Warm batten insulation

[Cpd]

I am insulating my old stone cottage and am happy to sacrifice space for insulation. Exactly how big is your barn ? My width after framing out and insulation / final finishes will only be 4540mm the walls upstairs will be :

 

stonework 700mm 

vented void 20-50mm 

50mmx50mm framing attached to wall (lots of work) filled with 50mm calotex and fully sealed and taped. 

25mm cross battens and infield with insulation 

70mm calotex stuck on and fully sealed (vcl) 

12mm osb glued and screwed through to cross battens where needed. 

plasterboard  

 

as @ProDave says it’s all down to detailing and I would not trust anyone except myself and my most trusted helpers

 

my gables are even more insulated and roof even more again...... everything is detailed to the mm. 

 

 

 

[Roz]

Thanks for your thoughts everyone. I will take it on board and mull it over!  I just had a meeting with our building control officer and he said we need to tank the walls - is that true even if you've got a taped vapour control layer on the insulation? 

Thanks in advance!

[Cpd]

15 minutes ago, Roz said:

I just had a meeting with our building control officer and he said we need to tank the walls

I would have thought that if the walls are out of the ground, are lime pointed on the outside and in fairly good shape AND you have a ventilation gap on the inside it would not need tanking, tanking lime walls on the inside could lead to a whole lot of problems as they will no longer be able to breath properly. If you are not having a ventilation gap then the build up would normally be a specialised  build up that allowed them to breath to the inside, including such things as lime based paints etc. Unless your a purist and as you already have limited space I can’t see you going down this road. I think you may need to visit one of the specialist websites, historic Scotland or the lime mortar association  as tanking really does sound wrong to me........   

[Roz]

2 minutes ago, Cpd said:

I would have thought that if the walls are out of the ground, are lime pointed on the outside and in fairly good shape AND you have a ventilation gap on the inside it would not need tanking, tanking lime walls on the inside could lead to a whole lot of problems as they will no longer be able to breath properly. If you are not having a ventilation gap then the build up would normally be a specialised  build up that allowed them to breath to the inside, including such things as lime based paints etc. Unless your a purist and as you already have limited space I can’t see you going down this road. I think you may need to visit one of the specialist websites, historic Scotland or the lime mortar association  as tanking really does sound wrong to me........   

Thanks cpd, it didn't sound right to me either. I don't see the need if there's vapour control on the insulation. He suggested blackjack... which looks like a nightmare for uneven walls. 

[Russell griffiths]

I think he is probably stuck in 1980, if he suggests you render the out side in a sand and cement render, kill him quickly and bury the body in your footings. 

 

Im not familiar with stone walls but from what I do know I think it should be allowed to breath

i would look for better clarification from a stone/lime pointing type body. 

[Nick1c]

We currently live in a granite barn. When we moved in it was freezing cold, had condensation running down the walls and cost £10/day in gas (you could still see your breath!). It has multifoil insulation in the roof, underfloor heating on the ground floor, sand & cement render internally was cement pointed and the external window cills were 1cm short on each side everywhere. 

We ditched the bottled gas boiler for an ASHP, rejigged the slate cills so they wrapped round the reveals, had the walls repointed in lime and the applied Beek BS+. 

The effect was beyond my hopes - heating bills well down (with a warm house), condensation much reduced. Starting from scratch I would have made the building as vapour open and airtight as possible, replacing the s&c with wood fibre insulation & lime plaster with breathable paint, together with properly insulating the roof & floor as much as I could. Could you not work on improving your floor & roof U-values in order to use breathable wall insulation?

[MikeGrahamT21]

Is there a particular reason for not wanting external wall insulation? You stand to lose an awful lot of thermal mass capacity which you may regret in the coming hotter years.

[Cpd]

2 hours ago, MikeGrahamT21 said:

thermal mass

...........just love it when someone brings these two words up.............. always good for a vigorous debate ! 

[Cambs]

On 02/02/2019 at 19:36, Roz said:

For our granite walled barn conversion.....

 

Green Building Store have done a few barn conversions to Enerphit standard.  Lots of resources on their website about IWI.  Here’s a starting point:

 

https://www.greenbuildingstore.co.uk/lower-royd-radical-retrofit-its-a-wrap/

 

[Cambs]

Oops, managed to post this several times

Edited February 8, 2019 by Cambs

[Cambs]

On 02/02/2019 at 19:36, Roz said:

For our granite walled barn conversion.....

