Get Sust! Issue 27

Material matters at EcoBuild

While the first day of the EcoBuild conference programme majored on drum-banging for the sustainability cause, day two really got down to the detail - focussing on materials.

The materials session was chaired by Tom Woolley, Professor of Architecture at Queen’s University Belfast who has recently published a comprehensive and well-illustrated guide to natural building techniques. His book examines the techniques required to build with earth, timber and straw bales, and analyses the principles of green building and the issues involved in planning and regulatory approvals. It also covers green roofs, lime and masonry, and hemp, plus natural insulation materials, and paints and finishes.

Perhaps the most significant presentation of the session was from Neil May, Managing Director of Natural Building Technologies, who pondered the question: ‘What is the point of green materials?’

Green materials - why bother?

His answer is that, while materials account for only 7 per cent of the whole-life energy use of a building, this percentage will increase as we progress towards lower-energy buildings. However, that’s not the only reason for the importance of green building materials. May says that the real benefits come because green materials are multi-purpose. Not only do they have low embodied energy; they can also offer greater thermal mass, reduce resource depletion and - crucially - promote a healthy indoor environment.

May told the EcoBuild audience that, with the Building Regulations paying ever greater attention to airtightness and increased levels of insulation, and with the widespread use of man-made (hydrocarbon-derived) building materials, there has been a dramatic increase in respiratory diseases and asthma. He is concerned that the next generation of low-carbon buildings might also be sick buildings, because moulds and the dust mites responsible for asthma thrive in the warm moist atmosphere of today’s buildings.

May’s solution is to choose vapour-open structures and hygroscopic materials that allow the building to breath. Mineral wool, for example, is vapour open, but is not hygroscopic - it doesn’t absorb and release moisture, so any surplus can accumulate and damage the building fabric.

On the other hand, May warns against being overly ambitious for green materials. “I call it the ‘aloe vera’ factor,’ he says, explaining that not so long ago, aloe vera became a popular ingredient in all sorts of skin preparations, as though it was the magic ingredient that could cure all ills. “You can’t expect natural materials to cure all; you have to use the right materials for the job,’ he says.

So how to choose? May presented a useful table summarising the properties of a wide range of natural and conventional materials (downloadable from his company’s website).

Don’t forget the 3 Rs

Jennie Price, the next speaker, on the other hand, approached the issue of materials from a rather different angle. In her role as Chief Executive of WRAP, she wanted to raise visitor’s awareness about the benefits of the three Rs - ‘reduce, reuse and recycle’. She quoted a recent study by Amec which found that the true cost of on-site waste can be hugely underestimated, not just the environmental cost, but the ‘practical’ costs too. For example, if it costs £85 to hire a conventional skip, it then costs £163 in labour to fill the skip, and a whopping £1095 for the unused materials that are thrown away - a bill of £1343 that could have been avoided or at least, considerably reduced. Price reminded the EcoBuild audience that there are several quick wins when it comes to avoiding this cost:

design-out waste
offsite manufacture
smart logistics
closed-loop recycling (e.g. dig one trench for all utilities).

And not to forget that WRAP has produced a toolkit to help designers along the three Rs route...

Materials with the S-factor

Materials also featured highly in a novel event during the afternoon session at EcoBuild - the S-factor competition, hosted by Sustain magazine.

The idea was to pit six brave contestants against each other in a gruelling ‘beauty’ contest modelled loosely on the BBC TV series Dragon’s Den - unfortunately without the all-important cash prize.

First up was Andrew Biggs of Akristos, demonstrating an unfired-clay/plasterboard block which is suitable for internal non-load-bearing walls. This product’s unique selling point (...to stick with the Dragon’s Den lingo) is that it takes waste materials from two different ‘streams’ - waste plasterboard from construction sites; and waste clay from the ceramics industry. Even better, very little energy is needed to produce the blocks because they are shaped by an extrusion process, then they dry naturally.

