Relaying roof on old stone house, what type of insulation?

DamoKen

Hi all, just moved into our "new" home a couple of weeks back and are planning on having it reroofed to resolve some leaks plus botched repair jobs over the years. We're also taking the opportunity while the roof is off to add insulation as there's currently none due to vaulted ceilings.

It's a pretty old property (circa 1850) with the original slate roof.

So the job we're getting done is to take off the original slate saving as much as possible and matching recycled slate to those slates that can't be saved, repair/replace valleys/batons etc where required, install an additional layer of batons to allow cross ventilation plus a waterproof membrane and also lay down insulation in the attic space following the ceilings down to the wall plates before putting the roof back on.

So main question is do I need to be concerned about what type of insulation and waterproof membrane is used? The roofing company we're going with seem to know their stuff, the project manager is very knowledgable and sympathetic with old properties and has assured us the materials used will not cause any breathability issues.

Is there any materials that are a definite no no? Haven't the quote to hand so can't name specifics but as far as I remember the insulation is standard rockwool.

Cheers

BryanF

Yes you need to tweak that spec to breathable membrane and consider ventilation of attic space assuming your insulating at ceiling?

Also considered intelligent vapour control on the warm side of the insulation, and please deal with cold bridge At the eaves/wall junction while the roof is off.

Edit: materials in an 1850's home include anything that starts with 'poly'

She's a b1tch in old homes where breathability is key.

Note breathability does not mean drafty

Consider other areas of improvement :Air-tightness & ventilation etc while your at this. Wiring etc would also be checked prior to roof / attic insulation

Metric Tensor

BryanF wrote: »

Consider other areas of improvement Auchincloss as ventilation etc while your at this. Wiring etc would also be checked prior to roof / attic insulation

Lol - I was googling this Auchincloss ventilation to find out what I was missing and if it would be useful on one of my jobs!!!!

Then I twigged!

BryanF

Sorry post corrected 'air-tightness'

DamoKen

BryanF wrote: »

Yes you need to tweak that spec to breathable membrane and consider ventilation of attic space assuming your insulating at ceiling?

Also considered intelligent vapour control on the warm side of the insulation, and please deal with cold bridge At the eaves/wall junction while the roof is off.

Edit: materials in an 1850's home include anything that starts with 'poly'

She's a b1tch in old homes where breathability is key.

Note breathability does not mean drafty

Consider other areas of improvement Air-tightness as ventilation etc while your at this. Wiring etc would also be checked prior to roof / attic insulation

Cheers for the reply Bryan. From chatting with the roofing company the felting should be breathable, I did stress it when they were inspecting it but will double check tomorrow. Looked up intelligent vapour control, is that a combination of the waterproof membrane and insulation type used? Can't remember this being mentioned but I can check this as well tomorrow although cost is a big factor, we're already very tight with the agreed cost so not sure how we could cover add ons. From the quote the insulation is 200mm rolls but doesn't say the type so assuming it's rockwool. Would that be sufficient or should it be thicker?

For ventilation they said they install cross battens to prevent condensation. Didn't mention anything about cold bridging but I'll definitely bring that up tomorrow as well.

Finally you mentioned check the wiring. Do you just mean any wiring in the attic will need to be considered when taking the roof off?

Thanks for the advice, new area for me and with the amount of other jobs I've been working on haven't had time to research anywhere near as much as I'd like to!

BryanF

It won't be rock-wool

Vapour control is nothing to do with waterproofing

200mm would be ok, not great

No point asking the building company about thermal bridging

If The price is agreed - what's the point of all the questions?

best of luck

DamoKen

BryanF wrote: »

It won't be rock-wool

What material should it be at a minimum if it shouldnt be rock wool? Would rock wool be a bad choice?

BryanF wrote: »

Vapour control is nothing to do with waterproofing

From what I read it's an intelligent membrane controlling the passage of moisture. It's also related to air tightness, hence I asked was it like a combination of the two.

BryanF wrote:

No point asking the building company about thermal bridging

Ok, who do I ask then?

BryanF wrote:

200mm would be ok, not great

What would be better?

BryanF wrote: »

If The price is agreed - what's the point of all the questions?

Price might be agreed but work hasn't started. Why wouldn't I ask questions to see if the work being doing is adequate? We'll be spending 30k including vat on this, would like to know if it's money properly spent. If there's room for improvement within budget now would be the time to do it no? Budget may be tight but if small tweaks could see massive improvements it's something worth considering at least.

Bigus

I had an architect recommend this simpler solution for the SAME type of property. I worked with this architect on high end jobs back in the day and he's really up to speed on efficiency, and I trust him.
After stripping , screw fix board insulation directly onto the old rafters, with screws through batons on top of the board insulation running vertically in the same direction and mirroring the old rafters , tape up insulation joints ,
then apply waterproof membrane over the "new" rafters which give a nice welling /pooling drape, and then horizontal batons for slates . Breathablity is apparently not and issue because no. Cold bridge.

Advantage for me is no refinishing or stripping the nice old ceilings inside and gaining good insulation for 100% of the roof and ceiling ,IE not just insulation between the joists, disadvantage maybe be a much bulkier looking roof , but it suits in my case , allowing much needed better overhangs of external walls and gables , to stop water drenching them from the very top currently.

In effect it's also like having 3 waterproof layers as well as gaining structural rigidity superior seem less insulation and less labour cutting and fitting insulation .

