Improving Your Home Energy Rating: Practical Tips

Why Improving Your Rating Matters

Whether you are trying to meet the NCC 2022 minimum of 7 stars or aiming for a higher rating for comfort and cost savings, understanding which design changes deliver the best improvement is essential. Not all changes are equal — some offer significant star rating gains for modest cost, while others provide diminishing returns. This guide covers the most effective strategies for lifting your NatHERS star rating.

Insulation: The Foundation of Thermal Performance

Insulation is typically the single most impactful factor in your star rating. There are three key areas to address:

Ceiling Insulation

The ceiling is the largest area of heat transfer in most homes. In heating-dominated climates, heat rises and escapes through an under-insulated ceiling. In cooling-dominated climates, the sun beating on the roof transfers heat downward into living spaces.

Minimum recommended: R4.0 in temperate zones, R5.0 to R6.0 in extreme climates
Impact: Upgrading from R3.5 to R5.0 can improve your rating by 0.5 to 1.0 stars
Cost: Relatively affordable — typically $1,000 to $3,000 for a standard home

Wall Insulation

Wall insulation is critical, particularly for homes with large wall areas relative to their floor area (such as two-storey homes). The required R-value depends on your construction type and climate zone.

Brick veneer: R2.0 to R2.7 batts in the cavity, depending on climate zone
Lightweight (weatherboard, fibre cement): R2.0 to R2.7 batts plus consideration of reflective sarking
Reverse brick veneer: This construction type naturally performs well as the thermal mass is on the inside

Floor Insulation

Floor insulation is particularly important for homes with suspended timber floors (stumped or raised). Concrete slabs on ground generally perform adequately without additional insulation in most climate zones, although edge insulation can help in cold climates.

Suspended floors: R2.0 to R2.5 underfloor insulation batts
Waffle pod slabs: The built-in polystyrene pods provide some insulation
Slab edge insulation: Particularly valuable in climate zones 6, 7, and 8 (cold climates)

Glazing: Windows Are Critical

Windows are typically the weakest thermal link in a home's envelope. Upgrading glazing can deliver substantial rating improvements:

Double glazing — reduces heat transfer through windows by approximately 50% compared to single glazing. Effectively essential for achieving 7 stars in most climate zones.
Low-E coatings — a microscopically thin metallic coating on the glass that reflects radiant heat. Low-E glass can improve the rating by 0.3 to 0.5 stars with minimal visual difference.
Triple glazing — offers superior performance but at significantly higher cost. Generally only cost-effective in the coldest Australian climate zones (zones 65-69).
Frame material — timber and uPVC frames perform better than aluminium. Thermally broken aluminium frames offer a good compromise between performance and durability.

As a general rule, invest in the glazing performance for your largest windows first, as they have the greatest impact on the overall rating.

Orientation and Layout

The orientation of your home relative to the sun is one of the most powerful — and free — design tools available:

Living areas facing north — in most of Australia, north-facing living areas receive winter sun for passive heating and can be shaded by eaves from summer sun
Minimise west-facing glazing — west-facing windows receive intense afternoon sun in summer, which is difficult and expensive to shade
Bedrooms on the south or east — these orientations remain cooler, which is desirable for sleeping comfort
Service areas (laundry, garage, bathroom) as thermal buffers — placing these rooms on the west or south side acts as a buffer between the living spaces and the harshest weather

Shading

Effective shading can significantly reduce cooling loads, particularly in warmer climates:

Eaves — properly sized eaves shade north-facing windows from high summer sun while allowing low-angle winter sun to enter. A minimum of 450mm eave width is common, with 600mm or more providing better performance.
External blinds and shutters — more effective than internal blinds because they block heat before it enters the glass
Pergolas and vegetation — deciduous trees and vines on pergolas provide summer shade and allow winter sun through

Thermal Mass

Thermal mass (heavy materials like concrete, brick, and stone) absorbs heat during the day and releases it at night. When used correctly, thermal mass stabilises indoor temperatures and reduces the need for mechanical heating and cooling.

Thermal mass works best when it is insulated on the outside (keeping the mass inside the insulated envelope) and exposed to winter sun through north-facing windows. A polished concrete floor receiving direct winter sunlight is a classic passive solar design strategy.

Draught Sealing and Ventilation

Reducing unwanted air leakage (draughts) while maintaining controlled ventilation is a balancing act:

Seal gaps around windows, doors, exhaust fans, and service penetrations
Use weather strips on all external doors
Install ceiling fans — the NatHERS software recognises ceiling fans and credits them for reducing cooling loads, as they allow occupants to feel comfortable at higher thermostat settings

Ceiling fans are one of the most cost-effective improvements available, particularly in warmer climate zones. Adding ceiling fans to living areas and bedrooms can improve the cooling load significantly for a modest investment of a few hundred dollars per fan.