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Instead of doing the heating and water heating in a piecemeal way, the Copes have integrated them in a large-capacity system.


Electricity is not involved in water heating or space heating.


At its heart is a large 600 litre stainless steel hot water cylinder made by Sigma Sheetmetal in Onehunga, Auckland, and installed in the attic space. A typical household has a 180 litre cylinder.


The water is heated by several sources, and put to several unusual uses.


The main heat source is four Israel-made Chromagen solar water heating collectors, with a total area of 11.2 square metres, on the roof.


A woodburner in the living room will also heat the water. In fact, the woodburner’s comforting flames will be largely for show - most of the heat will be taken off to heat water that circulates in the radiators, which are easier to regulate than a woodburner. It is expected the woodburner to provide for 90% of all required ‘boosting’ of the water temperature during the winter months.


A small diesel-fired condensing boiler for winter top-up is yet to be installed. Simon says the diesel boiler will take one-third of the cost of electricity to run per kilowatt hour of energy, and half the cost of gas. He’ll investigate substituting biodiesel, made from vegetable oil, at some stage. This part of the system is mainly for interest sake, as he expects to only use $2 to $3 dollars worth of diesel a month, for 3-4 months of the year.


The diesel boiler is 98% energy efficient because it recovers steam heat that would otherwise be wasted. It is a type that is rare in New Zealand but common in Europe, especially for central heating.


Realising the integrated system design was beyond their design capabilities, the Cope’s called in GasLab Ltd engineer David Howell.

Howell, whose main work at GasLab is testing gas appliances for certification, has found designing these systems an enjoyable mental exercise and is growing his business in this direction as clients demand his expertise.


Like the Cope’s, David has found his expertise to be greater than many others, due to practically trying all the alternatives and theories out in his own home first – rather than sell from a text book…”You soon learn what works or not with 3 other unbiased occupants testing and living with your ideas – they get refined and perfected pretty quickly, or Judy and the teenage kids will soon be hassling me!”, says David.


With 30 years’ experience in “wet” central heating systems, he has a formula for working out the energy flows.

The hot water is used not only for the usual suspects like showers and washbasins, but runs through heating radiators placed in every room of the house and office, through tubular towel rails and in copper piping installed below the tiled bathroom floors.


Howell says the diesel boiler needs little maintenance and needs less tuning than a vehicle engine because it’s run in a steady state. And it is odour-free. “The diesel’s actually pretty clean, I’ve tested it in the lab.”


He says in the UK, household diesel boilers sit beside a washing machine and are the same height. “There’s even a ‘kitchen cave’ model that sits under the kitchen bench.” Because the boiler is flued there’s no condensation inside the house.


He says it is becoming increasingly difficult in Europe to install standard non-condensing fossil fuel boilers because of tightening energy efficiency regulations and expects NZ to follow this lead in the future.


Howell is looking at using even larger hot water tanks, made of insulated plastics, to maximise the benefits of solar water heating. He estimates a 2000 litre timber-reinforced plastic tank would cost the same as a 600 litre stainless steel one. The large volume makes it easier to retain the heat.




Two 45kg Rockgas LPG cylinders standing outside the back door supply the stove, hob and barbeque. Reticulated gas was available in the...


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Water Heating And Space Heating

Solar Energy House C/- Simon & Kristina Cope | 19 Manapau Street, Meadowbank, Auckland 1072  |  New Zealand  |  Contact us now to arrange your tour