A head-to-head independent comparison of reflective foil and fibreglass mineral wool insulation. Performance, cost, suitability and our verdict.
How we score insulation types: Our independent ratings are based on thermal performance (20%), installed cost (15%), lifespan (15%), moisture & ventilation considerations (15%), ease of installation (10%), property suitability (10%), mortgage/resale considerations (10%) and sustainability (5%). No manufacturer or installer pays to influence these scores. Ratings are reviewed regularly — last reviewed August 2026.
This is the most common comparison question we receive. Both foil and fibreglass mineral wool are excellent loft insulation options for UK homes — but they perform differently depending on your property, loft conditions, and priorities.
| Factor | Foil Insulation | Fibreglass (Mineral Wool) |
|---|---|---|
| Our Score | application-dependent | 7.5/10 |
| Cost (semi-detached) | £200–£600 | £300–£500 |
| Installation time | 3–5 hours | 4–6 hours |
| Works in draughty lofts | ✓ Excellent | △ Moderate |
| Lifespan | 25–40 years | 40+ years |
| Mortgage risk | ✓ None | ✓ None |
| Annual saving (semi-det) | £150–£250 | £100–£200 |
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Choose foil if your loft has draughts, moisture issues, or difficult access. Foil installs faster and performs better in conditions where air movement would reduce fibreglass effectiveness. Our scoring system rates it application-dependent — our highest-rated loft insulation type.
Fibreglass mineral wool is ideal for straightforward, dry lofts with good access. It has a longer track record, a slightly longer lifespan, and may be marginally cheaper for very large properties. It is the most widely installed loft insulation in the UK for good reason.
For most UK homes, foil insulation edges ahead on our scoring system due to its versatility and faster installation. However, both are excellent choices and far superior to spray foam (4.0/10). The best option for your specific home can be confirmed with a free survey through our comparison tool.