Solid Wall Insulation

[SimonD]

11 hours ago, bighouseproblems said:

Yeah we have 9 rooms to retrofit, the smallest room apart from the bathroom is probably 4mx4m. The reason for not going natural is for a few reasons 1. Finding people who will do it contacted a few explained never heard back. 2. Cost which would be substantial 3. Noise levels the house is like a bomb shelter but we do have heavy goods vehicles coming past at times and would like it as quiet as possible. 4. Lastly I am starting to think about future proofing the house for solar and ashp with energy rates being what they are. £2,500 energy bill for the last year lol will probably be £5,000 this time next year ha. So in essence it's about coming up with a common sense solution that can be executed over the whole house in a relatively timely manner.

 

Fair enough.

 

10 hours ago, saveasteading said:

From recent reading, a masonry wall with lime mortar is going to breathe outwards. I can't see that encouraging evaporation into a warmish internal void is a good thing.

 

Yes, the wall can breathe outwards, but I'm not sure where you're reading information that implies encouraging evaporation to a warmish internal void isn't a good thing. Once you install the IWI the internal temperature of the wall reduces, especially in winter and that in turn reduces the capability of the wall to dry out to the inside but it will also likely affect the ability of the wall to dry to the outside and potentially introduce frost risk.

 

Current best practice guidance says to allow solid walls to breathe to both sides using some kind of moisture open insulation buildup and if you don't use a moiture open system then ventilate between the .

 

Without the correct IWI system buildup, using something like cavity batts may not be suitable at all. If the insulation does not absorb any moisture, then that moisture may collect as condensation and then run down the insulation inside the wall and collect there and it has nowhere to go.

 

For me there are some fundamental aspects missing from the puzzle you are both trying to solve.

 

The first is airtightness which has the greatest single effect on retrofit energy performance, so first look at your strategy for airtightness. Second is moisture management or the hygrothermal properties of the system buildup. Here are some quotations giving current guidance on best practice for solid wall IWI, with links below:

 

Quote

44. The lowest risk designs for internal wall insulation are consistent with the
existing moisture strategy of the building. For solid walled (traditional)
buildings, this is likely to be moisture open, so capillary active insulations
(such as woodfibre) and vapour open adhesives and finishes shall be chosen.
This does not involve the use of vapour barriers7, but will include an air
barrier. This allows drying to both sides of the internal wall insulation and
therefore maintaining the moisture balance within the wall. A Bristolian’s
Guide to Solid Wall insulation contains more information about this approach
and illustrates a series of vapour open designs for internal wall insulation.8
45. The risk of interstitial condensation with internal wall insulation can be high
due to warm internal air passing through or around the insulation and
airtightness layers and condensing on the cold wall, and/or from external
moisture within the masonry. The addition of a vapour barrier inside internal
insulation (IWI) on solid walls used to be regarded as essential, partly due to
inappropriate moisture risk assessment methods. However, it is now agreed
that, in many cases, this may cause more harm than good. Therefore, a
moisture open internal wall insulation build-up is recommended in the
insulation of solid walls, or alternatively a moisture closed system with a
ventilated cavity (of at least 25mm) on the cold side.

 

Quote

Insulation thickness
• Do not target a finished (i.e. post-
insulation) wall U-value of lower than 0.6
W/m2K – this typically means a maximum
insulation thickness of around 60mm.
This is because the more insulation you
put on the wall the greater the heat
resistance and the colder the wall, thereby
reducing drying potential and increasing
condensation risks. In addition, heat loss
modelling has demonstrated that, due to
unavoidable thermal bridging with IWI,
applying larger amounts of insulation
will generally have reduced effectiveness
(i.e. there is an optimum insulation depth,
beyond which the cost-benefit ratio
reduces signifcantly)

 

 

Quote

• All sources of acute damp should be
explored and addressed before installing
IWI. The wall should always be dry on the
inside (and most of the way through to the
outside) before any IWI installation

 

Quote

Moisture quality of insulation system
Always use ‘moisture-open’ insulation
systems for IWI, to ensure that walls can
dry to the inside as well as the outside of
the building – this will help minimise the
risk of moisture-related problems outlined
previously. Using moisture-closed
insulation systems reduces the wall's
capacity to dry, which is particularly
important if the wall is wet in any way due to
driving rain, residual damp, or condensation.
In this case, ‘moisture open’ means both
vapour permeable and capillary active. If
insulation systems are not capillary active
then further advice should be sought – if in
doubt, check and consult expert advice.

