Australian consumers only : USA & World enquires & information visit spicoatings.com - Authorised Australian & New Zealand Distributor
You can meet the code.
You can tick the R-value box.
You can install bulk insulation exactly as specified.
And the building can still overheat.
This is happening everywhere. Homes, offices, schools. Well insulated on paper, unbearable in summer reality. The problem is not always the amount of insulation. The problem is what kind of heat you are trying to control.
Most insulation systems were designed to slow conductive heat transfer. That works in winter. It does very little against intense solar radiation loading the external surface in summer.
That distinction matters.
When the sun hits a roof or wall, three forms of radiation arrive:
Near infrared is the main heat carrier. Once that energy is absorbed by the surface, it converts to heat and drives temperature rise inside the material. After that, the heat moves inward by conduction.
Bulk insulation only engages after the surface has already heated up.
By then, you are fighting stored heat, not preventing it.
On a dark metal roof, surface temperatures can exceed 70°C even when ambient air is 35°C. The insulation under that roof slows the heat transfer, but it does not stop the heat loading event.
This is why buildings feel like ovens late in the afternoon and remain hot well into the evening.
The physics is straightforward:
If you do not control step 1 and 2, you are already behind.
For solar spectrum distribution data see:
R-values measure resistance to conductive heat flow under controlled laboratory conditions. They do not measure:
This is critical.
An R4.0 bulk insulation batt performs well in a steady-state temperature difference test. But a roof in Australia is not in steady state. It is under dynamic radiation loading, especially in high UV and high NIR conditions.
The building envelope is being attacked by radiant energy, not just temperature difference.
The CSIRO explains the difference between conduction, convection and radiation clearly:
If radiation is the dominant heat source, then surface behaviour becomes the control point.
Not thickness alone.
Modern buildings often include:
That combination improves winter efficiency.
But in summer, if solar heat is absorbed into the external surfaces and roof structure, the building can struggle to release it. Insulation then traps internal gains from occupants, equipment and stored heat in materials.
The result is overheating.
The UK Committee on Climate Change has already warned that overheating risk is increasing in insulated dwellings:
The issue is not that insulation is wrong.
The issue is that insulation alone is incomplete.
If you want to reduce overheating, you must address:
Most standard paints focus only on reflectance numbers. Even then, many only reflect in the visible range, not the critical near infrared band where 53% of solar energy sits.
If infrared is absorbed, surface temperature still rises significantly.
This is why “cool colour” paints often underperform in real summer exposure.
Lawrence Berkeley National Laboratory outlines the importance of solar reflectance and infrared behaviour in cool roof performance:
But reflectance alone is not enough.
You must also limit how quickly heat travels into the substrate.
That is where advanced ceramic insulation coatings change the equation.
The most effective strategy is simple in principle:
Do not allow the solar radiation to become heat inside the substrate in the first place.
A high-performance ceramic insulation coating applied to the external envelope works at the surface level.
For example, Super Therm® is a multi-ceramic insulation coating applied at a dry film thickness of just 0.25 mm. Instead of relying on bulk thickness, it focuses on:
By stabilising the outer surface temperature, the internal structure does not reach extreme peak heat. That reduces the conductive drive inward.
The City of Adelaide Cool Roof Trial recorded internal temperatures up to 6°C below ambient on coated test buildings.
Details on testing and performance:
This is surface heat load control, not just insulation thickness.
If a building overheats even with insulation installed, ask three direct questions:
Insulation slows heat once it is inside the system.
Surface science prevents it from getting in.
That is the difference.
As climate conditions intensify across Australia and globally, overheating will not be solved by adding more bulk insulation alone. It will be solved by controlling radiation at the envelope.
Thickness has its place.
But surface physics wins the summer battle.
Super Therm® Testing and Results
https://neotechcoatings.com/super-therm-testing-and-results/
NASA Solar Radiation Overview
https://climate.nasa.gov/faq/14/is-the-sun-causing-global-warming/
CSIRO Energy Efficiency and Heat Transfer
https://www.csiro.au/en/research/technology-space/energy/energy-efficiency
Lawrence Berkeley National Laboratory – Cool Roof Research
https://coolcolors.lbl.gov/
The Problem: Misconceptions About Heat Transfer In the quest for energy efficiency, many rely on reflective insulation materials, believing that high reflectivity equates to superior thermal protection. This assumption overlooks…
Passive Cool Roofs That Cut Heat Load Before It Enters Your Building A cool surface is not a new idea. What’s new is treating the roof as a thermal management…
Looking to join one of the world’s leading coatings companies. Contact us if you’re a quality applicator looking for new products and markets!
Genuine SPI COATING PRODUCTS can only be purchased from SPI Authorised Representatives displaying the SPI Authorised Logo. Note: All reduced energy claims - results may vary in different conditions and locations.
