I am considering using hemcrete as the internal insulation on a C17 barn being converted. The original walls are 500mm ironstone and rubble, and probably about as airtight as a sieve. I've looked at everything from Vacuum Panels to Warmcell and Celotex, but limiting myself to affordable solutions, hemcrete seems to offer me some distinct advantages for about £35/m2 @ 200mm.
1. it has some thermal mass, so the building will "work" much like the original high-mass construction regulating temperatures.
2. it will provide a degree of air-tightness that would otherwise have to be created by using a separate process.
3. 200mm will give me a decent level of insulation.
4. fewer materials / stages required making the process less labour intensive and skill based.
5. it will be less affected by damp penetration than dry lining.
6. it will give a more sympathetic wall finish than flat boards.

However, there are a few un-answered questions:
1. will 200mm of hemcrete stuck to the upstairs walls represent a floor loading that will need to be taken into account?
2. how easy is it for semi-skilled labour to apply?
3. anything I've not thought of?

I've had some brief email discussions with manufacturer. It would seem that for my total wall area spraying is uneconomic as set up costs are quite high, also, as we're converting in stages, as part of the building is my office, we need to do it in stages. Casting in situ seems to be the way to go, and we may even try DIY, as it seems quite easy. My preferred builder has extensive experience in conservation projects (incl my 500yr old main house) and is familiar with lime - even makes his own lime plasters! He's keen to repoint the outside, as its quite poor in places, but we will probably leave that to the end of the project.
200mm is going to give me a u-value of about 0.28 which fits in with my whole building target, as I may need to "trade" relatively poor performance on the ground floor concrete slab, as we don't want to dig it up, and ceiling hts are marginal. We're in North Oxfordshire - I've not yet looked for suppliers, we're just at the specification stage, and at present have no funds available to proceed anyway.

I was looking at earth sheltered self build a few years ago, but local planning people put every known obstacle in the way, making it essentially impossible to build, and land here is very scarce and expensive - so I went for re-cycled housing instead. AGS has its appeals but the costs of going down below ground here are very high, I looked at ground source heat pumps, but couldn't make the maths work. We have ironstone, clay and radon to deal with. I may use AGS principles as an excuse for poor insulation on the floor - some compromise id due somewhere - at present the listed building people won't even let us put solar water heating on our ideal south facing roof.

Its difficult to find out as we can't dig near to the building, its all concreted over access, but judging by the garden nearby, and local knowledge, its pretty rocky down there - vast tracts of the village were quarried for ironstone until quite recently. The company quoting for a borehole seemed quite keen to dissuade me from going down, though theres plenty of underground water as every house in the street has a well, though all disused... so its not an impossible idea, just maybe an expensive one. At this stage I'm not ruling anything out. Overall heating strategy is wood pellet stove as we need to heat barn, main house and hot water.

I wonder why it is not possible to just render with hempcrete by hand in the same way as conventional renders? Or is it?

I have used many different render materials over the years but not hempcrete - I'd like to know more - Anyone know where there is a technical data sheet online?

Info on Hemcrete is available here ;

http://www.limetechnology.co.uk/pages/hemcrete.php?downloads=1

Thanks both

Am currently tryong to get my BCO to approve my use of hemcrete in my barn conversion but he hasn't said yes yet in spite of talking to the BCO who approved the LABC and to Lime Technology - the supplier. Lime Technology did some calcs and tells me 150mm is sufficient for a U value of .35 with 600mm rubble filled walls. Anyone else got this approved yet?

The BCO is doing his best to stop me using a limecrete floor as well - if he wins this battle, as he appears to be at the moment, is there any point in me still using hemcrete for the walls?

He says he want to see something like an LABC certificate for the limecrete method before approving it - which doesn't appear to exist. Ty Mawr have mailed him all the information they have but he says it's not enough.

Re: the walls, the architects preferred method is metal studs (cold bridging?) with Kingspan.

I'm happy to try sticking to my guns, but how do you prove you are meeting the regulation?

I thought my solution with a breathable floor and breathable, airtight walls ticks all the boxes. If the floor were concrete, I'm not sure the homgeneous hemcrete wall is going to work becaus as you said, any underfloor moisture is going to head straight for it.

tbhulse if the bco wont approve the spec then use another bco. you are not tied to using the local authority building control so move on to a supportive bco elsewehere or that operates privately

theres an labc certificate and plenty of other spec documents on the lime technology website. http://www.limetechnology.co.uk

Glad someone's doing this homework - thanks - will need it myself sooner or later.

I'm hoping to go to the seminar on the 25th too. My "Damp Man" has visited and has declared my rising damp as "minor" and feels tham the hemcrete lining I propose to use will be the best possible solution. I was looking at using 200mm but may trim that to 150mm as I'm slowly getting my head around the concept of dynamic u-values, so I reckon 150mm will get me part L compliance, and it will work rather better than 0.35 would suggest - add in my 0.18 roof insulation, and I'm getting close to a practical ideal.

Hey! Good for you!

I notice that Hempire states - ' can be applied to walls that are still damp' - I would suggest that anyone that does this is asking for trouble . Hemp MUST go onto walls where on-going dampness issues have been resolved. All the binders have a proportion of cement in them - they wont set in these sorts of thickness without them. Pozzolan is a coy way of saying cement in this instance - lets not be afraid of saying the word!