 

Links:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1019707/iwi-guidance.pdf

https://sdfoundation.org.uk/wp-content/uploads/2018/01/2015_bristolsolidwallinsulationguidance.pdf

 

Along with all of this, it is imperative that you consider your ventilation strategy along with your retrofit measures.

 

I'm not sure where either of you are getting your information about IWI systems and their appropriateness on solid walls, but it does seem to deviate from know best practice!

 

The final bit is to get the hygrothermal performance of your IWI properly modelled using something like WUFI.

 

[bighouseproblems]

1 hour ago, SimonD said:

 

Fair enough.

 

 

Yes, the wall can breathe outwards, but I'm not sure where you're reading information that implies encouraging evaporation to a warmish internal void isn't a good thing. Once you install the IWI the internal temperature of the wall reduces, especially in winter and that in turn reduces the capability of the wall to dry out to the inside but it will also likely affect the ability of the wall to dry to the outside and potentially introduce frost risk.

 

Current best practice guidance says to allow solid walls to breathe to both sides using some kind of moisture open insulation buildup and if you don't use a moiture open system then ventilate between the .

 

Without the correct IWI system buildup, using something like cavity batts may not be suitable at all. If the insulation does not absorb any moisture, then that moisture may collect as condensation and then run down the insulation inside the wall and collect there and it has nowhere to go.

 

For me there are some fundamental aspects missing from the puzzle you are both trying to solve.

 

The first is airtightness which has the greatest single effect on retrofit energy performance, so first look at your strategy for airtightness. Second is moisture management or the hygrothermal properties of the system buildup. Here are some quotations giving current guidance on best practice for solid wall IWI, with links below:

 

 

 

 

 

 

Links:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1019707/iwi-guidance.pdf

https://sdfoundation.org.uk/wp-content/uploads/2018/01/2015_bristolsolidwallinsulationguidance.pdf

 

Along with all of this, it is imperative that you consider your ventilation strategy along with your retrofit measures.

 

I'm not sure where either of you are getting your information about IWI systems and their appropriateness on solid walls, but it does seem to deviate from know best practice!

 

The final bit is to get the hygrothermal performance of your IWI properly modelled using something like WUFI.

 

Thanks Simon I am now reading through this doument link. I am also thinking of knocking up a rig something like a reasonable sized wooden frame which i can mount to an outside wall on the inside layer some osb or plasterboard off cuts with insulation and then a VCL layer and then seal it to the wall and possibly grab a govee hygrometer and place it inside. 

It won't be a true representation but i may give an indication of things alongside when i remove it after a week or two i can inspect it for moisture. 

[SteamyTea]

1 hour ago, bighouseproblems said:

govee hygrometer

Raspberry Pi ZeroW and a BME280 or DHT22 and you can log the temperature and RH.

 

[saveasteading]

10 hours ago, bighouseproblems said:

Your problem sounds a little more complex

 

As you ask...

 

Until  this last year I knew very little about stone buildings, but rather a lot about modern buildings. I expected to find readymade reports with the obvious solution for converting a stone farm building into residential.   No, there are many expert reports, and any number of firmly held views, but they vary considerably.

 

My findings include.

Lime mortar is essential for breathing as well as for allowing movement. Not a problem.

Granite is brilliant at not absorbing any rain, so most rain runs off. ditto not absorbing general dampness. Dense sandstone almost as good.

The 600mm wall construction includes a central core of rubble which is 40% lime mortar, and this helps control dampness and heat loss.

The insulating effect of a thick masonry wall is very much better than the standard formulae allow.

Problem dampness in such buildings fizzles out at about 1m above ground level.

(All the above dependent on good lime mortar and drainage.)

 

Conflicting views include:

To keep the moisture out of the building, add a 1m layer of bitumen tanking to the inside of the wall.  (Aberdeenshire references). 

OR don't do such a silly thing, as it keeps your wall damp,

 

Encourage inward air movement through multiple holes in the wall base, venting through cavity to eaves. (Argyll references, incl Bldg control)

OR Don't do this as you are losing all the insulation benefit of the masonry, and bringing damp outside air to the inside.

 

Use warm batten method, as all the evaporation will be outwards.

OR Don't do this as it is better to have an air gap and air flow.

BUT the latter will encourage evaporation inwards to the warmer void, which would otherwise permeate outwards.

