Internal Insulation - Solid Brick Wall

[Redbeard]

@jc89, I could not get my head round 100mm of WF giving 0.247, as usually it gives somewhere around 0.3+ on a 225 brick wall. I realise that the figure for Intello seems wrong. The Pro Clima datasheet gives a lambda of 0.04, giving an R value for the 1mm thick sheet of 0.025, not 1.0 as per your U value calc. Think I have got that right....

[jayc89]

1 hour ago, Redbeard said:

@jc89, I could not get my head round 100mm of WF giving 0.247, as usually it gives somewhere around 0.3+ on a 225 brick wall. I realise that the figure for Intello seems wrong. The Pro Clima datasheet gives a lambda of 0.04, giving an R value for the 1mm thick sheet of 0.025, not 1.0 as per your U value calc. Think I have got that right....

 

You're right, not sure how that happened. Updated figures;

 

 

My question really is whether that service void is suitable to separate the breathable from non-breathable materials. 

[jayc89]

Steico suggest something similar here - https://www.steico.com/en/solutions/renovation/internal-wall-insulation - under "Renovation type: Multi layer internal insulation" although that seems to suggest attaching the plasterboard directly to the VCL, which I don't understand - surely by doing so that would make the entire buildup less breathable. I expected a cavity/service void there to mitigate that.

[SimonD]

On 07/06/2022 at 23:37, jayc89 said:

Steico suggest something similar here - https://www.steico.com/en/solutions/renovation/internal-wall-insulation - under "Renovation type: Multi layer internal insulation" although that seems to suggest attaching the plasterboard directly to the VCL, which I don't understand - surely by doing so that would make the entire buildup less breathable. I expected a cavity/service void there to mitigate that.

 

If you look at the steico buildups there is one key difference. In the first example, the woodfibre is bonded directly to bare solid brickwork and therefore it doesn't require breather membrane or vcl. In the second example a vcl is used because there is an existing internal render on the masonry wall. Because this internal render is not likely to be very vapour permeable or hygroscopic, the vcl is used. Otherwise you end up with a risk of interstitial condensation at the face of the internal render.

 

Do you have bare solid brick or is your wall already lined with plaster to which you're intending to fix the iwi?

[jayc89]

1 hour ago, SimonD said:

Do you have bare solid brick or is your wall already lined with plaster to which you're intending to fix the iwi?

 

A mix. One room is already back to brick and waiting for "something" to happen. The others are wet plastered (lime), at some points it's nearly an inch thick, so I do have the option to knock this off to make back some of the space lost to IWI.

[SimonD]

22 hours ago, jayc89 said:

The others are wet plastered (lime), at some points it's nearly an inch thick, so I do have the option to knock this off to make back some of the space lost to IWI.

 

So these are your risk points. The lime on its own should be fine for woodfibre but the risk is what paints have been used on the lime that might render it unbreathable. It's not unknown to find some so-called breathable paints that actually have an sd value equal to a 10 meter thick wall!

[richo106]

This is a topic I am having struggles with. I can't have EWI but want/need to increase insulation level on my internal walls 

 

My current make us is:

Brick

65mm Cavity with blown insulation

Brick

 

I was planning on getting a parge coat over all the brickwork to help with airtightness

I can't guarantee that the walls aren't perfectly flat/square so i was thinking would the warm batten method prove quite tricky to get flush? (was thinking 50mm PIR)

Would it to better to have the gypliner system and rock wool?

 

As suggestions are greatly appreciated as i seem to be going round in circles with this issue

 

Many Thanks

 

 

  

[Redbeard]

In your situation you have to consider the interstitial condensation risk, or at least consider whether there might be one. Adding another layer - in this case separated by a skin of brick - further cools the inside of the external skin. I am a great believer in dynamic condensation risk assessment. WUFI is the only one I am familiar with, but I gather there is another. The BS 'Glaser' Method is a bit of a blunt instrument and makes assumptions which are simply not always true (for example that all the moisture in a 'sandwich' will come from inside).

 

Sadly I think, even now, there is a scarcity of WUFI-wranglers. Some merchants offer it 'free' for buying their materials. 

 

I have used the warm batten method a lot, and have 'championed' it (more that it's better than hiding vulnerable battens on the cold side than that it is the bee's knees, and always in the context that I am thoroughly 'sold' on rigid, dense, wood-fibre on the basis that if it functions without a VCL then there isn't a VCL to screw up myself or have subsequent 'generations' screw up for me), but I note now that the BEIS guidance for IWI effectively says 'vapour-open' (wood-fibre, cork, etc) or 'ventilated cavity. IIRC they say 25mm, which strikes me as too small, but that's gut-feeling, not physics. I also worry about 'real-life' situations actually giving you a properly-cross-ventilated, properly 'purged' cavity.

