NatHERS Existing Home Rating
NatHERS isn't only for new builds. An accredited assessor can visit an existing home, model it as it stands, and issue a star rating certificate — plus a shortlist of the upgrades that would lift it the most.
Typical star ratings by build era
| Home built | Typical rating | Usual weak points |
|---|---|---|
| Pre-1990 | 1.0–2.5 stars | No wall insulation, single glazing, heavy draughts |
| 1990–2003 | 2.0–3.5 stars | Thin ceiling insulation, poor sealing, large west glazing |
| 2003–2010 (5-star era) | 3.5–5.0 stars | Downlight penetrations, single glazing, minimal shading |
| 2011–2022 (6-star era) | 5.0–6.5 stars | Standard aluminium frames, gaps in insulation coverage |
| 2023 onwards (NCC 2022) | 7.0+ stars | Generally compliant — check as-built matches the certificate |
What the assessor does on site
Measure the dwelling
Room dimensions, ceiling heights, window and door sizes, orientation and overshadowing from neighbours or trees.
Identify construction
Wall type (brick veneer, double brick, weatherboard), roof and floor construction, and any accessible insulation.
Record glazing
Frame material, glass type, seals and any existing shading such as eaves, awnings or external blinds.
Check sealing
Draught paths around doors, exhaust fans, downlights, wall vents and chimneys — often the cheapest fix available.
Log fixed appliances
Hot water, heating and cooling, lighting, pool pumps and solar for the Whole of Home score.
Model and report
Simulation in accredited software, producing your star rating plus modelled upgrade scenarios.
Upgrades that lift the rating most
- • Top up ceiling insulation to R6.0 (+0.5–1.0 star)
- • Draught sealing doors, vents and downlights (+0.3–0.7 star)
- • Retrofit double glazing or secondary glazing (+0.5–1.5 stars)
- • Underfloor insulation on suspended timber floors (+0.3–0.8 star)
- • External shading to west and north glass (+0.2–0.6 star)
When an existing home rating pays for itself
- • Before a renovation, so money goes to the right fixes first
- • Supporting green home loan or rebate applications
- • ACT mandatory disclosure when selling or leasing
- • Marketing a comfortable, low-bill home to buyers
- • Settling arguments about heating costs with real modelling
Rate your existing home
Accredited assessors across Australia offer existing home ratings. Enter your postcode and we'll show you the closest ones.