 

And there is more.  The conflicting 'solutions' lead me to believe that I am as right as anybody else.

 

Right now there is a decent roof except for a few holes and farm access points, so water gets in and the inside of the wall (stone) is wet in areas.

(I am ignoring the areas of major damage through neglect, that we will rebuild in timber).

There are also 5 cart entrances and the weather whips through them.

Gutters need repair as do areas of the wall.

When repaired, the rain will mostly be carried well away. Driving rain seems to be uncommon, but may wet one wall at a time. Most of course will run to ground, which happens to be ultra-permeable.

No rising damp, even if such a thing exists (see other discussions).

 

Some damp will soak into the mortar joints (after passing through the external lime mortar parging) ( 2% of the face area??). It won't go very far in but would eventually reach the core where there is the 40% mortar to act as a holding area. Then it will be drawn outwards again as the face dampness evaporates, or downwards towards the permeable ground. Will much of that then travel through the inner skin? I don't think so.

A  picture for interest.

 

 

 

 

[saveasteading]

And an internal. There are 4 wings like this and an inner courtyard. This shows the hole in the roof where grain was heave in.

[Roger440]

17 minutes ago, saveasteading said:

 

As you ask...

 

Until  this last year I knew very little about stone buildings, but rather a lot about modern buildings. I expected to find readymade reports with the obvious solution for converting a stone farm building into residential.   No, there are many expert reports, and any number of firmly held views, but they vary considerably.

 

My findings include.

Lime mortar is essential for breathing as well as for allowing movement. Not a problem.

Granite is brilliant at not absorbing any rain, so most rain runs off. ditto not absorbing general dampness. Dense sandstone almost as good.

The 600mm wall construction includes a central core of rubble which is 40% lime mortar, and this helps control dampness and heat loss.

The insulating effect of a thick masonry wall is very much better than the standard formulae allow.

Problem dampness in such buildings fizzles out at about 1m above ground level.

(All the above dependent on good lime mortar and drainage.)

 

Conflicting views include:

To keep the moisture out of the building, add a 1m layer of bitumen tanking to the inside of the wall.  (Aberdeenshire references). 

OR don't do such a silly thing, as it keeps your wall damp,

 

Encourage inward air movement through multiple holes in the wall base, venting through cavity to eaves. (Argyll references, incl Bldg control)

OR Don't do this as you are losing all the insulation benefit of the masonry, and bringing damp outside air to the inside.

 

Use warm batten method, as all the evaporation will be outwards.

OR Don't do this as it is better to have an air gap and air flow.

BUT the latter will encourage evaporation inwards to the warmer void, which would otherwise permeate outwards.

 

And there is more.  The conflicting 'solutions' lead me to believe that I am as right as anybody else.

 

Right now there is a decent roof except for a few holes and farm access points, so water gets in and the inside of the wall (stone) is wet in areas.

(I am ignoring the areas of major damage through neglect, that we will rebuild in timber).

There are also 5 cart entrances and the weather whips through them.

Gutters need repair as do areas of the wall.

When repaired, the rain will mostly be carried well away. Driving rain seems to be uncommon, but may wet one wall at a time. Most of course will run to ground, which happens to be ultra-permeable.

No rising damp, even if such a thing exists (see other discussions).

 

Some damp will soak into the mortar joints (after passing through the external lime mortar parging) ( 2% of the face area??). It won't go very far in but would eventually reach the core where there is the 40% mortar to act as a holding area. Then it will be drawn outwards again as the face dampness evaporates, or downwards towards the permeable ground. Will much of that then travel through the inner skin? I don't think so.

A  picture for interest.

 

 

 

 

 

Blimey, is this still going on?

 

Ive said what needed saying. Simon has more patience than i and posted again above. With the answers. However, you still want to do something different. Im at a loss why?

 

 

[saveasteading]

8 hours ago, SimonD said:

IWI systems and their appropriateness on solid walls, but it does seem to deviate from know best practice!

I'm grateful for this and previous links.

Other than this, everything I have read suggests an inner timber structure, containing insulation, and wrapped with vapour/airtight barrier.

 

I can't see how the above extracts allow this standard industry construction, of full-fill cavity insulation. attached picture.

 

9 hours ago, SimonD said:

Insulation thickness
• Do not target a finished (i.e. post-
insulation) wall U-value of lower than 0.6
W/m2K – this typically means a maximum
insulation thickness of around 60mm.

