Insulating a house with solid stone construction

Andalya

Hello - looking for some advice as feeling a bit stuck with how to improve the EPC (and lower bills ) on our 300 year old cottage. According to the EPC certificate one of the main things we could do is insulate the walls and floors, but from what I can tell this seems impossible - both are solid. The walls are solid limestone with no cavity to insulate, while the floors are also solid (from what I can spy from our cellar, looks like it's hardcore and concrete) and in half of the house are above next-door's barrel vaulted cellar. Is there anything we can do - any other tips for making the place more efficient and warmer? The loft is already insulated and the windows are double-glazed so feeling a bit stuck!

stuart45

Is the exterior face stone or render?

FreeBear

Yes, you can insulate solid stone walls. But you do need to be careful in selecting the right materials so as to avoid trapping moisture in the walls. Cork and woodfibre boards topped off with a lime render/plaster would be my suggestion - Not cheap though. A hemp plaster would also work, but you need a very thick layer to make it worthwhile (a work colleague used hemp plaster to insulate her cottage. She is not impressed...).

Have a chat with someone like Mike Wye - They may well be able to recommend solutions for both the floors and walls - Perhaps stud walls filled with sheeps wool...

Andalya

@stuart45 - there's no fascia or rendering, just the stone the house is built from.

@FreeBear - thanks for the recommendation! We're a bit wary of anything that'll steal too much space from the rooms, especially since we have lots of weird little corners, but it definitely sounds like it warrants further investigation.

theoretica

One thing to work through, which is not expensive, is draft hunting.  The building will need some ventilation, but many old ones have more than they need, especially if you do not have fires of any sort.

BUFF

Historic Environment Scotland (& their offshoot, The Engine Shed https://www.engineshed.scot) have a lot of case studies/info/videos available - no doubt the English equivalent is similar.
2 things:
1) you have to watch out for causing issues via interstitial condensation 
2) it will probably take 20+ years for break even on the investment for solid wall insulation 

If you don't mind losing some headroom you could always insulate on top of the floors.

edgex

Andalya said:

while the floors are also solid (from what I can spy from our cellar, looks like it's hardcore and concrete) and in half of the house are above next-door's barrel vaulted cellar. 

If you've got a cellar, you've got access to the underside of the ground floor flooring.
Are you sure it's hardcore/concrete, as that would need a lot of support to hold up.
It's not floorboards on beams? Those you can insulate from underneath by putting the insulation between the beams & up against the floorboards.

WustyRex

How does 6mm lost from the intertrior walls sound ?  to give damp and insuilation layer that can then be plastered or returned to stone. (No need to stud walls, plasterboard, new skirtuing etc: Very quick and effective. 
Then a nano technology outer skin that is clear and offers a degree on insulation .

All doable .
had ours done by Decopierre Stonecoat  2 years ago. 
They offered a stone finish over External wall insulation, but price was a bit to steep, so we went for the inner skin. Noticed the difference immediately. 

FreeBear

WustyRex said: How does 6mm lost from the intertrior walls sound ?  to give damp and insuilation layer that can then be plastered or returned to stone. (No need to stud walls, plasterboard, new skirtuing etc: Very quick and effective. 
Then a nano technology outer skin that is clear and offers a degree on insulation .

Unless you are using something like Aerogel, 6mm of insulation is not going to provide any real improvement. On a solid stone wall, you also need to be mindful of breathability and not trap moisture within the wall - That will rule out most modern materials. Do not be taken in by buzz words like "nano-technology" or outlandish claims of performance without sight of hard data.