Thermal Performance Star Rating

For your all-electric HVAC and solar power project to be successful, it needs a holistic approach including the design and thermal performance of your home. Therefore, request a thermal performance Star Rating at the start of your new build or renovation.

For building approval, it is a requirement of the National Construction Code (NCC) that new homes and renovations are energy efficient. The NCC requires that new or renovated homes in Victoria and most other states achieve a Star Rating of at least 6 out of 10.

Discuss the factors affecting the thermal performance of your building design before undertaking your Star Rating to save time and money.

Your decisions around heating and cooling systems are affected by your building’s heat load requirements. Your decisions around other factors in your build will affect your heat loads. This includes your building structure, orientation and building product specifications.

If you are renovating a period home, you can build a high performing new section relatively easily with good design. However your existing building will be more difficult. 

Insulation and window glazing are the key elements but there are many others as well. For instance, your thermal performance Star Rating will be improved with the right application of shading, house orientation, room layout, ceiling fans, minimising downlights, etc.

If your inital thermal performance assessment is less then 6 Stars then your design will need some revision.

We can assist your thinking through the factors affecting your building’s thermal performance. We can provide you with an accredited thermal performance assessment for your building approval.

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FirstRate5 Thermal Performance Rating Software
NatHERS Energy Rating Scheme

The thermal performance Star Rating measures the efficiency of your building design and describes the likely heating or cooling loss from normal use over one year. It is like a Star rating for your fridge or dishwasher identifying energy efficiency.

To gain 10 Stars out of 10, your home would need to be completely passive requiring no mechanical heating and cooling equipment. In a state like Victoria with cold winters and hot summers, this is very difficult to achieve.

However, passive home concepts can be used to improve your thermal performance Star Rating. Improvement from 6 to 7 out of 10 is not too hard to achieve.

Your home’s thermal performance is calculated using approved software based on the Nationwide House Energy Rating Scheme or NatHERS. 

Follow this link for a simple explanation of NatHERS.

Hydrosol uses NatHERS approved software, FirstRate5, developed by Sustainability Victoria.

You will need to send us your building plans in order to undertake your thermal performance assessment. This includes the following:

  • Site plan
  • Floor plan
  • Elevations
  • Sectional views
  • Electrical plan

Also, key elements of your building structure need definition including:

  • Floor types
  • Wall types, external and internal
  • Ceiling types

Also, you will need to define your building product specifications. However, initially we can make assumptions and guide you if you are not sure. This includes:

  • Floor, wall and ceiling insulation
  • Ceiling and wall colours
  • Window glazing types
  • Roof and clerestory windows
  • External and internal doors
  • Floor coverings
  • Window coverings
  • Lighting, particularly downlights that penetrate the ceiling
  • Exhaust and ceiling fans
  • Shading

Factors that have a significant on your Star Rating include your windows as well as roof, wall and floor insulation. But do you need double glazed windows everywhere to achieve a 6 Star Rating? Well, not if you can make enough gains in other areas.

Areas to look at include:

  • Shading for optimal thermal performance in winter and summer
  • Installing larger windows on the windward side and smaller windows on the leeward side providing natural ventilation
  • Minimising downlights that penetrate your ceilings
  • Installing ceiling fans to aid summer cooling
  • Sealing exhaust fans to eliminate thermal bridging to the outside
Shading for Thermal Performance

Your house design starts with your local climate. Think through your building’s orientation to the sun and prevailing wind.

Victoria, for example, has a mild or cool temperate climate characterised by large temperature swings (diurnal range) between winter and summer. For a good energy rating you need a lot of northern windows, less eastern and western windows and minimal southern windows. This will maximise sunshine radiation and minimise heat loss through windows in winter.

A house with good thermal performance and Star Rating of 6 or more lends itself to all-electric heating, ventilation and cooling solutions. These solutions can be powered largely by your solar panels.

Hydrosol specialises in all-electric solutions including hydronic heat pumps. Hydronic heating is the best form of heating because it is silent and radiant. It does not blow heated air that can cause respiratory issues for asthma sufferers. Also, heat pumps can reverse cycle so can provide summer cooling. This is effective in a mild or cool temperate climate, particularly with ceiling fans.

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