Design Advice


Green House, an accredited thermal assessor, uses thermal modelling software to assess the thermal efficiency of a house design and identify options to increase its energy efficiency and comfort.

What is Thermal Modelling ?

Thermal modelling (also known as thermal assessment) evaluates the thermal performance of the building envelope elements (ie: walls, floors, roof) based on the site’s climatic data and building design to determine how thermally comfortable a house will be throughout the year without mechanical heating or cooling. This is the principle of passive solar design. Performance is dependant on:

  • aspect
  • windows
  • thermal mass
  • insulation
  • ventilation, and
  • zoning.

Passive solar design in a temperate climate is illustrated in the links below -

Summer >>
Winter >>

Why is Thermal Modelling needed?

All states in Australia require new houses (and renovations involving more than 50% of the building’s floor area) to meet minimum thermal performance standards as set out in the Building Code of Australia (BCA). The Australian Capital Territory (ACT) also has requirements for existing home owners to declare the home’s thermal performance at point of sale.

It is mandatory to use an accredited assessor to carry out the thermal assessment. A Thermal Performance Assessment conducted by Green House, can be used to show compliance. Elements of the design may need to be modified to ensure the minimum 5-star requirement is obtained.

How is a Thermal Modelling undertaken?

Green House, conducts thermal assessments by using BCA-approved computer software package (NatHERS, BERS, or FirstRate rating software).

The most efficient method is to assess the energy efficiency of the building structure at sketch stage to ensure critical elements are included at the beginning of the design process. Numerous options can be offered to the client to achieve the required energy efficiency, thus ensuring an optimal design. The design details are then finalised before the assessment is completed.

Green House, will provide you with a stamped assessment report (which is required by councils to be lodged with your Development or Building Application) and will stamp your plans accordingly. 

Preliminary Assessment Process

(1) Client collates concept plans and details        
(2) Concept plans and details are sent in pdf format by email to Green House,
(3) Job cost estimate is supplied to client for approval
(3) If approval is given, Green House, will complete a preliminary energy rating
(4) Options are discussed with the client and agreed upon.

Final Assessment and Endorsement 

(1) Client revises drawings and specifications     
(2) Client sends revised plans in pdf format by email to Green House,
(3) Energy rating completed by Green House,
(4) Endorsed copy sent to client for submission to building surveyor.