Will my house be colder after spray foam removal?

Foam goes onto the inner face of the roof covering, over and between the rafters. The rafters are the sloping timbers that carry the tiles or slates. When the foam is cut and scraped away, the rafters, the felt or membrane above them and the back of the covering are all exposed again. Nothing then sits between the warm air in the rooms below and the cold roof skin.

If the roof had no insulation before the foam went on, removal simply returns you to that position. If a layer of mineral wool lay along the loft floor first, some of it may survive, some may have been buried under overspray, and some may have been taken out by the installer. We look at what is left during the survey and photograph it, so the starting position is on paper before any decision is made.

There is no single figure for how much colder a house gets, and it would be wrong to invent one. The effect turns on how big the roof is, how many rooms sit directly beneath it, how well the walls and windows hold heat and how the household uses the building. A bedroom in the roof, with sloping ceilings and little else between you and the tiles, feels the change quickest. A two-storey house with a cold, ventilated loft above a plastered ceiling feels it less.

Draughts matter as much as insulation. Foam seals gaps as well as insulating, so some of the warmth people noticed after installation came from reduced air leakage. When the foam goes, small gaps around the eaves, hatches and cables can reopen, which is something to tidy up while the roof is accessible.

The usual replacement is mineral wool or a similar fibrous quilt, laid in one of two places. In a cold loft it goes along the ceiling joists, so the roof space above stays cold and ventilated. If the loft is a living room, the insulation follows the rafters instead, with an air gap kept above it. Our page on reinsulating the loft after spray foam removal goes through both layouts in more detail.

Approved Document L asks for insulation and any required air gap to reach at least the rafter depth, while allowing a lesser standard where headroom would suffer. On a rafter-level job, that trade-off between warmth and floor-to-ceiling height is worth settling before the quote, since a thicker build-up steals space from the room.

A fibrous quilt only works if air can move over it. Marley, reading BS 5250, asks for a 10 mm gap running the full length of the eaves when the pitch is above 15 degrees and the underlay is non-breathable, widening to 25 mm at 15 degrees or less. A steeper roof over 35 degrees, or one spanning more than 10 metres, also gets a 5 mm opening up at the ridge end. The eaves are the bottom edge, where the slope finishes above the gutter, and the openings there are slots or tray inserts pushed into the gap.

That is one reason a house can end up warmer and drier after reinsulation than it was under a poorly specified foam layer. Moisture has somewhere to go, so the timbers stay dry. The Energy Saving Trust warns that timbers in a roof which leaks, or which suffers condensation, can start to rot, and that is why we inspect the rafters as the foam comes off. See open cell and closed cell foam for how the two types differ.

The risk of a cold house is greatest when removal and reinsulation are split across weeks. A sensible plan books the new insulation straight after the rafters have been inspected and any repair has been made. If the weather turns while the work is under way, the roof covering stays on and the job happens from inside, so the house is not opened to the rain.

Winter is workable, and the page on removing spray foam in winter explains what changes. The main adjustment is sequencing: strip, inspect, repair and reinsulate in one run, rather than leaving a gap that the household has to live through. Ask for the order of work in the written quote.

Tenants feel a gap more than owners, because they cannot choose when it happens. If the home is let, the sequence matters even more, and our notes for landlords with spray foam cover access, notice and keeping the property comfortable during the job.

A garage or outbuilding is a different case. Often it is not heated at all, so there is no comfort to lose, and the live question is condensation. Read spray foam in a garage roof if that is your situation.

For the main house, the aim is modest: warm rooms, dry timbers and nothing added that the roof can do without. The survey ends with pictures taken on your loft and rafters, then a quote on paper that names the insulation we would fit once the foam is out, so you can compare the plan with how you want the house to feel. Our spray foam insulation removal page explains how to book the survey. Our guarantee on the workmanship runs for ten years, comes on paper, and we leave the site clear.