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Cut rock wool without dust

Updated: October 2026

You are in a loft with glass-wool quilt or a stack of stone-wool batts, and the last time you used a panel saw the fibre hung in the air. You will not cut rock wool without dust in the literal sense. A toothless or wave insulation knife throws less cloud than a coarse wood saw; a dusty loft still needs a mask. The six-row table is the [insulation knife comparison](/hub/cutting-tools/insulation-knife). Stroke and sheath sit on [how to cut insulation](/hub/cutting-tools/insulation-knife/sub/insulation-knife-how-to-cut). Peter F. wrote this for DIY & tools. A qualifying purchase can earn a commission at no extra cost to you.

You are in a loft with glass-wool quilt or a stack of stone-wool batts, and the last time you used a panel saw the fibre hung in the air. You will not cut rock wool without dust in the literal sense.

Our top picks

Spear & Jackson Spear & Jackson B98INS Predator insulation saw

Best overall

Spear & Jackson Spear & Jackson B98INS Predator insulation saw
8.4/10about £11.48
View offer
Bahco Bahco PC-22-INS insulation saw

Rank 2

Bahco Bahco PC-22-INS insulation saw
8.8/10about £15.92
View offer
Bahco Bahco 396-INS folding insulation saw

Alternative

Bahco Bahco 396-INS folding insulation saw
6.8/10about £19.99
View offer
On this page
  1. 1.Blades that match wool
  2. 2.Length and the roll
  3. 3.Dust and when to stop
  4. 4.Less cloud, still a mask

Blades that match wool

The Spear & Jackson B98INS Predator at £11.48, 4.2 from 122 reviews, is the toothless saw UK buyers praise on glass-fibre loft roll and rock wool: less tearing and less fibre cloud than a toothed saw, if you keep the strokes short. It is the best value when the job is fibre. It is not the thick-Kingspan saw. Fire batt sticks. The Bahco PC-22-INS at £15.92, 4.1 from 540, is the 550 mm wave saw and the top pick for a long hand blade with a large UK file. Reviewers cut mineral-wool slabs cleanly when the edge is sharp. You can use it on quilt. You do not have to, if the Predator already matches the roll. One name per job sits on the best insulation knife page. The Bahco 396-INS folding saw at £19.99 is the pocket option, 4.0 from 15 with two texts. That is a thin sample. The Everhard MK46000 is a 3-5/8 in roofing knife; skip it for a roll.

Length and the roll

The Centre for Sustainable Energy describes 270 mm as the usual mineral-wool loft depth. That is a loft figure, not a knife specification, and not a reason to compress the quilt. Wickes’ loft guide says not to compress. Cut the batt with the fibres still lofty. The Bahco PC-22-INS is 550 mm, which crosses a 270 mm batt. The Predator listing says 350 mm (14 in); Spear & Jackson states 270 mm toothless and 442 mm overall. Do not average them. A 270 mm blade is only just a through-cut on a 270 mm quilt. The folding 396-INS is sold in UK shops around 185–190 mm. The Amazon block claims 12 inches and 100 volts, so length on that listing is treated as not stated. Mark the roll while it is still supported, then cut against a straight edge. Short strokes slice; long strokes pull clumps. If the blade drags, hone it. There is no grind angle in the files. Cut the batt slightly over for a snug fit, without compressing the loft of the wool.
Spear & Jackson Spear & Jackson B98INS Predator insulation saw

Testsieger

Spear & Jackson Spear & Jackson B98INS Predator insulation saw
8.4/10about £11.48
View offer

Dust and when to stop

Low dust is not zero dust. ROCKWOOL’s UK safety data sheet gives a workplace exposure limit of 5 mg/m³ and 2 fibres/ml and says to prefer a knife, with extraction if you use a power tool. The FEF factsheet suggests a BS EN 149 FFP1 or FFP2 when loft dust cannot be predicted. Put the mask on before the bag comes off. Do not dry-sweep. Vacuum or dampen and lift. Wash itch in cool water. The knife is the less dusty option, not a safe-cut certificate. Stop if you cannot name the old material. Pre-2000 loft insulation can hide asbestos. Stop if there is no boarding over the joists, if the batt is fire-stopping, or if a warm roof must stay continuous under Approved Document L (2026), in force for most English work from 24 March 2027. Sheath the blade before you turn around on the joists. These blades are not the 3-inch pocketknife exception.

Less cloud, still a mask

If the job is glass-wool roll or rock wool, the Predator at £11.48 is the best value toothless saw in this set. If you want a 550 mm wave you can check against a 270 mm batt, the Bahco PC-22-INS is the top pick. If you only have a short batt and you accept two written reviews, the folding 396-INS is the pocket saw. Put an FFP1 or FFP2 on before the bag comes off. If the old loft material might be asbestos, stop.

Common questions

Is a folding saw long enough?
Sometimes, on a short batt. One 396-INS review cut 75 mm rock wool; another called the blade just long enough for 140 mm wood-fibre. The Amazon 12 in field is unusable. For a 270 mm loft quilt, the 550 mm Bahco is the length you can check. The folding saw has only two texts.
Which mask in a loft?
When dust cannot be predicted, FFP1 or FFP2 to BS EN 149, as the FEF factsheet and Wickes both say. ROCKWOOL’s 5 mg/m³ and 2 fibres/ml figures are a workplace exposure limit, not a DIY certificate. IKO’s FFP3 note is for PIR, on the board page.
Do I compress the roll to cut it, then leave it fluffy?
No. Wickes says not to compress the quilt. Cut it at the thickness you will lay. Squashing it to help a short knife, then fluffing it with your hands, puts fibre in the air and loses depth. The 270 mm figure from the Centre for Sustainable Energy is a usual loft depth, not a knife spec.
Why not the short Everhard?
The MK46000 is a 3-5/8 in roofing knife for ISO board. It will not cross a loft roll. The 4.7 from 371 is an amazon.co.uk star line; the texts in the file are from the United States. For wool, use the Predator, the long Bahco, or — with a thin file — the folding 396-INS.
What if the loft might be asbestos?
Stop. Do not cut unknown old insulation with this saw. Call a professional. The same stop applies if you cannot board the joists, if the batt is fire-stopping, or if a warm roof must stay continuous. A sharper blade does not make those jobs DIY.

Related pages

How to cut Kingspan

Insulation knife

Best insulation knife UK: loft wool or foil boards

Insulation knife buying guide: edge, length, sheath

How to cut insulation board: mark, guide, short cut

Sources

Public UK sources from the research digest. Listing prices, stars and review counts are the amazon.co.uk lines used for this comparison, checked on 19 October 2026.

  1. GOV.UK — Buying and carrying knives (retrieved 19 October 2026)
  2. Criminal Justice Act 1988, section 141A (retrieved 19 October 2026)
  3. ROCKWOOL UK mineral wool safety data sheet (retrieved 19 October 2026)
  4. FEF mineral wool health and safety factsheet (retrieved 19 October 2026)
  5. PrimeTools — Bahco PC-22-INS insulation saw (retrieved 19 October 2026)
  6. Spear & Jackson — Predator insulation saw B98INS (retrieved 19 October 2026)
  7. Centre for Sustainable Energy — loft insulation (retrieved 19 October 2026)
  8. GOV.UK — Approved Document L 2026 (retrieved 19 October 2026)