Fine tuning my IWI Solid wall (Warm Batten) design

[Iceverge]

34 minutes ago, Annker said:

so that all points me towards using metal studding.

 

It's dead straight on the pro side. 

 

On the negative side it is very conductive so ensure that the bottom of it is isolated from the cold. Be careful with wiring too that it doesn't get stripped by the metal. You might need to tie any studs metal or timber to the wall at an intermediate level if it feels wobbly. 

 

34 minutes ago, Annker said:

With that in mind I'm unsure how mineral wool batts could be kept in place, tight against the face of the brickwork

 

Get batts slightly thicker than the cavity thickness and wider than the gap between the studs. They'll just stay there then when you put them in.

 

Mineral wool on rolls won't. You'll need batts. 

[Iceverge]

I made a video, but I'm not happy with it. I'll remake later if I can escape my family for 30 mins. 

[lookseehear]

There's also the SWIP system which has insulating studs which can be pulled plumb and close off the gaps between studs and wall, however they might not work if you can't fix to the wall.

 

See Charlie DIYte on YouTube for a video demonstration.

[Annker]

I'm unsure if an Open Vapour buildup should be modelled in Ubakus, but when it is it shows a condensation risk.

Is that what we should expect and accept on the proviso that been vapour open the condensation can dry to the inside?

 

 

 

Same buildup but with the inclusion of Intello Plus VCL. @Redbeard I believe you were suggesting the inclusion of a VCL?

 

[Annker]

2 minutes ago, lookseehear said:

There's also the SWIP system which has insulating studs which can be pulled plumb and close off the gaps between studs and wall, however they might not work if you can't fix to the wall.

 

See Charlie DIYte on YouTube for a video demonstration.

I've seen that system/video. I think the princple is broadly OK but I hope to be able to produce a more robust install myself and at a lower price.

[lookseehear]

Just now, Annker said:

I've seen that system/video. I think the princple is broadly OK but I hope to be able to produce a more robust install myself and at a lower price.

 

Same! It really feels like we're searching for the same solution here - at least we'll have some safety in numbers!

[lookseehear]

17 hours ago, Iceverge said:

The parge is a mix of sand lime cement in the ratio 3:2:1.

 

What kind of Lime would you specify - quicklime? hydrated non-hydraulic? NHL 2/3.5? Thank you so much for making a video - I know that I and others will get a lot of value from it. 

[Redbeard]

I leave out the cement. I use a lot of Baumit products and would use probably RK38, or RK 70 if you have any left over from anything else (the latter being finer). Alternatively you could use plastering sand and lime putty - the advantage over bagged lime being that putty will keep for years as long as there is water over it - stops it absorbing CO2

[Redbeard]

24 minutes ago, Annker said:

 

Same buildup but with the inclusion of Intello Plus VCL. @Redbeard I believe you were suggesting the inclusion of a VCL?

 

Yes, I was, on the basis if mineral wool potentially being less moisture-buffering than wood-fibre. I like (expensive!) Intello as it's good for pessimists (tends to become more vapour-open in warmer weather so that *if* any moisture has got in during the winter it may be able to 'breathe' back out).

[Annker]

1 minute ago, Redbeard said:

 

Yes, I was, on the basis if mineral wool potentially being less moisture-buffering than wood-fibre. I like (expensive!) Intello as it's good for pessimists (tends to become more vapour-open in warmer weather so that *if* any moisture has got in during the winter it may be able to 'breathe' back out).

Yes its pricey but anything done at this stage will certainly be cheaper than rectifying works after decoration is done, its along that line of thinking that I'm happy to sell on my already purchased PIR at a loss.

 

WRT to using RK38. Do you use it neat by its self or with sand as a replacement for the lime in the parge coat. 

 

[Redbeard]

7 minutes ago, Annker said:

WRT to using RK38. Do you use it neat by its self or with sand as a replacement for the lime in the parge coat. 

 

RK38 and RK70 are lime/sand mixes, ready to use, with about 6mth shelf life (some say a year but I have had a few lumps lately!).

[Roger440]

5 hours ago, Redbeard said:

 

Yes, I was, on the basis if mineral wool potentially being less moisture-buffering than wood-fibre. I like (expensive!) Intello as it's good for pessimists (tends to become more vapour-open in warmer weather so that *if* any moisture has got in during the winter it may be able to 'breathe' back out).

 

Would you use the intello over a woodfibre and lime build up?

 

As opposed to not having the VCL at all as is normally suggested?

[Mike]

19 hours ago, Annker said:

So the parge coat primary deals with internal born moisture issues.

It stops moisture transportation (by airtightness), limiting internal born moisture being drawn into the wall build up?

Yes, stopping the movement of air stops moisture (and air) passing through the structure.

 

19 hours ago, Annker said:

The preference of mineral wool/fibre insulations over PIR, is primarily associated with external born moisture issues.

Mineral wool/fibre insulation's provide better drying to inside of any external borne moisture that makes its way to the interface of internal face of the brickwork and insulation layer?

