another benefit. Smartest use of available space, precise temperature control and healthy building materials are only a few of the improvements that fall into designing buildings according to stringent quality standards.
The building sector must take part in the development of sustainable communities. But these issues all have to be addressed in a global perspective. The improvements in energy efficiency have been considerable in the recent years. Even so, building type and location remain essential to an efficient strategy to lower GHG emissions.
-  Ministère du Développement durable, environnement et parcs (Québec), 2010. Québec 2009 inventory of greenhouse gas emissions and evolution since 1990. (in French) ↩
-  Office of Energy Efficiency of Canada, Comprehensive Energy Use Database Tables – Residential Sector, Quebec. ↩
-  Jonathan Norman et al., 2006, in Playbook for green buildings + neighborhoods – Construction impacts. ↩