Wood fibre Flexi batts vs IndiTherm Hemp batts vs Sisalwool Flexi batts

[mh12]

Currently there appears to be 3 products which fulfill the breathability criteria for IWI for Victoria/Edwardian solid brick wall contructions on the market which can be fitted between studs applied to the walls.

Woodfibre seems a very popular choice on this forum and currently heavily inclined towards this option.

Would it be possible to have your opinions on the other 2 products please-- IndiTherm Hemp batts and Sisalwool batts in terms of how they compare property-wise to wood fibre and in particular any contraindications for use for these products for IWI.

50mm Insulation Slabs (370mm & 570mm width)

Packs of 50mm slabs for walls, floors or roofs. Natural, safe and easy to install. Order online and get fast delivery throughout the UK.

www.sisalwool.com

IndiTherm Natural Hemp Flexibatt Thermal Insulation Batts - 50mm x 570mm x 1200mm (Pack of 8)

IndiTherm 040 Natural Hemp Flexibatt Thermal Insulation Batts are a healthy, soft-touch and flexible insulation solution that...

www.roofgiant.com

Thanks in adavnce

 

[mh12]

Sorry for the late addition to the above, 2 further queries if I may:

1) has anyone had direct experience with using either Sisalwool or IndiTherm Natural Hemp fibre batts or equivalent for IWI

2) If an external wall has a damp patch measuring approx halaf a sqaure metre on chimney breast from suspected rain water ingress from open top chimney then should IWI be avoided on this wall? Chimney caps will be applied to the disused chimney on the said wall to prevent further rain water ingress.

 

[Lacan07]

Currently there appears to be 3 products which fulfill the breathability criteria for IWI for Victoria/Edwardian solid brick wall contructions on the market which can be fitted between studs applied to the walls.

Woodfibre seems a very popular choice on this forum and currently heavily inclined towards this option.

Would it be possible to have your opinions on the other 2 products please-- IndiTherm Hemp batts and Sisalwool batts in terms of how they compare property-wise to wood fibre and in particular any contraindications for use for these products for IWI.

50mm Insulation Slabs (370mm & 570mm width)

Packs of 50mm slabs for walls, floors or roofs. Natural, safe and easy to install. Order online and get fast delivery throughout the UK.

www.sisalwool.com

IndiTherm Natural Hemp Flexibatt Thermal Insulation Batts - 50mm x 570mm x 1200mm (Pack of 8)

IndiTherm 040 Natural Hemp Flexibatt Thermal Insulation Batts are a healthy, soft-touch and flexible insulation solution that...

www.roofgiant.com

Thanks in adavnce

Surely it comes down to the differing U values. Apart from that id imagine they're much of a muchness. Wood fibre usually gets the nod due to superior insulation values.

 

[Lacan07]

Sorry for the late addition to the above, 2 further queries if I may:

1) has anyone had direct experience with using either Sisalwool or IndiTherm Natural Hemp fibre batts or equivalent for IWI

2) If an external wall has a damp patch measuring approx halaf a sqaure metre on chimney breast from suspected rain water ingress from open top chimney then should IWI be avoided on this wall? Chimney caps will be applied to the disused chimney on the said wall to prevent further rain water ingress.

View attachment 15315

Is it water ingress or is it historic salts?

You could take a (small) risk and just proceed with IWI, or belt and braces would be some kind of cow shit / fine coat skim before apply insulation.

 

[cags]

Using the Inditherm batts at the moment to externally insulate a modern (but traditionally built) log cabin with bad water damage and rot to the timbers (basically treating it like a solid wall and ensuring breathable materials throughout). Planning to finish with lath, insulating lime render, and then NHL3.5 skim.



Pros: smells faintly of hay, easy to handle without gloves, not too dusty. Flexible and rips up easily which is important for me as I need to stuff lots of irregularly shaped voids to make up where the timbers have rotted. The U value matches that of solid timber more closely than other materials which I'm hoping will help avoid cold bridging.

Cons: cost versus U value isn't the best but it was what my local MKM had that delivered in small enough quantities. Still reasonably messy. A pain in the hole to cut, best method seems to be to fold it, then kneel on it and hack with a Stanley blade along the fold.

The timbers themselves are fairly damp following application of a water-based boric acid/ethylene glycol antifungal and insecticidal treatment (the original source of water damage has been addressed). This should dry over the coming months as the ethylene glycol slowly evaporates and given all layers of the wall are vapour permeable the wall should dry out as a whole and provide good thermal performance.

Time will tell though!

 

[fernicarry]

A pain in the hole to cut,

I use these carving knife blades in a jigsaw. I compress the batt along the edge of the cut with a board which also gives something for the jigsaw to run along and set the whole lot on top of my little aluminium platform which has convenient lengthwise slots in it for the blade to poke through. This gives a really clean, factory-like cut edge.

