The Importance of Cross-ventilation

With air conditioning you can cool your home with a touch of a button. The importance of cross-ventilation in building is often neglected. But this is a mistake. After the orientation of your home in relation to natural light, cross-ventilation should be your most important consideration. Not only does it use fresh air to cool your house, it also prevents mould from growing in it. When done properly cross-ventilation can minimise or even eliminate the need for air-con. And all that fresh air can save you a lot of money.

There are four items you need to address to create a home with effective cross ventilation:

Prevailing Breezes

If you’ve lived in the area where you are building, then you’ll know the prevailing breezes. If you haven’t, ask your new neighbours, or your friendly local architect. Here in Newcastle where I practice, the nor-easter is a beautiful and reliable cooling breeze in summer. A southerly at the end of very hot days can cool your house down very quickly but you need to protect yourself from it in the winter. Remember that breezes can be affected by surrounding buildings and vegetation too.

Window Placement

By understanding the behaviour of the local breezes you get an idea of where windows or other openings should be placed to best advantage. It’s important to note that Cross ventilation isn’t very effective if the windows are more than 12m apart. If a window is behind a door that you will want shut more often than not there won’t be good cross-ventilation, either, without using another strategy to move air from one room to the next.

Window/Opening Type

Openings don’t have to be confined to windows. They might also be doors, louvers or ventilation grills and ducts. Your choice of opening needs to consider the room and how it will be used as well as your privacy and natural lighting requirements. Not all types of opening are equal when it comes to ventilation. Louvers typically offer the greatest ventilation, while awning windows, which open outwards on hinges from the top of the frame, one of the least.

Window/Opening Size

Don’t be stingy. You’ll regret it. The minimum requirements specified in the Building Code are nowhere near enough to provide good cross ventilation for cooling purposes. They are merely aimed at providing enough airflow to make a place habitable. But there’s a flipside to having the biggest possible openings, too. Buildings lose much of their heat in winter through glass surfaces. In summer glass surfaces can also lead to heat gain, so your windows and openings need to have protection from direct sunlight, whether through orientation towards the sun, or by using curtains, awnings and blinds. For a solid in-depth resource on passive design check the Your Home website. If you’re thinking of building, extending or renovating, it’s important to get things right before you build. Good passive design is something you don’t always immediately notice but it’s essential to getting the full enjoyment from your home.