6 min read
With Perth summers regularly pushing past 40 degrees, anything that keeps your home cooler is worth considering. Heat-reflective roof coatings - sometimes called “cool roof” technology - claim to do exactly that by bouncing solar energy away from your roof instead of absorbing it.
But do they actually deliver meaningful results, or is it marketing hype? Let’s look at the science and the real-world performance.
How Heat-Reflective Coatings Work
Every surface has two properties that determine how it handles solar energy:
Solar reflectance - how much sunlight is bounced back rather than absorbed. A standard dark roof tile might reflect 10-15% of solar energy. A heat-reflective coating on a lighter colour can reflect 50-70%.
Thermal emittance - how efficiently the surface releases absorbed heat back into the atmosphere. Per CSIRO, all non-metallic coatings sit at an emittance of about 90% regardless of colour, which is good - it means whatever heat is absorbed gets radiated away quickly. It also means emittance is not what separates one roof colour from another; reflectance is.
Traditional dark roofs absorb most of the sun’s energy and convert it to heat. That heat transfers through the roof structure into the cavity, then radiates down through your ceiling into your living spaces. A reflective coating interrupts this process at the first step - the roof surface stays cooler because less energy is absorbed in the first place.
The Numbers
The number the manufacturer will actually stand behind is a surface one. Dulux states that a charcoal InfraCOOL roof can achieve a surface temperature reduction of more than 10°C in hot weather — and immediately adds that this does not carry across to every colour. Its own FAQ asks “so will all colours be 10°C cooler?” and answers “No.”
Dulux also explains why it publishes total solar reflectance rather than temperature: TSR is the honest way to compare one colour against another, because a temperature figure depends on the day, the roof and the house as much as on the paint.
We won’t tell you how much cooler your rooms will be. Nobody can put an honest number on that from the roof alone, and the industry has been penalised for trying. CSIRO’s guidance on solar reflective coatings puts it plainly: “For most buildings, the application of a solar reflective coating as a single remedial action is unlikely to substantially reduce the indoor temperature.” What happens under your ceiling comes down to insulation, ceiling type, ventilation, whether your air-con ductwork runs through the roof cavity, and how the house is designed.
Does Colour Matter?
Enormously. Colour is the single biggest factor in how much heat your roof absorbs.
A white or very light-coloured reflective coating will outperform a dark reflective coating every time. The “heat-reflective” pigment technology helps, but it can’t overcome the physics of dark colours absorbing more energy.
Here’s the rough scale:
| Roof Colour | Solar Reflectance (Standard) | Solar Reflectance (Heat-Reflective) |
|---|---|---|
| White / Off-White | 60-70% | 75-85% |
| Light Grey / Cream | 35-45% | 50-65% |
| Medium Grey / Beige | 20-30% | 35-50% |
| Dark Grey / Green | 10-20% | 20-35% |
| Black / Charcoal | 5-10% | 15-25% |
A heat-reflective coating in a dark colour is still better than a standard dark paint - but a standard light-coloured paint will outperform a heat-reflective dark paint. If you want maximum thermal performance, go light and reflective.
What About the Dulux InfraCOOL Range?
Dulux’s InfraCOOL technology is the heat-reflective system we use. It’s formulated with infrared-reflective pigments that reflect the non-visible portion of solar energy (near-infrared) that standard pigments absorb.
This is particularly useful for medium and dark colours where homeowners want the aesthetic of a darker roof without the full thermal penalty. How much more solar energy an InfraCOOL colour reflects varies enormously by colour — Dulux publishes the total solar reflectance of each one, and the gain over the standard formulation is far larger on the darkest colours than on the light ones, which already reflect well.
It’s not magic - a dark InfraCOOL roof won’t perform like a white one - but it’s a genuine improvement for anyone who doesn’t want a white or cream roof.
Real-World Impact on Energy Bills
This is where it gets nuanced. The energy savings depend heavily on:
- How well insulated your ceiling is - good insulation already blocks most heat transfer, so reflective coatings add less benefit on top of well-insulated homes
- Whether you have ducted or split-system aircon - ducted systems with ductwork in the roof cavity benefit more because the cavity temperature directly affects duct efficiency
- Your home’s design - single-storey homes with large roof areas relative to floor area benefit most
- Existing roof colour - switching from dark to light delivers far bigger savings than switching from light to slightly lighter
Dulux itself declines to put a percentage on it, and says so directly: there are too many variables from site to site for it to confirm savings for every case. We’re not going to invent a figure it won’t stand behind. A cooler roof cavity is a real benefit; it is not a number we can promise on your power bill.
The energy savings alone won’t pay for a roof restoration - but they’re a genuine bonus on top of the cosmetic improvement, weather protection, and extended roof life you’re already getting.
When It Makes the Most Difference
Heat-reflective coatings have the biggest impact when:
- Your current roof is dark and you’re switching to a lighter colour
- Your ceiling insulation is minimal (common in older Perth homes)
- You have a single-storey home with a large roof-to-floor ratio
- Your air conditioning ductwork runs through the roof cavity
- You don’t have adequate roof ventilation - in a poorly ventilated cavity, reducing the heat input matters more
If you already have a well-insulated, light-coloured roof with good ventilation, the incremental benefit of switching to an InfraCOOL product is real but modest.
Is It Worth the Extra Cost?
Heat-reflective formulations typically add $500-$1,500 to the total cost of a roof restoration, depending on roof size. Given that you’re already paying for a full restoration anyway, the marginal cost of upgrading to a heat-reflective product is relatively small.
Our view: if you’re choosing a medium or dark colour, the InfraCOOL upgrade is worthwhile. If you’re going with a light cream or white, the standard Dulux Acratex coating already reflects a significant amount of energy, and the upgrade is a smaller improvement.
We can walk you through the colour options and their thermal performance ratings during the quoting process.
The Bottom Line
Heat-reflective roof coatings are not snake oil - the science is solid and the results are measurable. But they’re also not a substitute for proper insulation and ventilation. Think of them as one piece of a thermal comfort strategy, not a silver bullet.
The biggest gains come from combining a lighter roof colour with adequate insulation, good ventilation, and a quality coating system. If you’re restoring your roof anyway, upgrading to a heat-reflective coating is a smart, low-cost addition that pays dividends every Perth summer. Get a free quote online.
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