After the record breaking summer we’ve been having in Kelowna, I’ve been thinking a lot about passive cooling. Passive cooling systems use on-site energy, natural resources, and architectural design in order to cool a building through non-mechanical means.
In other words, passive cooling is separate from your regular heating and air conditioning unit. It cools the house without extra electricity use. Some systems, called hybrid cooling systems do use motors, fans and pumps to help the natural cooling along.
One of the reasons I am fascinated with passive cooling from a design aspect is because every house has a different ideal passive cooling program based not only on its location, but also the sun exposure, the wind, even the soil on the lot.
Passive cooling can be divided into two main techniques: preventative and modulation. Preventative, as the name implies, focuses on keeping the house from heating up to begin with, while modulation techniques attempt to dissipate heat that’s already accumulated.
Here in Kelowna, despite the recent heat, keeping warm in the winter is more of a concern than keeping cool in the summer, but that doesn’t mean that passive cooling can’t still be relevant in designing your new home. In fact, some passive cooling techniques, like bulk insulation and high performance windows can do double duty, keeping the house warm in the summer and cool in the winter.
Simple ventilation is the most obvious form of passive cooling. Any home builder can tell you that a well-ventilated house, in winter or summer, is a wonderful thing. Ventilation uses the wind, or the natural buoyancy of hot air to the advantage of the house by moving hot air out and drawing cool air in.
Evaporative cooling, using the process of water evaporation to cool the air in a simple, low power machine that can lower a building’s temperature by nearly 10°C., while radiant cooling uses water or another fluid to absorb heat during the day and dissipate it at night. Radiant cooling systems frequently make use of rooftop ponds the function of which can be reversed in the winter, absorbing heat and drawing it into the building below.
The least practical process, in modern terms, but one of the more interesting in design terms is earth coupling, or using the relative cool of the earth to insulate the building from excess heat or cold. A good example of the simplest earth coupling structures are the dugout shelters that used to cover the Canadian prairies in the 1800s. Being mostly underground, dugout houses were warm in the winter and cool in the summer. Most people wouldn’t want an entirely underground house these days, but there is also indirect earth coupling, which uses underground tunnels to channel air through the earth, where it cools, before being directed back into the house.
These are just some of the ways to build a passively cooled house. Building materials contribute to cooling and heating, as does the basic layout. If you’re interested in passive cooling, give us a call at 250.878.9411 or email me at firstname.lastname@example.org, and we can talk airflow.