Internal insulation on external stone mortar wall

Merrion1968

Hello all,

I'd like your advice on what insulation I can put on the inside of my old house extension to help with my energy efficiency. I've a few ideas - a hemp lime mix (against stone wall directly or with studwork?), rigid mineral wool and lime finish, Calsitherm climate board (calcium silicate boards), or Gutex thermowall board. But I'm no expert and I'm throwing around these terms with little actual knowledge or experience!

Its a very old house and the extension is built directly onto soil or concrete(probably!). Basically, should I be thinking insulating boards on studwork (with wool or paper to fill the void?), or the more basic direct laying of lime plaster onto the interior of the wall? Keeping the house breathable is paramount.

I'd appreciate any advice. Thanks

archtech

Its best to engage professional advice to prepare the best solution for your situation. Without doing some detailed analysis its hard to give definitive guidance. There's certainly 2 or 3 potential solutions that may work however it would be hard for one to recommend the best one for situation without examining the building fabric and doing some analysis.

Merrion1968

Thanks archtech. In fact I'm looking for someone to do just that right now!

Does anyone have any experience working with Calsitherm climate board or Gutex thermowall board?

Is there an Irish equivalent breathable insulating board on the market for indoor external wall installation?

BryanF

Merrion1968 wrote: »

Thanks archtech. In fact I'm looking for someone to do just that right now!

Does anyone have any experience working with Calsitherm climate board or Gutex thermowall board?

Is there an Irish equivalent breathable insulating board on the market for indoor external wall installation?

It sounds like you should Go with the Calisitherm board, but an on site inspection would be best first from arch/ conservation surveyor

cala

Merrion1968 wrote: »

Hello all,

I'd like your advice on what insulation I can put on the inside of my old house extension to help with my energy efficiency. I've a few ideas - a hemp lime mix (against stone wall directly or with studwork?), rigid mineral wool and lime finish, Calsitherm climate board (calcium silicate boards), or Gutex thermowall board. But I'm no expert and I'm throwing around these terms with little actual knowledge or experience!

Its a very old house and the extension is built directly onto soil or concrete(probably!). Basically, should I be thinking insulating boards on studwork (with wool or paper to fill the void?), or the more basic direct laying of lime plaster onto the interior of the wall? Keeping the house breathable is paramount.

I'd appreciate any advice. Thanks

have you thought of expanded polystyrene on a roll, if the internal wall surface is sound it is a very effective insulator and you ll notice a difference in the warmth of the room when its up

Merrion1968

I'm only aware of EPS for external insulation and since my house is listed this is not an option.

There is a Dublin based company that stocks Remmers products. One product is called iQ Therm boards which are stuck to the wall and then rendered and painted, all breathable products of course. Does anyone have any experience with these boards?

To me there seems to be quite a selection of breathable insulating boards on the market and anyone with any experience, good or bad, would be much appreciated. Even better, if anyone could recommend a solid supplier of them that would be great!

Thanks all

Kristopherus

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Hey, NEVER put your mobile no. on a public forum. Can you edit it out, please. Scammers & similar no-goods could well be lurking.

MissSteel

Hi Merrion1968,
Did you make a decision on your insulation yet? I am in the same boat, looking for breathable internal insulation for a period building. I was looking up open cell spray foam insulation last night, have you come across this in your research? I like the idea that it will be easier to insulate with a product like this without cold leaking in through joints etc.
Our wall is cement rendered externally, we originally wanted to remove this and re-render in lime, but our budget wont allow this at the moment.. however if we find we are having a problem with damp, we will have to revisit this.

Merrion1968

Hi MissSteel,

We plan on repointing the cut stone exterior wall with lime morter and for insulation we will apply a hemp lime mix for the interior, maybe even the commercially available Hempire stuff. Since the exterior is breathable we will apply a breathable interior layer to enable moisture movement throughout the wall. With adequate ventilation within the house we hope to make it work.

In your case with a cement exterior coating, the same idea might apply.

In my research I considered the following:

· Studwork inserted with rigid insulation material and covered with breathable insulating board with a coating of lime render e.g. Calsitherm climate board (calcium silicate boards), Intello Plus board (Passive House standard). Issues - bulky and expensive, threat of thermal bridging if not installed correctly.
· Gutex thermowall board – Lime render wall and install boards. Issues - bulky.
· Other ideas - rigid mineral wool and lime finish; breathable spray foam. Issues - excessive moisture trapment may rot materials.


So for me, its looks like a hemp lime mix. This will encourage movement of moisture and not bulk out the wall too much. It also means thats its a skill I can learn to do for myself when the plaster needs redoing/repainting etc.

I hope this is of some help...

MissSteel

Thanks Merrion, That was a great help! I have been looking up the Hempire website and it is very interesting. Can you tell me what thickness you will go for? I watched the video of them installing it and it looks simple enough. I was wondering though, do you attach breathable plasterboard to the battens to hold in the material, and plaster over the board... or do you plaster straight onto the hempire layer? Would you be planning on putting some sort of a breathable membrane between the stone and the Hemp?
I have emailed them for costings, so it will be interesting to see how much it will be! I have a plasterer pricing lime rendering our external walls too, so hopefully it wont be too scary!

Merrion1968

I havent done much research into Hempire to be honest although I have printed off a few documents from a UK Hempire website.

IN our case I think we will simply apply the hempire to the bare wall, no membrane, no studwork etc. It wont be the most insulated wall ever but it will be breathable and its suitable to our budget considering what needs to be done in the rest of the house. As for thickness of application, I'm not sure, I'll have to do more research on that but the professionals should be able to advise. After plastering onto the bare wall then we will paint with a lime wash or breathable paint.

In your case, "they" recommend 5 layers of lime on an outside wall exterior, 3 on the inside. But if the wall is already coated in concrete then there may be little to be achieved by removing it and replastering with lime - seems expensive. But plastering inside with breathable lime/hemp etc would be a good idea especially if water does get behind and accumulate behind the concrete. Have a think about ventilation - trickle ventilation, hit and miss vents, extractor fans, even PIV units to push the damp air out of the house through cracks, doors, windows etc.

BConnor

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