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Passive design: building a green house in Melbourne

A passively designed home does not require any mechanical heating and cooling and takes advantage of natural energy flows to maintain thermal comfort.  

Unfortunately, it is very difficult and expensive in some climates to achieve a completely passive home and in extreme climates there is usually some need for heating, cooling, mechanical ventilation and lighting. 

Nevertheless, applying passive design principles to any home with help reduce greenhouse gas emissions from heating, cool, mechanical ventilation, and lighting.

Basics of passive design: 

 1) Design for your climate.

Depending on your climate, you will employ different principles of passive design.  For example, if you live in tropical climate (hot and humid), you want to focus on keeping on your house cool and don’t have to worry about heating.  

You would have high temperatures all year round with minimum seasonal temperature variation and a very a low diurnal (day/night) temperature range.  

Therefore, you should:

  • Employ lightweight (low mass) construction (will not retain heat)
  • Maximize external wall areas to encourage movement of breezes through the building (ventilation)
  • Site the exposure to breezes and shading all year round (direction of breezes changes for different times of year and from location to location)
  • Shade whole building during summer and winter to reduce solar heat gain
  • Use reflective insulation and vapor barriers
  • Ventilate roof spaces
  • Choose light colored roof and wall materials to reflect a lot of the heat
  • Elevate the building to permit airflow beneath floors
  • Provide screened, shaded outdoor living/sleeping areas

    Whereas, in Melbourne, we have a cool temperate climate with hight diurnal (day/night) temperature range. 

We have four distinct season with hot dry summers and cold winters exceeding human comfort ranges.  

We should:

  • Use passive solar principles which keeps out summer sun and lets in winter sun in. 
  • High thermal mass to remain cool during summer and retain heat during winter. 
  • Insulate thermal mass including slab edges.
  • Maximize north facing wallsa and glazing, especially in living areas with passive solar access.
  • Minimize east, west, and south glazing.
  • Use adjustable shading or properly proportioned shading.
  • Use double glazing.
  • Minimize external wall areas to the east and west.
  • Utilize cross ventilation and night time cooling in winter.
  • Encourage convection ventilation and heat circulation.
  • Site new homes for solar access, exposure to cooling breezes and protection from cold winds.
  • Use reflective insulation to to keep out heat in summer.
  • Use bulk insulation to keep heat in during winter. 

 2) Choosing a site

3) Orientation

4) Passive solar heating

5) Passive cooling

6) Insulation and your building envelope, a term used to describe the roof, wall, windows, floors, and internal walls of a home

7) Thermal mass

8) Glazing (windows)

9) Shading… 

Will write more in the next blog about location and orientation


  • Active solar heating is along the same lines as passive design in that we strive to reduce our greenhouse gas emssions.  In active solar heating applications, heat from the sun is collected, stored and used primarily for domestic hot water heating but also can be used for space heating.
  • The reason that the system is called active is because pumps and fans are used to transfer captured heat to an area where it can be stored or used.