Hemcrete - better than zero carbon?

Still for sale!
34 bags Tradical lime and 28 Tradical hemp shiv - surplus to requirements.
Cost £750 before April price rise;  £495 - buyer collects from Mickleton

We could well have titled this post "the big pour" as it has rarely stopped raining these past two weeks. Thanks to stirring work by our tiler, most of the house has been temporarily felt and battened but the intensity of the rain has been such that within hours of it almost drying out, it becomes inundated again.  It can get pretty depressing carrying out a timber build whilst constantly struggling with the weather in the wettest, coldest and most miserable June on record. Indeed July so far seems on track for a similar record too.  Despite this Jason we have been preparing the shuttering to pour our hemcrete walls as soon as there is a break in the weather.

Tradical Hemcrete is a unique building material which many would claim is carbon negative as an acre of hemp absorbs 5 times more carbon dioxide than an acre of forest thus helping to mitigate the effects of climate change.

The hemp plant itself is extremely sustainable as it is ready to crop about ten weeks after planting and flourishes without the need for chemical treatment, such as pesticides, herbicides and fungicides.

Hemcrete uses the inner woody core of the stem (shiv) which was until recently regarded as a waste product. Supplied as a dry material in bags, it is mixed with lime binder in a large paddle mixer powered by hydraulics from the JCB telehandler which is also used on site to move the materials around. 

On Thursday last blue sky appeared for the first time and we decided to go ahead and make a start. Our installation is benefitting from the experience and creativity of Jason Watts Carpentry based in the Forest of Dean and working almost non-stop until 8.30 pm we  managed to complete more than a quarter of the walls.

The mixture which is tamped by hand into pre-prepared shuttering has very unusual properties making it ideal for an eco-build.  It has excellent thermal and acoustic properties performing significantly better than its rated U value of around .20 for a 300mm thick wall. 

It has a high thermal inertia meaning it is slow to change temperature and slow to produce a steady state. No other single material can meet the combined thermal performance and airtightness of hemcrete as a highly thermally efficient walling material.

All we need now is three more days or so to complete the rest of the walls.