This statement is rather shocking. Where does it come from?

I think 600mm of 3 core masonry is reckoned to provide 0.6 in itself.

 

Thinking while typing..... if there is no air gap, then there can be no evaporation.

.

[saveasteading]

3 minutes ago, Roger440 said:

Blimey, is this still going on?

Yes Simon has sent some very relevant references.

 

Your suggestions to date would suggest that nearly all farm buildings are incorrectly converted, and the architects and building inspector's are wrong too.

 

I am analytical, and need proof so if you have any, I'd be grateful

[bighouseproblems]

Having read through many articles and alot of advice from everywhere it appears you either go fully breathable or lime which has limiting factors on u values or you run the risk of condensation. I have someone coming over tomorrow to quote for the work and will see what there opinion is. But on the back of Simon's comments about ventilation in the cavity my only logical approach would be an airbrick in each of the walls but conservation area may cause problems or could a nuaire air mover be installed in the cavity created between the wall and insulation of about 30mm and vent into the loft space. If this would work it would not be that difficult to pipe down through the floorboards to the ground floor also. I guess it would just be the case of whether you could modulate the fan so that it was extremely low and I have a feeling they can be activated when humidity hits a certain level. This to me seems to solve all the problems???

[Roger440]

1 hour ago, saveasteading said:

Yes Simon has sent some very relevant references.

 

Your suggestions to date would suggest that nearly all farm buildings are incorrectly converted, and the architects and building inspector's are wrong too.

 

I am analytical, and need proof so if you have any, I'd be grateful

 

I didnt quite want to put it like that, but pretty much, yes.

 

Niether architects no building inspectors have to live with the consequences and subsequent costs. You do. Assuming you stay there long enough.

 

Go and have a look at a few older ones that have been converted. I did. I wont buy one. Essentially having to undo work done to do again and pay the premium for a "done" conversion.

 

People have been buggering up old houses with cement and gypsum for decades. Thats not debateable, its fact.  Mostly builders, building inspectors and a bit of architect help too. The industry is rife with people with no understanding of moisture. Do a search on some of Jeremys post on condensation issues with SIPS for example.

 

Im not expert, just an enthusiastic ametuer. But i know what i see. I also try to use logic. That helps too.

[Roger440]

6 minutes ago, bighouseproblems said:

Having read through many articles and alot of advice from everywhere it appears you either go fully breathable or lime which has limiting factors on u values or you run the risk of condensation. I have someone coming over tomorrow to quote for the work and will see what there opinion is. But on the back of Simon's comments about ventilation in the cavity my only logical approach would be an airbrick in each of the walls but conservation area may cause problems or could a nuaire air mover be installed in the cavity created between the wall and insulation of about 30mm and vent into the loft space. If this would work it would not be that difficult to pipe down through the floorboards to the ground floor also. I guess it would just be the case of whether you could modulate the fan so that it was extremely low and I have a feeling they can be activated when humidity hits a certain level. This to me seems to solve all the problems???

 

No, no no!

 

As per Simons post you are decoupling the wall from the "house" with all the issues that "might" bring.

 

 

[Cpd]

There are so many views on how to insulate an old building like this…. It’s always the same with one team firmly set in the traditional camp with lime being the key word and the other team at the very far end of the field talking about PIR and Gypsum ! If your stuck in the middle god help you…. Your either going to get converted by one side and hated by the other or both sides are going to kick the shite out of you for sitting on the fence. 
 

 

[Gus Potter]

Great thread this.. much to ponder. There is no easy answer / the perfect solution.

 

Having worked on the odd old building and converted steadings over the years while keeping up with modern approaches, new materials etc I'm often led back to first principles, practicality in terms of analysis (thermal performance in the real world) , keeping the cost down ( labour costs low = easy detailing for example) and to look ahead at future maintenance and how easy it would be to rectify an issue locally without trashing large areas of walls and the associated disruption.

 

For me the starting point is always to look outside first. Here is a list of some of the things I like to gather info on. Ground levels, soil drainage at the base of the wall, the pointing.. the shape of the pointing on a brick / stone wall is vitally important and that if rendered then the type of render, general condition,  drips on window and door cill details are examined as are flashings and anything else I can think of. For old buildings like saveasteadings the gable detail / cope and skew putts for example all need careful examination as do any chimneys an old flues.