Calahonda52

Bigus wrote: »

... . Breathablity is apparently not an issue because no Cold bridge. .

These two topics are not related: I presume you meant an

OP:
Is this gig done?
what is the existing finish on the inside of the vaulted ceilings?
Are they vaulted right up to the ridge board?

re this
we're already very tight with the agreed cost so not sure how we could cover add ons
however if the job is being done wrong, using the wrong materials, then.....

BryanF

DamoKen wrote: »

What material should it be at a minimum if it shouldnt be rock wool? Would rock wool be a bad choice?

From what I read it's an intelligent membrane controlling the passage of moisture. It's also related to air tightness, hence I asked was it like a combination of the two.

Ok, who do I ask then?

What would be better?




Price might be agreed but work hasn't started. Why wouldn't I ask questions to see if the work being doing is adequate? We'll be spending 30k including vat on this, would like to know if it's money properly spent. If there's room for improvement within budget now would be the time to do it no? Budget may be tight but if small tweaks could see massive improvements it's something worth considering at least.

It'll be fibre glass unless 'rock wool' was specified

Rock wool, cellulose, hemp, sheeps wool et al

No. I believe you mixed the vapour barrier up with 'waterproof' & 'insulation'

Any change will cost you more at this stage

Dardania

Bigus wrote: »

I had an architect recommend this simpler solution for the SAME type of property. I worked with this architect on high end jobs back in the day and he's really up to speed on efficiency, and I trust him.
After stripping , screw fix board insulation directly onto the old rafters, with screws through batons on top of the board insulation running vertically in the same direction and mirroring the old rafters , tape up insulation joints ,
then apply waterproof membrane over the "new" rafters which give a nice welling /pooling drape, and then horizontal batons for slates . Breathablity is apparently not and issue because no. Cold bridge.

Advantage for me is no refinishing or stripping the nice old ceilings inside and gaining good insulation for 100% of the roof and ceiling ,IE not just insulation between the joists, disadvantage maybe be a much bulkier looking roof , but it suits in my case , allowing much needed better overhangs of external walls and gables , to stop water drenching them from the very top currently.

In effect it's also like having 3 waterproof layers as well as gaining structural rigidity superior seem less insulation and less labour cutting and fitting insulation .

That's really smart, and seems so simple too.

DO you have any ventilation underneath insulation?

BryanF

Bigus wrote: »

I had an architect recommend this simpler solution for the SAME type of property. I worked with this architect on high end jobs back in the day and he's really up to speed on efficiency, and I trust him.
After stripping , screw fix board insulation directly onto the old rafters, with screws through batons on top of the board insulation running vertically in the same direction and mirroring the old rafters , tape up insulation joints ,
then apply waterproof membrane over the "new" rafters which give a nice welling /pooling drape, and then horizontal batons for slates . Breathablity is apparently not and issue because no. Cold bridge.

Advantage for me is no refinishing or stripping the nice old ceilings inside and gaining good insulation for 100% of the roof and ceiling ,IE not just insulation between the joists, disadvantage maybe be a much bulkier looking roof , but it suits in my case , allowing much needed better overhangs of external walls and gables , to stop water drenching them from the very top currently.

In effect it's also like having 3 waterproof layers as well as gaining structural rigidity superior seem less insulation and less labour cutting and fitting insulation .

To many things here to address
I'll see if I can find the time later

Dardania wrote: »

That's really smart, and seems so simple too.

DO you have any ventilation underneath insulation?

'Seems'
Felt should be breathable for a start and a better detail would be to use a vapour barrier than taping insulation joints - What happens at light fittings etc?

dathi

BryanF wrote: »

To many things here to address
I'll see if I can find the time later


vapour barrier than taping insulation joints - What happens at light fittings etc?

he is putting the insulation board above the rafter and not removing the ceiling

BryanF

Vapour barrier required , otherwise, it should at least be breathable.

Bigus

BryanF wrote: »

Vapour barrier required , otherwise, it should at least be breathable.

Not according to this architect that has experience in all sorts of technical builds and specialises in sustainable stuff now, he was never afraid of new and technical solutions.

BryanF

Bigus wrote: »

Not according to this architect that has experience in all sorts of technical builds and specialises in sustainable stuff now, he was never afraid of new and technical solutions.

Apologies, if I've rubbed you up the wrong way
I'd really appreciate answer to the following, thanks:
1. are you sure it was a 'water proof membrane' outside the insulation?
2. What type of insulation was it? Perhaps it was wood fibre or something 'sustainable'?

Maybe a detail of the build would help, would you consider uploading a picture(you can leave out any architect/personal info)

Without a vapour barrier on the warm side of the insulation a non-breathable build-up is a bad idea. A Sustainable 'professional' would normally use breathable natural materials. lots of people calling themselves sustainable, I suppose one could say there are different levels of commitment to 'sustainable' construction - sustainable in terms of lifespan, may not mean low embodied energy in manufacture, or from a sustainable source, or recycleable at end of life or carbon sequestering..

3. Would you mind clarifying: all materials from the inside out, highlighting whether insulation is between the rafters?

Calahonda52

Bigus wrote: »

Not according to this architect that has experience in all sorts of technical builds and specialises in sustainable stuff now, he was never afraid of new and technical solutions.

With all due respects, none of the above says he is right: experience, specialisation and no fear.

Bigus

The membrane yes is standard breathable , I mistakenly described it.

I'll try and get pics or another job he showed me .