Renovating a stone walled house

Carnmore

The house is single storey and circa 100 years old with solid stone and lime mortar unplastered walls about 450mm thick.

It consists of just two existing external walls (40m2) , a party wall, an extension to be rebuilt at the back and a roof to be renovated (slates removed, timbers repaired where necessary, felted, new roof battens and reslated using original slates.

The finished floor has been poured - rigid insulation board and cement.

For insulating the external walls, my architect and builder are recommending installing a steel stud wall to create an air gap and then dry lining with insulated plasterboard.

I'm on a budget and the cheapest method is insulated plasterboard as described above which would cost about €1k. Despite this cost and advice, I'm concerned about the breathability of the walls.

I would also prefer to use non-toxic materials where possible.

Would Calsitherm or Gutex be a better option or is insulated plasterboard okay?

The cost of Calsitherm including a lime scratch coat would be circa €10k..

Thanks in advance for any advice re this or in general.

Calahonda52

Make it airtight, with well insulated ceilings and consider MHVR
Have you a DPC in the walls?

what is the star of internal faces of external walls: are they smooth-ish
If so the fully bonded gutex is a good compromise

IMO the prosed solution is bs, especially once you get into the fine detailing
http://www.josephlittlearchitects.com/articles
https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx

Carnmore

Calahonda52 wrote: »

Make it airtight, with well insulated ceilings and consider MHVR

Yes I plan to install a MHVR - that would help with moisture removal as well as air quality?

Calahonda52 wrote: »

Have you a DPC in the walls?

No

Calahonda52 wrote: »

what is the star of internal faces of external walls: are they smooth-ish
If so the fully bonded gutex is a good compromise

Not really smooth

Calahonda52 wrote: »

IMO the prosed solution is bs, especially once you get into the fine detailing
http://www.josephlittlearchitects.com/articles
https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx

Calahonda52

Just re the MHVR, if you get one with a dehumidifier built in then it will really help to pick up the moisture in the air.
In case someone says you don't need it there were many days last summer ind the midland where the RH was so high that folk had to turn off the MHVRs

The gutex fully bonded will work as long as its no too crazy.. the bonding is not cheap but it does work.
You will need a service cavity outside the gutex.

Have you french drains around the outside of the house to lower the water table at the walls/foundations

Keep well.

BryanF

Calcium silicate over gutex in this instance

Carnmore

Calahonda52 wrote: »

Just re the MHVR, if you get one with a dehumidifier built in then it will really help to pick up the moisture in the air.
In case someone says you don't need it there were many days last summer ind the midland where the RH was so high that folk had to turn off the MHVRs

Because humid air was being brought inside?

Calahonda52 wrote: »

The gutex fully bonded will work as long as its no too crazy.. the bonding is not cheap but it does work.
You will need a service cavity outside the gutex.

A service cavity behind it for wiring / plumbing?

Calahonda52 wrote: »

Have you french drains around the outside of the house to lower the water table at the walls/foundations

It's soil up to the external plinth so I doubt it.

BryanF wrote: »

Calcium silicate over gutex in this instance

Why would it need both?

Wartburg

BryanF wrote: »

Calcium silicate over gutex in this instance

:eek::eek::eek:


You have an old house with 100 year old building materials and technologies. Please do not consider the use of insulated plasterboard, calcium silicate or even cement-based products. There is a wood fibre board available with a flexible backside to level uneven walls. On top, it gets just mechanically fixed to the existing wall, to prevent any difficulties with bonding. https://www.backtoearth.co.uk/collections/internal-wall-insulation-system

Gallant_JJ

BryanF wrote: »

Calcium silicate over gutex in this instance

I would agree

Lumen

Wartburg wrote: »

Please do not consider the use of insulated plasterboard, calcium silicate or even cement-based products.

Why not calcium silicate?

http://www.engineersjournal.ie/2016/03/22/27715/

"The CSB shows the largest fluctuations in moisture content (from 55 to 65 per cent) which mirror changes in RH room conditions with a slight time lag. This can be explained by the high moisture transfer properties of the CSB and illustrates its ability to buffer internal environmental conditions."

BryanF

Wartburg wrote: »

:eek::eek::eek:


You have an old house with 100 year old building materials and technologies. Please do not consider the use of insulated plasterboard, calcium silicate or even cement-based products. There is a wood fibre board available with a flexible backside to level uneven walls. On top, it gets just mechanically fixed to the existing wall, to prevent any difficulties with bonding. https://www.backtoearth.co.uk/collections/internal-wall-insulation-system

Can you outline your concerns with calcium silicate? for example the brand mentioned in the OP
I have specified & installed gutex, it’s a great product, In old stone walls will (any) cavity outside the gutex have a chance to dry out? There is a lot of variables, I like the diffusion open high PH of Calcium silicate with an old stone wall.

Carnmore

Is it worth digging up the newly poured concrete floor to install under floor heating (air to water pump)? The floor area will be about 70m2

BryanF

Carnmore wrote: »

Is it worth digging up the newly poured concrete floor to install under floor heating (air to water pump)? The floor area will be about 70m2

How will you heat it, if you go with rads? Have you a stove/back boiler planned?

Carnmore

BryanF wrote: »

How will you heat it, if you go with rads? Have you a stove/back boiler planned?

Condensing oil boiler with rads. And a dry woodburning stove in the middle of the living/kitchen area.

The drainage and plumbing in the screed floor need to be rearranged as the floor plan has been changed

Wartburg

BryanF wrote: »

Can you outline your concerns with calcium silicate? for example the brand mentioned in the OP
I have specified & installed gutex, it’s a great product, In old stone walls will (any) cavity outside the gutex have a chance to dry out? There is a lot of variables, I like the diffusion open high PH of Calcium silicate with an old stone wall.

