Below are some design guides and information for the most commonly used and widely available hempcrete binders and hempcrete blocks in the UK.

Whether or not you plan to use any of these binders or blocks the design guides and information sheets are well worth reading for handy tips and inspiration.

 

The Hemp Block Company

The Hemp Block Company have partnered with Sennini to bring a regular supply of high quality and low cost blocks to the UK with the long term goal to make the blocks in the UK under licence.

The blocks are perhaps the most low embodied energy hempcrete on the market since they contain only Hydrated Lime and Hemp Shiv. Probiotic cultures are added to the lime, they excrete C02 during curing and this ensures the lime carbonates fully throughout the entire block with no ‘dusting’ in the middle.

Their declared thermal conductivity is 0.07 Wm.K

 
 
 

Batichanvre by St Astier

There are probably more Battichanvre hempcrete buildings in the UK than any other binder. It does what it says on the tin and is the most forgiving of the commercial binders.

At 0.09 Wm.K for walling mix its declared thermal conductivity is not as good as other binders, however this is probably because the mix is specified denser than other binders and actually it still works very well if you reduce the binder and therefore lower the density.

 
 

Tradical by Llhoist

Of the Tradical downloads the ‘Tradical design guide’ is the most up to date.

Tradical produces two hempcrete binders: Thermo and PF70. They seem to have had the most thorough testing of the commercial binders and the Thermo has very good thermal conductivity figures at 0.074 Wm.K

It is the slowest to gain its initial set, although this has never caused me much of a problem on site.

 
 

Prompt by Vicat

I’ve used prompt quite extensively with hempcrete. I favoured it when casting infill panels as it doesn’t shrink away from the timbers at all on drying (a problem that doesn’t occur when spraying). It is also good for cold weather work as it is very exothermic and fast setting so you can reliably use it at lower temperatures than other binders.

However, you must be very diligent when using Prompt. It must have enough water, but not too much and you cannot use the hempcrete if it has been sitting around for more than 30-45mins after mixing. It will have already started to set and by throwing it into the shutters you break all the bonds that are forming and they will not form again. You will know if you have gone wrong as any material that had been left too long will be crumbly when you take the shutters off.

You can also mix Prompt with hydrated lime (see the download opposite) to lower costs and increase working time.

Prompt is classed as a natural cement. The limestone it is made from has naturally occurring impurities which give it a rapid and hydraulic set. The limestone is quarried, burnt and crushed, there are no additives or man made substances included.

Prompt’s declared thermal conductivity is the best of these three binders at 0.07Wm.K

 
 

Natural Building by William Stanwix