How to choose a loft insulation company: the questions to ask before you sign

Most installers are not dishonest. The problem is simpler: you do not know what a good job looks like until you have seen a bad one, and the company quoting you has seen hundreds. This guide closes that gap.

Start with how they found you

The single most reliable warning sign has nothing to do with insulation. It is how the conversation started.

If you rang them, or found them yourself and asked for a quote: normal. If they rang you, knocked on your door, or claimed to be "in the area", "from a register", or "checking properties for a government scheme": stop. No official register or manufacturer cold-calls homeowners about insulation, and genuine government-backed schemes do not need doorstep salesmen to find you. We hear from people every week who signed something on the doorstep and regretted it. If this has already happened to you, our guide to cold calls about insulation covers what to do next.

A company confident in its work does not need to catch you off guard to win the job.

The six questions that sort good companies from bad

1. "What exactly are you quoting for, per item?"
A proper quote is itemised: the material and brand, the thickness or depth being installed, the area covered, ventilation measures, boarding or loft-access work if any, and VAT. A single round number on one line, "loft insulation: £X", makes it impossible to compare quotes or hold anyone to anything. Ask for the breakdown. A good company already has it.

2. "What depth will I end up with, and what does that achieve?"
For standard mineral wool laid on the loft floor, current good practice in the UK is around 270mm of total depth. A company should be able to tell you what you currently have, what you will end up with, and roughly what that means in heat-loss terms. If you want to understand the numbers they quote, our plain-English guide to U-values explains what "good" looks like. A company that cannot explain its own numbers is selling by the roll, not by the result.

3. "How will you handle ventilation?"
This is the question that most separates professionals from cowboys. A loft needs to breathe: insulation pushed tight into the eaves, blocking airflow, is one of the most common causes of condensation, damp and mould in lofts, a problem that can cost more to put right than the insulation saved. A good installer will talk about eaves gaps, ventilation trays or baffles without being prompted. If they look blank at the question, end the conversation.

4. "What certification does the product and the installation carry?"
The product should carry recognised certification (for example British Board of Agrément, BBA, or equivalent), and the installer should be able to say which standard the installation is done to. This matters beyond quality: when you sell the house, a surveyor or a buyer's lender may ask for evidence of what was installed and how. Paperwork you get now is money protected later, something we see proven, painfully and often, on the spray foam side of our advice line.

5. "What guarantee do I get, and who stands behind it if you disappear?"
Any guarantee is only as strong as the company offering it. Ask whether the guarantee is insurance-backed, meaning it survives even if the installer stops trading. A 25-year guarantee from a company that is two years old is a hope, not a promise, unless someone else underwrites it.

6. "Can I have that in writing before I decide?"
Every answer above should arrive in writing without a fight. Then take your time. A genuine quote is still valid next week. Any discount that expires today is a pressure tactic, not a price, and pressure is the tool of companies whose work cannot win on its own merits.

Get more than one quote, and compare like for like

Three quotes is the practical number. Not because the cheapest wins, but because the outlier teaches you the most. If two quotes land near each other and one is half the price, that company has usually left something out: the ventilation work, the proper depth, or the part where they clear the old damp insulation instead of burying it. Use the itemised breakdowns from question 1 to compare the same job, not just the same headline number.

A note on materials

Most default quotes are for mineral wool on the loft floor: familiar and cheap on day one, but not automatically the best long-term buy, especially if you use your loft, plan to board it, or suffer hot bedrooms in summer. Modern certified multifoil systems (such as SuperFOIL) insulate at the rafters instead: performance that does not get crushed or slump over time, radiant heat reflected in summer, and a loft floor you keep. Whatever a company proposes, the same rule applies: ask for the independently certified figures (BBA or equivalent) for the exact product and build-up, never the brochure numbers. We have set out the full picture in our comparison of multifoil versus mineral wool. And if anyone proposes spray foam in your loft, pause and take independent advice first: it has consequences for mortgages and resale that no salesman will volunteer.

The short version

Good companies itemise, explain their numbers, raise ventilation before you do, carry real certification, offer guarantees that outlive them, and never rush you. Bad companies found you, quote one round number, and need an answer today.

If you are partway through this decision and want a second pair of eyes on a quote, that is precisely what we are here for. We are straight about what we sell: we supply and arrange certified SuperFOIL installations, and we will still tell you if standard mineral wool is all your loft needs. Speak to an adviser before you sign, not after.