As with the analysis of complex systems, the many inter-related factors influencing the thermal performance of dwellings mean that only a very simplistic analysis can be undertaken if manual means are used. This is why Government, in the early 2000s, began the development of a comprehensive thermal performance rating scheme for the country’s existing and future housing stock – HERS (Home Energy Rating Scheme). While the intentions were laudable the public was not then ready for star-ratings for houses, and also the poor performance of the housing meant that most only achieved 2 or 3 out of 10 stars. With a change in political ideology the scheme was put in abeyance and at the same time the NZ Green Building Council began development of its wider encompassing Homestar® rating process which only now, nearly a decade later, is beginning to be noticed by the general public.
An important part of HERS was to have an objective and calculated measure of the base passive solar performance of the housing, (before artificial heating or cooling is introduced), so a worldwide search was made of available thermal simulation computer software. The result was that EECA, (Energy Efficiency & Conservation Authority), brought across from Australia their AccuRate software and adapted it for NZ’s climate and housing styles, and labelled it AccuRateNZ. The software uses standardised historic climate data from the local official weather stations within each of 18 broad climate zones throughout New Zealand.
While the HERS process was superseded by Homestar®, the standalone AccuRateNZ software remains valid as an analysis tool, and also to demonstrate compliance with NZBC-H1 (Energy Efficiency) by the Modelling and Verification Methods – [ Refer to Dept of Building & Housing’s Codewords newsletter, issue 032, October 2008, pages 22 & 23: “Compliance with H1 Using AccuRateNZ” ].
The AccuRateNZ thermal simulation computer software is a sophisticated design tool used to analyse the energy requirements for each space in a dwelling for each hour of the day for each day of the year. 18 climate zones are used and the house can be analysed into up to 50 distinct volumes. These include the roof, sub-floor and garage spaces. The hourly calculated design temperatures throughout the year for each of these volumes, (necessary for the software to calculate the total annual heating & cooling energy deficit), can be extracted if needed to be used as a Brief for the design of the heating/cooling systems which may be required to maintain the seasonal comfort levels within the dwelling. Following an intensive four-day training course, and follow-up, Keith has been using AccuRateNZ since 2009.
The use of AccuRateNZ as a tool to customise the thermal performance design is equivalent to bringing in a structural engineer to design a tailor-made solution for a specific building and site.
When a house is being designed there are components, as well as its orientation, which are not able to be altered once construction is complete. As a consequence a house purchaser would be wise to consider if building to today's minimum standards will be adequate to cope with rises in the real cost of energy, and the future saleability of the home, etc. At present many homes are having insulation retro-fitted, (but only where it is not too difficult to access), at many times the cost it would have been if included at the time of construction. How can insulation be retro-fitted to an on-ground concrete floor? As a Registered Architect, Keith can give practical and sensible comment on buildable, and liveable, options.
Check out my latest article on EBOSS https://www.eboss.co.nz/detailed/keith-huntington
CONTACT DETAILS: Please feel free to contact Keith for his C.V. and summary of experience. tel: 04 499-3015 mble: 021 890 251 e-mail: keith@settlement.co.nz
Keith Huntington - B.Arch, Dip.Urb.Val, Dip Bus.Stud(Disp.Res), FNZIA, FAMINZ(Med), LEADR Registered Architect (RAB# 1372) and NZGBC Homestar™ Practitioner & Assessor (reg# 6868)
