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The honest guide toInsulation.
Cavity, solid wall, loft, internal vs external: which measure suits which fabric, and where the moisture risks sit.
Reading order: beginner first
Start at the top.
03 guides
- 01
Cavity wall vs solid wall: which does my home have, and how to tell
Most pre-1919 UK homes are solid wall; most 1919–1980s homes are cavity. The simple visual test is the brick pattern: cavity walls show stretcher bond only (rectangular faces); solid walls show Flemish or English bond with alternating short faces. Wall thickness at a window reveal also gives it away. Solid walls are typically 220 mm; cavity walls are 250–300 mm.
7 min read
- 02
Loft insulation in 2026: is the existing one enough?
Current UK Building Regulations target 270 mm of loft insulation. Around 42% of English homes have at least 200 mm, meaningful but below current standards. Topping up costs £450–£1,200 and typically pays back in 2–5 years.
6 min read
- 03
Solid wall insulation: internal vs external, and when each makes sense
Internal wall insulation (IWI) is cheaper and faster, can be done room-by-room, but reduces internal dimensions by ~50 mm per wall and disrupts decoration. External wall insulation (EWI) costs more, takes longer, preserves internal space, and can transform external appearance, though conservation areas often restrict it.
7 min read
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