Cutting and fitting mineral wool insulation

[SteamyTea]

I often read on here how people hate fitting mineral wool insulation, don't really know why.

When I went to the timber frame company in Redruth a few years back, the guys fitting the insulation rolled out the wool onto a large table, with the roll on a spindle frame, then thy had a saw that easily cut though it.

Very similar to when I used to cut up chopped strand mat and some glass fibre weaves.

I used to just use a Stanley knife into a thin slot on the cutting table.  Had a guide at the top to make sure the cuts where at 90° to the roll.  Marked off, on the cutting table, with a bit fat marker pen, the most common lengths.  Took seconds to cut up and not real mess or hassle at all.

If I needed a lot of thin strips, I just cut the roll up to the required width, then put it on the roll frame.

 

I have seen people cutting stuff up on the floor, or rolling off the roll and using scissors.  Never ends well.

 

So, why are people finding it so hard to cut and fit mineral wool insulation?

[JohnMo]

When I did my internal walls, I just used large scissors.

 

I think people hate it, because it makes you itch, cough if you don't wear overalls, gloves, glasses and face mask, if you do wear the safety gear you sweet buckets in a loft.

[ProDave]

The easiest way for the bulk of it, is SAW it to length with a large panel saw while it is still rolled up and bagged.  then when you unwrap it, you have rolls of your chosen width to suit your joist / rafter spacing.  You only then need to cut to length.

 

The Knauf Frametherm sort is a lot less itchy and irritating than most mineral wolo insulation.

[Thorfun]

I bought a Festool saw. Expensive but made light work of mineral wool and PIR. 
 

I grew to hate the job simply for the time it’s taken us. I’ve saved money but if I got the TF company to do it we’d probably be in a finished house by now. 😢

[Radian]

1 hour ago, ProDave said:

The easiest way for the bulk of it, is SAW it to length with a large panel saw while it is still rolled up and bagged. 

 

Yes, I find this works a treat. A 22" saw just about gets through a full roll. The rolls I got are 1.2m long with a handy cut marker halfway at 600mm

[saveasteading]

On 05/10/2022 at 21:36, ProDave said:

large panel saw

Agreed. The material cuts remarkably easily and exactly, as it is compressed within the packaging.

[Dobbie]

Hi - I'm looking to fit mineral wool or similar between pitched rafters. Is there any reason I can't use Knauf Loft roll instead of frametherm (ignoring u-values)? Will have vcl, 40mm Kingspan and then plasterboard below. 

Thanks! 

[ProDave]

9 minutes ago, Dobbie said:

Hi - I'm looking to fit mineral wool or similar between pitched rafters. Is there any reason I can't use Knauf Loft roll instead of frametherm (ignoring u-values)? Will have vcl, 40mm Kingspan and then plasterboard below. 

Thanks! 

Loft roll is soft and will be unlikely to just stay in place.

 

Frametherm is much stiffer and if cut slightly oversize will push in place on a sloping ceiling and just stay there.

 

 

Early in the build I put a single piece in the roof between the rafters as a test , and 6 months later it had not fallen out or even slipped.

[Dave Jones]

https://www.ebay.co.uk/itm/325252579211?hash=item4bba907f8b:g:AHIAAOSwEHpfCf1~

[Iceverge]

On 05/10/2022 at 20:08, SteamyTea said:

often read on here how people hate fitting mineral wool insulation, don't really know why.

 

 

What about the waste? Skips everywhere full of offcuts. Not everyone is a thrifty self builder. 

 

Also what about the waste of human time. A terrible issue in construction. Men (it's almost always men) putting hours and hours into silly tasks when there's a better way.

 

Lugging mineral wool batts up stairs, climbing up and down ladders hundreds of times per day. Measuring and cutting dozens and dozens of individual stud bays. 

 

All blown insulation here.  58 m3 of EPS beads installed in a day by 2 men in a truck and some hoses. Zero waste and mess. The only human suffering was a couple of hours of drilling with an SDS drill for the injection holes. With our wide cavity and OSB window bucks this could have easily been done via drilling OSB rather than concrete blocks. 

 

Similarly 50 odd m3  of cellulose done in an afternoon by 2 men and a lorry for the attic. One of the main reasons I choose this was that's it's almost impossible to end up with voids which with a trusses roof would be plentiful with mineral wool. One man feeding cellulose bales to the blower and one sitting on the hose. 

 

 

 

 

 

 

 

 

 

 

[ProDave]

1 minute ago, Iceverge said:

What about the waste? Skips everywhere full of offcuts. Not everyone is a thrifty self builder. 

I hate waste.  Another self builder here had bags and bags of glass wool offcuts.  I took them.  I used them all for insulating the posi joists around the perimiter where I had the tedious task of stuffing the void and the outer posi joist web with all these offcuts of glass wool.  I kept the larger pieces and insulated my entire garage walls  built up in layers.  It did not need to be as perfect as the rest of the house.

 

A lot of landfill avoided and some cost savings to me.