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?

The World Health Organisation’s Housing and Health Guidelines, published in 2018 (with considerable input from New Zealanders), proposes 18 ˚C as a safe indoor temperature to protect the health of general populations in countries with temperate or colder climates.

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.

Healthy homes standards

The Government introduced specific heating requirements for rental housing in the healthy homes standards announced in February 2019. The living room in a rental home will have to have a fixed heating device capable of achieving a minimum temperature of at least 18°C on cold winter days.

In average and larger homes the heater will need to be a heat-pump, wood burner or similar. In small homes a fixed electric heater around 1.5 kilowatts or greater will be sufficient.

Inefficient or unhealthy devices or those with very high operating costs will not comply. Unflued gas heaters, open fires and multiple small electric heaters will not comply with the standard.

The standards will apply to new tenancies from 1 July 2021 and to all rental homes from 1 July 2024.

More information

 

Updated: 27 February 2019