 

Green Building Store have done a few barn conversions to Enerphit standard.  Lots of resources on their website about IWI.  Here’s a starting point:

 

https://www.greenbuildingstore.co.uk/lower-royd-radical-retrofit-its-a-wrap/

 

[Roz]

23 hours ago, MikeGrahamT21 said:

Is there a particular reason for not wanting external wall insulation? You stand to lose an awful lot of thermal mass capacity which you may regret in the coming hotter years.

 

A couple - we're in a world heritage site so getting permission for that would be unlikely. Also, we like the character / look of granite barns.

 

@Cpd I don't know what thermal mass is so I won't get involved in that ? 

[Roz]

On 07/02/2019 at 22:56, Nick1c said:

We currently live in a granite barn. When we moved in it was freezing cold, had condensation running down the walls and cost £10/day in gas (you could still see your breath!). It has multifoil insulation in the roof, underfloor heating on the ground floor, sand & cement render internally was cement pointed and the external window cills were 1cm short on each side everywhere. 

We ditched the bottled gas boiler for an ASHP, rejigged the slate cills so they wrapped round the reveals, had the walls repointed in lime and the applied Beek BS+. 

The effect was beyond my hopes - heating bills well down (with a warm house), condensation much reduced. Starting from scratch I would have made the building as vapour open and airtight as possible, replacing the s&c with wood fibre insulation & lime plaster with breathable paint, together with properly insulating the roof & floor as much as I could. Could you not work on improving your floor & roof U-values in order to use breathable wall insulation?

I asked about this and apparently you can't just compensate by overloading the roof and floor in order to reduce that in the walls. I thought you might be able to! I'd like to do another barn in the future and if it's big enough we'll definitely go down the breathable route. Will be great to se how your project comes along

[MikeGrahamT21]

On 09/02/2019 at 09:32, Roz said:

 

A couple - we're in a world heritage site so getting permission for that would be unlikely. Also, we like the character / look of granite barns.

 

@Cpd I don't know what thermal mass is so I won't get involved in that ? 

 

Fair enough, that sounds like a good enough reason to drop EWI.

 

Thermal Mass, is probably better called Heat Storage Capacity, its is a materials capacity in which to store heat, and release it slowly to the environment, which in theory dampens the temperature from moving so much either up or down.

 

A room with IWI will warm up very quickly, a really fast response, because the insulation prevents the heat from having to warm the heavy masonry behind it, but in contrast the heat will dissipate quicker than it would had the walls stored some of that heat. This room would have a low heat storage capacity.

 

One with EWI allows the walls of the building to store the heat, with the EWI acting like a tea cosy, keeping the heat in the walls where you want it, so the room would take a long time to warm up initially, as you are warming not just the air, but also the masonry, however once warmed, it should keep a reasonably constant temperature with little heat input. This room would have a high heat storage capacity.

 

EWI should also help on a sunny hot day in summer, as the walls will be relatively cool, so any excess heat gets absorbed by the walls, keeping the temperature down, whereas in the room with IWI you would potentially get overheating unless you put measures in place to reduce this potential.

 

A free service such as this may help you simulate your plans, and understand thermal mass/heat storage capacity: https://www.ubakus.de/u-wert-rechner/?

This also models the Phase Shift, and temperature amplitude damping which i spoke about above, which are quite important. Site is in german, so use chrome to convert it.

 

Hope it helps.

[paulmb]

While coming late to this discussion I am facing a similar problem to the original poster. One architect suggested a similar warm battening approach but over a tanking membrane fixed mechanically to the wall. The tanking membrane has dimples that hold the membrane off the wall about 7mm and by proving vents in the wall any moisture in the wall is supposed to be able to escape. 

 

ive been searching for confirmation of this approach but had little success. The membrane supplier reported having used it on a barn conversion in combination with rock wall between the battens rather than a rigid insulation under the battens. 

 

Im leaning towards metal battens fixed to the wall and insulated plasterboard over. The alloy battens won’t rot and provide a 30 gap for air flow over the wall which with vents top and bottom should allow and rising and ingress moisture to escape.