Just noticed Timmy's comment re cement in the Hempire Product. There is no cement in it. They use ground glass to get it to set more quickly. There is some cement in the Hempcrete product. When they say it an be applied to damp walls, they are talking about walls which have been covered with inappropriate materials like cement renders and foil backed dry lining in stone cottages and hence where moisture has become trapped in the fabric of the building. The Hempire product allows this moisture to continue to dry out after application. This is my understanding from a demonstration they did at CAT in May.

Roll it roll it roll it, bandwagon keep on rollin' .....

This thread seems to have dried up somewhat. I'm stalled by the usual lack of finance, so cannot make much progress. Has anyone actually gone ahead and used hemcrete as an internal insulation system yet?

Now winter is creeping in and I'm heating my whole 500yr old Thatched cottage from one 4.5kw wood burner, I'm becoming more and more convinced by Lime Technology's theories on thermal mass. A totally non-scientific observation last night - the house was a 20C at midnight last night, by 8am it had dropped to 17C with an outside temperature of 1C - the only insulation added to the house if 200mm of fibreglass in the loft, and some totally non-functional unsealed double glazing - and new for this year, attempts at sealing the huge draughts around the windows. I was pleasantly surprised.

...also... just out of interest if I were to use 20mm of the stuff in lieu of 20 clay or 20 gypsum would there be any tangible benefits...?

j

Posted By: James Norton...also... just out of interest if I were to use 20mm of the stuff in lieu of 20 clay or 20 gypsum would there be any tangible benefits...?

j

Depends if you accept that the hot plate is the correct way to assess heat loss.

If you do then:
20mm of hemp [k =0.678W/mK]applied to a 600mm stone wall has a u-value of around 0.63W/m2K
20mm cement [k = 0.5W/mK] rendering applied to a 600mm stone wall has a u-value slightly better if you go to third decimal place

From http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2847&page=1#Item_29[belongs here really]:

Okay, whats going on here?

http://www.limetechnology.co.uk/upload/documents/1201787723_the_thermal_performance_of_tradical_hemcrete.pdf
gives thermal conductivity of 0.07W/mK

http://www.limetechnology.co.uk/upload/documents/1210172463_labccertificateweb.pdf
gives thermal conductivity of 0.679W/mK

How can there be such conflicting values?

I now have planning permission and listed building consent So it looks like I am actually going to do this: I know Tim Hulse was looking at this too, is he still about? Has anyone else used Hemcrete this way? I'd love to learn from someone else's mistakes, rather than be a pioneer!

Spraying is a complete non-starter for anything less than a complete new house - set up costs are huge, so casting in situ is the only option. I'm looking at applying 200mm on the external walls, and 150mm on the walls adjoining next door cottage, but I've not cleared that with the building control people as yet. I'm also thinking of using insulated vertical shuttering (i.e celotex) to define the vertical edges and leaving these in place - though not yet sure how I will fix them to the walls. Lots of unknowns - which is why I was hoping not to be the first!

500mm will give you a a very good u-value and very thick walls! We're limited to 200mm as our rooms are relatively small. Are you going to use temporary shuttering or build it and leave the supports in the walls? We keep coming up with new methods, but all theoretical at the moment.

I was hoping that someone else would be the first to DIY hemcrete, but no one has posted their experiences, and I could wait no longer...
Firstly Lime Technology are very helpful people, they sourced some multipro boards for me, and have provided lots of practical support, including sending a technical advisor to see me (I'm not that far away from them).
Today we bit the bullet and started the job. We're using a small cement mixer so have to use bucketfuls rather than whole bales, and we started with a 1 hemp, 1/2 binder 1/2 water mix. First load suffered some balling, so we added some large stones to the mixer and added the water gradually using a watering can. We found a dry build up in the back of the mixer that had to be dug into the mix as we went along, but quite quickly we developed a system, and managed to create 5m of wall 200mm thick and now 500mm high, it took about 5 hrs, but we were speeding up all the time. Bigger mixes helped, even though they took more TLC to get consistent. Although I know it will set, its hard to imagine stuff that looks like grey manure is going to be a sold surface any time soon.
Lessons learned - the shuttering may seem firm and stable when you start but watch it as you tamp, we had to redo the supports half way through, and hardboard isn't up to the job, if you want a flat wall (we don't - we're trying to preserve the quirky walls of our C15 barn). When you're dealing with old walls, your thickness will be "nominal". Your mix will improve as you go along, and I think you need to learn how your mixer behaves at first. Wear breathing mask and spend time sealing up the mixer for the dry mix stage. Overall its easy, though tomorrow I may have a huge pile of stuff all over the floor rather than an insulated wall.

How exciting! Thanks for posting your experience on here Jem. Please keep us updated on your progress, we are still going to use Hemcrete but probably not until next summer at the earliest.
Getting the hang of the mixing sounds similar to our experience of mixing lime mortar, there's no substitute for having a go yourself.
We need pioneers like you to lead the way!

Fantastic, jemhayward. Do you feel that there's a good thermal bond between the hemcrete and the masonry? Do you think it will be adhered, long-term, or merely touching?

Aha, so stops at floor level. What's beneath? another storey? floor thickness zone? basement? underfloor void?

Another question - is the rubble wall fairly solid, or full of internal void?

Fantastic picture! we are so geed up to do this now.

Any more details on the rockbar? size, length, drilled into wall and set with lime mortar? easy to source?
It has been suggested to us that we may need a timber frame internally to 'support' the hemcrete (i think basically to hold it against the wall), but I prefer your solution.

Ooh good question, I need to know this as well!