Buildings Made of Straw – New Ideas for a Traditional Technique
Since we looked at new approaches to the traditional practice of using straw bales in construction, there has been a huge surge in interest in this technology.
With some high-profile recent projects being delivered using straw building technology, we’re looking more closely at the benefits this brings to the builder, occupier and the building through it’s lifecycle.
Bristol firm Modcell, driven by Craig and Fergus White, have been at the front of a small group of specialists who have been developing new technology to bring straw to the level at which constructors can viably consider it’s application in modern buildings.
On the face of it, it’s a bit of a no-brainer: Carbon-negative, super-insulating, passive energy-saving and relatively cheap.
Whole-life costs could be dramatically reduced as up to 80% energy savings can be realised in comparison to current standard build systems. The ‘up to’ part rings alarm bells but no-one seems to disagree that the energy efficiency of straw construction are significant. Even if this headline figure proves a little optimistic, at even half of this figure, self-builders, private sector developer and the broader public sector would be daft to ignore the potential.
So what’s the downside? Well, there are limitations.
Height for one. As it stands, the accepted structural limit for walls constructed with timber or steel frames is 3 stories. You’re unlikely to ever see a ‘scraper made of straw but, no doubt, with innovators learning more and testing new ideas, the boundaries are sure to be pushed to greater limits.
Space is an issue. 10% of the footprint of a ‘normal’ straw bale building is taken-up by it’s thick walls. As above, this is likely to diminish as new systems are developed. Even so, to arrive at the same insulation values using bricks and mortar, you’d have to make the walls 20% thicker.
Costs-wise, building materials are, at the moment, cheap – the average bale costing a mere £2 (at current prices), it would seem that, for the time being, the raw material cost is compelling. Foundations are lighter as the structure will be lighter than brick and block. You expect to pay less for copper and heating systems as well.
Traditional rendering methods however can be very expensive and results can be very mixed. Flaws in the rendered can that lose you much of the benefits and lead to significant longer-term problems. Plenty of self-builders have, in hindsight, said they would have elected to use alternative methods suchas cladding. That said, case studies have shown that diagnosis and repair of detail issues can be easy and quick.
Insurers are becoming less wary of the unknowns of straw-build safety as more data is collected and validated. The upshot being that you’ll not find it hard to get insured but it may cost a fair bit more than you’d otherwise expect.
Values of finished houses were weak a few years back due to similar reasons, however this appears to be less of an issue now – fashion and TV development shows are playing their part in this.
But the most compelling argument is the potential to burn less fuel. Last I lookedm it wasn’t getting any cheaper and they’ve stopped making crude. If we had built our home from straw, we could have expected to reduce our heating bill by, say, 70%. This could have saved us £600 per year. Scale this up to school-proportions and you are into hefty figures.
Cheaper to build, cheaper to run, cooler in the summer, warmer in winter. Innovative, carbon-negative, different…cool?
Plenty of case-studies are now available, lots more information below.
For now, it’s the pioneers and the slightly more cavalier that are leading the way.
It’s hard to ignore the potential though.
- Images courtesy of Modcell – www.modcell.co.uk
Bristol Green House – dissertation on self-build straw bale construction
STRAWBALE BUILDING – community site
Andrew Morrison – ‘A world leader in straw bale education…’