Thermal performance
Thermal performance is how well a building's fabric resists heat flow with minimal heating and cooling, the property a NatHERS star rating measures.
Ask Chalkline about this →Thermal performance is how well a building’s fabric resists heat flow and holds a comfortable temperature with minimal heating and cooling. It is the property a NatHERS star rating quantifies, and the thing insulation, glazing, sealing, orientation and thermal mass all contribute to.
The logic is simple: better thermal performance means less heat lost in winter and less gained in summer, so less energy is needed to stay comfortable. The fabric levers that move it are:
- Insulation: ceiling, wall and floor R-values (bulk insulation and reflective).
- Glazing: the windows’ U-value and solar heat gain coefficient (SHGC), and single versus double glazing.
- Air-tightness: draught-sealing gaps, penetrations and the like.
- Orientation and shading: catching winter sun, blocking summer sun.
- Thermal mass: concrete and masonry that smooth out temperature swings.
NatHERS rates a dwelling from 0 to 10 stars by modelling the fabric. Since NCC 2022 the minimum for a new home is 7 stars, sitting alongside a separate whole-of-home energy budget.
For a builder the key point is that thermal performance is locked in at the design and fabric stage and is hard and expensive to retrofit. Hit the star target through the fabric, insulation, glazing and sealing, rather than oversizing the heating and cooling to brute-force comfort later. Get the energy assessor’s report before you finalise the glazing and insulation spec, because it drives both, and treat the assessed spec as a real construction requirement, not a number on a certificate.
Also known as: Building energy performance, fabric performance.
Category: Energy / Building science.
Related
See also
References
- NatHERS (verified 2026-06-01)
- NCC energy efficiency (Chalkline) (verified 2026-06-01)
Last updated: 2026-06-01. Verified: 2026-06-01. Quarterly review for currency.