Will Anderson: The Green House

If greenhouses are made of glass, what should green houses be made of? Choosing a construction material is like making a selection from a pudding trolley: the range of options is bewildering but most people soon home in on their favourites, ignoring untried delicacies. The industry is replete with enthusiasts of chocolate torte, crème brulee and even Black Forest Gateau, so the only way to be confident about your final choice is to insist on tasting them all.

I am currently feeling thoroughly replete after doing precisely this at two recent ecobuilding shows: Homes for Good in Taunton and Ecobuild in London.

Last week I found myself chairing a seminar in a lecture theatre made from straw bales in the centre of the Earls Court exhibition centre. As straw has excellent thermal and noise insulation properties, this was an ideal spot for a debate, though we were there only because the scheduled speaker started sneezing and had to be transferred out. Straw is a cheap and cheerful building material that ought to be used more widely, but suffers from the problems of minority status: most construction professionals (and insurers and lenders) don't want to know. So if you are keen to build with straw, talk to the enthusiasts. Amazon Nails, who built the lecture theatre, use straw to bring the experience of building to a wide range of people ( www.strawbalefutures.org.uk, 01706 814696).

Ecobuild also boasted a house made of Hemcrete™, a mixture of hemp and lime that is cast in-situ to create sturdy, warm walls ( www.limetechnology.co.uk, 0845 603 1143). Like walls made of straw or timber, Hemcrete is derived from a natural resource and so locks up carbon in the structure of the building. It is a very new material but it shows great promise.

In Taunton the Homes for Good organisers had outdone Ecobuild by siting their event in the Genesis Centre, a new building atSomerset College of Arts and Technology designed to show a range of sustainable building techniques in its fabric ( www.genesisproject.com). Genesis operations director Ian Moore showed me the four pavilions adjoining the main circulation space, each of which has a wall section stripped back to reveal constructions of earth, clay, timber and straw.

The Earth Pavilion has cob walls made from soil from the site mixed with straw and a binder, and rammed earth walls formed on-site with no additives. These materials could not be more local and require minimal energy to process.

The Clay Pavilion has a higher "embodied energy" as the bricks are fired, but these Ziegel blocks, from Natural Building Technologies ( www.natural-building.co.uk, 01844 338338), have a honeycomb structure that gives them far higher insulation properties than ordinary bricks. They slot together with glue, not mortar, so offer a rapid method of solid wall construction.

Timber is the most established material on show and has excellent credentials for carbon capture, embodied energy and thermal performance. It remains my personal lemon meringue pie, to be served with certification of sustainable forestry management ( www.fsc-uk.org).

As for that Black Forest Gateau, Masterblock were at Ecobuild promoting their new, greener concrete block: Enviroblock, made entirely from waste materials within a production process that meets international environmental standards ( www.masterblock.co.uk).

In practice, few puddings are permanently removed from the green building trolley. What matters is the recipe used, the source of the ingredients and the skills of the chef. Santé!

GREAT BUY

The market for building materials made from recycled products is growing rapidly. For a green house made of glass, try Stoneglass bricks made from recycled wine bottles by Akristos, featured at Ecobuild ( www.akristos.com, 01782 799993).

GREAT WEBSITE

An invaluable guide to products with green credentials can be found at the National Green Specification site ( www.greenspec.co.uk). It includes both mainstream mass-produced items and new innovative designs.