Black mould on roof timbers, damp insulation, musty smells. Loft condensation is common and fixable — but you need to address the right cause, not just the symptom.
Key fact: A significant amount of heat — often around a quarter — can escape through the roof if your insulation isn’t up to modern standards. Heat naturally rises, so without effective insulation in place, it escapes through your roof — increasing energy bills and reducing comfort in your home.
Every type scored across cost, efficiency, lifespan, risk, and installation complexity
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Check My Home in 30 Seconds →| Type | Score | Typical Cost | Annual Saving | Payback | Mortgage Risk |
|---|---|---|---|---|---|
| Foil Insulation Top Pick | application-dependent | £200–£600 | £150–£250 | 1–3 yrs | ✓ None |
| Fibreglass / Mineral Wool | 7.5/10 | £300–£500 | £100–£200 | 2–4 yrs | ✓ None |
| Underfloor Insulation | 7.2/10 | £400–£800 | £50–£100 | 5–8 yrs | ✓ None |
| External Wall Insulation | 7.0/10 | £6k–£15k | £200–£400 | 20–30 yrs | ✓ None |
| Internal Wall Insulation | 6.5/10 | £2k–£8k | £150–£300 | 10–20 yrs | ✓ None |
| Cavity Wall Insulation | 6.0/10 | £400–£800 | £150–£250 | 2–5 yrs | ✓ None |
| Spray Foam ⚠ | 4.0/10 | £1k–£2.5k | £100–£200 | 8–15 yrs | ✗ Major risk |
Spray foam warning: Multiple major UK mortgage lenders decline applications on homes with spray foam on roof timbers. See our full spray foam risks guide.
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