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Solid fuel burners unmasked


Solid fuel burners unmasked

4 November 2005

Solid fuel burners are more widely used than official figures suggest, says building industry research and testing provider BRANZ.

A BRANZ project measuring energy use in a random sample of 400 homes throughout New Zealand has found that slightly more than half of the households (52%) used solid fuel burners, which run on wood and coal.

BRANZ principal scientist Nigel Isaacs said the House Energy End-use Project (HEEP) found that solid fuel burners accounted for about 15% of energy consumed by households.

“This is a huge leap on the 5% indicated in the Ministry of Economic Development’s Energy Data File, the official view of energy use in New Zealand,” Mr Isaacs said.

He said the 10-year project had monitored consumption of all fuel types in order to be as accurate and comprehensive as possible. This had required the development of methods to monitor both portable LPG heaters and solid fuel burners – a first time this has been done anywhere in the world. Other studies had focused on electricity and gas-fuelled space heating because such appliances were widely used and their output was easy to monitor and analyse.

“Solid fuel burners appear to be at least as important as electricity for space heating. They are generally larger heat sources than portable gas or electric heaters, so a not unexpected consequence is that they are also the warmest, with houses heated by open fires being the coolest,” he said.

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The project also found that most households used their solid fuel burners at low output levels - typically between 0.5 kW and 4 kW - whereas testing for efficiency was generally carried out at full load, usually between 12 kW and 20 kW.

“This may well mean that the emissions from new solid fuel burners as they are used in houses are greater than when the appliance was tested in the laboratory.”

Mr Isaacs said the difference between test level output for appliance certification and actual output in the home had implications for government efforts to improve air quality.

“The HEEP findings will help develop better targeted environmental policies at a regional and national level. They also suggest that policies affecting solid fuel burners will have a bigger impact than previously believed.”

One reason solid fuel burners were a popular choice was that few houses had a mains gas connection – natural gas is only available in 14% of New Zealand houses, according to Statistics NZ’s ‘Household Economic Survey’.

The Household Energy End-use Project sampled 400 houses throughout the country to get a comprehensive understanding of how New Zealanders heated their homes and used energy. The 400 houses had 440 hot water cylinders, 65 wetbacks, 206 solid fuel burners, 42 open fires and 175 portable heaters. The project has been gathering information about patterns of seasonal home heating and room temperature variations.

The report also provides a comprehensive overview of household electricity uses, with power measurements taken from nearly 14,000 appliances.

It found that New Zealand homes have an average of 33 appliances, although one house had 82 appliances. The most popular appliance is the television, with nearly two per household.

The HEEP Year 9 Executive Summary and full report (140 pages) can be downloaded for free from the BRANZ website www.branz.co.nz or from the BRANZ Bookshop.

Long term funding support for this work has come from the Foundation for Research Science and Technology, and Building Research.

The research has been carried out by a team lead by BRANZ Ltd, with CRESA, CRL Energy Ltd and John Jowett (Consultant Statistician)


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