 

For @bighouseproblems the type of brick / it's porosity and mortar are of particular interest. Other things worth a look at are the aspect of the building, how sheltered is it from the drying / cooling effects of the wind, is it over shaddowed and where in the UK is it located..altitude and distance to the coast, the realtive humidity can often be a significant driver in a coastal location. each wall will behave differently so for economy / simplicity you are seeking a reasonable compromise. Yes, you can run computer models.. SEs for example use some complex finite element analysis.. but that is (hopefully) always coupled with common sense, reasoned judgement and appreciation of the limitations of the computer model. The same applies here.. any say computer analysis is only one part of the puzzle that helps you make an informed judgement.

 

In general for walls above ground I'm not a fan of sticking any butuminous or water proof stuff to the inside of the walls like render. Not a fan of chemical damp courses or other gizmos.

The idea of the warm batten is good in principle but.. you often have cross walls that form an integral part of the sturctural stability system of the building so you need to detail for that. Already it is getting more tricky. While on paper you can make a blank wall work the problems always seem to crop up in say the corners! To make it work you will need to detail well.. and live in the builders trousers for a while so you can keep an eye on their every move! 

 

Practically my first port of call would be to maintain a cavity between the external wall and your inner insulated envelope. You can essentially build a non load bearing stud partition. The studs can be fairly slender. You can bracket them mid height with plastic angle brackets to take the bounce out of the wall.. if you want to get carried away and are worried about metal brackets causing a repeating cold bridge. Next you can insulate beteween the studs with insulated plaster board over to prevent ghosting and to boost the insulation effect. Ghosting often happens particularly in kitchens. The studs are a little cooler so the fat condenses here and so does some of the moisture. This manifests as darker shading in your wall finish.

 

Now this all may sound like something out of the dark ages until you get a price from the builder to install and stick to the inevitable complex detail. If a problem occurs, usually under / over a window or in the corner then its often much easier to access an independant non load bearing frame than some other options.

 

Now in many cases you can introduce controlled trickle ventilation to the cavity in old buildings.. it needs some thought but often achievable.

 

I would encourage examining the simple stupid option in the round, cost this and then if you want to get more innovative at least you have a bench mark to work with.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[SimonD]

4 hours ago, saveasteading said:

Until  this last year I knew very little about stone buildings, but rather a lot about modern buildings. I expected to find readymade reports with the obvious solution for converting a stone farm building into residential.   No, there are many expert reports, and any number of firmly held views, but they vary considerably.

 

Amazing project by the way. Love the building and what you're trying to do. I'm rather jealous (or is that just Stockholm syndrome from difficult projects?).

 

Anyway, yes there are varied views and this is partly because we still don't fully understand the hygrothermal nature of buildings. However, there is a certain consensus building, especially with regards to retrofit in older buildings which is evidence based as opposed to firmly held views. I think the situation is improving from where it was even 5 years ago. Generally, it does seem to be falling on the side of moisture open materials to reduce risks.

 

4 hours ago, saveasteading said:

My findings include.

Lime mortar is essential for breathing as well as for allowing movement. Not a problem.

Granite is brilliant at not absorbing any rain, so most rain runs off. ditto not absorbing general dampness. Dense sandstone almost as good.

The 600mm wall construction includes a central core of rubble which is 40% lime mortar, and this helps control dampness and heat loss.

The insulating effect of a thick masonry wall is very much better than the standard formulae allow.

Problem dampness in such buildings fizzles out at about 1m above ground level.

(All the above dependent on good lime mortar and drainage.)

I'm with you on much of this although I'd say the one thing missing is salts and their effect on moisture within the walls. Your 1 st meter or so of dampness is likely to contain quite a bit which will soak up more moisture and delay its drying out, but with also add to the amplitude of damp/dry cycles.

 

4 hours ago, saveasteading said:

Conflicting views include:

To keep the moisture out of the building, add a 1m layer of bitumen tanking to the inside of the wall.  (Aberdeenshire references). 

OR don't do such a silly thing, as it keeps your wall damp,

 

Encourage inward air movement through multiple holes in the wall base, venting through cavity to eaves. (Argyll references, incl Bldg control)

OR Don't do this as you are losing all the insulation benefit of the masonry, and bringing damp outside air to the inside.

 

Use warm batten method, as all the evaporation will be outwards.

OR Don't do this as it is better to have an air gap and air flow.

