Energy

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

Combined convection and radiant heaters

Any hot surface provides both radiant heating and convection heating, with the radiant heating component increasing as surface temperature increases. Above about 80°C, a heater surface is primarily providing radiant heating.

On this pag

  • Wall-mounted panel heaters
  • Oil column heaters
  • Undertile heating
  • Hydronic underfloor heating
  • Embedded electric underfloor heating.

Heaters with heated surfaces that can be touched without causing burns provide fairly equivalent levels of both radiant and convection heating. These heaters typically have a large, warm surface, which is oriented vertically. Air that touches the surface is heated and rises, forming convection currents. At the same time, radiant heat is directed across the room. Where air flow is driven by a fan, convection heating will take precedence.

Mixed convection/radiant heaters are typical of heaters used in living rooms and bedrooms. They provide comfort through gentle convective air movement and some radiant heating on the skin.

Wall-mounted panel heaters

Wall-mounted panel heaters can provide a low wattage, safe heating option for bedrooms and hallways where additional, permanent heating is required. They can be hard wired into a standard power outlet and are cheap to purchase and easy to install.

They should not be installed below windows, and for older houses without wall insulation, heaters should not be located on external walls.

Oil column heaters

Oil column heaters are portable plug-in units. They have a relatively low purchase cost but are expensive to run on an uncontrolled rate. Because they generally do not have a fan they can give uneven heating and are less suitable for draughty homes or rooms with high ceilings.

Micathermic heaters

Micathermic heaters have a heating element that is surrounded by sheets of mica, a mineral that is a good conductor of heat. They can be portable like oil column heaters, or be mounted to a wall. They are usually thinner than other heaters and typically don’t have a fan. Micathermic heaters warm up faster than oil column heaters, and because they are lighter they are easier to move around. They provide background heating.

Undertile heating

Electric cables installed directly beneath tiles with a floor sensor and a programmable thermostat can be a cost-effective and energy-efficient system to keep the warm feeling in a bathroom, en suite, toilet or entry area.

Undertile heating systems require RCD protection and a 1.5 or 2.0 mm2 (depending on wattage) two-core plus earth dedicated supply circuit. The programmable thermostat must be located away from any damp area zone.

Hydronic underfloor heating

With hydronic underfloor heating, water is heated and circulated through pipes embedded in the floor. The water may be heated using solar radiation (known as ‘solar hydronic’), or using a boiler powered by gas, wood, electricity, or a combination of these. Some types of heat pump can also supply the heat for hydronic underfloor heating.

Specific advantages of a heated floor include:

  • the heating system is unobtrusive and doesn’t take up any floor space
  • heat is released evenly across the whole floor area
  • the ‘cold foot syndrome’ is eliminated because heat is emitted at floor level
  • heat will continue to be radiated from the slab after the heating has been switched off.

Underfloor heating can also offer thermostatic control, and does not create draughts or noise. But it is only moderately responsive – it can take some time for a room to warm up after a hydronic system is switched on. Up-front costs are high, and some maintenance will be required.

Other advantages and disadvantages will depend on the fuel source. Solar hydronic systems are energy efficient, since they rely on free solar energy, but may not provide heat when it is needed, and may need a gas, oil or electric boost. See space heating – energy sources for information on the pros and cons of gas, electricity and oil.

Embedded electric underfloor heating

Embedded electric floor heating systems can be installed to suit specific areas, such as a bathroom, where other forms of heating are difficult. Installations require a floor sensor and a programmable thermostat for maximum efficiency.

Installation requirements include:

  • a 2.5 or 4.0 mm2 two-core plus earth (depending on wattage) dedicated supply circuit
  • RCD protection with protection not exceeding 30 mA – the exception is MIMS (mineral insulated metal sheathed) cables complying with 2.5.3.1 of AS/NZS 3000
  • cables in accordance with NZS 6110
  • a well insulated slab (50 mm minimum polystyrene slab insulation) with edge insulation.

Embedded electric floor heating systems are generally expensive to operate.
For more detail, refer to BRANZ Bulletin 586 Embedded floor heating.

Radiators

Radiators – in which warm water is circulated to a radiator in each room – have similar advantages and disadvantages to underfloor hydronic systems. With radiators, the water is most commonly heated in a boiler powered by gas, though some may use wood, oil or electricity. Some types of heat pump can also supply the heat for radiators.

More information

 

Updated: 16 November 2017