Warm batten insulation

[Roz]

For our granite walled barn conversion, I had read about the 'warm batten' method of insulating. Whereby you have

 

500mm granite wall,

Celotex or similar, foamed and taped at joints, creating one large sheet across walls. 

Timber battens over the insulation.

More insulation and services between the battens.

Plasterboard.

Skim

 

The idea being that it's more airtight than e.g. using insulated plasterboard and you have less cold bridging. 

 

(I recognise the breathability issue with using celotex or similar in our barn conversion, but we do not have the space for a natural insulation, so it's not going to happen unfortunately.)

 

Does anyone have any thoughts on this method vs insulated plasterboard? 

[Ed Davies]

How would the PUR relate to the granite wall? Would it be stuck to it or would there be an air gap? Is the granite flat enough to stick it?

[Roz]

Just now, Ed Davies said:

How would the PUR relate to the granite wall? Would it be stuck to it or would there be an air gap? Is the granite flat enough to stick it?

 

I'm not completely sure about this is the website I originally was reading about it on seems to be down. I'm not sure if the PUR is just held in place once the battens are up.

 

No air gap though!

[Simplysimon]

do you need the insulation inside? ie is the granite showing on the outer wall. if not it would be better to have the insulation on the outer surface

 

damn this is taking longer to type after corrections due to alcohol

 

sorry

 

[Roz]

1 hour ago, Simplysimon said:

do you need the insulation inside? ie is the granite showing on the outer wall. if not it would be better to have the insulation on the outer surface

 

damn this is taking longer to type after corrections due to alcohol

 

sorry

 

Yes has to be internal insulation 

 

? glad you’re having a good weekend 

[Russell griffiths]

Think from a practical point, not an insulation point

how will you build this, how long will the screws need to be to fix to the wall ?

if the walls aren’t perfectly flat your battens will be all over the place and will need packing out to make level

my thought would be to build an internal stud wall either in light steel track n stud or standard timber

then insulation behind this and in between studs, leave a gap for services, fit a clever two way vapour membrane 

 

what ya think. 

[Russell griffiths]

just an image to understand metal studs with insulation. 

[Ed Davies]

13 hours ago, Roz said:

No air gap though!

 

I'm with @Russell griffiths, from both a practical and moisture safety point of view I think it would be better to treat the granite as just a rainscreen, with the usual ventilated cavity behind it, which helps keep most of the wind and water off the main structure. Then you're just left with the fairly minor puzzle of building a conventional timber (or steel) wall with insulation but not being able to put insulation or sheathing on from the outside.

[Cpd]

If you built a timber / metal  frame within the stone walls as @Russell griffiths states and used pir and created a vcl on the warm side, could you then leave a vented void between the stone work and the insulation ? I am not sure how this would effective the risk of  inter terrestrial condensation but I’m sure this Could be modelled with the right software. If you did away with a service void and ran your services “retro....” you would eliminate the “plasterboard tent” @ProDave says is such a common occurrence and should (heaven forbid) there be any gaps. They could then be Identified  easily and quickly sealed up. I have an uneven gable wall that I need to deal with, it’s 1m thick (stone, rubble, stone) and my intention was to put up 25mm-50mm Celotex against the wall fully sealed, then a studwork wall against this filled with more calotex and sealed and then 25-50mm on the inside covering the whole wall. This would then have plasterboard attached directly to it with foam. If there was any condensation it would be on the stonework and as this is a vented void and it “SHOULD” dry out ........the dangerous part of this is the word “SHOULD”........ and I need to eliminate this to “WILL” 

[Roz]

We can't really afford to lose the space by putting in a void behind the insulation...  

 

It sounds like you were originally going to do something similar to us @Cpd but with an extra layer of insulation on top. Unless you mean you were going to have a void too, as I see you mentioned it was a 'vented void'

 

[scottishjohn]

yep you building a house inside a house --so would need VCL barrier etc 

vented void from bottom right to top or into roof space,or blocked and vented at top of walls to outside

If you think of your 200 year old stone house  with lathe and plaster etc 

there was a void from below ground floor up all the walls into roof and that caused a nice draft to keep everything dry, they did not heat houses like we do  

so think in those terms and insulated vapour barrier house inside stone exterior

bear in mind that if old stone work it should only be pointed with lime based mortar --as cement based will not allow it to breath and moisture go out of walls 

 

Edited February 3, 2019 by scottishjohn

[Roz]

1 minute ago, scottishjohn said:

yep you building a house inside a house --so would need VCL barrier etc 

vented void from bottom right to top or into roof space,or blocked and vented at top of walls to outside

If you think of your 200 year old stone house  with lathe and plaster etc 

there was a void from below ground floor up all the walls into roof and that caused a nice draft to keep everything dry, they did not heat houses like we do  

so think in those terms and insulated vapour barrier house inside stone exterior

 

 

Is the VCL not included on foil faced insulation? 

[scottishjohn]

15 hours ago, Roz said:

For our granite walled barn conversion, I had read about the 'warm batten' method of insulating. Whereby you have

 

500mm granite wall,

Celotex or similar, foamed and taped at joints, creating one large sheet across walls. 

Timber battens over the insulation.

More insulation and services between the battens.

Plasterboard.

Skim

 

The idea being that it's more airtight than e.g. using insulated plasterboard and you have less cold bridging. 

 

(I recognise the breathability issue with using celotex or similar in our barn conversion, but we do not have the space for a natural insulation, so it's not going to happen unfortunately.)

