Fine tuning my IWI Solid wall (Warm Batten) design

[Redbeard]

1 hour ago, Iceverge said:

Maybe @Redbeard has more experience than me. 

 

Hello! Not with mineral wool, I am afraid. I have not used mineral wool as an internal insulant. I think I would be a little uncomfortable using it without a VCL, as even the 'rigid' grade of rockwool used for EWI is not as dense as 'basic' (140kg/m3 - 180kg/m3) rigid WF in terms of moisture-buffering ability, although at apparently 110kg/m3 it's not so far away). If you are finishing with plasterboard you could (at a cost) use an intelligent membrane such as Pro Clima's 'Intello'.

 

Yes, for reveals use as much insulation as you can get in without 'losing' the window or door frame.

 

If you were taking the risk of no VCL then you could buy the EWI grade of rockwool and plaster directly to it, with the necessary mesh reinforcement, effectively as per thin-coat EWI.

[torre]

On 15/10/2024 at 13:18, ab12 said:

some sort of ventilation system put into the property... PIV or decentralised MHRV etc

I would avoid relying mostly on PIV in an old property and use MVHR or continuous DMEV instead.

 

If there's a lot of moisture internally, PIV has to push that out somewhere, and that's likely to be into any gaps etc, where it may condense, potentially making any damp problem worse, whereas MVHR or continuous extract will help ensure more of the moist air is pulled out of the property.

[lookseehear]

23 hours ago, Redbeard said:

 

Hello! Not with mineral wool, I am afraid. I have not used mineral wool as an internal insulant. I think I would be a little uncomfortable using it without a VCL, as even the 'rigid' grade of rockwool used for EWI is not as dense as 'basic' (140kg/m3 - 180kg/m3) rigid WF in terms of moisture-buffering ability, although at apparently 110kg/m3 it's not so far away). If you are finishing with plasterboard you could (at a cost) use an intelligent membrane such as Pro Clima's 'Intello'.

 

Yes, for reveals use as much insulation as you can get in without 'losing' the window or door frame.

 

If you were taking the risk of no VCL then you could buy the EWI grade of rockwool and plaster directly to it, with the necessary mesh reinforcement, effectively as per thin-coat EWI.

 

Thanks for this. What attracted me to the method of parge for airtightness and rockwool/service void/plasterboard finish is that it decouples the airtightness from the services (no taping socket backboxes etc). It seems simpler from an execution perspective and I think this would work well with our builder and help me stay on top of the quality of the work. It isn't that I don't think he'll do a good job, but I think that we still have work to do when it comes to selling the importance of airtightness. I'm also wary that the more rigid the insulation board is, the less able it will be to match the uneven shape of the stone walls, and the more likely we are to have voids.

 

If we were to use a parge coat of NHL 3.5, rockwool within a CLS timber 'batten' frame, Intello Membrane then Plasterboard (and I assume a skim of gypsum), does that mean that all sockets/holes need to be taped to the Intello membrane?

 

Our project is a combination of extension, reorganisation and renovation, so anywhere we can create a simple solution will be big positive.

[lookseehear]

On 27/10/2024 at 13:49, torre said:

I would avoid relying mostly on PIV in an old property and use MVHR or continuous DMEV instead.

 

If there's a lot of moisture internally, PIV has to push that out somewhere, and that's likely to be into any gaps etc, where it may condense, potentially making any damp problem worse, whereas MVHR or continuous extract will help ensure more of the moist air is pulled out of the property.

 

Thanks for this - I think we're likely to use a combination of centralised and decentralised MVHR, as we can likely get ducting to 2/3 of the house relatively easily, but the final 1/3 will be more tricky. This definitely makes sense to me.

[Redbeard]

6 hours ago, lookseehear said:

If we were to use a parge coat of NHL 3.5, rockwool within a CLS timber 'batten' frame, Intello Membrane then Plasterboard (and I assume a skim of gypsum), does that mean that all sockets/holes need to be taped to the Intello membrane?

How about the above but with added 25 x 38 (?) counter-battens over the Intello, forming a service void so that the elecs are inside the air-tightness/VC layer?

[Annker]

Posting a revision to my thinking on my particular warm batten arrangement.

 

Detail aside there is a potential installation issue that has been at the back of my mind, and that is the fixing of the battens through the PIR sheets and into the brick wall.

There are a few tricky steps with this:

• Quality of the fixings.
  • I had planned to use concrete screws which depending on substrate can either get a good fixing, a loose fixing or blow out the substrate; dry clay bricks are particularly prone to blowing out and that is the substrate in my situation.
• Positioning of the fixings:
  • Ideally the fixings are centred on bricks, this will be difficult to achieve given the PIR sheet will be installed against the brickwork hiding all the joints and bricks 
• Compromised VCL 
  • Drilling through the batten and PIR with a hammer action masonry bit will certainly blow out the back of the batten and PIR. I suppose this damage to the VCL could be reduced by drilling a pilot hole with timber spade bit until the brickwork face is reached but regardless the drilled hole through the VCL is a potential moist air route.
•  Plumbing the battens 
  • Where some battens need to be pulled out from the wall to plumb this again will contribute to the likelihood of moist air routes

Giving the above I'm considering how this alternative arrangement may work:

• PIR is fixed to brickwork face solely with low expansion foam.
• Metal studding (stood away from the PIR by 10mm or so) provides the framework to carry the plasterboard.
• Metal studs are fixed solely with a floor track and head track (perhaps a strongback is added) thereby no fixing penetrate the VCL.

