Surface Behaviour, Radiative Cooling and the Question Most People Avoid

The question most people avoid is this: What happens at night and winter?

The heat reflective paint industry loves simple messages.

“Cooler roofs.”
“Lower surface temperatures.”
“Radiative cooling technology.”

And in peak summer, those statements can be true.

But buildings do not live in one season. They live in cycles – hot days, cold nights, dry winters, humid transitions across different Australian environments. If we are serious about performance, the real question is not:

How cool does it get at 2pm?

It is:

How does the surface behave across a full 24-hour and seasonal cycle?

That is where the conversation changes.

The Rise of Radiative Cooling

Radiative cooling coatings are engineered to do two things:

• Reflect solar radiation.
• Emit heat strongly in the mid-infrared spectrum to the sky.

On clear summer days, especially in dry climates, this can reduce peak surface temperature. In laboratory conditions, some systems can even cool slightly below ambient.

That is impressive.

But here is the part that rarely gets discussed.

The sky is also a cold sink in winter.

On clear nights, effective sky temperature can sit well below ambient air temperature. A highly emissive surface does not switch off seasonally. If it is designed to radiate strongly, it will continue radiating heat rapidly after sunset — including in winter.

That means:

• Faster night-time surface cooling
• Greater internal heat draw
• Higher dew-point crossing risk
• Increased condensation potential
• Increased heating demand

Radiative cooling is not wrong.

It is simply directional.

It is optimised for shedding heat, not controlling it.

The University of Adelaide Report – A Telling Moment

When the University of Adelaide reviewed roof performance in the City of Adelaide Cool Roof Trial, their report noted that there was little measurable cooling impact in certain conditions.

Some interpreted that as a weakness.

It was not.

It was a reflection of climate reality.

In moderate conditions, especially when ambient temperatures are not extreme, a coating designed purely to over-cool will not show dramatic temperature drops. And that is often desirable. A building envelope should not be chasing extremes. It should be seeking stability.

The real performance in the Adelaide trial was seen where it mattered: internal temperature reductions of up to 6°C below ambient in specific test conditions using Super Therm®. That result was achieved not through aggressive radiative dumping, but through controlled solar heat blocking.

The distinction is important.

The Canberra Case Study – Why Winter Matters

Canberra is not Darwin. It is not Dubai.

It is a mixed climate with:

• Hot, dry summers
• Clear, cold winters
• Strong night-time radiative conditions

In one tiled residential roof application, Super Therm® was applied to one section while the adjacent roof remained unprotected.

During winter, the uncoated tile roof behaved exactly as physics predicts:

• Rapid radiative heat loss after sunset
• Surface temperatures falling below ambient
• Increased internal heat draw

The coated section behaved differently.

Because Super Therm®:

• Reduced daytime heat loading
• Lowered thermal diffusivity at the surface
• Moderated radiative exchange
• Reduced temperature swing amplitude

The coated roof cooled more slowly overnight and remained closer to ambient air temperature.

The result?

Improved overnight thermal performance compared to the unprotected roof.

Not because it was “hotter.”
Because it was more stable.

That is thermal control, not thermal extremism.

The Real Problem: Thermal Volatility

Buildings fail when surfaces are unstable.

Large peak-to-trough temperature swings drive:

• Material fatigue
• Condensation cycles
• Corrosion under insulation
• Increased HVAC cycling
• Occupant discomfort

Most reflective paints focus only on reducing peak temperature.

Most radiative cooling systems focus on increasing emissive dumping.

Super Therm® focuses on something different:

Surface thermal behaviour management.

How Super Therm Works Differently

At approximately 250 microns dry film thickness, Super Therm® is not bulk insulation. It does not rely on thickness.

It relies on physics.

It combines:

• 97% UV reflectance
• 99% infrared heat blocking
• 96.1% total solar heat reduction
• Low thermal diffusivity
• Low density multi-ceramic structure
• Controlled emissive behaviour

One of its proprietary ceramic compounds is extraordinarily low in density. This reduces surface heat loading capacity and limits energy absorption at the boundary layer.

The coating interrupts heat before it enters the substrate.

That is the critical difference.

Radiative cooling coatings primarily manage what happens after heat is absorbed.

Super Therm® manages what happens before heat loads.

Pros and Cons – An Honest View

Radiative Cooling Systems
Pros:

• Excellent peak summer performance in consistently hot climates
• Strong daytime heat rejection

Cons:

• High emissivity can increase winter heat loss
• Can increase night-time cooling beyond desirable levels
• Often optimised for laboratory summer metrics

Traditional Reflective Paints
Pros:

• Reduce some solar absorption
• Lower cost

Cons:

• Limited infrared blocking
• Minimal impact on thermal diffusivity
• Little control of seasonal behaviour

Super Therm^® Insulation Coating
Pros:

• Blocks heat across the solar spectrum
• Reduces peak temperature
• Reduces night-time heat collapse
• Dampens temperature swing
• Reduces dew-point crossing events
• Performs in mixed climates

Cons:

• Not designed to achieve extreme sub-ambient cooling
• Requires correct application thickness
• More technically sophisticated than simple reflective coatings

In other words, it is not chasing a headline temperature drop.

It is delivering year-round stability.

The Only True Insulation Coating?

Most so-called “insulation paints” rely on reflectance claims or hollow microspheres without measurable heat blocking across the full spectrum.

Super Therm® is a multi-ceramic insulation coating developed through structured ceramic compound research, originally in collaboration with NASA engineers. It operates at the radiation stage, modifies surface heat behaviour, and reduces total heat load before conduction becomes dominant.

At 250 microns dry film thickness, it does what bulk systems require centimetres to achieve — but through a different mechanism.

It does not replace all insulation.

It changes the rules at the surface.

And that is why it stands apart.

The Bigger Picture

We can keep chasing the coolest roof at 2pm.

Or we can design for:

• Stability
• Reduced volatility
• Lower condensation risk
• Balanced seasonal performance
• Real-world mixed climates

Radiative cooling has its place.

But intelligent surface control across seasons is a more mature engineering solution.

And in that category, Super Therm® remains the only true insulation coating engineered for full-cycle thermal behaviour – not just summer headlines.