More-or-less, but there's a graduation of behaviours. In simplified form:

• Closed cell foams don't absorb moisture so condensation will tend to run down the wall (and the wall-facing side of the insulation if its in contact with the wall).
• Foil-faced PIR can absorb some moisture from the wall (but not through the room-side foil facing), so some condensation may get absorbed while the rest runs down.
• Mineral wool is hydrophobic so although some condensation may run into the fibres it won't get absorbed, though some may be held between the fibres (or start to run through them if it gets really wet).
• Many natural insulations behave differently. Instead of absorbing moisture (taking in liquid water) like synthetic insulations, they adsorb it (take moisture vapour out of the air and bind it within the fibres) before it condenses to to liquid, reducing the risk of condensation. Which is why a real wool jumper still feels warm even when 'wet'. It also dries well by reversing the adsorption process.

Consequently natural insulations are the preferred option, provided they're not going to be subject to high relative humidities for extended periods (typically not more than 80% RH for more than 3 months of the year in winter) - which is partly why I'm using hemp insulation on my current renovation in France. However natural insulations do cost more. Also worth knowing that sheep's wool has been be problematic due to the risk of moth attack, though the 'Ionic Protect' process claims to have overcome that.

 

Mineral wool would be second choice.

[Redbeard]

38 minutes ago, Roger440 said:

Would you use the intello over a woodfibre and lime build up?

 

As opposed to not having the VCL at all as is normally suggested?

 

Not if (as I usually do) I'm using rigid (140-180kg/m3) WF. If I were using flexi WF (c50kg/m3) I would (and indeed did) use Intello.

[Mike]

8 hours ago, lookseehear said:

Would it be fair to say that flexible wood fibre would be a step up from mineral wool here from a moisture buffering perspective?

Yes.

[Mike]

6 hours ago, Annker said:

I'm unsure if an Open Vapour buildup should be modelled in Ubakus, but when it is it shows a condensation risk.

Ubakus doesn't help much with any construction. It only shows a moment in time. It's what happens over a period of weeks or months that important (i.e. how long will it stay wet, how quickly will it dry out).

[Iceverge]

13 minutes ago, Mike said:

Ubakus doesn't help much with any construction. It only shows a moment in time. It's what happens over a period of weeks or months that important (i.e. how long will it stay wet, how quickly will it dry out).

 

Agree it's a simple tool. 

 

It defaults to -5 as an exterior temperature which is unrealistic in the british isles for long periods.

 

A winter average temperature of maybe +5 is more realistic and gives a better appreciation of the lightly long term state of drying in the wall. 

[Redbeard]

For reliable moisture modelling you really need a dynamic model like WUFI or one other whose name I cannot remember. At least one supplier of WF does WUFI as part of their 'offer'.

[Iceverge]

 

 

Its a bit long but I hope it might help. 

 

[Annker]

5 hours ago, Iceverge said:

 

 

Its a bit long but I hope it might help. 

 

Fair play to you for taking the time to make this, much appreciated @Iceverge, I haven't watch it yet but will do this evening.

[lookseehear]

7 hours ago, Iceverge said:

 

 

Its a bit long but I hope it might help. 

 

 

I've just watched it - definitely helpful and clears up some of my thinking. Thank you!

[Roger440]

22 hours ago, Redbeard said:

 

Not if (as I usually do) I'm using rigid (140-180kg/m3) WF. If I were using flexi WF (c50kg/m3) I would (and indeed did) use Intello.

 

Can i ask what the logic is that drives that decision?

[ab12]

On 20/11/2024 at 21:03, Iceverge said:

The parge is a mix of sand lime cement in the ratio 3:2:1.  It is applied to make the interior face of your external walls as your airtight layer.  You should return it on any internal walls by say 3-600mm  to avoid any leaks at this junction. 

 

I choose 63 mm CLS timber because it is the thinnest studwork lightly to be any way straight. You could screw it to the wall but it'd need a lot of shims and drilling to get it straight and fixed. If you feel it us still wobbly you could fix it through with a hammer in fixing here and there to the wall. You'll need to shim it to avoid it being pulled out of line though

 

Fix a top and bottom plate using a vertical laser level, mark your centres and cut your studs to fit and you'll be through it in no time by comparison. 

 

I would probably use 400mm centres but for the most efficient use of labour I would make sure its a snug fit for whatever your preferred batt insulation is. 

 

Normally 12.5mm plasterboard is best kept to 400cc.

 

 

Hi Iceverge

Thank you for the video, very informative.

Just couple of questions

1) The studs that'll be fixed vertically between the sole plate and top plate, will any insulation go behind these? I suspect not.

2) How are these to be screw fixed to the sole and wall plates? As in I'm trying to visualise where the screws will go from these to the wall and sole plates?

Thanks

[ab12]

General question: Say if a house ground floor with 2 floors above 

 

Would there be an issue/compromise if IWI was not applied to ground floor externally facing walls but only applied to 1st and 2nd floor externally facing walls?

 

When I say issue I mean risk of condensation to ground floor externally facing walls as the IWI is not continuous from ground floor to 2nd floor.

 

Ground floor has some beautiful age old coving which other family members want to retain.

 

Thanks

[ab12]

Sorry, unable to edit previous post, was meant to add

 

Regarding IWI and the breathable option of wood fibre batts fitted between battens would you cover this with standard gypsum plasterboard OR wood wool board?

 

Irrespective of which of the above option is chosen the whole idea is to make the insulation breathable so breathable paints will be required for the IWI walls. 

 

I can only assume these will be much more costlier than standard wall paints and also there is the question of where to source these from, specialist companies such as mike wye, celtic sustainable etc. I dont think these are available from the likes of your local B and Q, Wickes etc.