Appreciate any critique of this method.

The PIR has been purchased (bought some months ago during some manner of flash sale) so even though some disagree with its use it has not to be used, plus the fact that the job needs to get done asap now.

 

 

 

   

Edited yesterday at 13:08 by Annker

[BadgerBodger]

@Annker

 

I am planning a barn conversion with IWI. I think we are considering similar strategies. 
 

Architects preference was for natural breathing solution but my preference was for a more commercial bag it up and stop it moving solution. 

In the most extreme case the external walls deviate 200mm from plumb…. We have an internal steel frame and are looking at  currently looking at a minimum 50mm ventilated cavity, treated timber stud with PIR infill between. Likely 120mm. VCL to the inside face counterbatten and then PIR backed board to the front which will also be used to cloak the steel frame (potentially with and addition 25mm board to further limit cold bridging). Window openings will have VCL dressed through to the frame and the PIR bonded board will form the reveal which will vary I depth but be a minimum of 350mm deep. 
 

I’m considering the use of a breather on the outside face of the stud to protect the timber better but I think it might be unnecessary and make buildability challenging. Currently planning erecting stud frames at ground level and offering up for fixing to steel. 
 

If I were in your position, and wanting square wall I’d batten up at fixed centres and plumb with packers before affixing the next product. IMHO VCL could then be either to front or rear of PIR and dare I say it if you’re just driving improvement but without a specific figure you could just use foil faced PIR and tape with alutape… that’s the rougher side of me. Compromised VCL is almost always inevitable and I take one of two approaches I see as being practical and pragmatic. Either tape VCL to timber battens using some butyl tape strips then PIR backed PB could be directly affixed with the butyl tape “self healing) the fixing point OR (and this is how I always approach it) sandwich the VCL between two sheet products. In this case PIR and PB. The “trapped” nature of the fixing point and sandwiching between two impermeable products means leakage is minimal. The first option is a belt and braces version of the latter. 
 

Also might be worth considering a gypliner system… these can form a void of 30mm if I recall. Quick, easy, cheap and maintains a continuous cavity…

 

https://www.british-gypsum.com/Systems/wall-linings/gyplyner-single#description

 

Other variants exist

 

Edited yesterday at 15:17 by BadgerBodger
Addition of gypliner

[Annker]

50 minutes ago, BadgerBodger said:

@Annker

 

I am planning a barn conversion with IWI. I think we are considering similar strategies. 
 

Architects preference was for natural breathing solution but my preference was for a more commercial bag it up and stop it moving solution. 

In the most extreme case the external walls deviate 200mm from plumb…. We have an internal steel frame and are looking at  currently looking at a minimum 50mm ventilated cavity, treated timber stud with PIR infill between. Likely 120mm. VCL to the inside face counterbatten and then PIR backed board to the front which will also be used to cloak the steel frame (potentially with and addition 25mm board to further limit cold bridging). Window openings will have VCL dressed through to the frame and the PIR bonded board will form the reveal which will vary I depth but be a minimum of 350mm deep. 
 

I’m considering the use of a breather on the outside face of the stud to protect the timber better but I think it might be unnecessary and make buildability challenging. Currently planning erecting stud frames at ground level and offering up for fixing to steel. 
 

If I were in your position, and wanting square wall I’d batten up at fixed centres and plumb with packers before affixing the next product. IMHO VCL could then be either to front or rear of PIR and dare I say it if you’re just driving improvement but without a specific figure you could just use foil faced PIR and tape with alutape… that’s the rougher side of me. Compromised VCL is almost always inevitable and I take one of two approaches I see as being practical and pragmatic. Either tape VCL to timber battens using some butyl tape strips then PIR backed PB could be directly affixed with the butyl tape “self healing) the fixing point OR (and this is how I always approach it) sandwich the VCL between two sheet products. In this case PIR and PB. The “trapped” nature of the fixing point and sandwiching between two impermeable products means leakage is minimal. The first option is a belt and braces version of the latter. 
 

Also might be worth considering a gypliner system… these can form a void of 30mm if I recall. Quick, easy, cheap and maintains a continuous cavity…

 

https://www.british-gypsum.com/Systems/wall-linings/gyplyner-single#description

 

Other variants exist

 

Not sure if you missed it but my initial design is warm batten, meaning the battens are fixed on the warm side of the insulation layer.

I wouldn't be too keen having the battens cold side of the insulation as I think you are suggesting, correct me if Im wrong!