 

Of your 2 possibilities gypliner (which I have never used, BTW) could give you the ventilated cavity.

[richo106]

I know insulation backed PB in very expensive in comparison to PB and insulation but what about some 50/80mm PIR backed PB dotted and dabbed?

 

Would this be a good option? My problem with this fixed items to it and the cost but it would negate any even walls etc

 

Any opinion on this?

 

 

[jayc89]

On 09/04/2022 at 12:51, nod said:

I wouldn’t fix anything directly to the walls 

By far your best option is gypliner either Boarded with insulated pb or wool batts and boarded with 12.5 PB

Or depending on your budget A combination of both 

 

I assume the cavity made between the solid wall and the studs would need to be somehow ventilated?

 

If we were to do this and fit 50mm wool batts within a metal stud frame, wouldn't the studs and any services (sockets etc penetrating the insulation) act as a cold bridge?

Is there a way to cross-batten to allow for a service void between the studs holding the insulation and those the PB is fixed to?

[Annker]

@jayc89Im interested to hear if you settled on a IWI build up detail yet?

I hopefully (buying a victorian house atm) have a similar project coming up, where EWI is not an option.

 

With IWI It seems to be a challenge to find the balance between achieving a warm house but avoiding the risk of Interstitial condensation.

I'm wondering if an alternative solution is forget about installing any wall insulation and instead reallocate that part of the budget to further upgrade the insulation in the roof and floors, heating system, external windows and doors? 

 

[jayc89]

10 hours ago, Annker said:

@jayc89Im interested to hear if you settled on a IWI build up detail yet?

I hopefully (buying a victorian house atm) have a similar project coming up, where EWI is not an option.

 

With IWI It seems to be a challenge to find the balance between achieving a warm house but avoiding the risk of Interstitial condensation.

I'm wondering if an alternative solution is forget about installing any wall insulation and instead reallocate that part of the budget to further upgrade the insulation in the roof and floors, heating system, external windows and doors? 

 

 

I've not done too much on ours yet. I'm finishing off the last of our screeding this weekend where I have left taller perimeter up-stands around the external walls so I can continue the PIR up the walls at a later date, or I can just cut them down again if I decide not to. Right now, I plan to use the "warm batten" method where you stick PIR direct to the wall, tape up to reduce air flow, and screw battens through it, I then plan to in-fill those battens with additional PIR, taping again, before cross battening for a service void and then PB. Cross battening isn't required, but I prefer it so all services can be ran on the warm side. I could also install an airtight membrane before cross battening as a belt and braces approach. 

I've come to the conclusion that there are no hard and fast rules. Many anecdotal tales of people dot and dabbing insulating plasterboard to walls, without any reported problems, many people also saying that's a terrible idea.

 

I've taken the stance that;

1) air-tightness is important, warm, moist air cannot be allowed to move between the thermal envelope and the colder wall. Specific attention needs to be paid at junctions such as floor joists pocketed into walls etc.

2) Too much insulation could be a bad thing. Solid brick walls still need some way to let moisture escape, it is likely to get in some how (driving rain, leaking gutters etc etc) it can no longer dry to the inside so some heat needs to continue to pass through to push that moisture back to the outside. This of course assumes the outer face is pointed well using lime, and isn't rendered with sand/cement etc. 

It's a pretty marmite subject so I'm sure someone will be along with a different view soon

[Roger440]

10 hours ago, Annker said:

@jayc89Im interested to hear if you settled on a IWI build up detail yet?

I hopefully (buying a victorian house atm) have a similar project coming up, where EWI is not an option.

 

With IWI It seems to be a challenge to find the balance between achieving a warm house but avoiding the risk of Interstitial condensation.

I'm wondering if an alternative solution is forget about installing any wall insulation and instead reallocate that part of the budget to further upgrade the insulation in the roof and floors, heating system, external windows and doors? 

 

 

Thats the route i toook with out current house, and if the next one comes off, will likely do the same again.

 

You did, however, miss off air tightness. On anything this old, it will be an air leakage catastrophe!

 

[Roger440]

7 minutes ago, jayc89 said:

It's a pretty marmite subject so I'm sure someone will be along with a different view soon

 

The problem is, every situation is different. Some will get away with solutions that simply dont work on another house. There just so many vairables.

 

On our current house i worked on a worst case scenario. Could i have got away with less? Could i have left the concrete floor in? Maybe. But you cant and wont know until its too late. While the place is stripped, taking up the old floor and installing an insulated lime floor wasnt that big a leap, though not cheap either. Overkill? Maybe. But ive given it the best possible chane of eradicating the damp issues.

