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Insulation for a narrow roller shutter box

Updated: 22 October 2026

A shutter above a kitchen door can look ordinary from the room and still leave almost no spare space once the curtain is fully raised. You open the inspection lid and look for insulation for a narrow roller shutter box. The listing that says narrow is still 13 mm thick. This page measures that fat roll, then chooses the 13 mm mat, the 3 mm roll, or no lining. Wider listings are on the [roller shutter insulation comparison](/hub/heating/roller-shutter-insulation). Peter F. read those amazon.co.uk pages and public fitting notes on 21 October 2026. There was no lab test. A qualifying purchase can earn a commission at no extra cost to you.

A shutter above a kitchen door can look ordinary from the room and still leave almost no spare space once the curtain is fully raised. You open the inspection lid and look for insulation for a narrow roller shutter box.

Our top picks

Schellenberg Schellenberg 66267

Best overall

Schellenberg Schellenberg 66267
8.6/10about £17.28
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Schellenberg Schellenberg 66257

Rank 2

Schellenberg Schellenberg 66257
8.4/10about £35.61
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Schellenberg Schellenberg 66272

Best value

Schellenberg Schellenberg 66272
8.2/10about £4.45
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On this page
  1. 1.Measure the fat roll, not the empty slot
  2. 2.What the 13 mm listing means by narrow
  3. 3.What the 3 mm rolls can and cannot do
  4. 4.If it already rubs

Measure the fat roll, not the empty slot

Public guides do not agree on clearance, and none of them is a British Standard. One note says subtract 10–15 mm and take the next thinner board. Insulate Window asks for 10–15 mm beside the fully raised roll. Measure with the curtain fully inside the box, as Trocellen asks. A slot that looks like 40 mm with the curtain down can tighten to 16 mm once the roll fattens. That 16 mm is the figure you set against 13 mm and against 3 mm.

What the 13 mm listing means by narrow

Schellenberg 66257 (B006JJ3E4A) is labelled for narrow boxes and for boxes close to doors. The bullets still say 13 mm, at £35.61 when we logged it. Narrow on that bullet means tight beside a deep lintel, not a box with almost no spare millimetres. On a 16 mm gap the mat would leave about 3 mm, so skip this row. Nearer 40 mm, 13 mm can leave a 10–15 mm margin, though it still fails a 3–5 cm rule.
Schellenberg Schellenberg 66267

Testsieger

Schellenberg Schellenberg 66267
8.6/10about £17.28
View offer

What the 3 mm rolls can and cannot do

Schellenberg 66267 (B01M12RO34) is the 3 mm roll, at £17.28 in our log. The UK listing prints WLG 035 and Fabric. Schellenberg's shop page prints WLG 033. Do not average the labels. A rule of thumb puts 3 mm near 0.09 m²K/W, and one thermal-camera comment said a thin lining barely showed. On the 16 mm example, 3 mm leaves about 13 mm. If the curtain already touches the shell, 3 mm is still too much. Fitting steps are on the how to fit roller shutter box insulation page. A roomier box is on the roller shutter insulation buying guide.

If it already rubs

A scrape on the way up means take material out, not stick a thinner strip on top. avtechnical.co.uk notes that excess thickness can damage a motor or tear a strap. Run one full cycle with the lid off. If the slats meet the lining, peel it off. Do not shave a 13 mm mat to a guessed thickness. A 15 mm side panel only covers a cheek, and it still needs clearance at the axle. Leave the box alone when you cannot see a gap, or when the curtain already touches the shell. Moving the axle, or freeing a stuck lid, is a fitter's job.

Common questions

The bullet says 13 mm is for narrow boxes. Is that my box?
Only when your fully raised gap is bigger than 13 mm plus clearance. Schellenberg 66257, amazon.co.uk B006JJ3E4A, is still a 13 mm mat at the £35.61 we logged, including boxes close to doors. Narrow on that bullet means tighter than a deep lintel, not a roll that nearly fills the shell. A 16 mm gap is already too small. A door roll is often fatter than a window roll.
What gap do I need before 13 mm is sensible?
You need the tightest fully raised gap to stay above 13 mm after clearance, and publishers do not share one number. One note says subtract 10–15 mm and take a thinner board. Another wants 10–15 mm left beside the roll. A third wants 3–5 cm. None of that is a British Standard. Sixteen millimetres fails. Nearer 40 mm can pass the tighter notes if a full cycle with the lid off still runs clear.
Is 3 mm worth fitting if a camera comment saw no difference?
Only where 13 mm would rub and a small effect is enough. Schellenberg 66267, amazon.co.uk B01M12RO34, was £17.28 in our log. A rule of thumb puts 3 mm near 0.09 m²K/W, against about 0.37 m²K/W for 13 mm. One thermal-camera comment said a thin lining barely showed. Fit it when a few millimetres remain. Skip it if the curtain already touches the shell. Do not merge the UK WLG 035 line with a page that prints WLG 033.
The curtain already scrapes. Should I add anything?
No. If the raised curtain already touches the shell, add neither the 13 mm mat nor the 3 mm roll. A scrape after an earlier lining means peel that piece off. avtechnical.co.uk warns that excess thickness can damage a motor or tear a strap. Watch one cycle with the lid off. If the axle must move, or the lid is stuck, call a fitter.
Why do guides say 10 mm, 15 mm and 3–5 cm?
They are separate rules, not a UK standard. One says subtract 10–15 mm and pick a thinner board. Another says leave 10–15 mm beside the raised roll. A third says leave 3–5 cm. One mat cannot meet both ends of that spread in a tight box. Measure the fat roll, keep the lining thinner than the tightest gap, and run a full cycle before the lid goes back.
Who should leave the box alone?
Leave it if you cannot see a clear gap around the raised roll, if the curtain already touches the shell, or if the lid will not come off without force. Also leave it if only 3 mm might fit and you want a change you could see on a camera, because that comment was small. A 15 mm cheek board still needs side clearance. If the axle or a motor has to move, call a fitter.

Related pages

Best roller shutter box insulation in this set

Mat or side panels

Roller shutter insulation

Roller shutter insulation: thickness, faces, fixing

How to insulate a roller shutter box, step by step

Sources

Public UK and manufacturer sources named below. amazon.co.uk prices, stars and review counts are from the saved extracts for B01M12RO34, B006JJ3E4A and B006JJDVNY. Page updated October 2026. This is not a lab test.

  1. Approved Document L, Volume 1 (2021, 2023 amendments) (retrieved 21 October 2026)
  2. Energy Saving Trust — draught proofing (retrieved 21 October 2026)
  3. Passipedia — insulating roller shutter boxes (retrieved 21 October 2026)
  4. Schellenberg 66272 side panels (retrieved 21 October 2026)
  5. Schellenberg 66257 shop page (retrieved 21 October 2026)
  6. Fire Protection Association — cavity barriers (retrieved 21 October 2026)
  7. amazon.co.uk — Schellenberg 66267 (retrieved 21 October 2026)
  8. French 66267 page noting WLG 033 (retrieved 21 October 2026)