Energy

Designing homes to conserve energy and use it efficiently, from sources that cause least environmental harm.

Space heating

Space heating accounts for around a third of energy use in an average New Zealand house, so improving the energy efficiency of space heating has the potential to provide significant economic and environmental benefits.

On this page:

  • Key considerations
  • How much heating is required?

Energy consumption for heating and cooling can be reduced in most homes by using passive design features such as correct orientation thermal insulation and thermal mass as well as incorporating effective passive ventialtion to maintain indoor air quality. However, even with good passive design, many New Zealand homes will need some form of active heating for at least part of the year.

Key considerations

The key design decisions will include:

  • the type of heat required (i.e. radiant or convective) in each part of the house – also see space heating options by room
  • the type of heating source (heat pump, electricity, gas, solid fuel, oil, or solar)
  • the location, number and capacity of heating units – including whether to use central or room-by-room heating, and whether to use portable or built-in heaters
  • the control systems used – for example, whether to use thermostats, and if so whether to use one thermostat for the whole house or one for each room; in general, heating should be controlled either manually or by thermostat to ensure that heat is only provided where and when it is needed
  • how heat is distributed around the building – for example, through natural convection or an active system such as fans or ducts – to ensure spaces are warmed when needed.

Space heating should be discussed early in the planning process to provide the opportunity to place the heat source(s) in the optimal positions in the house.

In general, the aim should be to keep building occupants comfortably warm while minimising energy use (in particular, use of energy that generates harmful emissions). Other major considerations include: fire risk; noise; impact on air quality; cost of installation and use; and life span of the heating source.

How much heating is required?

Much of the research into the link between indoor temperature and health has focused on at-risk populations. There is evidence that for more vulnerable people such as the sick, disabled or elderly, all living and sleeping areas should be maintained at a temperature of at least 16ºC.

Factors that influence indoor air temperature (and occupants’ perceived air temperature) include:

  • outside air temperature range
  • relative humidity (both outside and inside)
  • exposure to direct sunlight (which is warming)
  • ventilation air flow (which is cooling)
  • stratification (i.e. warm air rising within a space)
  • occupants’ activities, ages and personal preferences
  • draughts and air leakage, generally in older, less airtight homes.

Active ventilation may help reduce the amount of air that needs to be heated by bringing in warm air from other rooms and/or by creating positive pressure, which prevents cool air from getting into the heated space.

As a rough guide, older non-insulated houses will require approximately 150 W/m2 of energy for heating, and houses insulated to NZ Building Code requirements will require around 120 W/m2. For example, a 15 m2 room in an uninsulated house will require a 2250 W or 2.3 kW (150 x 15 m2) heater; if the room is insulated, an 1800 W or 1.8 kW (120 x 15 m2) heater is required.

Heater sizing calculator

On EECA’s Energywise website there is an interactive Heater sizing calculator. This allows you to work out the heating requirement for particular rooms, taking into account things such as the part of New Zealand you live in, type of insulation, number of external walls, window size, and so on.

More information

 

Updated: 15 February 2017