Thermal Performance

Taking Advantage of Your Garden for Thermal Comfort

If you’ve thought about other ways you can cool down your home, you might have thought about putting your yard to good use. Trees and plants can provide your home with the necessary shade in summer, divert breezes across a greater area span and even help absorb heat from your home. This strategy makes your landscape provide an auxiliary function of keeping your home comfortable (on top of making your neighbours envious).

So how can you influence your surroundings to help your home?

Shading

Shading will help to limit the amount of solar radiation on the home during early morning and late afternoon, when the summer sun is low in the sky. During winter, however, the sun is still needed to increase the heat gain of the dwelling.

Vegetation should therefore ideally be placed on the eastern and western facades, without obstructing winter solar heat gains on the northern facade. On the northern side of the dwelling, preferencing deciduous trees can limit the obstruction of much needed solar heat gain in winter.

Summer and winter solar access and shading (YourHome)

Selecting Plants for Shading

There are many different options for you to choose from. For shading purposes though, you may want to consider the following points when choosing:

  • Picking deciduous plants will let winter sun through and exclude summer sun
  • Trees with higher canopies will help to shade roofs and larger portions of the building
  • Shrubs are suitable if you want to target certain windows for shading
  • Wall vines and ground cover will help to insulate against summer heat and reduce reflected radiation

Breeze Paths

Where space allows it, trees can help to divert breezes towards the building during summer (or deflect it during the winter months). Usually trees and shrubs will be a better option over artificial structures, as they can provide evaporative cooling to passing air and reduce the heat of summer winds.

Plant placement and diverting cool breezes into the dwelling (YourHome)

Getting a good idea of how to take advantage of breezes will most likely mean getting a wind rose for the area. If you’re unfamiliar with wind roses, you can have a look at the Bureau of Meteorology’s helpful explainer on what they are and how to read them.

Evapotranspiration

Evapotranspiration refers to both the evaporation of water droplets from tree and plant-leaf surfaces, as well as the water that has transpired from the leaf pores. In passive design, vegetation on building roofs and walls or screens try to take advantage of this effect to reduce the heat load of the building.

This is more common in Europe and North America than it is in Australia. However, there is increasing interest in bringing the practice here and some jurisdictions have started adding guidelines on how this can be implemented in new designs. You should contact your state or local council to find out if they have resources available.

Further Reading


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