This Month’s Hot Topic…is Heating

31 July 2018
Posted by: Evolution
Time to read: 5 mins.

This Month’s Hot Topic…is Heating

A Comparison and Assessment of the Best Central Heating Systems on the NZ Market

With electricity prices rising and fluctuating, finding the right heating for your home is a key component to a healthy, comfortable home.

World Health Organisation guidelines recommending a minimum temperature of 18˚C, and this recommendation applies to all occupied rooms in your house.

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Whilst a few individuals might feel comfortable at lower temperatures, the majority of people, especially vulnerable groups like children, the elderly and people who are ill, require 18˚C-22 ˚C, not only to be comfortable, but to be healthy.

This temperature recommendation also improves the health of the home.  Cold air cannot hold as much moisture as warm air.  Condensation forms on cold surfaces as the moisture liquifies.  This condensation can be visible, like on your windows, but can also occur where you cannot see it, such as inside your exterior walls.  Moisture in insulation compromises its function and causes slumping, leaving gaps where heat escapes more easily.

Heating homes is good for the occupants and for the building.  Central heating regulated by a thermostat delivers the best outcome.  In this article, we will address the pros and cons of systems on the market in New Zealand that meet this criterion.

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Thermostat for easy control of temperature in the home.

Diesel Boiler to Radiators or Underfloor Heating

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  • Pros: Economical to run/ Moderate initial investment/ Comfortable heat
  • Cons: Susceptible to price fluctuations for diesel/ Requires filling up of tank/ Radiators occupy space internally/ Not sustainable

Diesel Boilers that can be run through Radiators and/or Underfloor Heating. – The central boiler can be controlled by a thermostat.  Whilst they are generally cost-effective (approximately 15.5c/kwh), the obvious downside is the reliance on finite resources that are susceptible to price fluctuations and are not sustainable.  Another consideration is that a tank needs to be installed outside the house and be re-filled intermittently.  Lastly, the radiators occupy space within the interior that can limit the placement of furniture and décor.

Ducted Heat Pump

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  • Pros: Moderate initial investment/ Economical to run/ Can be used as Air Conditioner/ MHRV system can be integrated/ Sustainable
  • Cons: Creates air movement internally/ Ducts located in ceiling

Our second choice would be centralized ducted Heat Pump, which is also a more affordable initial investment.  The advantages are that a Heat Pump can also be used for air-conditioning during the summer months, negating the need to install a separate system.  Additionally, a Mechanical Heat Recovery Ventilation (MHRV), or balanced ventilation, can be integrated with the Mitsubishi Heat Pumps.  The downside to a ducted Heat Pump is that the forced air can dry the air and the ducts are usually installed through the ceiling.  Considering heat rises, the ideal placement of the heat source is ground level. 

Hydronic (Air-to-Water) In-Slab/Underfloor Heating

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  • Pros: Very comfortable heat/ No air movement/ Heat originates at ground level and rises/ Very economical to run/ Can be operated off Photovoltaic Panels with slab acting as a battery/ Sustainable
  • Cons: High installation costs/ Requires separate HVAC system/ Cannot be used to cool house in summer

If the budget allows for an initial investment into the best system, we would recommend the hydronic (Heat Pump that converts air-to-water) system with dual functions of heating water for the home and diverting any excess into the in-slab piping.  The great advantage of this set-up is not only getting excellent output for the energy (4kwh output for every 1kwh consumed), but by using Photovoltaic (Solar) panels to generate power, the hot water in the cylinder and slab acts a storage, or battery.  In other words, the return on PV panels is multiplied and less dependent on the buy back off the grid without having to invest in solar batteries.

Geothermal Heating-Ground-source Heatpump

  • Pros: Very economical to run/ Very comfortable heat/ Can be used to cool house in summer/ Very sustainable
  • Cons: Very High installation costs (requires deep trenching)/ Requires separate MHRV system


ground source heat pump

Ground source underfloor heating

Another optimal choice that also involves high initial investment is a Ground-source heat pump, which uses the energy stored a few meters below the earth’s surface by harnessing heat through a ground heat exchanger and moving it through pipes into the home in winter.  Conversely, it pulls the heat from the dwelling and expels it into the ground during summer.   Less electricity is used and the natural, renewable energy from the earth is used instead of fuels like diesel or gas.

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Threepwood home, Evolution energy-efficient home by Rilean Construction

To maximize the return on investing in central heating, specifying an efficient, airtight thermal envelope to Evolution standards is key.  In fact, when a home is built to better thermal specifications, the spacing between pipes in underfloor heating can be increased, bringing down the cost of installation.  These savings can be put towards a Mechanical Heat Recovery Ventilation (MHRV) System, which ensures the home and the people in it live with constant fresh air at a constant comfortable temperature. 

Keeping our homes warm and dry is not about luxury; it’s about health and maintenance.  Clearly, creating an efficient thermal envelope, with good, comprehensive insulation and no drafts or air leaks, is the first step.  The next is identifying which heating type suits the needs of a home and its occupants best.


Need more tips on how to Control Condensation?  Click here.

Want to know why Airtightness and Vapour Check Membranes (like Intello) are important?  Click here.

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