Wood fibre vs wood wool

[KJKJ78]

This stuff:

ISOLAIR Multi Wood Fibre Insulation Board - Unity Lime Products

Isolair Multi wood fibre insulation board is a breathable multipurpose board that can be clad & rendered. Suitable for roof, internal & external walls

unitylime.co.uk

should be what you’re after

You are absolutely wonderful!!! Thank you. When you don't have a clue you read a lot to get the info, then people go off on tangents, some people are really nerdy (in a good way but it simply confuses me) and then you have to try and pick through all the suggestions to get a suitable one. I really think there should be a Period Property For Dummies website.

 

[KJKJ78]

This stuff:

ISOLAIR Multi Wood Fibre Insulation Board - Unity Lime Products

Isolair Multi wood fibre insulation board is a breathable multipurpose board that can be clad & rendered. Suitable for roof, internal & external walls

unitylime.co.uk

should be what you’re after

and still stick to 60mm do you reckon?

 

[Lacan07]

Oh my, I am now very confused!! Can anyone tell me if this is correct...

External facing stone walls need internally insulating so I'm thinking of going with wood fibre due to all the discussions above. I was going to use this: https://unitylime.co.uk/shop/brand/pavatex/pavadry-pavatex/ but noticed it uses OSB which I didn't think was particularly breathable.....but then I read about wood fibre insulation which I have decided 60mm would be the most sensible because of the dew point comment (further up the chain). So will the Pavadry be ok and if I don't go with the Pavadry, do I need to buy wood fibre insulation and wood fibre boards? Arrghhh. I want whatever it is mounted directly to the lime plastered wall.

Does that make any sense at all?

You need wood fibre 'board' which is mechanically fixed to your lime plastered walls.

60mm sounds like a good plan, there are various brands like the one linked above by Twig or try 'Steico' who are the most common name in field.

 

[Lacan07]

and still stick to 60mm do you reckon?

that depends on how thick you're stone walls are?

For standard 9" solid brick wall they say no more than 80mm

 

[KJKJ78]

THICK THICK stone!

 

[Kearn]

THICK THICK stone!

Then frankly there’s really no benefit in adding insulation, the stone will do that for you, once it is fully dry

 

[Lacan07]

THICK THICK stone!

As Kearn says if you've got super thick stone walls then don't bother, maybe just consider using insulating plaster as your base when you plaster the walls.

 

[Claud]

that depends on how thick you're stone walls are?

For standard 9" solid brick wall they say no more than 80mm

So 60-80mm is the best for 9inch brick.. Going thicker is bad because the dew point is moved to the inside of the wall? I'm going to use woodfibre soon but decided to add mine to a timber stud against the wall and cover in wood wool board to plaster.

 

[KJKJ78]

Then frankly there’s really no benefit in adding insulation, the stone will do that for you, once it is fully dry

OH!!! Erm...it won't make any difference at all? Since I've removed the plaster the room is absolutely freezing and that's been when it was 17 outside. I'm not sure the thermal mass on its own is enough to prevent me dying of cold as I'm on the top of a hill and it is VERY windy.....

 

[Kearn]

Not once the correct balance has been achieved, no.

What plaster did you remove?
Is the wall bone dry?
Have you allowed it time to heat up and become a thermal store.
What’s your heating approach?

If you wish to heat your airspace as per a modern shell, then by all means try to insulate the walls and keep the heat airborne.
Old buildings work with a low constant heat, which allows the fabric to absorb and retain heat.

Old buildings don’t change their equilibrium at the speed we wish them to…

You don’t actually say how thick the walls are, or their construction and materials. But if wind is making the inside of your house cold, there may be other issues.

Money would be far better spent on secondary glazing, finding and filling gaps, heavy curtains etc…

And if you want some further research, Heritage England have recently published research about the potential risk of adding internal insulation to old builds…

 

[KJKJ78]

Ok so the 53cm solid stone walls were covered with gypsum plaster, chipboard, more plaster, bitumen paint and then wooden panelling. Upon removal the wall seems to be dry apart from I'm one main area (previous thread on this where I said I would investigate further!). After investigating it could be because of the higher ground outside in comparison to inside (potentially doing a Zebcolm trench) but could also be a leaky window. Nothing particularly obvious and the wall was barely wet but all the plaster had blown. Under the window it was slightly damp. Have unpiled a lot of the window stone to let air in and leaving it to dry out). So it might become bone dry or I might find the issue but as I say, it was pretty good for a wall covered in non breathable materials for 25 years so it could just be that!

There is currently an oil boiler (I've only been here 3 weeks) so I don't know how that was being used e.g. constant temp or blasting on and off. I'd love a heat pump but I don't think I can get the grant as my EPC is E, HOWEVER, as I type i am having a survey with thermal imaging so we shall see.

 

[KJKJ78]

Oh and can you send me a link to the report as I can only seem to find stuff from Historic England?

 

[a twig]

I think this is what Kearn is referring to:

https://www.michaelhornsby.co.uk/assets/Uploads/documents/eehb-insulating-solid-walls.pdf

Broadly it highlights the risks of using inappropriate materials, installing materials badly leading to interstitial condensation, and the risk of over-insulating internally and thus losing the thermo-regulation benefits of the mass of the solid wall.

Having done both I definitely saw a benefit in using 25mm wood wool internally vs insulating plasters, but I’m sure others experience varies

 

[KJKJ78]

Ah I see!! Yes I think I've read that before actually. Regarding fitting it all properly, I'm going to make sure I quiz builders without giving them the answers to see if they know what they are doing

Thanks both!!

 

[Kearn]

Ok so the 53cm solid stone walls were covered with gypsum plaster, chipboard, more plaster, bitumen paint and then wooden panelling. Upon removal the wall seems to be dry apart from I'm one main area (previous thread on this where I said I would investigate further!). After investigating it could be because of the higher ground outside in comparison to inside (potentially doing a Zebcolm trench) but could also be a leaky window. Nothing particularly obvious and the wall was barely wet but all the plaster had blown. Under the window it was slightly damp. Have unpiled a lot of the window stone to let air in and leaving it to dry out). So it might become bone dry or I might find the issue but as I say, it was pretty good for a wall covered in non breathable materials for 25 years so it could just be that!

There is currently an oil boiler (I've only been here 3 weeks) so I don't know how that was being used e.g. constant temp or blasting on and off. I'd love a heat pump but I don't think I can get the grant as my EPC is E, HOWEVER, as I type i am having a survey with thermal imaging so we shall see.

There’s a reason the plaster has blown. And you won’t necessarily feel the damp by touch, you will feel it be being in a cold room. seeming dry and being dry are very different things.

What you’ve removed is a hellish mixture of impermeable rubbish which won’t have let the wall breath and regulate moisture for decades. The wall will be damp. And worse case you’re looking at 20 ish months at the old 1mth/inch guide. It may not be so severe, but there’s no doubt that wall is now digging with relief and releasing its trapped moisture.

Getting an old house balanced is a waiting game…

 

[KJKJ78]

Ah gotcha!! So I should give it a good length of time to dry out or there's not much point walloping something else on even if it is vapour permeable!

Tbere wasn't any mould etc. Which surprised me as other houses I viewed which were also covered in crap, definitely had mould issues too!

I've never been good at waiting so perhaps now is the time to practice!! Thanks for all the info

 

[KJKJ78]

And it turns out that the heat loss calculation is within the limits for the government grant so I might get a heat pump! Then the house doesn't have to go from hot to cold to hot again all the time.