Hempcrete insulation

Robin2020

Member
Livestock Farmer
20220122_083838.jpg

Just wondering if anyone has experience of using hemp as insulation or the latest innovation of spray on hempcrete.
I am toying with the idea of insulating my small mill conversion with spray on. An architect up the road did it and you get a wonderful natural look. Also no messing with batons and boards.
The pros seem to be:
Environmental impact
Natural look and smell
Go as thick as you like and sticks to anything....suits uneven walls.
Similar price to other options (all in).
Suits old buildings.
Breaths well
Maintains R Value
Cons:
Need 3 x thickness of standard insulation for same R Value.
Not as fire resistant!!
A concern with damp walls but can go on tanking....but then you lose breathability.
Requires specialist machinery that mixes the product at end of hose....so no DIY.
board.
Not ideal I'm my small building if it has to be 250mm thick!!
Any thoughts...
 

renewablejohn

Member
Location
lancs
For a start ignore the normal info on insulation values as by the looks of it you have thick dry stone walls and normal insulation rules do not apply. If you want informed information for that construction the best research I have seen has been carried out by Edingburgh University on actual solid walled houses in Edingburgh. Now for an insulation lime product have a look at a cork mix like Ecocork which I would use in your situation and its only 20 mm depth. For more advice I have always found the people at Ty Mawr to be very helpful. I would also recommend the Lime courses they do if they still do them as it was very hands on and I learnt a lot.
Forgot to say if the wall breathes you will not have a damp wall so long as you dont bridge the stone construction. Many people plaster to the floor which is a big mistake as the plaster will act as a wick for moisture to spread up the wall. Better to stop the plaster 6 inches from the floor and let the breathable stone do its job. You can always cover the gap with a wide skirting.
 
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For a start ignore the normal info on insulation values as by the looks of it you have thick dry stone walls and normal insulation rules do not apply. If you want informed information for that construction the best research I have seen has been carried out by Edingburgh University on actual solid walled houses in Edingburgh. Now for an insulation lime product have a look at a cork mix like Ecocork which I would use in your situation and its only 20 mm depth. For more advice I have always found the people at Ty Mawr to be very helpful. I would also recommend the Lime courses they do if they still do them as it was very hands on and I learnt a lot.
Forgot to say if the wall breathes you will not have a damp wall so long as you dont bridge the stone construction. Many people plaster to the floor which is a big mistake as the plaster will act as a wick for moisture to spread up the wall. Better to stop the plaster 6 inches from the floor and let the breathable stone do its job. You can always cover the gap with a wide skirting.

@renewablejohn - are you saying limeplastered stone walls are not as bad as all that for heat loss?

I have lime plastered walls and I get quite a few cold spots which mould grows on. I know in one way the answer is more ventilation but that will also be heat loss. What breathable insulation would you recommend on the internal walls? Cork? Woodfibre? Hemp render?
 

renewablejohn

Member
Location
lancs
@renewablejohn - are you saying limeplastered stone walls are not as bad as all that for heat loss?

I have lime plastered walls and I get quite a few cold spots which mould grows on. I know in one way the answer is more ventilation but that will also be heat loss. What breathable insulation would you recommend on the internal walls? Cork? Woodfibre? Hemp render?
The thing you have to understand and backed up by the research is that a thick DRY well pointed solid wall is a very good insulator. What you describe been there got the T shirt but also the solutions. Your right with ventilation I have virtually sealed my house with no opening windows and scandinavian double seal doors. Now sealed because were animals all the moisture we generate needs to be extracted so I have installed Partel MVHR units which are very effective at extracting the moisture but still retaining the heat in the building. The units work in pairs so as one unit extracts the other unit pumps the same volume of air into the building. As for mould thats just a feature of modern paint and damp walls. A quick roller over the mould area with neat bleach (make sure you wear safety glasses so you dont get bleach in your eyes) and the mould will magically disappear.
For insulation on solid walls so long as the walls are thick and dry I would always use a lime cork product. Its not only the walls which is important but the floor as well for which I do like the foamed glass solution with underfloor heating and no plaster bridging between floor and wall.
 