 

I'm familiar with gyplyner however the issue with it in my situation is that it is required to be fixed to the wall; in contrast to my proposal of metal studs which don't necessarily need fixing to the wall; floor and head track fixing will suffice.

 

That looks like an interesting project you have there, spacious and I think the arrangement you have designed will work well. Ventilated cavity is a good option although one I dont have space for on my own project.

 

[BadgerBodger]

@Annker I see.
 

I can’t tell, are you planning to use a VCL or use the PIR as the VCL?
 

If the latter… Would the infilled stud option with insulation between not be an option akin to mine then? The difference being your VCL sits outside in the “cavity” and the stud frame is on the “dry” side. An infilled stud allows for better optimisation of space if it is scant.  Service routes could the. Be routed in the PIR or you could use a nominally deeper stud to allow the PIR to sit at the back and have service void to the front? 
 

I appreciate that may not result in a “warm batten” design but I would consider it as an option. 

 

 

Edited 22 hours ago by BadgerBodger

[Annker]

1 hour ago, BadgerBodger said:

@Annker I see.
 

I can’t tell, are you planning to use a VCL or use the PIR as the VCL?
 

If the latter… Would the infilled stud option with insulation between not be an option akin to mine then? The difference being your VCL sits outside in the “cavity” and the stud frame is on the “dry” side. An infilled stud allows for better optimisation of space if it is scant.  Service routes could the. Be routed in the PIR or you could use a nominally deeper stud to allow the PIR to sit at the back and have service void to the front? 
 

I appreciate that may not result in a “warm batten” design but I would consider it as an option. 

 

 

Yes, I meant to clarify that the PIR will be the VCL.

And yes insulation infill between the studs is an option but then continuity of the insulation layer is lost and its also more faffing to fit and fit well.

My vote would be for a continuous uninterrupted, say, 50mm insulation layer; rather than a, say, 90mm insulation layer between stud that may also be a bit gappy. Although I have made no calculation to support that opinion!   

 

A word of caution regarding running services (specifically cabling) within PIR. Anecdotally at least I hear that running electrical cabling within PIR may present a fire risk.  

 

I've researched the hell out of IWI in a solid walled building, and the one thing I'd say is take absolute opinions and desk study theory's with a pinch of salt, there are many ways to skin this cat.

No two properties are the very same and there is clear evidence that an approach that worked/failed in house A has been shown to work/fail in house b.

For example, site location and aspect play a significant role but are frequently overlooked 

A house built on a well sheltered site on free draining sand in Kent is going to be less sensitive to dampness than one built in a marshy Welsh valley. 

[BadgerBodger]

Yes, I’m inclined to agree. There doesn’t seem to be a single solution for all scenarios. 
 

interesting observation regarding the PIR and wiring. I imagine it’s a retained heat issue, something that can likely be overcome by oversizing the cabling for experience with other cable overheating issues. Something I’ll discuss with my architect for sure. 

[Iceverge]

11 hours ago, Annker said:

Appreciate any critique of this method.

The PIR has been purchased (bought some months ago during some manner of flash sale) so even though some disagree with its use it has not to be used, plus the fact that the job needs to get done asap now.

 

Sell the PIR again or put it in the floor. 

 

Airtight the house rigidly, (can be done room by room)

 

Parge for the walls, tape the windows, airtight paint for joist ends and anything tricky.

 

Ensure you return the parge to all internal walls too by at least the thickness of the wall. 

 

 

Build 63mm CLS studs internally independent of the wall. Fit mineral wool batts and plasterboard. 

 

Provided yiu do a good job with airtightness its's a very safe, cheap and easy install. The PIR is really not a good idea. 

 

 

[Annker]

10 hours ago, Iceverge said:

 

Sell the PIR again or put it in the floor. 

 

Airtight the house rigidly, (can be done room by room)

 

Parge for the walls, tape the windows, airtight paint for joist ends and anything tricky.

 

Ensure you return the parge to all internal walls too by at least the thickness of the wall. 

 

 

Build 63mm CLS studs internally independent of the wall. Fit mineral wool batts and plasterboard. 

 

Provided yiu do a good job with airtightness its's a very safe, cheap and easy install. The PIR is really not a good idea. 

 

 

Just wondering if some specific instance has come about that has you against PIR?

I ask because previously your opinion was that PIR would be fine in this situation.

 

Appreciate that you are just offering an opinion that I'm asking for, and its welcomed!

 

[Iceverge]

1 hour ago, Annker said:

because previously your opinion was that PIR would be fine in this situation.

 

Don't think I said this. Remind me. 

 

1 hour ago, Annker said:

Just wondering if some specific instance has come about that has you against PIR?

 

Have a look at this recent thread. 

 

The walls were previously done with kingspan PIR and plasterboard. I very much doubt anything was done about Airtightness. 

 

Look at how damp all the structure is behind the removed boards. Similarly note the rot in the timber lintels. 

 

A house that was internally dry for at least a century suffered these kinds of problems in just a few years because of inappropriate internal insulation. 

 

Edited 1 hour ago by Iceverge