7 May 2010

On Hemcrete

Yesterday I saw my first Hemcrete house under construction, a large selfbuild in Kent. I managed to get to site to see the hemplime mixture getting fixed to the timber frame background, and to chat to the guys from Denstone Construction who were fixing it. Fascinating talk it was too. Denstone’s expertise is in ICFs but they are happy to try anything innovative. Hemplime is certainly innovative, but is it the future?

Where it scores, of course, is in the low-embodied energy or eCO2 as the manufacturers like to term it. For many people, low-embodied energy materials represent the future of homebuilding, more so than the technically challenging but material-blind standards such as Passive House. But the amount of effort and skill required to wrap this timber-framed in HempLime gave me pause for thought about whether it really represents a step forward. Denstone had had to design and install a shuttering system (pictured) in order to get the insulation into place: they had come up with a system based on plywood sheets held in place by rebated studs which were in turn held in place by extra long screws going into the frame. The insulation then has to be mixed on site (the hemp shiv arrives in bags, and is mixed with a lime binder), hoisted up the scaffolding, poured into place and then patted down gently with a podger.

Then it has to be left to dry. “It’s really a summer job – you wouldn’t want to do this in winter or when it’s too wet.”

On the other hand, it looks great, like nothing else you’ve seen on a building site.

1 comment:

  1. Annalie RichesMay 11, 2010

    We have completed a housing scheme (26 units) of sprayed lime hemp. Much quicker than tamped and with no need for shuttering, it can be sprayed from the outside or inside. The main issue was the mess. We are very pleased with the results, we've lime rendered on top, with no cracking. As its sprayed from the outside airtightness was good. The houses feel more solid than normal timber framed houses.
    Annalie Riches (Riches Hawley Mikhail Architects)