24/02/2026
Does Render Colour Affect Thermal Performance — Especially with Wood Fibre Insulation?
Architects often face this question when specifying natural insulation systems:
“Does the colour of my render really change the thermal performance of the wall?”
The answer is yes, but only slightly, and not in the way you might expect.
Darker renders absorb more solar energy, meaning the external surface can be 10–20°C hotter on a sunny day than a light-coloured façade.
But when that render sits on wood fibre insulation, the story changes.
Wood fibre has both low thermal conductivity and high thermal mass, it slows heat flow and dampens temperature swings.
As a result, even when the outer surface gets hot, very little of that heat reaches the interior.
So in energy terms, the difference is marginal, often just a few percent at most.
Where colour does make a real difference is in durability and movement:
Higher surface temperatures cause more expansion and contraction,
Which can lead to microcracking or premature ageing of the render.
That’s why most wood fibre EWI manufacturers recommend light tones (LRV > 20–30) to limit thermal stress.
So, when specifying external finishes:
Treat render colour not only as an aesthetic decision, but also as part of the wall’s thermal and material strategy.
It’s a subtle design choice that can extend façade life, preserve vapour permeability, and maintain system integrity over time.
naturheld Baumit UK Acara Concepts Ltd
