Prepare your Plans for NatHERS Assessment
NatHERS thermal comfort modelling must be conducted by following strict protocols and NatHERS national administrator rules and guidelines. In addition to that, software specific technical notes as well as BASIX thermal comfort protocol must be followed by the letter.
Compliance with these requirements are rigorously being observed and audited by various Assessor Accreditation Organisations and non compliance could result in suspension or cancellation of an accreditation licence.
A certain level of information must be presented on the design plans before a NatHERS thermal assessment can be completed.
We would require a final and frozen set of architectural plans for our assessment including sections, elevations and windows and glazed doors sizes and opening types. The following information are required to be on the plans:
- Floor plans and layouts, elevations, sections, site plan and other typical architectural design plans
- Name and functionality of all spaces
- Unit numbers (for multi dwelling projects)
- True north orientation
- Correct scales and numeric dimensions
Material Types and Colours
The generic construction type of various building elements must be specified at the time of NatHERS assessment. As a result, we would need to know the wall types, floor types, roof and ceiling types of a dwelling as a minimum. This information will be directly reflected on the NatHERS certificates and if they change during the design, the model must change and be re-simulated in order to address these changes. If the colours are not specified for various envelope building elements, defaults should be nominated by the assessor.
Windows and Glazed Doors
According to NatHERS thermal comfort protocol, assessors are obligated to model only the projects which show the dimensions and opening type of all the windows of each dwelling. This requires the designers to provide that information either on the plans or in form of a windows schedule. We require windows dimensions (Height X Width) and opening type (Fixed, Sliding, Awning, etc.) before we can start the NatHERS thermal modeling. The method of showing this information is entirely up to the decision and preferences of the design team. The simplest and also the most effective way of showing this information is by providing a single line of text on the floor plans beside each window.
NatHERS assessment of a single dwelling or dwellings in a multi dwelling developments.
NatHERS thermal comfort assessment and BASIX certificate for a single dwelling development.
NatHERS assessment and BASIX certificate for dual occupancy or a townhouse development.
NatHERS thermal modeling and BASIX certificate of a multi unit residential development.
Please note that the guidelines on this page are all derived from government regulatory documents and protocols. Therefore these are the minimum set of information that we require as the NatHERS national administrator and the NSW department of planning have mandated. The good news is, all this information is what is already provided in the vast majority of design plans and project descriptions so all you have to do is to read the guidelines and make sure nothing is missing.
What is NatHERS thermal comfort modeling and why do we need it?
The thermal comfort component in the BASIX NatHERS certification service exists to make sure the occupants of a building experiencing the most comfortable and healthy environmental conditions of their house while the economy and practicality of the construction are also considered.
By including this in energy efficiency targets, greenhouse gas emissions are reduced along with better management of existing infrastructure used for heating and cooling requirements of individual houses.
Ways of completing the thermal comfort section of BASIX
A thermal comfort assessment can be done in two ways:
- Do-It-Yourself (D.I.Y) Method : This method involves a simple assessment for single dwelling houses that use standard construction materials and methods. It is almost too simple as it does not factor in a number of other significant considerations in an energy assessment process. Once completed, it cannot be later amended by a certifier without incurring costs for issuing a brand new certificate. The cost of procurement and compliance with the DIY BASIX certificate are also generally higher than the NatHERS modeling way.
- NatHERS Simulation method : This method involves a more detailed assessment using specialised NatHERS thermal comfort modeling software that can simulate larger construction projects and incorporate more materials and construction methods. It also accommodates for more complex designs and multi dwelling developments and allows for finding the best compromise between performance and construction cost.
How does the new DIY work?
The DIY Method means that you would need to commit to minimum insulation levels and select glazing and shading that will ensure that the estimated heating and cooling loads do not exceed the maximum loads, per BASIX requirements.
These heating and cooling loads are based on the Nationwide House Energy Rating Scheme (NatHERS) climate zone, the windows, shading and (if any) proposed skylights to your development.
However, the DIY method can only be used if the following preconditions are met:
- the conditioned floor area is not more than 300 square metres
- the dwelling is either single or double storey
- the dwelling must not contain open mezzanine area exceeding 25 square metres
- the dwelling must not contain third level habitable attic room
- the glazing area is between 10% and 40% of the conditioned floor area
- there are no more than 40 windows and glazed doors in the dwelling (combining windows of the same orientation is not allowed)
- the total area of skylights is not more than 3 square metres.
There are a significant number of limitations if you choose the DIY option, especially for a larger house – as only certain types of shading are available and overshadowing is only counted if it is directly in front of the centre, at the base of the glazing.
This is why the simulation method, conducted by an assessor will always provide the most accurate results, factoring these outcomes in.
Certifying NatHERS thermal comfort
- Certifying a BASIX Certificate → A BASIX Certificate is one that is issued by the Secretary of the Department of Planning and Environment in relation to the sustainability of a proposed development. Check that the address/lot details shown on the plans reflect the Assessor Certificate and the BASIX Certificate to match the development application/ construction certificate/occupation certificate.
- Check the Accredited Assessor Details → This is an individual who is accredited by an Accrediting Organisation to conduct simulations for the Thermal Comfort Index of BASIX. It’s a requirement that the simulation for BASIX thermal comfort is conducted by a NatHERS accredited assessor. These individuals have an assessor number to identify them (ABSA or BDAV number).
Checking the assessor certificate details → Each assessor certificate has a unique Certificate number shown on the Assessor Certificate that can be recognised by an accrediting organisation.
- Checking the heating and cooling loads →
- For single dwelling projects, it’s important to check that the heating and cooling loads shown in the BASIX Certificate are the same as on the Assessor Certificate.
- For single dwelling projects, it’s important to check that the heating and cooling loads shown in the BASIX Certificate are the same as on the Assessor Certificate.For single dwelling projects, it’s important to check that the heating and cooling loads shown in the BASIX Certificate are the same as on the Assessor Certificate.For single dwelling projects, it’s important to check that the heating and cooling loads shown in the BASIX Certificate are the same as on the Assessor Certificate.
The maximum heating and cooling loads in assessing the thermal comfort of a dwelling is based on the climate zone in which the development zone is under. These are determined individually in perspective of this, and good performance of heating/cooling alone will not be undermined by poor performance in the other.
Solutions to excessive heating or cooling loads
If the heating load is significantly higher than the heating load cap, then you can consider reducing the heating loading in the following ways:
- Reduce heat loss during winter by selecting glazing with a lower U-value
- Increase the amount of sun entering the windows by moving them to north, north east or north west (and in some cases to the east or west)
- Reduce the size of windows facing south, south-east and south-west
- Reduce the size of eaves or levels of shading – or even removing the shading devices for glazing
With the exception of single clear or double clear glass, and aluminium or timber/uPVC/ fibre glass frames, the frame and glass descriptions are for references only. BASIX compliance is checked by satisfying the acceptable range of U-value and SHGC value as shown on the certificate.
If you are still unable to pass DIY, you may need to consider changes to the design of your house and/or its orientation. However, by using NatHERS Simulation method generally no design changes are required and the list of requirements can be fine tuned so that the best performance and cost solution that satisfies the BASIX requirements is found.
If the cooling load of your project is significantly higher than the cap, you can consider reducing the cooling load by:
- Selecting glazing with a lower SHGC value to reduce heat gain during summer;
- Reducing the area of windows facing west, east or northwest;
- Increasing the size of eaves or levels of shading.
Similar to heating load requirements, NatHERS thermal comfort modeling can be used to preserve the overall design of the building while compliance with BASIX thresholds are achieved.