To make it clear - both systems either wood fibre or calcium silicate are suitable materials for an internal wall insulation, because of their diffusable and temporary moisture storing properties. GUTEX is doing great wood fibre insulation products as all the other wood fibre insulation manufacturers like Steico, Schneider, Pavatex, UngerDiffutherm etc. too. Personally I´d rather prefer another manufacturer, because they have almost thirty years of experience with the board and matching plaster.
You can easily destroy the entire moisture storing capacity of wood fibre and calcium silicate boards, by applying a wrong plaster or coating on top.
I´m surprised about your suggestion with the Gutex and Calcium Silicate on top, because I can´t follow the sense of it. Calcium Silicate has a lower thermal conductivity in comparison to wood fibre. The capacity to store moisture is bigger with the calcium silicate but do you really need that higher capacity in this particular case, by having a mHVR installed?
There´s more attention needed to make sure that the structure will have no gaps/voids between the existing wall and the internal insulation layer. That´s why I recommended the wood fibre board with the flexible backside, to level the existing uneveness.

Wartburg

Carnmore wrote: »

Condensing oil boiler with rads. And a dry woodburning stove in the middle of the living/kitchen area.

The woodburning stove is definitely the right heat source for your building structure, because she creates the radiant heat, which heats and dries your walls too. Try to use this source as much as you can.

BryanF

Wartburg wrote: »

To
I´m surprised about your suggestion with the Gutex and Calcium Silicate on top, because I can´t follow the sense of it...

? Where did I suggest this

but do you really need that higher capacity in this particular case, by having a mHVR installed?

?

There´s more attention needed to make sure that the structure will have no gaps/voids between the existing wall and the internal insulation layer.

? That’s why the calcium silicate is a better option than the wood fibre.

Wartburg

Have to apologise for my misunderstanding regarding "calciumsilicate over gutex".
As far as I remember, the original question went towards insulation. What thickness of the calcium silicate board do you want to install, by knowing it has the worst insulation value of the recommended materials? I like the idea of calcium silicate in areas like window reveals in existing houses, to prevent mould there and I already used Redstone calcium silicate blocks, to reduce the humidity in a damp basement bedroom in my native country almost 10 years ago.
In general: there´s no magic material that solves all problems and that´s why I would highly recommend to the get a calculation regarding insulation performance and risk of moisture/condensation done upfront, by an independent building technician/ engineer without any dependence to a particular product/ supplier.

Carnmore

Wartburg wrote: »

I would highly recommend to the get a calculation regarding insulation performance and risk of moisture/condensation done upfront, by an independent building technician/ engineer without any dependence to a particular product/ supplier.

What type of building technician/engineer should I be looking for? My architect and different builders I have spoken to want to dry line the walls and have no particular knowledge or appreciation of using natural, breathable materials.

Wartburg

I know it´s the hardest part but even by the fact that we´re living on an island, there should be someone out there, who´s specialised in the refurbishment of cottages in a sustainable and efficient way. I know it seems that some suppliers are doing a fantastic job by supplying their ecological building systems. They provide you with plenty of technical aspects and even calculations, but these are more or less all tailored to the product they (want to) sell. You might need to do a bit of online research to find access to people, who restored their cottages already.

JonathonS

You may find some useful info in this blog. Its a bit clunky to navigate around but there is some really good info on restoring an old stone cottage.

https://limewindow.blog/

robp

Carnmore wrote: »

Yes I plan to install a MHVR - that would help with moisture removal as well as air quality?

MHVR is only worthwhile if you get to a sufficient level of airtightness. If you cant get to that level basically your draughts cancel it out. Check what kind of airtightness you can aim and then decide on MHVR.

Wartburg

robp wrote: »

MHVR is only worthwhile if you get to a sufficient level of airtightness. If you cant get to that level basically your draughts cancel it out. Check what kind of airtightness you can aim and then decide on MHVR.

Based on your location, you probably know the required maximum level of air changes per hour to comply with the regulations over there;).
I would treat the renovation of a stone walled house slightly different in comparison to new builds when it comes to ventilation. There´s more need to get the building well ventilated because of the risk of high humidity and radon levels than considering the efficiency of a mechanical heat recovery ventilation. That´s why a continuous mechanical ventilation is the way to go. Some of these systems do offer the bonus of heat recovery without a big extra in money and installation work.

thewiseowl12

https://www.boards.ie/discussion/comment/106707666#Comment_106707666

Sorry to resurrect an old thread - just have queries on a choice between PIR, Gutex and calsitherm for a dry lining application.

Basically I have a 1940's solid block on the flat house with external pebbledash. I want to dryline the front for aesthetic reasons as EWI is not an option.

There is condensation on the walls at present, but I presume that is from moisture within the house as opposed to wind drawn rain for example, though I could of course be wrong - I'm not sure how to check this.

The three systems I've looked at are

1) 82.5mm pir backed plasterboard, which would get to a U value of 0.27

2) 50mm calsitherm, very expensive of course, with not a great U value afterwards

3) 100mm Gutex thermoflex between studs with VCL then plasterboard with an end U value of .33

(1) and (3) I could do myself, as they involve studs on the wall and then I could just tape and join the sheets as opposed to getting the special compounds and lime plaster.

Obviously (1) is the cheapest by far - if there is no wind driven moisture would it work in my setting?

Otherwise would (3) be the best option?

Thanks.

Lumen

Resurrecting this thread with a question about a block built house is going to cause confusion.