One strip of decking looks distorted. The surrounding boards seem ordinary. Then, at a particular hour, a bright rectangle slides across exactly that spot. The afternoon has supplied a useful clue.
Differentiate ordinary sunshine from a reflection
AZEK's technical bulletin warns that reflected light from some energy-efficient glazing can produce unusually high surface temperatures and damage exterior materials. This is different from a deck simply feeling hot under bare feet.
Document the moving pattern
From a safe position, photograph the reflection, affected boards, and time of day. Share the product identities with both manufacturers. Ask about a compatible way to reduce the reflection and any warranty implications. Do not apply an arbitrary film to the window or experiment by concentrating light on another sample.
Before the next step
- Record when and where the bright patch appears.
- Check both window and decking product details.
- Settle the heat-source remedy before ordering replacement boards.
Resolve the reflection before paying for another board. If the whole deck simply feels hot underfoot, that's a different decision: compare ordinary deck heat, colour, and shade before blaming a window.