Shading technology

Figure 1. An example of a roof overhang, one type of shading technology.[1]

Shading technology is a broad term that describes additions to a building that prevent over-heating or cooling of the space. These additions include, awnings, blinds, deciduous trees, and roof overhangs.[2] Shading is an old, but still underutilized, form of passive solar heating and cooling. Compared to other methods, these design features are generally simple to implement and fairly inexpensive. As well, the use of shading technology is beneficial as it can help reduce the costs related to heating and cooling of a space, and thus these technologies are considered a part of energy efficient building design.

Types of Shading Technologies

As mentioned above, there are several different types of technologies that use shade to manage the temperature inside buildings. Some of the major types are explained below.

Roof Overhangs

Roof overhangs are simply portions of a roof that extend out beyond the wall of a home.[3] These are designed with a specific length so that during the summer the overhang blocks the higher Sun from hitting a portion of the roof during the day. In the winter, the Sun is lower and more of its light is let through to warm the house.

Figure 2. Diagram showing how a roof overhang works in the summer, on the left hand side, versus the winter on the right hand side.[4]

The height of the Sun in the summer and winter varies with elevation, but this method can be used to warm and cool houses many places around the world.

Figure 2 shows both the summer and winter sun. The overhang is long enough to shade the Sun during summer but short enough to allow sunlight in during winter. This keeps sunlight out during summer, keeping the internal living space cool. The opposite is true in the other half of the year. The overhang allows solar radiation to enter the building, warming up the internal living space.

Deciduous Trees

Planting deciduous trees in front of windows that receive a large amount of solar radiation can help to moderate the temperature inside the home.[3] In the summer months when the tree has its leaves, the amount of solar radiation into the home is limited. Conversely, in the winter when the tree loses its leaves more Sun is allowed in and the home is warmed.

Figure 3. An example of shading using a deciduous tree[4]

Figure 3 shows both the summer and winter sun. During summer, shown on the left, the leafy tree prevent excessive amounts of solar radiation from entering the building, keeping the internal living space cool. The opposite is true in the other half of the image during winter. A bare tree allows adequate amounts of solar radiation to enter the building, warming up the internal living space.

Internal Filtering

Finally, objects inside the home can be used to shade how much solar radiation is allowed to enter the home. Objects inside a room can block or filter sunlight - especially water elements such as fish tanks. When incident sunlight hits the fish tank the water absorbs some of the heat and works to keep the room inside cool. As well, the use of curtains and blinds can prevent some solar radiation from heating up the room, however external shading works slightly better in this case.[3]

References

  1. Wikimedia Commons. (October 17, 2015). Eaves Lining [Online]. Available: https://upload.wikimedia.org/wikipedia/en/a/af/Eaves-lining.jpg
  2. W. Feist. (October 17, 2015). First Steps: What Can be a Passive House in Your Region with Your Climate? [Online]. Available: http://passive.bg/files/files/83dede941ff2a5e60dd8e0d1cbfc24acFirstStep.pdf
  3. 3.0 3.1 3.2 Architecture . (October 17, 2015). Passive Solar Heating and Cooling [Online]. Available: http://architecturerevived.blogspot.ca/2013/10/designing-passive-solar-heating-and.html
  4. 4.0 4.1 Australian Government. (October 17, 2015). Shading [Online]. Available: http://www.yourhome.gov.au/passive-design/shadinghttp://www.yourhome.gov.au/passive-design/shading