Cavity wall insulation guides
Plain-English answers on suitability, cost, grants, damp, guarantees and the rules in each UK nation, checked against official sources.
Is my home suitable for cavity wall insulation?
The checks that decide whether a cavity wall can be filled: cavity width, condition, exposure, damp and access.
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How cavity wall insulation is installed, step by step
What happens from survey to making good: drilling pattern, filling, barriers, notification and paperwork.
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Mineral wool or polystyrene beads: which cavity fill?
An honest comparison of the two common cavity fills: where each suits, fire, moisture, price and cables.
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How much does cavity wall insulation cost in 2026?
Guide prices by house type for filling, topping up and removing cavity insulation, plus what changes the price.
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Cavity wall insulation grants in 2026: what is still open
ECO4 to 31 December 2026, the end of GBIS, the Warm Homes Plan, and the schemes in Wales, Scotland and Northern Ireland.
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Signs of failed cavity wall insulation
Damp patterns, cold spots and outside clues that point to a problem with a cavity fill, and what else they can mean.
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Should I remove my cavity wall insulation?
When extraction is the right answer, when it is not, and what to ask before you pay for removal.
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Does cavity wall insulation cause damp?
How a cavity is meant to work, the ways a fill can carry moisture, and the causes that have nothing to do with insulation.
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How to tell if your walls already have cavity insulation
Patched drill holes, the EPC, the guarantee and a borescope: the four ways to find out.
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Cavity wall insulation guarantees explained
What a 25-year cavity insulation guarantee covers, how to check you have one, and how claims work.
Read the guide →Cavity wall insulation and building regulations by UK nation
Building notice or self-certification in England and Wales, no warrant in Scotland, an application in Northern Ireland.
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Driving rain exposure and cavity wall insulation
Why the west and the coasts need more care, and how a survey judges exposure for each wall.
Read the guide →Landlords: cavity wall insulation and EPC C by 2030
What the October 2030 standard means for private landlords in England, and why the cavity is usually the first measure.
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How much does cavity wall insulation improve an EPC rating?
Why a filled cavity moves the rating, what else matters, and how to check what your EPC assumed.
Read the guide →VAT on cavity wall insulation
Zero-rated installs in homes until 31 March 2027, 5% after, and when the standard rate applies.
Read the guide →Cold calls, claims companies and cavity wall insulation
How to spot pressure selling around free insulation and failed-installation claims, and how to check a company.
Read the guide →Find out if your walls can be filled
Free survey with an install quote. Written result. Fixed price before any work.