BUT the latter will encourage evaporation inwards to the warmer void, which would otherwise permeate outwards.

 

Some of this is evidence based, some of it isn't. I think there is a fair wind blowing in the direction of the principle of not to tank the inside of the wall with imperveous materials on an old building such as yours.

 

When you speak of bringing damp outside air in and encouraging evaporation to the warmer void which would otherwise permeate outwards does not follow the typical laws of vapour pressure in buildings. Typically, although not exclusively or always, a house will have a higher vapour pressure to the inside than to the outside. This typically means that the moisture will travel outwards where the air is for the most part dryer. So whilst the wall may be able to dry to the inside, this vapour will travel towards the outside, by whichever means of least resistance - this may be through the walls, or through the ventilated cavity, or even a window.

 

4 hours ago, saveasteading said:

And there is more.  The conflicting 'solutions' lead me to believe that I am as right as anybody else.

 

I'd like to clarify, just in case it's needed, that I'm not suggesting your solution is wrong. I'm merely pointing out that there may be problematic details in what you're proposing that unecessarily add risk to your solution when it comes to moisture.

 

For me the consensus is pretty clear. You either go for a solution that is attached directly to the wall and takes the form of a moisture open (vapour and capillary open material),,  if suitable on your wall depending on its dampness, or you go for a separate inner leaf which provides a ventilation cavity, which may use a vcl, or maybe not.

 

4 hours ago, saveasteading said:

I'm grateful for this and previous links.

Other than this, everything I have read suggests an inner timber structure, containing insulation, and wrapped with vapour/airtight barrier.

 

I do hope they're of assistance because I know what a pain this process can be. An inner timber structure could very well work, and as I said, I'm not dissuading you from this. The question is more what the correct detail needs to be for the buildup.

 

4 hours ago, saveasteading said:

I can't see how the above extracts allow this standard industry construction, of full-fill cavity insulation. attached picture.

 

It's because we're talking a completely different context. To quote another source (link below):

 

Quote

Most insulation systems are designed and
developed solely to limit heat loss and to avoid
interstitial condensation from water vapour
generated internally. They do not take account of
how they affect the movement of moisture and
salts already in a traditional wall. So they
can easily:
exacerbate existing problems
create new problems, such as the
displacement of damp and salts and the
decay of timbers in contact with the walls
create health risks for the occupants,
for example from mould growth
be affected by the moisture, reducing their
performance and sometimes failing entirely
Where walls have been damp for a long period of
time it can take years for them to dry out.
The selection and design of insulation must take
account of the drying-out process, both before
and after installation, and the presence of residual damp and salts.

 

Link: https://historicengland.org.uk/images-books/publications/eehb-insulating-solid-walls/heag081-solid-walls/

Another link is re solid wall insulation is Scotland but a bit more out of date: https://www.changeworks.org.uk/sites/default/files/Solid_Wall_Insulation_in_Scotland.pdf

 

Do not confuse modern new buildups with what might work on a historic building - that's what has caused so much historical damage in the first place.

 

4 hours ago, saveasteading said:

This statement is rather shocking. Where does it come from?

I think 600mm of 3 core masonry is reckoned to provide 0.6 in itself.

 

This is from one of the referenced sources of the current government best practice guidance I linked to. If you read the document I link to above from Scotland, a similar point is mentioned: that in some circumstances using thinner IWI is better due to the problems associated with cold bridgig etc. so more insulation becomes counter productive.

 

Given the value you can get from your existing 600mm walls, have you looked at using a moisture open solution that could go directly on the wall? This to me seems like an ideal candidate, at least worthy of serious consideration as it seems to mitigate many of the issues you face with having an internal stud wall IWI. It is also supported by a sigificant volume of current guidance.

 

I appreciate this is different from @Gus Potter's excellent suggestion, and think it would be worthwhile exploring detailed buildups with each system to compare the various costs, complexities, outcome and viability of each side by side.

 

There is also the slightly crazy option of leaving the wall uninsulated for now until the walls dry out and then consider your options further down the road.

[Iceverge]

EWI an option?
 

 

[Al in nl]

Hi,
The void is not needed if you use capillary open insulation. Simon D +1
Such as, wood fibre stuck via lime to wall. Limecrete blocks with limecrete infill between block and wall. Or any light earth mix from wall to inner leaf. DIY work mainly.
No damp open foil. Rely on a plaster layer for airtightness. 

