Loft insulation FAQs

There is no single number, and anyone quoting one over the phone is guessing. Price is driven by the floor area of the loft, the depth and condition of any existing material, how easy the space is to get into and move around, whether old insulation needs removing and disposing of, and which product the roof actually calls for. Our cost guide breaks each of those down. The survey is free, and the price we write after it is fixed.

Current building regulations guidance for a cold loft is 270mm of mineral wool, which is roughly the depth of a house brick stood on end and then some. Many London lofts still have 100mm — the standard from decades ago — or less. Topping up from 100mm to 270mm is one of the most cost-effective energy improvements available to a UK homeowner. Going beyond 270mm gives diminishing returns; going below it leaves money on the table every winter.

A straightforward insulation job in a typical three-bedroom house is a half-day. Add raised boarding and you are looking at a full day. A complete makeover with insulation, boarding, lighting and a new ladder is a day, occasionally spilling into a second morning if the loft is unusually large or awkward. We tell you which it is when we quote, not when we arrive.

No. Loft insulation, boarding and loft ladders are all maintenance and improvement works that fall well outside planning control. A loft conversion — turning the space into a habitable room with structural alterations and dormer windows — is a different matter and normally does need building control approval, and sometimes planning permission. We do not carry out conversions.

Almost certainly not, though it may change which product makes sense. Very shallow roof spaces, modern trussed roofs with dense webbing, and rooms-in-roof all present access challenges rather than insurmountable ones. Where headroom is the binding constraint, multifoil at 40mm does work that mineral wool would need far more depth to match.

They go above the insulation line, which means the space around them is now colder than it was — so they must be lagged, and the tank should be insulated on its sides and lid but never underneath. Leaving warmth from the house below to rise into the tank is the only thing keeping it from freezing in a hard winter. We deal with this as part of the job rather than leaving you to discover it in January.

Yes, but only if the boarding is raised. Screwing chipboard directly to 100mm joists over a 270mm layer compresses the wool to a third of its depth and destroys most of its thermal value — a very expensive way to store Christmas decorations. Raised boarding on battens or loft legs keeps the full depth intact and gives you a flat, safe deck on top.

Correctly installed, no. Incorrectly installed, absolutely. The mechanism is simple: insulating the loft floor makes the roof space colder, and cold surfaces are where moisture condenses. The defence is ventilation — a clear airflow path at the eaves that carries that moisture back out. If insulation is stuffed into the eaves and blocks that path, you have built a condensation trap. Read our guide for the full picture.

SuperQuilt is a multilayer foil insulation — reflective outer faces with insulating layers between — around 40mm thick. Its advantage is performance per millimetre, which matters when you are insulating at rafter level in a room-in-roof and every millimetre comes out of your headroom. For a standard cold loft floor with plenty of depth available, mineral wool is more cost-effective. See the comparison.

Only when it needs to go. Sound, dry mineral wool can usually be left in place and topped up over — cross-laid at right angles to bridge the joists — which saves you the cost of removal. Material that is damp, contaminated by vermin, contains old loose-fill, or has collapsed to nothing does need to come out, and we bag it and take it away. We tell you which applies at survey stage, with the disposal cost shown separately.

Usually, yes, and often significantly — loft insulation depth is one of the inputs an assessor records directly. Going from 100mm to 270mm typically moves the rating, though by how much depends on everything else about the property. We hand over the product documentation and declared performance figures so your assessor can record the improvement rather than assume the worst case.

We cover the whole of Greater London plus large parts of Surrey, Kent, Essex and Hertfordshire — more than two hundred areas are listed on our areas page, each with local detail. The list is not exhaustive, so if your area is missing, call and ask.

Government-backed schemes for insulation do exist and eligibility usually turns on household income, benefits received, and the property's current energy rating. We are not a scheme-funded installer, which means we have no incentive to oversell your chances. Our funding guide explains how the main schemes work and how to check eligibility through official channels rather than through a company that cold-called you.

Tell us, and we come back. Insulation is not a job where defects appear years later — if something is wrong, it is wrong on day one and it is visible. We would far rather spend an hour putting it right than have it sit there annoying you. Our contact details are on every page for exactly this reason.