Mainly I've used Indinature under the floor where its slight squishiness makes it easier to fit between not perfectly regular joists. I've started using it for IWI in the room I'm working on at the moment, again its ability to conform to different shapes and depths is useful as its a rubble stone wall (parged to be flat-ish).

I tried wood fibre boards a few years back and found they were too rigid to fit unless the gap was perfectly square. If you are fitting into new studwork that should be less of a concern. I think some brands have a bit more give than others so ideally you'd want to get some samples to see what you fancy working with before committing to a pallet load.

For me Inidinature is a combination of it being good to work with, available over-the-counter not too far away and fairly economical per area. Less worried about absolute U-values, things can only get better in this place IMO. If the job never gets done or ends up poorly detailed then the U-value is moot anyway. I can also get Breathaplasta and membranes in the same place. Indinature seem to have quite a good story in terms of sustainabiltiy, although you may wish to take that stuff with a pinch of salt, but surely better than having materials trucked over from the continent.

 

[mh12]

Lacan07, cags, fernicarry... a collective thank you for the contributions. Immensely helpful.

Fernicarry, you've mentioned Breathaplasta. Have had a google and not able to identify whether it is actually lime based product? I suppose it must be if manufacturer states that its breathable.
How did you find its application compared to standard gypsum plaster? I guess what im trying to determine is whether an experienced plasterer should be able to use this product.
edit....breathaplasta is hydraulic lime from the product spec sheet (pre-mised hemp lime plaster for internal use only).

 

[mh12]

Is it water ingress or is it historic salts?

Good question. Tbh I'm not entirely sure. I mean the house has been unoccupied for several years and so no fires lit up in the fireplace so I thought most likely rain water ingress from uncapped chimney.
I mean it would be extremely to determine which it is, just dont know how to.

 

[Cubist]

Using the Inditherm batts at the moment to externally insulate a modern (but traditionally built) log cabin with bad water damage and rot to the timbers (basically treating it like a solid wall and ensuring breathable materials throughout). Planning to finish with lath, insulating lime render, and then NHL3.5 skim.

View attachment 15324

Pros: smells faintly of hay, easy to handle without gloves, not too dusty. Flexible and rips up easily which is important for me as I need to stuff lots of irregularly shaped voids to make up where the timbers have rotted. The U value matches that of solid timber more closely than other materials which I'm hoping will help avoid cold bridging.

Cons: cost versus U value isn't the best but it was what my local MKM had that delivered in small enough quantities. Still reasonably messy. A pain in the hole to cut, best method seems to be to fold it, then kneel on it and hack with a Stanley blade along the fold.

The timbers themselves are fairly damp following application of a water-based boric acid/ethylene glycol antifungal and insecticidal treatment (the original source of water damage has been addressed). This should dry over the coming months as the ethylene glycol slowly evaporates and given all layers of the wall are vapour permeable the wall should dry out as a whole and provide good thermal performance.

Time will tell though!

Coo, is that a log cabin?

 

[fernicarry]

How did you find its application compared to standard gypsum plaster

I've only used the thermal stuff so far to level out the stone to take the hemp batts. I'm no plastering expert and hate doing most wet trades since I tend to end up wearing most of the material but it went on easily enough. It dries very quickly compared to putty based lime plasters and I get the impression its formulated to behave in a way that appeals to tradespeople more used to modern stuff.

 

[a twig]

Lacan07, cags, fernicarry... a collective thank you for the contributions. Immensely helpful.

Fernicarry, you've mentioned Breathaplasta. Have had a google and not able to identify whether it is actually lime based product? I suppose it must be if manufacturer states that its breathable.
How did you find its application compared to standard gypsum plaster? I guess what im trying to determine is whether an experienced plasterer should be able to use this product.
edit....breathaplasta is hydraulic lime from the product spec sheet (pre-mised hemp lime plaster for internal use only).

From their website:

Breathaplasta is comprised of a blend of limes and so has characteristics of both types of construction lime. This makes Breathaplasta a very versatile product and well suited to a wide range of applications across several different building types and ages – from heritage to new build.

Breathaplasta is predominantly a high-quality, ultra-fine non-hydraulic building lime blended with a small amount of moderately hydraulic lime (NHL 3.5) and a mineral that acts as a pozzolan. Supplied pre-mixed in powder form, Breathaplasta simply requires the addition of water to create a smooth blended plaster mix

Hydraulic lime or non-hydraulic lime? | Adaptavate

The world of building limes can be a confusing place.

adaptavate.com

 

[Lacan07]

Good question. Tbh I'm not entirely sure. I mean the house has been unoccupied for several years and so no fires lit up in the fireplace so I thought most likely rain water ingress from uncapped chimney.
I mean it would be extremely to determine which it is, just dont know how to.

