Hemp lime plaster

sinnerboy

I'm looking to renovate and extend an old 600mm stone wall cottage in Co. Leitrim.

Has anyone tried using hemp lime internally beyond 50mm thick ?
I'd like to push for 75mm or even 100mm if thats practical. If anyone has tried this did it work ( i.e. adhere well )
What lambda value for the hemp lime?

This product data indicates U Value of 1.07 for 50mm over 500 limestone.
http://www.lime.org.uk/directlinkdownloads/10226Ty-Mawr_lime_hemp.pdf

I'd like to get to 0.6 if I can...

redeight

From the Tradical website the lambda value for hempcrete is 0.09 w/mk.
By my calculations that gives a u value of 0.9 for 100mm ..? Another source gave a lambda of 0.07.
I have used a lot of hemp and lime renovating a cottage and barn over the last 6-8 years. It is possible to put it on thickly but the thicker you put it on the harder it is to apply. I would say that the thickest I have ever applied it would be approx 60mm. It tends to fall away from the wall when you apply it this thickly.
To get a really thick coat you could either do it in two coats or you could put timbers on the walls and pack the hemp lime mix in.
Although the u values aren't great here are other benefits that should be considered.
Hemp and lime will greatly reduce problems with drafts in an old building because as you plaster the wall you will pack it into every little nook and cranny. It can also be used to re seat lose stones (although anything big should be dealt with properly using lime mortar well in advance of plastering).
Another benefit is reduced thermal bridging. There are other benefits too but you probably already know all about them !

sinnerboy

By my calcs using the lambda of 0.12 from this

I get to U value of 1.07 - similar to the table in the first link I posted to.

Thanks - this is really the only way to treat our old stone buildings imo.

BryanF

"Hempcrete has a λ value of ~0.076 - 0.11 W/m.K when mixed with a mild to moderate hydraulic lime consisting of ~85% hydrated lime and ~15% clay or pozzolans. For floor slabs, a more hydraulic lime is used and sand is added to improve strength and water resistance λ value ~ 0.13W/m.K. For the ceiling insulation and the internally insulating stone wall coating, a pure hydrated lime is used and a higher percentage of hemp to provide a more insulating and lighter mixture λ ~0.08W/m.K. ." (p21
http://gse.cat.org.uk/public_downloads/research/hemp/Hemp_Cannabis_Sativa.pdf)

http://projects.bre.co.uk/hemphomes/HempHousesatHaverhillfinal.pdf

http://projects.bre.co.uk/hemphomes/HempThermographicReport.pdf

http://www.nnfcc.co.uk/tools/guide-to-building-with-hemp-lime-composites-nnfcc-07-001/at_download/file

http://gse.cat.org.uk/public_downloads/research/hemp/Neal_Holcroft.pdf

http://www.lee-evans-elements.co.uk/pdfs/Straw_&_Hemp_Lime_Thesis.pdf

http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-05192008-140409/restricted/PhD_AE_Appendix_3.pdf

http://gse.cat.org.uk/hemp-building-research

http://www.josephlittlearchitects.com/documents/hemp_lime_paper.pdf

http://www.constructireland.ie/Vol-4-Issue-10/Articles/Design-Approaches/Ecological-innovation-at-Down-hemp-lime-house.html

http://www.hempcrete.com.au/pdf/Role%20of%20Low%20Impact%20Building%20Materials%20in%20Sustainable%20Construction.pdf


some light reading for you...:D

sinnerboy

No6

Brian what are you doing down our neck of the woods!! dont be assuming that the cottage has all nice stone with lime mortar walls, they are generally stones held together with muck and a lime wash if you are lucky!!:D

I think for 100mm you should be looking at a limecrete against the wall with a lime render finish, you'll probably need to provide some form of support so It may get thicker than you's want

BryanF

.

bazzer30

First time on Boards

I have a 100 year old story and half farmhouse in need of extensive renovation.

The extension is going to be a contemporary style and i caan achieve a passive standard on that easily, the old 500mm limestone walls are a different story, all the information I have is on modern materials for both internal and external insulation and nobody has given me satisfactory info on their performance for damp issues either how it gets out in the external insulation or how to prevent it coming in the internal case.

Basically i worry about breathability as work that was done on the house in the eighties (sand cement render and aluminium windows made matters worse), I just started researching other methods.