[jayc89]

7 minutes ago, Roger440 said:

 

The problem is, every situation is different. Some will get away with solutions that simply dont work on another house. There just so many vairables.

 

On our current house i worked on a worst case scenario. Could i have got away with less? Could i have left the concrete floor in? Maybe. But you cant and wont know until its too late. While the place is stripped, taking up the old floor and installing an insulated lime floor wasnt that big a leap, though not cheap either. Overkill? Maybe. But ive given it the best possible chane of eradicating the damp issues.

 

Totally agree. Location is also a big one. I suspect fitting impermeable insulation in an area that's susceptible to driving rain could also be problematic. Luckily for me, we're not in one of those areas.

[Annker]

15 hours ago, jayc89 said:

 

I've not done too much on ours yet. I'm finishing off the last of our screeding this weekend where I have left taller perimeter up-stands around the external walls so I can continue the PIR up the walls at a later date, or I can just cut them down again if I decide not to. Right now, I plan to use the "warm batten" method where you stick PIR direct to the wall, tape up to reduce air flow, and screw battens through it, I then plan to in-fill those battens with additional PIR, taping again, before cross battening for a service void and then PB. Cross battening isn't required, but I prefer it so all services can be ran on the warm side. I could also install an airtight membrane before cross battening as a belt and braces approach. 

I've come to the conclusion that there are no hard and fast rules. Many anecdotal tales of people dot and dabbing insulating plasterboard to walls, without any reported problems, many people also saying that's a terrible idea.

 

I've taken the stance that;

1) air-tightness is important, warm, moist air cannot be allowed to move between the thermal envelope and the colder wall. Specific attention needs to be paid at junctions such as floor joists pocketed into walls etc.

2) Too much insulation could be a bad thing. Solid brick walls still need some way to let moisture escape, it is likely to get in some how (driving rain, leaking gutters etc etc) it can no longer dry to the inside so some heat needs to continue to pass through to push that moisture back to the outside. This of course assumes the outer face is pointed well using lime, and isn't rendered with sand/cement etc. 

It's a pretty marmite subject so I'm sure someone will be along with a different view soon

I really do like the theory of the warm batten approach but I am apprehensive about the practical application of getting in right in a refurbishment setting given that you likely need to fitted around numerous insite elements.

The other issue I have with it is the wall build out thickness. Although I'm in SE England where space is a premium and the reduction in floor area in some already small rooms is not ideal. However perhaps that isn't such an issue for your particular house.

 But I think you have correctly identified the key principles: meticulous fitting of the VCL warm side and ensure maximum breathability of the existing brick wall; do everything possible to stop warm moist domestic air moving from inside to brickwork wall, failing that ensure said moisture can leave brickwork wall unhindered. 

[Annker]

15 hours ago, Roger440 said:

 

Thats the route i toook with out current house, and if the next one comes off, will likely do the same again.

 

You did, however, miss off air tightness. On anything this old, it will be an air leakage catastrophe!

 

I believe there is a lot going for this approach, one of the biggest selling points is its much easier to ensure the finished article is right, and the original design of the house (period features) are similarly easily maintained in their original position. However for me the most appealing feature is that interstitial condensation risk is minimised.  

 

It would be interesting to be certain of the true heat loss from uninsulated walls, I say this as I've read recent articles which claim that heat loss modelling software does not accurately model heat loss through solid walls.

Perhaps we should query research regarding the need of insulation for companies selling insulation! Not looking to set a conspiracy theory here but perhaps for solid walls throwing insulation isn't the answer.  😃

 

[Gone West]

1 hour ago, Annker said:

I say this as I've read recent articles which claim that heat loss modelling software does not accurately model heat loss through solid walls.

That may be because some solid walls are more solid than others. Our 600mm stone walls have a rubble layer in the centre so could lose less heat due to the air surrounding the rubble, than a 600mm solid concrete block wall.  The more accurate the data fed into modelling software the more accurate the results.

[Annker]

1 hour ago, Gone West said:

That may be because some solid walls are more solid than others. Our 600mm stone walls have a rubble layer in the centre so could lose less heat due to the air surrounding the rubble, than a 600mm solid concrete block wall.  The more accurate the data fed into modelling software the more accurate the results.

Yes understand what you mean, certainly a solid wall in one house may have an entirely different composition than a solid wall in other house, and even different sections of the same solid wall could have a varying composition.

However the thrust of these articles were more so that recent study's show that the modelling typically underestimates the thermal performance of solid walls in general. 