See if you can tightly attach some cling film or similar to the damp patch, you could use some small nails or some gaffa, it should stick to the dry plaster. During a wet spell any moisture that may appear on top of the cling film could indicate moist internal air is being attracted to the site.

I have a similar problem on my chimney breast. There used to be a leak there but I've since removed the stack down to loft level and its dry as a bone but I still get a damp patch in exactly the same place.

 

[Kearn]

From their website:

Breathaplasta is comprised of a blend of limes and so has characteristics of both types of construction lime. This makes Breathaplasta a very versatile product and well suited to a wide range of applications across several different building types and ages – from heritage to new build.

Breathaplasta is predominantly a high-quality, ultra-fine non-hydraulic building lime blended with a small amount of moderately hydraulic lime (NHL 3.5) and a mineral that acts as a pozzolan. Supplied pre-mixed in powder form, Breathaplasta simply requires the addition of water to create a smooth blended plaster mix

Hydraulic lime or non-hydraulic lime? | Adaptavate

The world of building limes can be a confusing place.

adaptavate.com

I

Lacan07, cags, fernicarry... a collective thank you for the contributions. Immensely helpful.

Fernicarry, you've mentioned Breathaplasta. Have had a google and not able to identify whether it is actually lime based product? I suppose it must be if manufacturer states that its breathable.
How did you find its application compared to standard gypsum plaster? I guess what im trying to determine is whether an experienced plasterer should be able to use this product.
edit....breathaplasta is hydraulic lime from the product spec sheet (pre-mised hemp lime plaster for internal use only).

it’s to be avoided really, unknown origin NHL 3.5 base plus additives to create a quick set. Chances are it’s going to set so hard any porosity properties are long gone.

From various accounts, any gypsum trades can apply it as its effectively add water and go in small quantities, due to limited working time. Any traditional plasterer would likely hate it and be unwilling to use it. Plus they could do it with the right materials for less than these overpriced bags.

 

[cags]

I use these carving knife blades in a jigsaw. I compress the batt along the edge of the cut with a board which also gives something for the jigsaw to run along and set the whole lot on top of my little aluminium platform which has convenient lengthwise slots in it for the blade to poke through. This gives a really clean, factory-like cut edge.

Legend thank you so much.

Coo, is that a log cabin?

It is indeed! Installed 20-25 years ago by previous owners. Some eejit put up a pitched roof greenhouse right next to it so that rain soaked the cabin wall every time it rained (and of course no guttering), leaving some of the 8-12 inch diameter logs literally completed rotted through A few other things that ideally would have been done differently (would not have used pine, and I'd have taken the bark off before installing) but apart from the problem wall it's sound and warm! Fully plumbed, electric, wifi etc, has a full bath and kitchenette as well as log burner.

 

[cags]

 

[Cubist]

Wow, that's gorgeous and I want one. I'm intrigued though by its history, do you know much about it?

 

[mh12]

Plus they could do it with the right materials for less than these overpriced bags.

Can you please expand on this. Which sort of materials did you have in mind as a substitute for Breathaplasta to achieve the same effects i.e breathable plaster

 

[Kearn]

Lime.

No nasty additive and chemicals to aid workability / increase set times.

I also believe it’s quite a pricey bag of muck, compared to pre-mixed putty or even having your plasterer hot mix on site.

‘Breathaplaster’ sadly does not equal breathable plaster.

 

[mh12]

Lime.

No nasty additive and chemicals to aid workability / increase set times.

I also believe it’s quite a pricey bag of muck, compared to pre-mixed putty or even having your plasterer hot mix on site.

‘Breathaplaster’ sadly does not equal breathable plaster.

Sorry, I meant in term of product name.
It's a challenge to find lime based plasters from local building merchants in the West Midlands.
Made me wonder why is this. Market economics?, supply and demand?

 

[a twig]

It’s general lack of interest in conservation / restoration work from the majority of trades, if you’re lucky you’ll find a merchant that sells an NHL3.5 - usually Limelite or similar.

A lot of merchants will sell blue circle hydrated lime in a powder that can be knocked up into putty with water, as hydrated lime is often used in other cement based mixes.

If you want anything else you’ll need to find a specialist supplier - either online and pay pallet shipping costs (£40-£60) or hopefully find one in sensible driving distance - depending on where you are in the West Mids these people might be a possibility:

The Traditional Lime Company,
Church Farm,
Leckhampton,
Cheltenham,
Gloucestershire,
GL530QJ

If you are going to order online, worth planning your projects ahead to fill your pallet and make the shipping as economical as possible