: :  Renewable Energy   : :  Passive Solar Heating and Daylighting

Passive Solar Heating and Daylighting

Passive solar heating and daylighting is a simple and natural way to take advantage of the Sun’s energy.  This is done by designing a building in such a way so as to optimise the natural light and heat received from the Sun.  Most notably, the location and orientation of the building are key in this process.  In the northern hemisphere (assumed throughout this article), the south side of a building receives the most sunlight and therefore large south-facing windows are usually included in the design.  Note that in the southern hemisphere the north face of a building would receive more sunlight,  and near the equator the sun generally tracks an east to west trajectory, hence designs in these locations must be adjusted accordingly.  

As expected, the implementation of a passive solar design is typically most effective when integrated into the initial architecture of new buildings.  This allows for maximum gains by optimising the orientation of the buildings, the materials used for construction, and the size and position of glazed areas.  Design features such as sunspaces and trombe walls naturally incorporate these attributes.  A sunspace (analogous to a greenhouse) positioned on the building’s south side will be heated by direct sunlight and, with the addition of proper ventilation, this heat will circulate throughout the building.  A trombe wall, also positioned on the south side, is a particularly thick wall designed to absorb as much heat as possible during the day and slowly release this heat into the building throughout the night. This trombe wall will typically consist of a highly absorbent material painted black and will often include a glass (or plastic) pane directly in front of the wall to help retain the heat.  By designing windows, openings, and reflective surfaces, daylighting (the natural use of sunlight to light the interior of a building) can easily be achieved; even in north-facing rooms.  For example, the installation of high windows near the peak of the roof, along with open access, will allow light to bounce throughout the building providing pleasant natural light.  The implementation of these designs may add expense but by utilising this free solar energy and incorporating effective insulation and draught-proofing, any increase in the initial construction cost is easily paid back through reduced energy bills and long term savings are inevitable.

Although solar heating and daylighting is generally a desirable effect, it is possible, particularly during the hot summer months,  that too much heating and daylighting can produce an uncomfortable environment. Therefore, design features such as overhangs, fresh-air ventilation, or facilities to close off sunspaces, help to cool passive solar buildings in the summer.