Solar Loads

Robust design advice on how to manage solar loads in all parts of your building, throughout the changing seasons.

In the built environment, thermal loads are caused by heat transferred from the sun through the building envelope, and by heat from the earth. Any surface that separate the building inside from the outside environment is defined as the building envelope and includes walls, roofs, floors, and windows. Material choices, envelope design, and orientation dramatically affect the amount of solar radiation that enters the building envelope.

Some common ways that heat flows into or out of a building are:

• Via the floor, through the ground.
• Solar radiation entering through windows and heating interior surfaces.
• Solar radiation warming up exterior building surfaces.
• Air leaks via cracks and openings.
• Outside air being introduced to the building to provide fresh air and ventilation.

The degree to which each of these impact the building loads and the occupant comfort depends on the temperature and humidity.

Understanding where heat energy is gained and lost in your design is an important first step towards successful passive design strategies. Solar loads can have huge benefits in terms of building comfort and energy requirements, but need to be controlled. For instance, when it’s hot and sunny, it is usually necessary to reduce solar radiation entering the building using external shading and windows with low solar heat gain. On the other hand, in the winter, it’s often desirable to capture this free solar energy in some way as it helps to heat up the building and reduce artificial heating energy requirements.