The thing you have to understand and backed up by the research is that a thick DRY well pointed solid wall is a very good insulator. What you describe been there got the T shirt but also the solutions. Your right with ventilation I have virtually sealed my house with no opening windows and scandinavian double seal doors. Now sealed because were animals all the moisture we generate needs to be extracted so I have installed Partel MVHR units which are very effective at extracting the moisture but still retaining the heat in the building. The units work in pairs so as one unit extracts the other unit pumps the same volume of air into the building. As for mould thats just a feature of modern paint and damp walls. A quick roller over the mould area with neat bleach (make sure you wear safety glasses so you dont get bleach in your eyes) and the mould will magically disappear.
For insulation on solid walls so long as the walls are thick and dry I would always use a lime cork product. Its not only the walls which is important but the floor as well for which I do like the foamed glass solution with underfloor heating and no plaster bridging between floor and wall.

Its mould on limewash! The upstairs rooms are vaulted and I think the mould just settles on coldest spot. I probably don't keep them warm enough.
 

Robin2020

Member
Livestock Farmer
For a start ignore the normal info on insulation values as by the looks of it you have thick dry stone walls and normal insulation rules do not apply. If you want informed information for that construction the best research I have seen has been carried out by Edingburgh University on actual solid walled houses in Edingburgh. Now for an insulation lime product have a look at a cork mix like Ecocork which I would use in your situation and its only 20 mm depth. For more advice I have always found the people at Ty Mawr to be very helpful. I would also recommend the Lime courses they do if they still do them as it was very hands on and I learnt a lot.
Forgot to say if the wall breathes you will not have a damp wall so long as you dont bridge the stone construction. Many people plaster to the floor which is a big mistake as the plaster will act as a wick for moisture to spread up the wall. Better to stop the plaster 6 inches from the floor and let the breathable stone do its job. You can always cover the gap with a wide skirting.
Great advice...thanks. I will look into this. Damp is an issue as 2 sides of the barn ate sunk into the hill. ..
 

Robin2020

Member
Livestock Farmer
The thing you have to understand and backed up by the research is that a thick DRY well pointed solid wall is a very good insulator. What you describe been there got the T shirt but also the solutions. Your right with ventilation I have virtually sealed my house with no opening windows and scandinavian double seal doors. Now sealed because were animals all the moisture we generate needs to be extracted so I have installed Partel MVHR units which are very effective at extracting the moisture but still retaining the heat in the building. The units work in pairs so as one unit extracts the other unit pumps the same volume of air into the building. As for mould thats just a feature of modern paint and damp walls. A quick roller over the mould area with neat bleach (make sure you wear safety glasses so you dont get bleach in your eyes) and the mould will magically disappear.
For insulation on solid walls so long as the walls are thick and dry I would always use a lime cork product. Its not only the walls which is important but the floor as well for which I do like the foamed glass solution with underfloor heating and no plaster bridging between floor and wall.
Thanks for this..very useful. I've put a lot of effort into the pointing inside and out. Nicely sealed.
 

dave mountain

Member
Livestock Farmer
4x2 CLS studs screwed to walls (or set off slightly), infill with 75mm celotex, plasterboard, skim, paint, job done

vent holes through exterior wall for airflow behind celotex
 
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renewablejohn

Member
Location
lancs
Great advice...thanks. I will look into this. Damp is an issue as 2 sides of the barn ate sunk into the hill. ..
Looking at your photo's it does look like you need a 1 metre deep french drain putting in on the sides into the hillside. I have one on my farmhouse as one wall is 1 metre below soil level. It has clean limestone as the french drain fill and drain pipe at the base. Large welsh slate sheets seperate the french drain limestone from the stone of the house. It works very well and the walls are dry despite being in very wet Lancashire.
 

renewablejohn

Member
Location
lancs
Yes got planning but waiting on regs drawings. I guess building control will chip in then. Pretty sure I would have a big fight if I chose not to insulate...
Dont be guided by planners they know nothing. English heritage is your friend and will tell the planners what needs to be done hence why I managed to get 3G glazing, scandinavian doors, en suite bathrooms etc etc in a listed building. Had originally been told by planners I could not have any of that. Big thing with English Heritage was the Partel MVHR system as according to them in a Listed Building it was the best way to "protect the fabric of the building" and now I have it working I can understand why. Was not cheap but worth every penny as it extracts the moisture but retains the heat and with a wife who has asthma also keeps pollen out the house as an added benefit.
 

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