Sustainability 101: Natural Ventilation

Written by: Steve Socha

Welcome to the Sustainability 101 educational blog series! In our blog today, we will be focusing on natural ventilation.

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The use of natural ventilation is an advantage regarding the cost and environmental impact on energy use. Not only does natural ventilation provide air circulation to ensure healthy and comfortable conditions for building occupants, it also provides free cooling without the use of mechanical systems and hence, energy consumption. Natural cross-ventilation reduces energy-consumption for mechanical cooling during summer months. Buildings are ideally designed to encourage natural cross-ventilation through their relationship with breeze patterns and ability to capture prevailing winds.

The siting and wind direction of a building play an important role in ventilation. Careful consideration of a building site will provide opportunities for maximizing the level of natural ventilation that can be achieved. With that being said, buildings and their openings should be positioned to take advantage of prevailing winds and the directions of natural breezes. 

A wind rose is a graphic that shows how wind speed and direction are typically distributed at a particular geographic location. From the Toronto wind rose below, we can see that the strongest wind comes from the northwest direction. Each geographic location has its own wind rose and careful consideration of this will help to orient new buildings and their window placement.

Operable windows should be placed to take advantage of natural breezes. Placing them on opposite sides of the building promotes horizontal cross ventilation. Placing operable windows both high and low will cause vertical ventilation, known as stack effect.

During the heating season, the warmer indoor air rises up through the building and escapes at the top either through operable windows, or other openings. The rising warm air reduces the pressure in the base of the building, drawing cold air in through either open doors, windows, or other openings. During the cooling season, the stack effect is reversed.

Indoor Air Quality (IAQ) refers to the concentration of contaminants in the air as they affect occupant health and comfort. Superior Indoor Air Quality is achieved with healthy material selection and an optimum ventilation strategy, ensuring a healthy and a comfortable environment.

This concludes the Sustainability 101 blog series!

*The Sustainability 101 lecture series is made as a supplemental learning initiative for high school students across Ontario