Last updated: 14 October 2026
By using Loft Insulation Calc at loftinsulationcalc.com (‘the site’, ‘we’, ‘us’), you agree to these terms. If you don't agree, please don't use the site.
Estimates are for planning only
The calculators give planning estimates of U-values, insulation depths, quantities and costs. They're meant to help you prepare for a project and compare options. They aren't:
- professional, engineering, surveying or legal advice;
- a substitute for a survey by a qualified surveyor, an assessment by an energy assessor, or the advice of a registered installer;
- a SAP or RdSAP calculation, an Energy Performance Certificate or a U-value calculation for building control; or
- a guarantee of how much material a job will take, what it will cost, or how your home will perform.
Results depend on the information you enter and on the assumptions explained in our methodology. Real homes differ: joist sizes, obstructions, uneven surfaces, damp, product changes and the quality of installation all affect the outcome.
Check before you buy or build
Before you start, check:
- the Building Regulations. Some insulation work counts as renovation under Approved Document L, and some projects need to be signed off by building control. The rules in Wales and Scotland differ from England's. If in doubt, ask your local building control body;
- whether your home is suitable. Cavity wall and solid wall insulation in particular need a survey, and some homes need specialist advice on moisture and condensation;
- the product. Thickness, λ and coverage vary between brands. Follow the manufacturer's data sheet and installation instructions; and
- current prices. The prices on this site are typical figures from a given date, including promotions, and will change. Installed costs are rough estimates, not quotes.
Where the site and a manufacturer's instructions, a professional's advice or the Building Regulations disagree, follow the instructions, the advice and the regulations.
Safety
Insulation work can be hazardous. You're responsible for working safely and for deciding when to call in a professional. In particular:
- Step only on joists or on boards laid across them. A ceiling won't take your weight.
- Electrics. Don't disturb wiring, keep insulation clear of recessed downlights unless they're designed to be covered, and ask an electrician if you're unsure.
- Ventilation. Keep the eaves of a cold loft and the airbricks under a suspended floor clear.
- Asbestos. Pebbly loose fill in a loft may be vermiculite, which can contain asbestos. Don't disturb it, and follow the HSE's guidance.
- Protective equipment. Wear an FFP2 mask, goggles, gloves and long sleeves when handling mineral wool or cutting boards.
- Installer-only work. Cavity wall insulation and blown loft insulation should be installed by trained, registered installers.
No warranty
We work to keep the data accurate and sourced, but the site and its content are provided ‘as is’ and ‘as available’. To the extent the law allows, we make no warranties or representations of any kind, express or implied, about its accuracy, completeness or fitness for a particular purpose, and we can't promise it's free of errors or up to date.
Limitation of liability
To the extent the law allows, we aren't liable for any loss or damage arising from your use of the site or your reliance on its estimates, including the cost of materials or labour, damage to property, or any indirect or consequential loss. The site is free and provided for general information, so it's not reasonable to rely on it as the sole basis for a decision.
Nothing in these terms excludes or limits liability that can't be excluded or limited under the law of England and Wales, such as liability for death or personal injury caused by negligence, or for fraud. If you use the site as a consumer, nothing in these terms affects your statutory rights.
Links to other sites
The site links to third-party sites such as GOV.UK, the Energy Saving Trust, manufacturers and retailers, mainly as sources. We don't control those sites and aren't responsible for their content, products, prices or privacy practices. A link doesn't mean we endorse the site or what it sells. If the site ever carries affiliate links, our affiliate disclosure explains how they work.
Using the site
You're welcome to use the calculators and share links to results. Please don't copy the site's content or data in bulk for republication, interfere with how the site works, or use it for anything unlawful.
Privacy
How we handle information is covered by our privacy notice. In short: no accounts, no cookies, and calculations run in your browser.
Changes
We may update these terms from time to time. The date at the top shows when they last changed. If you keep using the site after a change, the updated terms apply.
Contact
Questions about these terms: info@loftinsulationcalc.com