Room-in-roof insulation with multifoil: a proper walk-through from survey to handover

If you've got a third bedroom or home office up in a converted loft that's freezing in February and unbearable in July, you're not imagining it. 'Room-in-roof' — the technical name for an attic that's been converted into living space — is one of the most common sources of misery and lost heat in UK housing, particularly in 1970s–90s builds where the conversion was done before modern insulation regulations bit. A room-in-roof adds £200–£400 a year to the energy bill versus a properly insulated one, and drops 4–7°C below the rest of the house in winter.

The good news: in most cases, a 2-day multifoil retrofit fixes it — without losing the headroom or the month of disruption that a full strip-out and re-board would take. Here's exactly how we do it.

Why multifoil for this job specifically

A typical 1980s room-in-roof has 50–100mm of rafter depth and an existing plasterboard ceiling on the slope. Your options boil down to two. Option A: rip everything out, deepen the rafters, fit 120mm PIR, re-board the whole room — around £6,500 and three weeks of disruption. Option B: fit multifoil over the existing slope with battened air gaps on both sides, then over-board and skim — around £2,300 and two days of work. For most homeowners the maths is obvious; for a landlord with a tenanted property it's not even a debate.

What our surveyor actually checks on the day

1. Rafter depth and condition. Multifoil works in 50mm+ depths, and battening gives us the air gap it needs either side.
2. Existing insulation. Sometimes there's 25mm of old mineral wool up there already — we either work over it or strip it depending on condition.
3. Vapour issues. Staining, mould or condensation history tells us which vapour control layer specification to use.
4. Eaves and ridge ventilation. Multifoil is vapour-impermeable, so cross-ventilation has to be right.
5. Junction details. Dwarf walls, purlin pockets, and the junction between sloping ceiling and party wall all need individual treatment.
6. EPC and grant eligibility. We run the ECO4 and LA Flex check on the spot — no sending you away with a 'we'll get back to you'.

The install — two days on site

Day one: we protect carpets and furnishings, batten out the existing plasterboard slope (25×38mm tile lath at 400mm centres), tape and seal every junction, then install Actis Hybris HCONTROL with all overlaps taped to BBA spec.

Day two: second batten layer for the inner air gap, 12.5mm plasterboard over the battens, joints taped and skimmed. You end up with a room that looks identical visually but has a U-value of 0.18 W/m²K instead of the 1.4 W/m²K it started at — an eight-fold improvement in heat retention.

Grant funding — who gets this free

Room-in-roof multifoil is an eligible ECO4 measure under heating measure category H4. You qualify if anyone in the household receives one of the qualifying benefits, or if the property passes through LA Flex (Routes 1, 2 or 3 — income below £31k, a cold-sensitive health condition, or an EPC E–G rating). Where you qualify, the install is fully grant-funded — zero contribution from you.

Self-funded: £1,800–£2,800 inc VAT depending on area and access. No deposit — you pay on satisfactory completion.

Life after install — what you'll actually notice

• Winter room temperature rises 4–7°C for the same heating input.
• Summer overheating drops noticeably — the foil layer reflects solar gain back outward through the roof line.
• Condensation on the slopes (a common pre-install complaint) usually stops within two weeks as the inner surface temperature rises.
• Energy bill saving £180–£420 a year depending on previous insulation level and how often the room was used.

For a free room-in-roof survey including an instant ECO4 / LA Flex eligibility check, book online or ring 0800 229 4094. No cost. No obligation. No pressure.