The Nationwide House Energy Rating Scheme

A NatHERS Certificate provides information about a building’s thermal performance, meaning how well that building operates without mechanical heating or cooling.

If you are building a new home or undertaking major renovations, you need to meet minimum state and territory building energy efficiency requirements based on the National Construction Code.

The Thermal Performance of your Home

A house with good thermal performance is more comfortable to live in, has lower energy bills and produces fewer greenhouse gas emissions than a house with poor thermal performance.

The Nationwide House Energy Rating Scheme (NatHERS) provides homes with a star rating out of ten based on an estimate of a home’s potential (heating and cooling) energy use.

By providing a ‘measuring tape’ for energy efficiency, NatHERS helps to make Australian homes more comfortable for the inhabitants and help residents to save on energy bills through maintaining a comfortable temperature.  

Good design can reduce the amount of energy needed to keep a home comfortable, with no or little additional construction cost.

The Thermal Performance Assessment

The Thermal Performance Assessment is carried out by accredited assessors. Using sophisticated computer simulation software, the Assessor is able to model the home’s ability to maintain a comfortable temperature year round with a minimum requirement of energy consumption.

If the Assessment complies – a NatHERS Certificate is produced.

Classifying Conditioned and Unconditioned Areas of the Dwelling

Each room in the dwelling is classified into Conditioned (living, kitchen, bedrooms) or Unconditioned  (bathroom, toilet garage etc.) areas.

It achieves this by measuring the heating and cooling loads of each conditioned zone within the home. These heating and cooling loads are arrived at by imputing all relevant building and design information into the Software.

To achieve compliance for a Basix Certificate the Heating and Cooling loads must both have a score less than the benchmarks set by the NSW Dept of Planning for that style of dwelling, in that climate zone.

Outside NSW the total heating & cooling load generally has to achieve 6 Star or better.

All certificates include information on:

• The dwelling’s key design features
• Building materials
• Parameters used to generate its star rating. 

The NatHERS Certificate must be used when demonstrating compliance to the NCC NatHERS pathway.

It allows builders, certifiers and regulatory authorities to quickly confirm that the building has been built to the design on which the energy rating assessment is based. 

What is the NatHERS Assessment Process

Minimum information required by the NatHERS Assessor to produce a NatHERS Certificate:

Site Information: 

• Area
• Orientation of true north
• Climate zone (post code or address)
• Overshadowing elements like adjacent buildings
• Lot and DP number of the development site,

Dwelling Information: 

• Full dimensions
• Layout and usage of each room
• Construction materials for all windows, external and internal walls, floors, ceilings and roofs
• Dimensions and location of all shading elements and eaves

Steps to Produce a NatHERS Certificate

1. The building components are entered into the computer software and a simulation of the energy required to heat and cool the dwelling is calculated.
2. Based on the Assessment of the building a unique NatHERS rating is determined and allocated to the dwelling. The resulting Heating and Cooling loads combine to produce a star rating. A NatHERS Certificate and Stamps for the plan set are then produced for each dwelling from these calculations. The NatHERS Certificate notes the full specification for all components of the dwelling. See example NatHERS Certificate below.
3. In NSW the Heating and Cooling loads of the assessment are entered in the BASIX online tool in the Thermal Comfort section. A Basix Certificate is then produced and the plans are updated to indicate all the minimum Basix (Water & Energy) commitments.
4. The Nathers and Basix Certificates along with the stamped plan set are now ready for submission to the Certifier and/or Council for Development Approval.

What are the features of an energy efficient house?

Building Orientation – The Design of Your Home

The goal is to allow the sun to heat your home in winter but prevent its hot rays from entering during summer.

In summer, most of the heat enters the home via the roof, east and west windows and the walls.

In winter, windows facing north and walls will receive the maximum warmth from the sun.

It is desirable therefore, to design living areas to face north. Poor orientation design makes it difficult to maximise passive-solar design principles.

Indoor living and entertaining areas should be orientated on the north side of the home, with other rooms to the south. This theory allows for warm and bright living areas and cooler bedrooms in the summer.

