Do I need to insulate around window reveals? – CIJA? | Ep.25

In this episode of Can I Just Ask…, we answer a question that comes up again and again: do I need to insulate my window reveals? The short answer is yes — and here’s why. As you insulate a façade and warm the internal air, that air holds more moisture, and any cold, uninsulated surfaces left behind (like the masonry around a window) become prime spots for condensation and mould. The window opening is always the weak point. The good news is you don’t need to return full-thickness insulation into the reveal — just enough to shift the path of heat flow. With wood fibre, around 20mm of reveal board does the job, whatever the thickness of the rest of your insulation, and where space is really tight, thin alternatives like aerogel-backed boards come into play. The key throughout is continuity: keep the reveal insulation unbroken and well sealed against the window unit to raise the surface temperature and keep things warm and dry. Watch the full explainer above.