Passive solar heating can even out day and night temperature variations

Passive Solar Heating & Cooling

Design for Seasons are specialists in Passive Solar Heating & Cooling designs, building energy efficient sustainable homes.
On average 39% of energy consumed in Australian homes is for space heating and cooling. Passive heating and cooling home design can reduce this burden.

Passive Heating

Passive solar heating is basically allowing the winter sun into the building and trapping that thermal energy within the fabric of the building.

Careful consideration should be given to the following:

  • Northerly orientation of daytime living areas.
  • Appropriate areas of glass on the northern facades.
  • Shading of glass.
  • Thermal mass for storing heat.
  • Insulation and draught sealing.
  • Floor plan zoning based on heating needs.
  • High performance glazing where required.

Passive solar heating works by trapping solar radiation by the greenhouse action of correctly oriented windows exposed to full sun.

Trapped heat is absorbed and stored by materials with high thermal mass, such as bricks, concrete, rammed earth, and stone inside the house. It is re-released at night when it is needed to offset heat losses to lower outdoor temperatures. It effectively evens out day and night temperature variations.

Thermal mass should be located predominantly in the northern half of the house where it will absorb most passive solar heat. You could consider the use of low thermal mass materials such as timber frame construction and high levels of insulation in south facing rooms.

Daytime living areas should face north. Ideal orientation is true north and can be extended to between 15° west and 20° east of north.

Bedrooms require less heating and can be located on the southern side of the house, but this can vary depending on preferences for northern or early morning eastern sun.

Bathrooms, laundries and garages again require less heating and can be located to the west or south west to act as a buffer to hot afternoon sun and cold rain bearing winds, or to the east and south east.

Compact floor plans minimize external wall and roof area, thereby minimizing heat loss.

A balance should be achieved between minimizing heat loss and adequate day lighting and ventilation.

To assist with the distribution of heat you could consider heat shifters. This is a simple fan and ducting system, costing little to run and install, which moves air from warm areas to cooler areas.

Heat shifters can also redistribute warm air that collects at the ceiling back down to floor level.

Passive Cooling

Passive cooling your home will save on energy bills, reduce your impact on the environment, and make your home more comfortable. This is achieved through good passive cooling design.

Pergola with Angled Louvres

The main elements of design for passive cooling are:

  • Reducing heat gain through correct orientation, glass area and insulation.
  • Effective shading.
  • Maximising air movement.
  • Capturing cooling breezes.
  • Nighttime cooling
  • High thermal mass construction
  • Use of light coloured roofs and walls to reflect solar radiation

Cooling breezes are often in the form of nighttime cool air currents in late evening and early morning. These breezes should be directed into the house at night to cool the interior and high thermal mass construction. High thermal mass can be concrete floors and masonry or rammed earth walls.

The thermal mass is cooled down and will remain cool throughout the following day.

A whole house fan located centrally in the building is an effective means of assisting the movement of cool air into the interior. Ceiling fans are another simple low cost way of creating air movement.

An appropriate depth of eaves overhang is the most effective way to shade windows and walls.

Trees and high bushes offer an effective form of sun protection on west and east walls.

Pergolas can provide shade to windows and outdoor living areas. Vines, closely spaced slats or angled louvres are examples of coverings for pergolas. The angled louvres are most effective facing north where the high angle summer sun is stopped but the low angle winter sun penetrates through into the living areas.

The roof receives the most amount of direct sunshine. As a result heat becomes trapped in the roof space and will pass through the ceiling and into the rooms below. A light coloured roof to reflect unwanted heat, and appropriate levels of insulation will dramatically reduce heat penetration into the rooms.

If mechanical cooling is required then evaporative coolers should be considered as a first choice.

Evaporative coolers can save 50% of the initial cost and up to 80% of the operating costs of refrigerated air-conditioning