Air will loop around the void.

Rockwool needs the void.
Gypsum plaster sucks up water, so needs a void.
Gypsum plaster does allow water to pass through it but holds onto a lot. Hence all the mold you get with gypsum plaster board. Not recommend with solid walls.
Your choice is not using existing wall to help keep house airtight and build a new airtight layer.

Airtight means lower heating bills.
Have you looked at where the dew point would form with your build up? Ubackus gives an idea of the drying time. If you switch over to the german language version of the website and have the browser do auto translate, you get help articles. Further, the drying times can be ignored if the build up is capillary open.
Really its best to keep the build up capillary open So that any water can simply get out of wall as fast as possible.
Most natural solutions deal with sound really well. But is money.

PIR solution I would place direct on sandstone with a layer of render/something to even out airgaps. In US you'd spray foam it. But that will stick to the sandstone, very hard to remove, and generally not advised. Take your chances.
As for outside, if it had a lime render on it, put a harled lime(or similar) render on it. Such a render gives a much greater surface area, dries much quicker. If your changing the roof, extend the eaves if possible, less water will hit wall.
Have you read the SPAB books?

[SteamyTea]

2 hours ago, Al in nl said:

The void is not needed if you use capillary open insulation. Simon D +1
Such as, wood fibre stuck via lime to wall. Limecrete blocks with limecrete infill between block and wall. Or any light earth mix from wall to inner leaf. DIY work mainly.

There the damp/water takes longer to dry on my bathroom tile grout, mould forms.

What stops mould forming with this sort of wall makeup?

Or does no one ever check?

[saveasteading]

16 hours ago, Iceverge said:

EWI an option?

No it isn't, as we want to retain the character. Strangely there are very few constraints from the planning permission, but it is our desire to maintain the appearance as much as possible.

The eaves don't overhang at all, with just the slates reaching the existing and future gutters.

 

There is so much useful and admirably pragmatic information above that I will review it tomorrow without the beer at my side. The referenced documents will take a little longer.

 

 Just one follow-up query to lob back for now.   The cavity fill rockwool detail.  In what way is this fundamentally different to our situation?

 

Brick skin in the Rockwool standard detail, as compared to existing masonry.

Full fill cavity batt, touching the outer and inner skin.  Applies to both.

Block inner wall  as compared to stud wall filled with insulation, but new build to probably have vapour barrier and airtight barrier.

Plaster finish as compared to plasterboard finish.

 

((I have liked and specified full-fill insulation for many years, mainly because it is idiot-proof. (Bricky cannot leave empty drinks cans in the void because it messes with the 'bond' of the insulating slabs. Bricky can't drop snots of mortar into the void and bridge the cavity). Perhaps it is my combination of designer /contractor as I am surprised that it isn't more widely used.))

I have realised in doing this, that many people in the industry don't know about the product and assume that there has to be an air-gap, whereas the wholepoint is that there is no air-gap, no air circulating, and no dampness crossing.

 

And to tick off 2 things that occurred re previous messages.

1. risk of the dampness freezing in the outer wall because it will be cold....It has been exposed to the weather, in and out, for 20 years, and was a draughty shed for 120 years before that.

2. Salts forming.....again it has been there for 140 years and any salts will be long gone.

 

Admission   Dew-point......Not something I fully understand, in the context of where is the moisture coming from, where will it go, and is that a problem? More thought and study required.

 

I will return after study. Perhaps together we will resolve the issue for ever. The 'Buildhub' solution.

 

 

[Iceverge]

sorry for the confusion. the ewi query was directed @bighouseproblems

[SimonD]

15 hours ago, saveasteading said:

In what way is this fundamentally different to our situation?

 

It's because you're dealing with a wall that's been there for 140 years and is built with different materials that deal differently with moisture. Hence why you can't just supplement a partial  newbuild wall buildup onto this existing wall. Remember, your full fill cavity batt wall buildup will still need a cavity tray and means to direct any collected moisture out of the cavity - this would cleary be problematic, as you've found, with your existing wall where the moisture has nowhere to go should it collect on the inside. This is quite likely given the complexities of detailing vapour control within such a retrofit project.

 

This is where capillary open materials work well because they effectively absord this moisture and pass it through their structure to a dryer atmosphere.

 

15 hours ago, saveasteading said:

And to tick off 2 things that occurred re previous messages.