[Roger440]

4 hours ago, Annker said:

I believe there is a lot going for this approach, one of the biggest selling points is its much easier to ensure the finished article is right, and the original design of the house (period features) are similarly easily maintained in their original position. However for me the most appealing feature is that interstitial condensation risk is minimised.  

 

It would be interesting to be certain of the true heat loss from uninsulated walls, I say this as I've read recent articles which claim that heat loss modelling software does not accurately model heat loss through solid walls.

Perhaps we should query research regarding the need of insulation for companies selling insulation! Not looking to set a conspiracy theory here but perhaps for solid walls throwing insulation isn't the answer.  😃

 

 

The most critical factor to its thermal performance is, "is it dry?". 

 

A wet wall is a disaster. And lots of them are. Usually as a result of inappropiate materials.

 

 

 

 

[larry]

We've started putting in Woodfibre IWI about a year ago. I've used both the rigid boards (e.g. Steicotherm) and the cheaper flexible boards between battens (e.g. Steicoflex). I didn't use a VCL; for the rigid boards used the ready mix lime plaster you can buy and did that myself (low standards!) and for the flexible boards just put PB over the top on counterbattens (taped and jointed and then painted with breathable paint ontop). Found that Tikkurilla paint did a good range of breathable paints at a not completely ridicilious cost and seemed good quality. No problems so far but it's only been a year.  

 

Has made a noticable difference to otherwise cold rooms and very much looking forward to doing the rest of the house when work isn't quite so busy... 

[Roger440]

36 minutes ago, larry said:

We've started putting in Woodfibre IWI about a year ago. I've used both the rigid boards (e.g. Steicotherm) and the cheaper flexible boards between battens (e.g. Steicoflex). I didn't use a VCL; for the rigid boards used the ready mix lime plaster you can buy and did that myself (low standards!) and for the flexible boards just put PB over the top on counterbattens (taped and jointed and then painted with breathable paint ontop). Found that Tikkurilla paint did a good range of breathable paints at a not completely ridicilious cost and seemed good quality. No problems so far but it's only been a year.  

 

Has made a noticable difference to otherwise cold rooms and very much looking forward to doing the rest of the house when work isn't quite so busy... 

 

Maybe im missing something in your description, but plasterboard is not breathable. Thereby negating your other efforts.

[larry]

32 minutes ago, Roger440 said:

 

Maybe im missing something in your description, but plasterboard is not breathable. Thereby negating your other efforts.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9580

 

Thanks Roger. I'd read conflicting things, if I'm honest. This link is interesting reading. 

 

Certainly can't be worse than the multiple layers of wallpaper, lining paper and vinyl paint that I stripped back before.... 

 

The good news is though I've got a natural experiment having tried both approaches. I promise to report back on here if the plasterboarded room falls down in ten years!!!

 

[Roger440]

11 minutes ago, larry said:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9580

 

Thanks Roger. I'd read conflicting things, if I'm honest. This link is interesting reading. 

 

Certainly can't be worse than the multiple layers of wallpaper, lining paper and vinyl paint that I stripped back before.... 

 

The good news is though I've got a natural experiment having tried both approaches. I promise to report back on here if the plasterboarded room falls down in ten years!!!

 

 

Its interesting. But i still wouldnt have used plasterboard. Im basing that of my own practical experience.

 

Of course, you may get away with it, if your moisture levels are suitably low. Which of course is why one person solution is anothers failure.

 

As per my earlier post in this thread, why take the chance. Keep all the build up as permeable as possible.

[jayc89]

The house work is on a massive go slow at the minute, SWIMBO now has me turning my attention to getting certain rooms ready for xmas!

The IWI is on hold until we get new windows fitted, next year now, but I have been pondering how best to tackle it in the mean time. Another thought crossed my mind. I know spray form insulation is frowned upon within the roof space due to associated condensation risks around the timbers. However I don't believe mortgage companies take the same view when applied against walls. Would it be viable to build out a 50mm metal stud wall, approx 25mm from the existing brickwork and have foam sprayed behind and between those studs? It strikes me as a potential solution to both thermal insulation and air tightness as the foam should expend into gaps harder to reach when taping...

 

My understanding is closed-cell foam is pretty similar in u-value to rigid boards and we could, potentially, request open-cell foam around the first floor joists to allow for some vapour permeability, with the understanding that the u-value would be poorer there. (Or just pack these areas with wood fibre (or similar) and protect them when spraying)

 

Are there are downsides to such approach, other than cost (I can't believe how much spray foam insulation costs compared to rigid boards!), I've heard anecdotal evidence of spray foam shrinking/cracking (which would render it useless), but I don't know how old those comments were, is it still a problem with today's materials and methods?