 

Does anyone have any thoughts on this method vs insulated plasterboard? 

how thick can you stand these new walls to be --that will dictate what you can do .

yes foam plasterboard+pir  ,but with very serious VCL very well sealed

 

[scottishjohn]

Just now, Roz said:

 

Is the VCL not included on foil faced insulation? 

yes and no -but can you be sure it won,t come through the edges -for the sake of fitting a membrane behind  and tape sealing it ?

I look upon the foil as a a layer to reflect cold away more than as a seal 

 

[Roz]

6 minutes ago, scottishjohn said:

how thick can you stand these new walls to be --that will dictate what you can do .

yes foam plasterboard+pir  ,but with very serious VCL very well sealed

 

About 60mm in the barn section. Originally our SE had specified 52mm kingspan insulated plasterboard fixed to galvanised steel battens. I guess this would give it a bit of an air gap. But I was worried about the joints. 

 

But then I was reading about the 'warm batten' method specifically in relation to insulating solid stone walls. We could do 20mm insulation, 20mm battens with insulation between, plasterboard. Realistically this would be 25mm insulation, 25mm battens with insulation between as I can't seem to find 20mm boards of insulation. 

 

We were planning to tape all of the joints of the insulation. But could fit VCL. Does it go behind the plasterboard? That would be fine. 

Edited February 3, 2019 by Roz

[Russell griffiths]

Only put about 1 minutes thought into this, could you put up steel track n stud wall and spray foam the back side against the granite fully filling to the face of the studs. 

 

Stud wall 70 mm, gap behind for wobbly granite 10-15 mm total 100mm with plasterboard 

so 88mm of closed cell spray foam. 

I really can’t think of anything you can use that will go that thin

do you have to comply with building regs as I don’t know what the minimum would be for that. 

[Roz]

4 minutes ago, Russell griffiths said:

Only put about 1 minutes thought into this, could you put up steel track n stud wall and spray foam the back side against the granite fully filling to the face of the studs. 

 

Stud wall 70 mm, gap behind for wobbly granite 10-15 mm total 100mm with plasterboard 

so 88mm of closed cell spray foam. 

I really can’t think of anything you can use that will go that thin

do you have to comply with building regs as I don’t know what the minimum would be for that. 

We don't want to lose this much space. We do have to comply but they're happy with the level we had proposed on drawings (52mm insulated kingspan plasterboard), but 25mm+25mm celotex plus plasterboard is equivalent U value. 

 

What are the main objections to the warm batten method? 

Edited February 3, 2019 by Roz

[Roz]

I originally saw warm batten detailed on superhomes.org.uk but the website seems to be down and has been for a while. You can still find their drawings about it on pinterest, but not the explanation. 

[Russell griffiths]

Have you got a link. 

Lots of things look good on paper, but I always think from the point of how are you going to fit it

 

[Jeremy Harris]

48 minutes ago, Roz said:

 

Is the VCL not included on foil faced insulation? 

 

Yes.  All that's needed is to tape the joins and make sure that the insulation foil faces don't get damaged (no harder to do than making sure any other membrane-type VCL doesn't get damaged).

 

Care needs to be taken with detailing around the edges to make sure the VCL is contiguous, but again this isn't any more difficult that using a membrane-type VCL, or any different to using a panel-type VCL come to that.

[Roz]

We could fix the timber studs to the joists above and concrete floor below with a horizontal timber, then fix the vertical timbers to this? Had originally planned to screw through them into the insulation but perhaps this isn't needed. 

 

I can't tell because the website is down but it's possible the information was originally here: http://www.superhomes.org.uk/resources/internal-wall-insulation-1/

 

Here's another link with some information about it though : https://www.diydoctor.org.uk/projects/insulatingwalls.htm

[Roz]

Does anyone agree it would have benefits r.e thermal bridging in comparison to just using insulated plasterboard?

[Miek]

3 hours ago, Roz said:

We could fix the timber studs to the joists above and concrete floor below with a horizontal timber, then fix the vertical timbers to this? Had originally planned to screw through them into the insulation but perhaps this isn't needed. 

 

If you want a 50mm thick insulated wall then I can't see this working without the wall being very wobbly. You would want 95mm studs minimum I would think if you are only supporting at ceiling and floor. 

With a thin wall it would be easy enough to include a few intermediate fixings through to the stone wall to help sure it up. Lots of variable thicknesses of packing material would be needed I expect. 

3 hours ago, Roz said:

 

 

[ProDave]

What you are describing is what I see regularly on Scottish stone houses. Usually done VERY badly.

 

The inside face of the stone wall is way too irregular to just fix insulation to and hope for it to be flat.

 

Usually a 50mm frame is installed, as already noted with the thin studs being supported at intervals with fixings and packers from the stone wall.

 

If you are lucky a bit of insulation might be poorly fitted between the studs before the plasterboard. Usually though  nothing.

 

And the last poor detail that makes it so rubbish is the top and bottom of the gap so created is usually open so cold air enters from the loft creating the ubiquitous "plasterboard tent"

 

To do this properly, you need to make your frame fixed to the walls.  Then line the entire wall with well detailed and well sealed sheets of insulation paying particular attention to seal the top bottom and all edges (expanding foam?) so no air can enter behind from outside.  Then on the inside of your now well sealed insulating box you need to fix battens to create a service void so pipes and cables can all run inside without penetrating the insulation and letting cold in.

 

It all comes down to getting the detail right.

[Roundtuit]

4 hours ago, Roz said:

We don't want to lose this much space. We do have to comply but they're happy with the level we had proposed on drawings (52mm insulated kingspan plasterboard), but 25mm+25mm celotex plus plasterboard is equivalent U value.

Wasn't your starting spec insulated plasterboard fixed to galvanised steel battens? Not sure how that can fit within a 60mm build-up? Perhaps you have a little more space to work with than you think?