Top 3 Insulation Materials That Beat the Aussie Summer Heat

16 October 2025

Australian summers are no joke, and in Melbourne, the combination of dry heat and scorching afternoons can quickly turn homes into ovens. While many people think insulation is only for keeping warm in winter, it’s just as effective at keeping homes cool in summer.

By slowing down the transfer of heat, insulation helps create a comfortable indoor environment, reduces reliance on air conditioning, and cuts down on energy bills. However, not all insulation materials perform equally well in hot conditions.

Here, we’ll explore the top 3 insulation materials that stand up best to Aussie summer heat, and why OZ Homes Insulation is the trusted choice to install them in your home.

Why Insulation Matters in Summer

On a 35°C Melbourne day, the roof cavity in a brick veneer home can reach more than 60°C. Without proper insulation, that heat quickly transfers into living areas, forcing your air conditioner to work overtime.

Insulation acts as a barrier to heat flow. It reduces conduction (heat moving through solid materials), convection (warm air circulating through gaps), and in the case of reflective foil, radiation (sun’s radiant heat entering through the roof).

The result? A home that stays cooler for longer, lower cooling costs, and a big step towards energy efficiency that meets Australian Standards (AS/NZS 4859.1) for thermal performance.

Top 3 Insulation Materials for Aussie Summer Heat

1. Glasswool Insulation (e.g. Earthwool)

What it is:
Glasswool (also called fibreglass insulation) is made from recycled glass spun into fine fibres. Products like Earthwool are widely used in Australian homes.

Why it works in summer:
Glasswool has excellent thermal resistance (R-Value), meaning it slows heat transfer effectively. It’s ideal for Melbourne roofs and walls, where most summer heat enters.

Pros:

Affordable and widely available
Strong year-round performance
Fire resistant and non-combustible
Meets Australian compliance standards

Cons:

Needs professional installation for safety and effectiveness

Best used:
Roofs and external walls in both new builds and retrofits.

Case in point: OZ Homes Insulation recently upgraded a family home in Werribee with Earthwool ceiling batts, reducing the client’s cooling bills by almost 30% during their first summer.

2. Polyester Insulation

What it is:
Polyester insulation is made from synthetic fibres, often containing a high percentage of recycled plastic.

Why it works in summer:
Polyester has excellent thermal properties, providing stable indoor temperatures in hot conditions. It also reduces draughts and works especially well under suspended timber floors, where hot air can seep in.

Pros:

Non-irritant and safe to handle
Great for families with asthma or allergies
Long-lasting and durable
Low environmental impact if recycled content is used

Cons:

Slightly more expensive than glasswool

Best used:
Underfloor insulation and walls in homes where comfort and air quality are priorities.

Example: In Brighton, OZ Homes Insulation fitted polyester underfloor batts in a period home, creating a cooler, draught-free environment perfect for summer living.

3. Reflective Foil Insulation

What it is:
Also known as sarking or foil board, reflective foil is designed to reflect radiant heat away from the home.

Why it works in summer:

Unlike bulk insulation, foil doesn’t rely on thickness, it reflects up to 95% of radiant heat. When combined with glasswool or polyester, it provides superior summer performance.

Pros:

Excellent for hot, sun-exposed roofs
Lightweight and easy to install
Water resistant and adds moisture control

Cons:

Less effective in winter on its own
Works best when paired with bulk insulation

Best used:
Roof spaces, especially in homes exposed to western or northern sun.

In Point Cook, OZ Homes Insulation combined foil sarking with Earthwool ceiling batts, creating a high-performance barrier that kept the top-storey bedrooms significantly cooler during summer.

Bonus: Natural Alternatives

For eco-conscious homeowners, materials like sheep’s wool or cellulose provide sustainable insulation options. While effective, they’re less commonly used due to higher costs and limited availability

How to Choose the Right Material

The best insulation for your home depends on several factors:

Roof vs. wall vs. floor – different materials perform better in different areas
Budget – glasswool is cost-effective, while polyester offers premium comfort
Family needs – polyester is allergy-friendly, while foil is unbeatable for radiant heat
Sustainability goals – natural fibres may appeal if eco-living is a priority

The right solution often involves a combination of materials. For example, foil plus glasswool in the roof delivers exceptional summer comfort.

That’s where OZ Homes Insulation comes in. We’ll assess your home and recommend the most effective, compliant, and affordable solution for your lifestyle.