Solar shading

Many cultures have learnt how to avoid this undesirable heating by shading the sunny side of the building during the summer. Suitable shading can provide good indoor climate control thereby avoiding air conditioning during the summer whilst helping with heating during the winter. To design good shading, it is necessary to know how the solar radiation reaching the building throughout the day during the different seasons.

Shading can be accomplished by many different means, depending on the location, the type and geometry of the building and the preferences of the designer. The basic principle is to place the shading so as to reduce the solar radiation during summer and to facilitate the solar gain during the winter.

The following are the most common options.

• deciduous trees – leaves provide shade during the summer but fall down in the autumn
• shutters which are preferably mounted outside the window; these can have the sunlight falling on the window during the summer during the night in winter
• blinds – comprise slats which can be inclined to control light (and heat): may be mounted either horizontally (Venetian blinds) or vertically
• external horizontal surface – mounted above the window to cut off direct solar rays when the sun is high in the sky (summer, middle of the day); however, when the sun is low in the sky (winter and early morning and late evening during the summer) the rays can fall upon the window and enter the room
• awning – an external blind that can be extended or retracted depending upon the strength of the sunlight during the summer
• solar panels, flat or tubular, can be used to shade facades or terraces

Examples of solar shading are illustrated.

Solar heating

The basic characteristics of heat can be utilised to provide solar heating during the winter. The simplest method is by absorption of solar rays by an external, south-facing wall which enables heat to be conducted through to the inner wall of the dwelling. To be most effective, walls should not be shaded by trees or lie in the shadow of adjacent buildings for any length of time.

Transmission of light through windows allows infra-red rays to heat the air in the room by convection. If the external window pane is coated with a suitable reflective layer on the inside, then the infra-red rays are reflected back into the room so retaining the heat.

The larger the thermal inertia of a building, the more heat can be stored during the daytime thus reducing the need for heating during the night.