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How to fit insulation panels

Updated: 23 October 2026

You have already matched a product to a job, and you want to know how to fit insulation panels without pulling them off again next week. Foil falls off, polystyrene sheds beads, and vacuum-packed foam stays flat. Those failures belong to different materials. This page assumes you are fitting something already compared. If you are still deciding, start with the [insulation panels comparison](/hub/diy-supplies/insulation-panels). Peter F. used the captured listings, United Kingdom reviews and public UK fitting notes on 21 October 2026. We did not fit these products in a lab. A qualifying purchase can earn a commission at no extra cost to you.

You have already matched a product to a job, and you want to know how to fit insulation panels without pulling them off again next week. Foil falls off, polystyrene sheds beads, and vacuum-packed foam stays flat.

Our top picks

Triplast Triplast EPS 70 24-sheet pack

Best overall

Triplast Triplast EPS 70 24-sheet pack
7.8/10about £80.89
View offer
Fabian Clarke London Fabian Clarke 5 m radiator foil

Best value

Fabian Clarke London Fabian Clarke 5 m radiator foil
7.2/10about £14.99
View offer
JAMELO JAMELO 12-pack polyester tile

Alternative

JAMELO JAMELO 12-pack polyester tile
6.4/10about £21.99
View offer
On this page
  1. 1.Three ways these products fail on the wall
  2. 2.Foil behind a cold radiator
  3. 3.Cutting the EPS sheets
  4. 4.Tiles, wedges, and the butyl mat
  5. 5.When fitting is the wrong job

Three ways these products fail on the wall

Stop if the wall itself has to change. A new thermal element, a party wall, a damp or rusty van skin, and foam next to a flue or a heater are professional jobs. Approved Document L is the limit on a new roof, wall or floor, not a worksheet for a 25 mm sheet. Reflector rolls fail at the fixing and the gap. Polystyrene fails as beads and fragile edges. Foam and butyl fail on adhesive, and on thickness after the packet is opened. Reopen the insulation panels buying guide if you bought the wrong family.

Foil behind a cold radiator

Turn the heating off and let the radiator cool. Mencap and the Energy Saving Trust start with the valve at zero. Measure the wall you can reach. Cut with scissors, clean the wall, and put the shiny side towards the room. Fix the pads to the foil, then press. The Environment Centre uses the same order: measure, clean, cut around the brackets, slide the sheet in, and press. If the roll will not slide, do not force it. Buy more pads before you leave a Fabian Clarke 10 m roll bare against the plaster. JMIATRY is only 0.32 m wide, and two of six United Kingdom reviews describe glue that fails when the wall gets hot. Whether the roll is worth buying is the radiator reflector foil page.
Triplast Triplast EPS 70 24-sheet pack

Testsieger

Triplast Triplast EPS 70 24-sheet pack
7.8/10about £80.89
View offer

Cutting the EPS sheets

Triplast’s pack is 24 sheets of 1200 × 600 × 25 mm. Mark the line and make shallow passes with a utility knife. EWI Store’s note is the same idea: light passes track straighter, and a saw leaves a jagged edge. Support the offcut and work over a sheet, because the beads travel. Do not default to a hot wire in a closed room. The cut gives off fumes, which is NSEAD’s warning. There is no adhesive in the box. One reviewer used wallpaper paste, which is an outbuilding lining, not a cavity. Press the sheet onto a flat, dry surface. If the aim is a new thermal element, stop. At a listing lambda from 0.038 W/(m·K), 25 mm is about 0.66 m²K/W of the sheet, not a finished wall.

Tiles, wedges, and the butyl mat

Reviews of Saiqiang and of the 48-piece pack say vacuum-packed tiles arrive flat. A hairdryer, a couple of days, or a steamer brings some of them up. If the foam smells, or stays near 15 mm against a 1 inch title, fit only the tiles that recovered. The 48-piece bullets say no adhesive is included. Saiqiang’s glue often fails. JAMELO’s glue can be too strong for paint, and one review says not to buy it if you rent. temproad is nine butyl sheets at 13.9 kg. Look for a roller before you peel. Two United Kingdom reviews say the tools were missing, and one buyer did receive a roller. If the first peel barely sticks, stop. A paint-thinner wipe in one review is not a recipe. A rusty or damp van skin is where you call someone.

When fitting is the wrong job

In England, Table 4.2 is 0.15 W/(m²·K) for a new roof in an existing dwelling and 0.18 for a wall or floor. A party wall is Approved Document E, and a foam tile is not how you meet it. No saved listing here names a Euroclass. If you are unsure whether the radiator wall is external and insulated, an Energy Performance Certificate is the clue, not the foil advert.

Common questions

Do I turn the heating off before fitting foil?
Yes. Let the radiator go cold. Mencap’s sequence starts with the valve at zero, and the Energy Saving Trust says the same. JMIATRY reviews already blame heat for glue failure. Fit it cold, then put the heating back once the sheet is pressed flat.
Which side of the foil faces the room?
The shiny side faces the room. That is Mencap’s instruction, so the reflector sends heat back into the room rather than into a cold outside wall. The listing bullets do not all say this. Reversed, the useful face sits against the plaster.
What if the roll is thicker than the gap?
Do not force it. One buyer returned Fabian Clarke foil as too thick, and another review says the bubbles are nearer 2 mm than the stated 4 mm. JMIATRY is stated at 7 mm. Measure the cold gap. If the sheet will not slide, that roll is the wrong product.
How do I cut 25 mm polystyrene without filling the room with beads?
Mark a line and make several shallow passes with a utility knife, with the offcut supported, over a sheet that catches the beads. A saw leaves a jagged edge. A hot wire is not the default in a closed room, because the cut gives off fumes. Do not cut over a carpet you care about.
How do I get vacuum-packed foam back to thickness?
Open the pack and wait. Reviewers use a hairdryer, a few days, or a steamer on the 48-piece pack. Stop if the foam smells or stays near 15 mm against a 1 inch title. Fit the tiles that recover. Do not glue a flat tile and hope it swells on the wall.
Can I peel JAMELO tiles off a rented wall?
Treat that as a no. Reviews say the adhesive can be too strong for paint or too weak, and one review tells renters not to buy them. If you cannot mark the wall, this pack is the wrong fixing.
When should I stop and call someone?
Stop for a new thermal element, a cavity or external wall, a party wall, a damp or rusty van skin, or foam next to a flue or a heater. Also stop if temproad arrives without tools and will not stick. Do not invent a solvent. A cold outside-wall radiator, a shed lining and a recovered foam tile are the jobs this page describes.

Related pages

Acoustic foam versus thermal panels

Insulation panels

Best insulation panels for the job you actually have

Insulation panels: which listing you should ignore

Radiator reflector foil: when a roll is worth buying

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Shelf prices are the stored capture, not a live check on 21 October 2026. Updated 23 October 2026.

  1. Approved Document L Volume 1, Table 4.2 (retrieved 21 October 2026)
  2. Energy Saving Trust, radiator reflector panels (retrieved 21 October 2026)
  3. Energy Saving Trust, quick DIY jobs (retrieved 21 October 2026)
  4. Energy Saving Trust, product standards (retrieved 21 October 2026)
  5. BEWI Jabfloor datasheet (retrieved 21 October 2026)
  6. Ikoustic, sound-reducing foam (retrieved 21 October 2026)
  7. Resonics, which acoustic foam (retrieved 21 October 2026)
  8. Veedub Hub, campervan insulation (retrieved 21 October 2026)