Sustainability Unit

Energy efficient house design for the tropics

Naturally comfortable houses are low energy houses !

• Ceiling fans provide low energy cooling if you only use them whilst rooms are occupied
• Light coloured roofs (or zinc alum) reflect the heat
• Use orientation and shading to eliminate direct sun on walls:
  • Orient house from east to west (within 20 degrees)
• Minimise east and west wall areas and avoid windows on east and western walls to prevent low morning and afternoon sun heating up the house
• Correctly sized eaves can provide permanent shade to north and south windows and walls (northern verandas make sense)
• Plant tall trees on the east and west sides of the house to shade walls
• Tall trees on north and south shade roof (minimise mid-height foliage to let breeze through for naturally ventilated houses). Consider leaving half roof unshaded if solar panels are to be used

Design for natural ventilation

• Use the breeze for cross ventilation through openings in opposite walls and internal partitions 
• Maximise the area of windows (e.g. louvres) that can be opened
• Orientate house to catch the breeze (whilst still minimising sun on east and west walls)
• A long narrow floor plan catches the breeze best.
• Trees and shrubs act to cool the air passing through the house.
• Don't use exposed concrete on ground immediately outside the house as it heats the air.
• Roof space ventilation draws the heat out.
• Dirty flyscreens block more breeze. Consider using openable flyscreen shutters.

Minimum insulation standard:

• Light coloured well ventilated roofs: foil/sisalation
• Other roofs: R1.5 batts and foil/sisalation
• Full shading of wall is much more important than wall R-value. Unshaded, masonry walls store heat and release it well into the night.
• Shelter windows with louvres, canopies, shutters or fixed overhangs - then you can enjoy the cooling effect of rain.

View wall R-value comparison table

NOTE:  House designs depending on full air-conditioning for comfort are not very suitable for our tropical climate nor environmentally sensitive.  Energy costs will be high when air-conditioning is running and comfort levels will be low when air conditioning is switched off.  Occupants can have difficulty acclimatising to outside temperatures.

Design for Air-Conditioning

The better your house seals and is insulated, and the less glass area, the less energy air-conditioning will use. 

Keep the heat and moisture out and the cool in!

• Shade walls and choose the highest wall R-value possible

View wall R-value comparison table

Windows

• Medium sized with the greatest possible openable area per window, and placed for cross ventilation, so you don't have to air-condition all the time.
• Heavy snug fitting curtains and pelmets prevent cooling energy loss from radiation and air flow against glass.

A square floor plan minimises external wall area and therefore reduces cooling energy loss through walls.

Exposed heavy construction materials (e.g. concrete and bricks) inside insulation barrier store cooling energy.

Combined air-conditioning and naturally ventilated houses

Many houses in tropical regions have some air conditioned spaces and some naturally ventilated spaces or the same spaces are naturally ventilated and air-conditioned at different times.

Design of each area should follow principles for natural ventilation or air-conditioning as relevant.

Walls separating naturally ventilated and cooled spaces should be insulated and have doors to limit loss of cooled air.

Note: In January 2003 Minimum Energy Performance Requirements were introduced into the Building Code of Australia. These requirements are a minimum, meeting them is not the same as adopting best practice energy efficient design.