Thermal performance is a critical factor in home design. It influences how well a house retains heat in winter, stays cool in summer and ultimately how comfortable and energy-efficient it is to live in.
For Australian renovators and builders, understanding the thermal properties of different building materials can help create a home that performs well year-round, especially in a climate as varied as ours.
What is thermal performance?
Thermal performance refers to how well a material resists heat transfer. In building terms, it’s about how materials absorb, store and release heat, which directly impacts heating and cooling needs.
Better thermal performance generally means:
- Reduced reliance on air conditioning or heating
- Lower energy bills
- More stable indoor temperatures
- Improved comfort all year round
Materials play a major role in how a building responds to temperature changes—both inside and out.
Key material properties to consider
There are two main ways materials affect thermal performance:
- Thermal mass: A material’s ability to absorb and store heat. High thermal mass materials like concrete or brick absorb heat during the day and release it slowly at night.
- Insulation value (R-value): A material’s ability to resist heat flow. Higher R-values mean better insulation.
Common materials and their thermal behaviour
Here’s how typical building materials stack up in Australian homes:
1. Brick and concrete
- Thermal mass: High
- Insulation value: Low unless paired with insulation
- Best used: In passive solar designs where sunlight can heat the thermal mass in winter.
- Considerations: Requires good shading and insulation to avoid heat gain in summer.
2. Timber
- Thermal mass: Low
- Insulation value: Moderate
- Best used: In lightweight construction or cooler climates.
- Considerations: Doesn’t store heat but can reduce heat transfer when used with insulation.
3. Steel
- Thermal mass: Very low
- Insulation value: Poor
- Best used: Where structural strength is required, paired with high-performance insulation
- Considerations: Conducts heat easily, so thermal breaks and insulation are essential.
4. Autoclaved aerated concrete (AAC)
- Thermal mass: Moderate
- Insulation value: Better than standard concrete
- Best used: In walls and floors where lightweight and thermal efficiency are both needed
- Considerations: Can help maintain stable internal temperatures when designed well.
5. Glass
- Thermal mass: Low
- Insulation value: Poor unless double glazed or Low-E
- Best used: In controlled quantities for passive solar gain
- Considerations: Choose performance glazing to reduce heat loss and gain.
Glazing and windows
Windows are a major factor in a home’s overall thermal performance. Options like:
- Double glazing
- Low-E coatings
- Thermally broken frames
…can significantly reduce unwanted heat transfer through windows, which are typically the weakest thermal link in the building envelope.
Designing for performance, not just materials
Thermal performance is not just about material choice—it’s also about where and how materials are used. Good design will consider:
- Orientation: Maximising natural sunlight in winter and minimising it in summer
- Insulation: Pairing thermal mass with insulation to reduce heat transfer
- Ventilation: Using breezes and airflow to cool a home naturally
- Sealing: Eliminating gaps and leaks that allow unwanted air movement
Regulations and compliance
In Australia, the National Construction Code (NCC) sets minimum energy efficiency requirements for new homes and major renovations. Tools like NatHERS (Nationwide House Energy Rating Scheme) assess a home’s thermal performance and give it a star rating out of 10.
Using materials with good thermal properties can help meet or exceed these requirements while improving comfort and cutting long-term energy costs.
| Material | Approximate R-Value (per 25mm thickness) | Thermal Mass | Notes |
|---|---|---|---|
| Brick (single skin) | 0.18 | High | Low insulative value; often used with cavity insulation |
| Concrete (dense) | 0.20 | High | Needs insulation for good performance |
| AAC (Autoclaved Aerated Concrete) | 0.80 | Moderate | Better insulator than standard concrete |
| Timber (e.g. pine) | 0.90 | Low | Naturally insulating; varies by species |
| Steel (galvanised) | ~0.00 | Very low | Poor insulator; always requires thermal break and added insulation |
| Glass (single pane) | 0.16 | Low | Should be upgraded to double glazing for energy efficiency |
| Glass (double glazed, 6mm/12mm gap) | 1.8–2.0 | Low | Improves insulation and reduces heat gain/loss |
| Insulation – Glass wool batts | 0.6–1.5 (per 25mm) | N/A | Varies by density and thickness; higher R-values available |
| Insulation – Rigid foam board (XPS) | 0.9–1.2 (per 25mm) | N/A | High R-values in thinner profiles |
Final thoughts
Choosing the right building materials can have a big impact on your home’s performance. While no single material does it all, combining high thermal mass with effective insulation and smart design will help create a home that’s more comfortable, energy-efficient and future-ready.
If you’re renovating or building new, speak to your designer or builder about which materials best suit your climate, budget and sustainability goals.
