Heating

A warm home is a healthy home. We review the options.

Healthy homes

Household air temperature should ideally be between 20 and 24^oC, and not drop below 18°C, but New Zealand homes are often much colder than this. When temperatures drop below 16°C, levels of condensation, mould and mildew increase, resulting in an increased risk of respiratory diseases. Keeping the home warm reduces the build up of moisture.

Good insulation, ventilation, heating and cooling will give you a more comfortable and healthy home to live in. When homes are cold, conditions such as asthma are worse and people’s resistance to infectious diseases seems to be lower.

Clause E3 Internal moisture of the Building Code requires safeguards against 'fungal growth or the accumulation of contaminants on linings and other building elements'. Fungi, in the form of moulds or rot can endanger human health. Fungi grow best in damp environments. Having a warm home keeps it drier and gives fungi less opportunity to grow.

Another health risk is from dust mites which accumulate in carpet, underlays and soft furnishings. They can bring about allergic reactions. There are treated carpets on the market that help eliminate common triggers of allergies and provide effective control of bacteria, mould, mildew and fungi.

Plan your heating needs

When thinking about heating systems for your new home, you need to consider:

Cost and efficiency.
Appearance.
Which sections of the house you want heated all the time and which aren’t so important.
Ventilation and airflow.
Insulation.

There are two types of heating - passive and non-passive. We outline the non-passive options below. For information about passive options, see Passive design for energy efficiency.

Non-passive heating options

Non-passive heating uses an artificially supplied energy source. The options include:

Underfloor heating. There are two types, either:
- Piped hot water which can be heated by solar, electricity, gas and diesel, or
- Electricity

In new homes the underfloor heating is usually laid in the concrete floor slab during construction. However, underfloor heating can be installed with a wooden floor, which makes it possible to install it into an existing home. The advantage of this type of heating is that it distributes heat evenly and does not create any draught. It is crucial to insulate the floor to stop the heat escaping from the edges or into the ground.

Central heating either heats water, which is then pumped around the house to radiators, or uses gas or oil to heat air which is then circulated through grilles throughout the house. It is effective for heating the entire house, rather than just some rooms.
Gas heaters. These range from small portable gas heaters that either run off natural gas or LPG, to flued gas heaters that remove gas by-products and use fans to circulate hot air more efficiently. Non-portable natural gas and LPG appliances must be installed by licensed gasfitters and operate in a sufficiently large space with adequate ventilation. Incorrectly installed, faulty or poorly maintained heaters can produce deadly concentrations of carbon monoxide. Unflued gas heating cannot be used in bedrooms. Unvented gas heating also fills the air with moisture.
Woodburners and fireplaces are often installed for their ambience, or because people have a good supply of wood to burn, but these are relatively inefficient as a large percentage of the heat goes up the flue or chimney. Other heating will usually be necessary to reach areas away from the fire, or flues can be installed to channel heat to other areas of the house. Solid fuel heaters can only be installed with a building consent.
Air-conditioning to cool and heat.
Ceiling-mounted fans cool in the summer, circulate warm air in the winter.
Electric heaters.
Heat pumps work by the expansion and compression of gas, and operate as both a heating and cooling system.

All woodburners installed after 1 September 2005 in buildings on a section smaller than two hectares must be designed to have a discharge of less than 1.5 grams of particles for each kilogram of dry wood burnt, and a thermal efficiency of not less than 65%. See reg 22 of the Resource Management (National Environmental Standards Relating to Certain Air Pollutants, Dioxins, and Other Toxics) Regulations 2004. For more information about National Environment Standards see the Ministry for the Environment website. It includes information about woodburners that meet the Regulations. Woodburners can also be used with a ‘wetback’ which heats the domestic water supply and saves on gas or electricity. Care needs to be taken when using water heated by a wetback as it can get extremely hot. It is a Building Code requirement that hot water must be delivered at a temperature that avoids the likelihood of scalding (G12.3.6).

Alison had a heat pump installed in her new home. The heat pump agent studied the house plans and advised on the right model. Alison has found the costs of running the pump reasonable and is happy with its performance. It heats the area evenly and is easy to use. It can be automatic or she can alter it manually to suit the weather conditions. It filters the air rather than adding dust to the atmosphere and can be set to cool in hot weather.

More information

For more information about heating, go to consumer.org.nz which has articles about bathroom heaters, choosing a heater, convection heaters, dehumidifiers, electric fan heaters, heat pumps, oil-filled heaters, solar hot-water systems, and woodburners. Note: you need to be a member to access this information.

For about $800 Phil and Natalie had a heat transfer unit installed in their ceiling cavity. It operates off a variable thermostat, has its own isolation switch in the ceiling, and very effectively distributes heat from a sun-drenched lounge into bedrooms. The bedrooms are on the eastern side of the home and were previously noticeably colder than the rest of the house all year round, but especially in winter.

Now the whole house is warmer and the bedrooms are heated for no more than the cost of running a fan in the ceiling, using the heat from sunlight alone. The only downsides are the sound of the air being sucked into the unit in the lounge, and the bedroom outlets can create a little too much breeze.