John Grindrod of Econoplas also brought a new material to the platform. He hoped his great idea would be his pension! His company takes mixed polymers (waste plastic), adds water, and squeezes the mixture to create strong and durable ‘macro-porous’ blocks which are to be used as drainage materials instead of aggregates. In true DD fashion, Grindrod demonstrated the ‘feature’ of his block by recruiting a member of the judging panel to pour a glass of water onto the block while Grindrod caught the run-off underneath. Impressive stuff. The material has already been used as drainage in London’s Jubilee Gardens (at the foot of the London Eye) and for numerous golf courses and amenity areas around the country. It can also be used as drainage for, say, green roofs, without the need for a geotextile.

The judges grilled Grindrod over the embodied energy of his product but he came out on top, explaining (without revealing his secret formula) that the material is extruded from waste plastic and no additional heat is applied - friction alone is enough to heat the waste to its de-nature point.

Next came David Garlovsky of InnoTherm who had his USP in a bit of a tangle - was he marketing a product or an education tool? Turns out he was doing both. His idea is to engage school children in the idea of recycling by taking their jeans and turning them into insulation.

It wasn’t quite as described, though, because Garlovsky confessed under cross-fire that he can’t yet use materials recycled locally - as a nation, we just don’t collect enough. At the moment he uses fashion-industry waste, but his aim is to raise awareness of this alternative use for recycled textiles in the hope of prodding the market forward.

The finished product is highly insulating. An 89mm sheet is equivalent to 100mm of conventional insulation. It’s breathable, easy to install, and suitable for DIY or professional use in lofts and walls. On the down-side a low-melting-point polyester is added to the material to help it stick together, and a breather membrane is required for installations where the material could become moist. At that point someone in the audience asked about mice... but Garlovsky said that in his experience the ammonia-smell given off by the fire retardant was enough to put them off!

Mice were also of concern to Craig White and Tim Mander who, sporting matching corporate-branded T-shirts, were unmistakably the ModCell team. Their clever product is a prefabricated hemp/straw/paper panel which they say ‘puts the fab back into prefab’. Basically this is tightly packed straw or hemp bales stacked within a wooden frame then coated in a protective lime render. Apparently they’ve only once had a rodent problem... The unfortunate animal had been ‘harvested’ and packed into a bale which was rendered in situ and left overnight to dry. Next morning there was a small ‘escape hole’ high up in the wall but no sign of the creature which presumably had high-tailed it back to the nearby fields.

ModCell’s product can use straw, hemp or paper for its cellulose insulation core; and the duo say their system can be used to build large-scale ‘carbon negative’ buildings, because each 3 x 3 panel has 598kg carbon sequestered into its fabric and offers insulation values up to three times better than current building regulations. Their system has been used to build an extension at the University of West of England’s School of Architecture, and York City Council’s Eco-Depot. And one final advantage claimed is that the panels are built by ‘flying factories’ - the team identifies a local source of straw or hemp, and aims to construct the panels within 10 miles of the site, thus cutting transport embodied energy to the bare minimum.

Other contenders for the coveted S-factor prize were Aidan Quinn who has created a 6.2m x 4m (diameter) ‘Eco-Pod’ that’s a dome-shaped dwelling for two people; and Solar Century who put the case for their latest development - the C21e solar electric rooftile.

And the winner was... Econoplast

Learn more:

	•	Tom Woolley’s book ‘Natural Building - A Guide to Materials and Techniques’, is published by Crowood. ISBN: 978 1 86126 841 9. Available from www.crowood.com or via the author www.qub.ac.uk/schools/SchoolofPlanningArchitectureandCivilEngineering.
	•	Read Neil May’s article on breathability in buildings (download pdf) from www.natural-building.co.uk/recent-articles.htm.
	•	WRAP is at www.wrap.org.uk.
	•	S-factor contenders included: www.akristos.com; www.econoplas.co.uk; www.recovery-insulation.co.uk; www.modcell.co.uk; www.solarcentury.com.
	•	Sustain magazine is at www.sustainmagazine.com.