Sustainability 101: Passive Solar
Written by: Steve Socha
Welcome back to the Sustainability 101 educational blog series! Our blog for this month will focus on passive solar design.
Passive Solar design refers to the use of the sun’s energy for the heating and cooling of living spaces. In this approach, the building itself, or some element of it, takes advantage of heat energy from the sun. This makes use of the massive amount of energy that nature gives us for free and will evidently result in more savings and reduced need to impact the environment through construction and/or usage.
Passive systems are simple, have few moving parts, and require minimal maintenance. They don’t rely on mechanical systems, which require maintenance, and replacement.
Some examples of passive solar strategies are:
1) Windows placed for optimal heat gain in the cold Canadian winters, shading devices and solar chimneys to shield from the hot summer sun, and thermal mass for both seasons. These are all common elements found in Passive Solar design.
2) Shading devices and solar chimneys create or reinforce the effect of hot air rising to cause air movement for cooling purposes. The resulting suction created by a difference in pressure, pulls cooler air into the building from lower, shaded spaces. This is known as stack effect.
Daylighting involves placing windows and openings so that during the day, the sun provides natural and effective indoor lighting, this means a reduction in the need to turn on the lights. Particular attention is given to daylighting while designing a building to maximize visual comfort and to reduce energy use.
Properly sized and positioned window shading will allow for maximum solar heat gain in the winter, while limiting unwanted solar heat gain during the summer. A correctly sized overhang or shading device will completely shade a window at solar noon on June 21st, this is the date of the summer solstice.
A light shelf is a horizontal surface that reflects daylight deep into a building. They can also serve dual-purpose by acting as internal shading devices. Light shelves are placed above eye-level and have high-reflectance upper surfaces, which reflect daylight onto the ceiling and deeper into the space.
Sun angles are used to calculate the optimal size of a shading device, depending on the building’s geographic location. The sun follows a predictable path, depending on the geographic location that you are in. This information is readily available through charts, and in many 3D modelling programs.
The consideration for window sizes are impacted by the direction they face. Windows that face east or west will require larger overhangs, or vertically-mounted shading devices. Shading windows from the summer sun will help to maintain comfortable conditions inside a building and will mean less dependency on air conditioning to cool the interior spaces.
3) Thermal Mass is the ability of a material to absorb, store, and release heat when there is a change in temperature. Thermally-massive building materials such as concrete, stone, and tile, have a high capacity to absorb and store excess heat, often provided from the sun throughout the day, which is then released into the space when the ambient temperature falls below that of the thermal mass.
Materials with high thermal mass passively reduce indoor temperature fluctuations without the consumption of energy. It is these kinds of sustainability methods that we prefer!
Stay tuned for our next blog in the Sustainability 101 series!
*The Sustainability 101 lecture series is made as a supplemental learning initiative for high school students across Ontario
