An efficient option for thermal control

by Darren

With advanced heat-reflective technology, a Chromadek® roof can become cooler, even when exposed to the sun.

Seeing a building as a combination of materials that can each contribute to thermal efficiency is a promising avenue in innovative construction. With the advent of developments in innovative materials, a Chromadek® roof exposed to the sun can really become cooler as it gets hotter.

Thermal Efficiency graph

Heat reflectivity explained
The logic behind heat reflectivity, as an aspect of thermal efficiency, starts with the explanation that dark colours absorb most of the visible light striking a surface, while lighter colours reflect most of that solar energy. It is just like wearing a light-coloured shirt on a hot day will probably be cooler compared to a dark shirt.

This would suggest that colour is an indication of how much visible solar energy will be reflected. The amount of infrared energy that is reflected is often a function of the colour as well. New pigment technology has been introduced into Chromadek® and Chromadek Ultim® to change that assumption. New infrared (IR) reflective pigments in the Chromadek® and Chromadek Ultim® paint systems increase total solar reflectance (TSR), while contributing to a lower surface temperature.



Four of the colours of the Chromadek® range, Charcoal Grey, Dark Dolphin, Buffalo Brown and Aloe Green, utilise an advanced thermal technology paint system that incorporates a heat-reflective pigment, providing up to an 8°C cooler surface temperature, with improved durability. The durability of an exterior coating is measured according to the colour-coated surface’s capability in maintaining gloss, colour and film integrity.

How does heat-reflective Chromadek® work?
The heat-reflective pigments in heat-reflective Chromadek® are chemically inert and highly stable. It prevents the coating from directly absorbing energy, resulting in less heat build-up and longer lifecycles (less fading).

To gain insight into heat-reflective Chromadek®, a demonstration entitled “The heat-reflective aspects of Chromadek®, what you imagine you can see” captures the strides made in paint technology that enable Chromadek® to become cooler.

The demonstration shows the visible contrast between the same heat-reflective and non-heat-reflective Chromadek® colour. It also draws attention to the heat-reflective colour appearing lighter, therefore cooler, due to the heat-reflective pigment, while the non-heat-reflective colour remains darker, therefore hotter. In addition, a darker colour can be configured through the application of heat-reflective pigment to function as a lighter colour.


Practical context
Where annual cooling loads dominate, a highly reflective and highly emissive colour-coated steel roof is optimal for reducing energy consumption. Where annual heating loads dominate, an unpainted galvanised steel roof is more desirable because of its low infrared emittance.

The benefits of heat-reflective Chromadek®:
–    Lessened peak loads on energy consumption.
–    Improved roof durability, since less thermal cycling leads to constant temperature.
–    Contributing to green and sustainable building by reduced air-conditioning usage and costs.
–    Reduced heating consumption and costs.
–    Improved thermal comfort.

–    The increased total solar reflectance (TSR) threshold for Chromadek® ensures that fading will not occur prematurely.

With more than meets the eye, Chromadek® is a steel colour-coated roofing choice ideally suited for South Africa’s climatic conditions.




ArcelorMittal South Africa

Tel: (016) 889 3661

Email: online.marketingsa@arcelormittal.com

Website: www.chromadek.com


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