Design, technology make for a cooler home
|Homes at Langford's Westhills development get the Power Smart Homes stamp of approval. A District Energy Sharing System provides cooling, heating and hot water through geo-exchange.|
Siting, insulation, windows and air flow all help keep a home cooler
There are a lot of things you can do to keep cool in the home you already have, including the tips listed in this home cooling piece on bchydro.com. But what about the home you might consider renting or buying in the future?
As building technology places an increasing focus on energy efficiency, there new ways to keep cool. Doug Overholt, representative for the Power Smart New Home program, offers some comments.
"We've come to expect levels of comfort that may really be overkill," says Overholt. "If we use simpler strategies, such as proper insulation, overhangs to shield the hot sun, and proper siting and air flow, we can achieve good effects much more efficiently.
"Buyers demand certain appliances and colours of granite countertop all the time, and they're nice to have. But if you demand efficient design and technologies from your builder, you're not only going to be more comfortable, you're going to save money in the long run."
Siting: Where a house is built
As green building awareness grows, so has a practice called "passive design", reducing a home's need for mechanical heating and cooling by situating it so that it makes the most of solar heat in the winter, and is protected in the summer.
"What you want is an attractive design that will still keep the sun out of the rooms from 11 a.m. to 4 p.m. in summertime," says Overholt.
You may not have the luxury of building a home from scratch, but if you're buying, consider whether your prospective home will be comfortable and efficient as the seasons change. A few things to consider:
- Will you be over-exposed to glaring sun during the hottest time of the year?
- Does the living area have windows placed so you can catch natural cross-breezes?
- Do you have options for planting greenery that will help provide strategic shading?
Starting with a home that's naturally situated for comfort will help you keep energy bills lower in the long run.
Insulation: It's not just about heat
As Canadians, we tend to think of insulation as the stuff that keeps us warm during long chilly winters. But it's also a critical element in staying cool.
"Insulation inhibits the transfer of radiant heat from the sun," says Overholt. "If you have proper insulation in your attic, you don't really need that much cooling. Plus, when it's coupled with appropriate attic ventilation, it helps protect your roof shingles so they don't become brittle as quickly."
If you're buying a new home, the BC Building Code requires appropriate levels of insulation. But if you have an older home — especially one where the upstairs becomes uncomfortably hot in summer — add insulation to improve your comfort in summer (and save money in winter too).
Windows: Overhangs, low-e and more
Windows are a home's eyes on the world, and the way we get natural light indoors. But without some planning, they can also quickly over-heat your home (and drain it of warmth in winter).
"You can have big south-facing windows; you just need proper overhangs," says Overholt. "In the summer, overhangs provide shade during the critical high-sun times of the day. In winter, because of the declination [angle] of the sun, the light comes under the overhangs and helps warm your home."
The choice of window makes a difference too. If you're building, buying, or renovating, ask about ENERGY STAR® windows and check our windows offers page for ways to save with B.C. manufacturers and retailers.
A feature called the "solar heat gain co-efficient" on the label of new windows tells you how much it will absorb heat from sunlight (the co-efficient ranges from 0 to 1; the lower, the better). New windows are coated with a microscopically thin layer that helps reduce heat flow through the glass — these are called "low-e" coatings (for low-emittance).
"There's also a product called laminated glass, a plastic sheet coating between two layers of glass," says Overholt. "If it's coupled with low-e, it gets rid of 99 percent of UV rays, which reduces heat and protects your furniture and drapes from fading. It also provides a security feature, since it's very hard to break."
Take note: If you're adding low-e film to existing windows, Overholt suggests you check claims carefully, as product performances vary.
Of course, one of the easiest ways to reduce solar gain through your windows is to use blinds or curtains. But Overholt argues that built-in overhangs for shading, and getting the right window in the first place make more sense.
"People pay thousands of dollars for a view," he says. "You don't want to have to block it out during the best part of the day."
If you're considering renting or buying in a high-rise with a great view — check the windows and make sure you'll be able to enjoy it.
Air flow: Keep it moving
"You don't need a system to bring in cool air if you circulate the air in your home," says Overholt. "Typically, any air movement will be experienced by the body as cooling."
If you have a forced air heating system in your home (or are installing a new one), look into adding a high efficiency variable speed motor [PDF, 100 KB] — this is often an upgrade feature offered on a furnace. While a typical furnace fan can only reduce its speed to move 800 cfm (cubic feet per minute) of air, a variable speed motor can efficiently operate as low as 200 cfm.
"It's called a 'ventilating rate' rather than a 'heating rate,'" says Overholt. "It allows you to circulate air through your home at low speed so it doesn't feel like a draft, but it does it at the same efficiency so you're not incurring a huge electricity cost to circulate the air."
Another piece of technology often used in new energy efficient homes is the heat recovery ventilator (HRV), which conserves energy by pre-heating air coming into the home using the warm air that is being vented out.
"We normally associate HRVs with heating, but a fully ducted HRV — with separate ducts going to the bedrooms and living area — can provide a fresh distribution of air and a cooling effect," says Overholt.
Heat pumps: Geothermal is most efficient
Homes with geothermal heating systems draw warmth from deep in the ground during winter. In summer, they can operate in reverse, extracting heat from your home and transferring it back to the ground.
Because the heating and cooling is provided by the actual temperature of the earth, geothermal is a very efficient way to heat and cool.
Air source heat pumps also use a similar transfer technology but take advantage of the difference in outside and indoor air temperatures.
However, Overholt recommends some caution around the claims often made about heat pumps. Both systems use a mechanism similar to that in a refrigerator system to transfer heat into or out of a home.
"Especially for new construction, we're seeing the argument that 'you get the cooling for free,'" says Overholt. "But really you don't, because you're still having to pay for the electricity required for heat pump compressors and pumps. Every time you run your heat pump to cool your home, it's like having a second refrigerator running, albeit an efficient one."
How much cool do you need?
If you live in B.C.'s interior region, home cooling may be a necessity. But if you're not in the sun-parched interior, think hard about whether you really need to spend extra energy on cooling.
Overholt says based on a standardized comfortable indoor temperature, in the Lower Mainland we experience 3,300-3,500 " degree days" of heating in a year. [Degree days are calculated by how extreme the heating or cooling needs are, over how much time.] By contrast, we experience about 44 "degree days" of cooling. Sure, it gets hot — but maybe a floor fan and a tall cool drink will get you through.
Building a new home? Learn about incentives for energy efficiency provided by the Power Smart New Home Program.