Green Building Forum - Sheepswool vs Woodfibre for walls Sat, 02 May 2026 10:18:20 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306881#Comment_306881 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306881#Comment_306881 Tue, 01 Oct 2024 22:42:27 +0100 bobso
Trying to internally insulate our old coal shed. (now a study, which has been previously plastered (badly) and has various wires/ cables in the walls.

Trying to do this in natural (read water permeable materials) to help control moisture/ warmth in the shed.

Two options seem to be open to me:

1) Sheep’s wool - So Bricks, Breather membrane, Wool, AVCL, Plasterboard (and held up by battens as thermal bridges) But does let us hang pictures/ shelves to the studs.

2) Woodfibre - So Bricks, Lime coat, Woodfibre, Lime plaster (not too many thermal bridges, but hanging shelves etc difficult),

Which is best from a breathability / insulation perspective? While the coal shed isn’t wet; but it is single skin brick... Likely can do 100mm of either insulation, so both work out at a U of approx. 0.3.

If we go sheep’s wool, which seems easier to install / more like what our builder has experience with (And less lime plaster!), how much prep of the internal wall do we need to do? - i.e. does it have to be smooth etc for the membrane to go on? - Or would an old plaster and paint be ok?

Thanks for any insights!]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306882#Comment_306882 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306882#Comment_306882 Wed, 02 Oct 2024 09:57:54 +0100 Doubting_Thomas
So personally wood fibre is the way to go. I've never physically installed it myself but have spoken to plenty of people who have, and it seems to be quite user-friendly to the novice. Essentially you lime plaster up the underlying wall substrate (which acts as an airtightness layer) and the soft woodfibre adapts to the wall surface. Then lime plaster over the top and use a breathable paint.

When I specified this approach to an art gallery we were worried about hanging things, but you can get board-faced woodfibre boards specifically designed to give a flat inner surface and which can accept some fixings. We actually had the room to add a sacrificial timber stud & plasterboard lining which was free-standing about 25-50mm inside the IWI that acted as a services zone for wiring etc. too. Depending on your floor space, either of those approaches might work for you.

Hopefully @sgt_woulds will be along shortly to give you more specific industry info.]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306884#Comment_306884 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306884#Comment_306884 Wed, 02 Oct 2024 11:36:35 +0100 djh https://www.backtoearth.co.uk/guide/internal-wall-insulation-with-plasterboard-finish/ or you can get special wide screw-in plugs e.g. https://www.backtoearth.co.uk/product/spiral-fixings-insulation-systems/ or you can glue in a piece of solid wood and fasten into that. (copious epoxy fixes many things).

Is the shed single skin brick? If so how do your designs prevent damp (rain) from penetrating through the brick and whatever is inside? i.e. where's the drainage plane?]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306886#Comment_306886 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306886#Comment_306886 Wed, 02 Oct 2024 15:31:29 +0100 Peter_in_Hungary Posted By: bobsoWhile the coal shed isn’t wet; but it is single skin brick
And probably doesn't have a DPC (?)
I would be concerned about any insulation that would degrade / rot if it got damp.

If it were mine I would be thinking of EPS fixed with adhesive and moisture resistant plasterboard over that again fixed with adhesive. Lightweight things (pictures) fixed to the plasterboard and any shelves screwed through to the brickwork.

For shelves I would use vertical shelf rails with the bottom of the rails sitting on the floor, they can look a bit utilitarian but they take the load off the wall.]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306892#Comment_306892 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306892#Comment_306892 Wed, 02 Oct 2024 21:46:17 +0100 Artiglio It was built in 1935 so had a damp course in the walls but npthing in the solid floor. Floor came up for drainage and tovrun additional ventilation to the under floor void in mainhouse, so a dpm went in for good measure and 100mm celotex. Walls have little exposure to the weather , i bonded 40mm of steico to and baumit plasters over. Made sure the roof and gutters were good.
3 years later no problems whatsoever. It serves as a boiler /utility room with a wc separate at one end. So always warm and has an extract for the mvhr . Certainly not a text book approach. As for fixing to walls, i use 60mm plastic wall plugs, drill to full depth of the woodfibre/plaster, glue the plug in with an foaming pu adhesive, trim off any excess plug, fine for light loads ( pictures, holding cabinets in place) i see it as being as good as a standard plasterboard fixing.]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306898#Comment_306898 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306898#Comment_306898 Thu, 03 Oct 2024 11:06:04 +0100 Peter_in_Hungary Posted By: ArtiglioIt was built in 1935 so had a damp course in the walls......... Floor came up for drainage............... so a dpm went in for good measure................ . Walls have little exposure to the weather...................It serves as a boiler /utility room with a wc separate at one end. So always warm and has an extract for the mvhr
All important factors in governing the success of the project.

If bobso's project is missing these features then account should be taken of the missing ones. IMO A DPC and weather exposure being the important ones.]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306899#Comment_306899 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306899#Comment_306899 Thu, 03 Oct 2024 13:29:47 +0100 fostertom Posted By: djhIs the shed single skin brick? If so how do your designs prevent damp (rain) from penetrating through the brick
Posted By: bobsoWhile the coal shed isn’t wet; but it is single skin brick
but does that mean 9" or 4.5"?]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306913#Comment_306913 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306913#Comment_306913 Fri, 04 Oct 2024 11:15:49 +0100 bobso
To clarify it is double brick thickness (but no cavity). Mostly structure seems in good nick having taken the plaster off the walls last night. We also have a DPC.

Project wise:

Based on no positive sheeps wool votes - I'm planning to fill in any previous brick holes with a rough lime plaster, then mount wood fiber boards, followed by another lime plaster coat.

Presume I don't need any breather membranes in this? - Are rigid boards (isolair), or softer (pavatex) type boards better?

Which is better greenlime, steico or Pavatex itself? - Or are they all the "same"....?

DPC wise - We've got one... So with the floor up, we're tanking in a DPM membrane to make it better and then going to take that up behind the insulation.

Thanks everyone for their help, just building control people to please next!]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306914#Comment_306914 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306914#Comment_306914 Fri, 04 Oct 2024 13:06:24 +0100 Doubting_Thomas
Maybe also have a read of this:

https://woodfibreinsulation.co.uk/choosing-the-right-wood-fibre-insulation-manufacturer/


For what it's worth I think the woodfibre does the equivalent of a breather membrane in its dense construction, so I don't think you need a separate one, but WUFI should tell you this.

Clearly keeping moisture from getting through the brickwork behind it is the key thing to ensure.]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306916#Comment_306916 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306916#Comment_306916 Fri, 04 Oct 2024 17:05:01 +0100 Peter_in_Hungary Posted By: bobsorying to internally insulate our old coal shed. (now a study, which has been previously plastered (badly) and has various wires/ cables in the walls.
Posted By: bobsojust building control people to please next!


It sounds like it wasn't / isn't a coal shed and has already been used as something else - So do you need to get BC involved?]]> Sheepswool vs Woodfibre for walls https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306920#Comment_306920 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18205&Focus=306920#Comment_306920 Fri, 04 Oct 2024 20:53:14 +0100 djh Posted By: Doubting_ThomasMaybe also have a read of this:

https://woodfibreinsulation.co.uk/choosing-the-right-wood-fibre-insulation-manufacturer/Thanks. Excellent link.]]>