Internal Room Layout

Rooms with similar uses should be grouped together to create zones and doors to separate these areas. This allows areas that are being cooled or heated to be closed off from those that are not.

Ideally, wet areas such as kitchen, laundry and bathrooms should be close together to minimise the need for long hot water pipes.

This reduces loss of heat from the pipes and the cost of heating water (less wastage of cold water whilst waiting for it to heat up)

Windows and Shading

Windows, eaves and awnings let sunlight in, or block it out at different times of the year, which helps keep the inside temperature comfortable throughout the seasons. Windows can act as solar gatherers in winter and ventilators in summer.

Deciduous vegation grown on the north face of a home can provide shading in summer, whilst allowing the sun to warm your home in winter. Solar pergolas can achieve the same outcome.

Curtains reduce air circulation, and consequent heat loss, through the window glass during winter and heat leakage into the home during summer when the curtains are drawn.

Skylights Skylights can reduce your daytime lighting requirements.

Insulation

There are many types of insulation – varying methodology and location within the building play an important role in either reflecting or retaining heat for our home comfort.

Walls, ceilings/roofs and sometimes floors need insulating. Careful material choices also help to keep the temperature right. Light colours tend to reflect the sun’s heat, while darker colours absorb it.

Lighting

Energy efficient lighting is essential to the long term energy expenses of the home. Light globes should be compact fluorescent ones or LED ones. An incandescent 60-watt bulb, for example, gives off 800 lumens of light. And LED bulbs, which are more energy efficient than their incandescent counterparts, can deliver the same amount of light using as little as 10 watts.

Draught Proofing

Check and install window and door seals to prevent draughty, cold breezes entering your warm sanctuary.

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Why do I need to get an early assessment for my sustainable, energy efficient home?

• Building approval for your chosen house design needs to meet the provisions of the National Construction Code.
• An accredited home energy assessor knows how best to exceed the minimum standards for energy efficiency.
• An accredited home energy assessor will model your house design in National Home Energy Rating Scheme (NatHERS) thermal performance software to demonstrate that it achieves a rating of 6 stars or more.
• An accredited home energy assessor can give you assistance to optimise the energy efficiency of your design.
• It is beneficial to have this assessment done earlier rather than later ie. At the design stage rather than when seeking building approval from your local certifier.
• You NEED to be involved!
• The NatHERS software is an excellent assessment tool and an experienced energy assessor with an interest in sustainability can provide incredibly useful advice during the design stage.
• Earlier rather than later is the CHEAPEST and EASIEST time to make changes to improve your Energy Rating.
• Some things like maximising your passive solar gain in winter and getting your window and eaves sizes right do not result in increased building cost, but they will definitely reduce running costs.
• Improving your rating from 6 to 7 Stars equates to around a 30% reduction in predicted energy use per square metre for heating and cooling.
• An 8 Star design is predicted to need only half the energy of a 6 Star design of the same size
• This means MONEY SAVINGS and REDUCTION of greenhouse gases.
• The number one thing for maximising sustainability and affordability is to build the least house necessary.
• A well-designed small footprint home can function as well or better than a poorly designed, oversized home.
• A good builder is important to ensure that the design for your sustainable house is turned into reality and that the final build has the Star rating that the plans said it would.
• Some performance testing – thermal imaging to ensure insulation is thoroughly installed and/or blower door testing to ensure the house is well-sealed maybe desirable in your building contract.

More Information about NatHERS Certificates:

For more information about NatHERS, please visit the NatHERS website – www.nathers.gov.au.

View Example NatHERS Certificate:

Please click this link to open a sample NatHERS Certificate:

https://nathers.govcms.gov.au/sites/default/files/2020-04/NatHERS%20Certificate.pdf

NatHERS Certificates from Basixally Energy Assessments

Ian Ferguson at Basixally Energy Assessments has had extensive experience for all types of developments that require NatHERS certification throughout NSW.

By using a trained professional to complete your NatHERS Certification, cost savings during the construction stage and ongoing occupation of the dwelling can be achieved.

Our ongoing, up to date research and training guarantees our commitment to customers to continue to provide reliable, affordable and prompt service. Ian regularly participates in industry training and networking to identify and utilise the latest products and developments in the housing industry