Passive Design
Designing the building and the spaces within it to benefit from natural light, ventilation and even temperatures.
Controlling Temperature
The World Health Organisation recommends 16°C as the minimum room air temperature for habitable spaces.
Most people are comfortable with temperatures in a range of 18°C and 24°C, though this can depend on humidity, amount of air movement (draughts), what occupants are doing, how old they are, and whether they are getting radiant heat from direct sunlight.
Reasons for homes getting too hot or too cold
- Reasons why some houses get too cold
Lack of sun, inadequate insulation, heat loss through air gaps, and lack of thermal mass can combine to make homes too cold in winter.
- Reasons why some houses get too hot
Lack of shade, poor ventilation, lack of insulation (which would reduce radiated heat gain through the roof), low thermal mass, and reflected heat gain from nearby surfaces all combine to make a home too hot in summer.
Using passive design to control temperature
Designers can control temperature through the use of insulation, ventilation, and orientation of windows, glazing type and shading, and thermal mass.
- Some features of passive design in summer
Using insulation, thermal mass, shading, and planting to reduce heat gain, and ventilation to provide cooling reduces the amount of heat build-up.
In summer, thermal mass absorbs the sun’s heat to keep the house cool. At night in summer the house can be ventilated to allow the heat to be lost into the cooler night air.
- Features of passive design in winter
In winter, thermal mass will absorb heat from the sun during the day, as well as from supplementary heat sources, and release that heat as temperatures fall at night.
Most houses require some form of conventional supplementary heating during winter. The extent to which it is used will vary with the regional climate, and the degree to which passive techniques have been used in the design.
For your clients
To help your clients understand passive design, refer them to www.smarterhomes.org.nz/design/passive-heating and www.smarterhomes.org.nz/design/passive-cooling.