I am tempted by hemp lime insulation on the internal walls, any info on external insulation like calcite, could or should they be used in tandem? any rough idea of approximate cost per metre square?

BryanF

bazzer30 wrote: »

First time on Boards

I have a 100 year old story and half farmhouse in need of extensive renovation.

The extension is going to be a contemporary style and i caan achieve a passive standard on that easily, the old 500mm limestone walls are a different story, all the information I have is on modern materials for both internal and external insulation and nobody has given me satisfactory info on their performance for damp issues either how it gets out in the external insulation or how to prevent it coming in the internal case.

Basically i worry about breathability as work that was done on the house in the eighties (sand cement render and aluminium windows made matters worse), I just started researching other methods.

I am tempted by hemp lime insulation on the internal walls, any info on external insulation like calcite, could or should they be used in tandem? any rough idea of approximate cost per metre square?

Your dead right to be concerned about vapour movement, many 'pushers':) of modern materials have little understanding of moisture flows and interstitial condensation issues. I'd stay clear of all poly based materials and as you've found out cement mortars if possible.

the calcite issue is more prevalent where you use an EPS/ phenolic type board and where you have gaps between the boards the moisture squeezes out causing hassle on the render. with something like the hemplime, you do what been done for hundreds of years and apply lime wash coats every second year. If you use an EWIS the better manufacturers expect (with their mineral wool and cement render recommended for old stone walls), that an inhibitor is re-applied every five years or so.

It does sound like you've a ventilation issue to solve too from the 80's retro-fit, but lets stick with the Hemplime for now.

solve dampness first by addressing the main sources of moisture that occur due to weak-points at the footings and eave/roof overhangs.
then its about the right lime/hemp mix with the right installer, with supervision! particularly the lime render finishing must be good (i understand some less competent tradesmen have given the material some bad press in the past, but then what material hasn't suffered the same fate)
there's no reason why it cant be used in tandem on both internal and external walls. to get an reasonable u-value you would require quiet a thickness so a bit on both int & ext would seem appropriate, however some sort of modelling (Wufi or a least a considered calculation of the due point would be a good idea before install + consideration of the other factors like ventilation etc..

i understand that dryining with 100mm or so is between €100-140 per msq, depending on quality of render finish (ie rustic or clean lines + amount of opes etc) not sure about the external but I'd amagine its roughly the same, again depending on the particulars.

BryanF

I should add re cost: that many who go for hemplime get involved themselves as there's only a hand-full of good installers in the country and like many other wet trades theres alot that a lay person can do (with some guidance), minus the plastering of course

bazzer30

Thanks for the info

I am tempted to do the work myself, i'll need to mull over it some more

BryanF

100mm hemplime (with timber studs) internally in an old cottage.
has anyone priced or worked out the m2 cost of materials? (ie excluding labour)

gears

http://www.brebookshop.com/details.jsp?id=321427

Everything you ever wanted to know about Hemp Lime... Probably

BryanF

Not really answering my question, yes I've read it, here's a copy of it:

http://www.nnfcc.co.uk/tools/guide-to-building-with-hemp-lime-composites-nnfcc-07-001/at_download/file

gears

BryanF wrote: »

Not really answering my question, yes I've read it, here's a copy of it:

http://www.nnfcc.co.uk/tools/guide-to-building-with-hemp-lime-composites-nnfcc-07-001/at_download/file

Sorry but my intention wasn't to answer your question but help the OP.

And thanks for the link but I have my own copy

therightangle

sinnerboy wrote: »

I'm looking to renovate and extend an old 600mm stone wall cottage in Co. Leitrim.

BryanF wrote: »

100mm hemplime (with timber studs) internally in an old cottage.
has anyone priced or worked out the m2 cost of materials? (ie excluding labour)

Can I ask are either of you going with certified material, or maybe not as it is on the inside?
And, depending on the previous answer, did you come across a price/sqm?
Finally, is installing 100mm rather than 50mm possibly introducing more risk of interstitial condensation? My understanding is that 50mm is more the norm.

BryanF

therightangle wrote: »

Can I ask are either of you going with certified material, or maybe not as it is on the inside?
And, depending on the previous answer, did you come across a price/sqm?
Finally, is installing 100mm rather than 50mm possibly introducing more risk of interstitial condensation? My understanding is that 50mm is more the norm.

not necessarily certified

there may be some increase in interstitial condensation as thickness increases but my understanding is using such materials allow for a breathable process to take place.