Editors' blog
Anna Simpson, 9 Mar 2010
In last week’s episode of ‘Lark Rise to Candleford’, two women vied for a rare opportunit...
Hempsulation
Innovative insulation acts as carbon sinkBiological materials don’t get much more versatile than hemp. Its latest incarnation is as a building material with solid sustainability credentials. Lhoist, the world’s largest producer of lime products, now offers an insulation solution whereby hemp and lime fibres can be sprayed between timber frames to form a fully breathable insulated wall with laudable thermal performance.
Since hemp absorbs CO2 as it grows, this ‘Tradical Hemcrete’ is in effect a permanent carbon sink. It’s a key feature in the award-winning Three Gardens development [right] in Elmswell, Suffolk, used in each of the 29 houses and credited with removing a tonne of CO2 from the atmosphere for every 20m2 of wall. That’s a very positive contrast, when producing the mineral wool typically used for the equivalent area of insulated cavity wall actually emits about two tonnes of CO2.
Research sponsored by the Pilkington Energy Efficiency Trust shows that the hemp-based product has a satisfyingly measly thermal conductivity of 0.26W/m2k; impressively close to that of mineral wool at 0.25W/m2k.
So how does it compare on price? Mike Haynes, product manager at Lhoist, claims that despite relatively small-scale production, the Hemcrete walls at Three Gardens are near parity to the cost of conventional walls. With all new UK homes required to be zero-carbon by 2016, economies of scale could tip the balance in its favour. And Hemcrete, Haynes adds, is “exactly the kind of product developers will need to consider if they are to make zero-carbon buildings a reality”.
– Jon Wallace
4 February 2008
Add new comment
Invisible insulation: hemcrete removes a tonne of CO2 for every 20m2 of wall at the Three Gardens development in Suffolk
Forum for the Future
works with leaders from business and the public sector to create a green, fair and prosperous world
Registered charity number 1040519
Comments
Forum for the Future welcomes constructive comment and differing opinions. We reserve the right not to publish messages which we believe are commercial or designed to disrupt discussion. We moderate comments according to these guidelines.
Comments may be published in Green Futures print magazine.
You seem not to mention that
You seem not to mention that hempcrete binder Tradical hemp mix is imported from France and contains cement upto ~20% and that the embodied energy of lime can also high in modern centralised kilns, making the figure of locking up CO2 very questionable.
The hemp supplied for LHoist is generally grown monocultured and fertilised. Recent evidence has shown that NO2 land use due to fertiliser is becoming a very important Green house gas from farming land as it many times more potent than CO2.
Further more a U-value is quoted and called thermal conductivity hiding the fact the walls are a lot thicker than standard walls to acheive the same value.
Having said that, hemp hurds (the stuff used for horse bedding) are readily available and cheaper and the binder used can be pure NHLlime(2-3.5) without Lhosit's cement additions and Lime can made using none fossil fuels and cement can't.
Hemp is also very well suited be grown organically and hemcrete doesn't need to be sprayed (using lots of energy and diesel to do so!!) onto the walls it can easily tamped into formwork arround a timber frame as it was in the Haverhill Housing Project.
That CO2 maybe locked up in hemp and lime walls is possible however using industrial processes to blow it on the wall, having 20% cement in the mix, importing from France and using hemp grown in monoculture make this highly unlikely!