We all eagerly await the arrival of summer. But once the sun really starts beating down, depending on where we are, the heat can quickly become overwhelming.
While the temperature increase can always be managed with air-conditioning or ventilation systems, it can be far less expensive to go straight to the source of the problem—and there are a variety of effective methods for doing just that.
Hot spots and risk factors
The hottest days of summer lead to increased risk of overwhelming heat:
- in dwellings with insufficient or no insulation (in the roof or attic as well as the exterior walls);
- inside homes with abundant south- and west-facing windows.
“In June in Montreal, the average south-facing window will take in more than 7.5 kWh of energy in a day—roughly equivalent to a 700-watt baseboard heater running at full strength for 12 hours (the daily sunlight time during that month).”1
Like unshielded glass, solid surfaces such as concrete, brick and asphalt can cause overheating as well: they store heat during the day and then slowly release it, long after the sun has set.
Take action, sure, but how?
Blocking sources of sunlight shining through glass surfaces—in doors, windows, or skylights—is an effective way of correcting the situation. There are two specific methods:
- Blocking from the inside, using blinds or curtains;
- Blocking from the outside, by means of shutters, sun-shading screens, awnings or trees on the south side of the house (hardwoods are the best type of tree, offering beneficial shade in the summer months but letting the warming sun’s rays through in winter).
Protection from the inside
Indoor shading systems are useful, but they allow heat into the house: sunlight gets through the glass and strikes the shade surface. The most common types of indoor shading accessories are:
- Adjustable slat blinds, either horizontal (Venetian) or vertical, made of wood, fabric, aluminum or PVC;
- Roll shutters made of the least translucent material possible;
- opaque fabric curtains; and
- Louvered blinds, most often wooden, installed on the inside of windows.
In hot weather, these systems must, ideally, be in place before direct sunlight begins. The problem is, they block the view and a welcome source of natural light for the house’s occupants.
Blocking from outside
There are various types of exterior shading systems, including window-glass coatings, awnings and exterior shutters.
Most windows, door windows, solariums, etc. on the market now feature low-emissivity (low-E) coatings. This double glazing comprises a thin, invisible metal oxide film on the outer surface of the innermost glass pane.
In summer, the coating blocks part of the sun’s radiation, while in winter, it retains some heat, which would otherwise escape from the home through conduction.
If your windows don’t have the coating, you can apply window film to existing glass. It will reject ultraviolet radiation as well some infrared radiation—i.e., heat.
Another solution is to install awnings, either retractable or stationary, to shade your home’s doors and windows (especially those facing south and west).
According to a study by the Canadian Centre for Housing TechnologyPDF file, retractable canvas awnings are an excellent—if not the best—method of lowering air-conditioning costs in summer.² These adjustable awnings allow maximum solar gain during the cold season (keeping the heating bill down), while reducing the risk of overheating in summer. Tests showed that residents who install awnings on south-facing windows can expect cooler temperatures (both in the rooms with awning shade and those without it). As a result, their cooling bills are lower.
Stationary awnings made of fabric, aluminum or corrugated polycarbonate are less versatile, but still provide a significant shading effect on very sunny days.
There’s another big advantage of awnings, whether retractable or stationary: these decorative elements don’t block the view to the outside. At worst, they slightly reduce the level of natural light inside.
Before you buy, check the product’s build quality: its design, framework and shading material. Awnings must also be properly installed, solidly fixed to the building so as to be highly wind-resistant (you want an awning to stay attached to your house, not wind up in a neighbour’s yard!). If the awning is a stationary model, it must also be sufficiently well built to withstand snow accumulation.
Shutters are most often of the hinged type, with slats. Until the mid–20th century, wooden doors and hung windows very often included shutters. Nowadays, installing them isn’t as easy: a casement window that swings outward, for example, won’t allow it.
There are other types of shutters: retractable, folding, sliding… Retractable shutters, for example, are common in Europe but rarely seen in Quebec. Also known as roll shutters, rolling shutters or roll-up shutters, they consist of interlocking slats with a polyurethane foam core that, once lowered, form a screen in front of a door or window.
The disadvantages of roll shutters are that they attenuate natural light and hinder the view outside. However, they result in substantial savings on heating costs in winter when rolled down at night, and in summer, they guard against overheating during the day. A study by the National Research Council of Canada has shown that even if they are closed only halfway, roll shutters can lower air-conditioning requirements by two-thirds during the three hottest weeks of summer.
NB : pas de lien/référence pour cette étude, alors que vous en avez pour les deux autres citées ?
To sum up, there are plenty of ways to keep your house from overheating. The key is to determine your needs, if applicable, and then choose the solution or solutions best suited to those needs, and your budget.
1 Écohabitation, Contre le chaud et le froid : les volets roulants, une solution pour le Québec
2 Canada Mortgage and Housing Corporation, Summer Shading Performance of AwningsPDF file (study by the Canadian Centre for Housing Technology)