Energy Usage Analysis – AccuRateNZ

Through EcoRate Ltd I provides a range of professional services relating to the importance of maximising energy conservation through design.  My interest in solar energy began with a visit to the DSIRO laboratories when at secondary school and continued with studies at the School of Architecture and beyond.


With the purpose of Maximising Energy Conservation through Design, EcoRate Ltd provides a range of professional services relating to the Passive Solar Design of standalone dwellings, medium-density housing, multi-storey apartments, etc., using AccuRateNZ thermal simulation computer modelling.  These include:

  • The provision of assessments (during the design and construction documentation stages) of proposed dwellings to check for compliance with the NZ Building Code – clause H1 (Energy Efficiency) by the Modelling/Verification Methods using AccuRateNZ software.
  • The exploration of alternative materials, construction methods, fenestration arrangements, and even planning and orientation options.
  • An objective analysis of the dwelling to model the annual Network Energy deficit (electricity, gas, oil-based fuels, etc.) required to bring it up to internationally recognized comfort levels, or the Cllient’s particular Brief. This is for both heating and cooling before any heating/cooling appliances are installed or operated.
  • The extraction of the calculated hourly temperatures (over a year) for each room, the roof and subfloor spaces and the garage as used by the software to establish the overall annual network energy deficit. This spreadsheet can be used as a Brief for the design of the Occupier’s preferred heating/cooling systems and appliances.


These services are provided as secondary consultancies to Architects and Designers, or by direct engagement with Developers, Builders and Home Owners.


As with the analysis of all sort 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 of calculation are used.  This is why Government, in the early 2000s, began the development of a comprehensive thermal performance rating scheme to objectively evaluate the country’s existing and future housing stock – HERS (Home Energy Rating Scheme).  To provide the necessary computer power EECA (Energy Efficiency & Conservation Authority) undertook a world-wide search   after which it brought cross from Australia Australia’s AccuRate software and adapted it for NZ’s climate and living styles, and labelled it AccuRateNZ.  While the forward thinking intentions were laudable, the Public was not ready to be told how poorly their homes performed and so, with a change in political ideology and the cost, the scheme was put in abeyance.


The use of AccuRateNZ as a tool to customise the thermal performance design of a house is equivalent to bringing in a Structural Engineer to design a tailor-made solution for a specific building and site.


There are many urban myths surrounding passive solar design and sustainable architecture, especially with regards to insulation, glazing and thermal mass, to name just a few of the primary influences.  There is no simple formula (multi-variable inter-related factors are virtually impossible to resolve manually) to define the ideal relationship between the three; instead each design (in its location) needs to be specifically analysed by sophisticated software.  The AccuRate ‘Chenath’ computer engine is still the core of Australia’s NatHERS thermal performance analysis.  This is where I, using AccuRateNZ and my architectural experience, can provide an objective measure of your proposed design and can suggest sensible thermal improvements that are practical, buildable and, most importantly, liveable.


Since 2014 I have been writing articles on thermal performance and sustainability matters for EBOSS’s (Architectural Product Library) monthly ‘Detailed’ postings.  These are available at:

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