UK home insulation · quote workbench
Cavity-wall insulation cost, normalised
Put every installer on the same net wall area. Keep survey, access, repairs, vents, making good, VAT and confirmed funding visible before comparing totals.
Wall and quote scope
Use one shared area and separate every confirmed scope item.
Blank quote sheetLike-for-like
Saved quote options
Keep up to three options in the current browser session. Scope differences stay visible instead of disappearing into one headline number.
| Option | Comparison area | Material / installation | Gross total | Out of pocket | Remove |
|---|
Reusable evidence
Data behind the worksheet
The calculation fields and outputs are documented. Government stock context is kept separate from your individual quote; national estimates do not decide whether a particular home is suitable.
Inzonex Engineering Learning
A cost method you can audit
What the result answers
It answers one practical question: what does this documented material plan or installer quote cost when all compared options use the same area, scope, VAT entry and confirmed funding?
What it does not answer
It does not model annual heat or bill savings, certify a construction, determine moisture or ventilation risk, confirm tax treatment, select an installer or decide funding eligibility.
Sources checked
- Household Energy Efficiency Statistics, detailed report 2025 — Department for Energy Security and Net Zero
- Insulation: energy-efficient home guidance — UK Government
- Tax on shopping and services: energy-saving products — UK Government
- Great British Insulation Scheme: homeowners and tenants — Ofgem
- Cavity wall insulation — Energy Saving Trust
- Competent person schemes for cavity wall insulation — UK Government
Four visible steps
Set one comparison area
External perimeter × wall height minus measured openings gives a common net wall area.
Choose rate or fixed quote
Do not add both. Enter the basis that appears on the installer document.
Expose enabling work
Survey, scaffold, damp or masonry repairs, vents and making good stay as named fields.
Compare evidence, not promises
Save options and ask each installer to document suitability, scope, guarantee and scheme membership.
The LearningResource, HowTo and EducationalOrganization structured data describe this visible free learning module and the Inzonex Engineering Learning collection. They do not claim accreditation or professional certification.
Questions answered
Cost and scope questions
How is cavity-wall insulation cost calculated?
The tool calculates gross external wall area from perimeter and height, subtracts measured openings and then applies either a quoted rate per square metre or a fixed installation quote. Survey, scaffold or access, remedial work, vents and making good remain visible line items.
Can this calculator tell whether my walls are suitable?
No. Wall construction, cavity width and condition, damp, exposure to wind-driven rain, defects, services and ventilation require an actual survey. The quote checklist helps record what an installer assessed; it does not replace that assessment.
Should every installer quote cover the same wall area?
Not necessarily, which is why the page calculates a shared net wall area and shows cost per net square metre. Ask each installer to state measured area, exclusions, access, remedial work, making good and guarantee or scheme details before comparing totals.
Does the cavity-wall calculator apply grants or VAT automatically?
No. Funding is deducted only when you enter a confirmed amount, and VAT is the rate shown on the quote. The tool does not infer current scheme eligibility, tax treatment or installer competence.
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