1. risk of the dampness freezing in the outer wall because it will be cold....It has been exposed to the weather, in and out, for 20 years, and was a draughty shed for 120 years before that.

2. Salts forming.....again it has been there for 140 years and any salts will be long gone.

 

Okay, so the wall has been exposed to the elements for its entire life and may potentially have gone through many freeze/thaw cycles already. Maybe this isn't therefore an issue in your particular case, but it is relevant to anyone else looking to do a retrofit in an existing solid wall house (which is totally relevant to the op).

 

The salts have potentially accumulated with the wall for its lifetime due to the buildings historical use but either way it's currently speculation and due to experience better to assume the presence of the salts rather than not.

 

In your particular case, however, it's important to consider how your conversion project is going to change the environmental conditions for the walls as you're going to be adding both heat and moisture, and vapour pressure etc. to a wall that has not ever been subjected to this. Therefore, understanding and considering things like interstitial condensation risks and moisture transport within and through those walls in light of the new conditions is essential.

Edited February 19, 2022 by SimonD

[SimonD]

19 hours ago, SteamyTea said:

There the damp/water takes longer to dry on my bathroom tile grout, mould forms.

What stops mould forming with this sort of wall makeup?

Or does no one ever check?

 

There are plenty of studies to understand this, but it would require a veritable tome, but in brief:

 

If you have a wall built using waterproof principles such that it is designed not to absord or allow ingress of moisture then any and all moisture released into the building requires removal entirely through ventilation (regardless of the means of ventilation).

 

With a moisture open wall, the materials in the wall can absorb peak loads of moisture released into the building and then slowly release than moisture back into the atmosphere. It's works similarly to decrement delay in insulation and has the effect that it flattens the relative humidity curve within the house. If the entire wall buildup uses moisture open materials, the pore structure will allow the moisture to travel through the entire wall structure too. From studies it has been found that hygroscopic buildups can reduce relative humidity within the building by as much as 25%, which will obviously reduce risks of mould formation. Not only that, it reduces total ventilation requirements, the capacity of which is typicaly designed in order to remove moisture from the building.

 

The other side to it is that materials like lime plaster inhibit the growth of mould and bacteria.

[SteamyTea]

56 minutes ago, SimonD said:

 

There are plenty of studies to understand this, but it would require a veritable tome, but in brief:

Shall have to go looking for some when I have time.  Though it seems most are by product interested groups.

57 minutes ago, SimonD said:

The other side to it is that materials like lime plaster inhibit the growth of mould and bacteria.

Same with this.  I have seem lichens (a bacteria infected fungus) growing on lime, so while it may be better than concrete, I am not convinced.

 

I agree that ventilation is becoming more and more important, and it is going to be hard to convince builder and building users that they have to have it, and use it properly.

[SimonD]

2 hours ago, SteamyTea said:

Though it seems most are by product interested groups.

 

The easily accessible ones written for more public consumption tend to be but there are a lot of decent non-product specific studies in the more academic and building physics resources of you can get to it.

 

2 hours ago, SteamyTea said:

I have seem lichens (a bacteria infected fungus) growing on lime, so while it may be better than concrete, I am not convinced.

 

Mould and bacteria will eventually grow on pretty much anything, given the right condition won't it? I think it mostly about ensuring you build in a way that doesn't provide these conditions rather than rely on a single specific material or solution.

 

2 hours ago, SteamyTea said:

I agree that ventilation is becoming more and more important, and it is going to be hard to convince builder and building users that they have to have it, and use it properly.

 

I learnt more about the behaviour of hygroscopic materials etc. through the study of ventilation than the study of the specific materials themselves. Not long ago there was a government study that found that the majority of new builds don't even meet minimum building regs for ventilation. Hence why I think we'll soon be seeing mechanical ventilation in homes mandated, but we'll have to see whether builders can even do that right.

[Simplysimon]

there are quite a few stone buildings which have been retrofitted to passive standards

https://www.greenbuildingstore.co.uk/holmfirth-farmhouse-radical-retrofit-internal-wall-insulation-iwi-strategy/

[SimonD]

26 minutes ago, Simplysimon said:

there are quite a few stone buildings which have been retrofitted to passive standards

https://www.greenbuildingstore.co.uk/holmfirth-farmhouse-radical-retrofit-internal-wall-insulation-iwi-strategy/

 

The Diathonite they used looks like an amazing product, but does it half cost, especially at 60-80mm thickness.