' the Woodlouse: Strawbale Frenzy


Wednesday, 9 June 2010

Strawbale Frenzy

Last week I was on a fantastic Building With Straw-bales course run by amazonails and held at the Centre for Alternative Technology (CAT), near Machynlleth in Wales.  The course was massively inspiring and motivating, to the point that on the train home I ended up eulogising about the virtues of straw building to a young couple (un)lucky enough to be standing in the same vestibule as me on the train between Birmingham's New Street and International. At Birmingham International I met a couple of friends who I was staying the night with, and despite having arrived 2.5 hours late (due to a poor, overworked train from Machynlleth which was overheating "due to the hot weather" that day) I still managed to have a crack at persuading them the best way to build their planned extension was (of course) with straw, before finally giving in to tiredness and need for bed.

I think the rampant evangelical fervour has now calmed slightly, but the course certainly confirmed and amplified everything I'd been suspecting about what a truly genius way to build, straw is.  Here's some reasons why: 

  • It's renewable.  It's grown in fields,  a waste product of grain production.  Also, any carbon absorbed by the the grain as it grows is locked up in the straw in your walls.  It will only be released again if your house is demolished and the straw exposed to the elements and allowed to rot.  Incidentally, the oldest existing straw-bale houses have already lasted 100 years and are growing strong.  Somewhere below is a photo of some 400 year old straw, bound up in clay plaster, looking as good as new,  Completely golden, perfectly preserved straw has been found in the ancient Egyptian tombs.
  • It's much cheaper than virtually any other building material.
  • Together with clay or lime plaster/render it forms a moisture-vapour permeable construction (a.k.a: breathable).  Similarly to expensive waterproof jackets - it keeps the rain and other weather out, but draws moisture from the inside of your home outwards, where it evaporates.  This eradicates internal damp patches and toxic mold (with the caveat that your straw-bale home is well designed and built, with a decent size overhang of roof, and attention to detail around joins with doors and windows - this is easily achieved however).
  • It's incredibly insulating.  You are building your walls from 100% insulation.  A straw-bale wall 45cm thick (standard bale width) has a U-value of 0.13 W/m²·K (1).  The lower the U-Value the better the insulation.  Current UK building regulations require a U-Value for walls of 0.35 W/m²·K  (2), much higher (less insulating) than that provided by straw.
  • It is incredibly fire proof, when rendered/plastered both sides with clay/lime.   BRE fire-testing showed such a wall resisted fire for 2 hours and 40 minutes.  At this point the only 'failure' was a crack in the render that allowed smoke to permeate through to the other side of the wall.  The straw did not burn.  Straw-bale construction has even been tested and approved for use in bush-fire areas of Australia.
  • It's fun.  And easily accessible without prior building experience.  There's something infectiously cheerful about playing with straw and building stuff with it.  It's a very easy material to handle, the various techniques for shaping, sizing, fitting and compressing your bales are all straightforward and quick to learn.  Applying the first layers of clay plaster by hand is also lots of fun, though as a potter (especially one who currently hasn't been able to make more pots for nearly a year) it's probably not surprising that I love getting my hand in some lovely sloppy clay.
  • It's quick.  It is possible to be too quick in fact - bale frenzy being a recognized phenomenon leading to leaning walls or misshapen door frames where too-big bales have been forced into place next to them.  But even with careful building (leading to well-shaped walls and doors that fit) it's easily faster than many conventional building techniques.
And if that isn't enough, the spaces straw-bale building creates tend to be incredibly comfortable, healthy spaces, generally lovely places to be, which sounds to me like ideal home material.

That description pretty much describes the experience of the course as well, at least in terms of people and atmosphere.  I'm not generally very good in new group situations but very quickly felt incredibly comfortable around the random mix of enthusiastic and excitable and generally lovely people I was messing around in straw and mud with.  Others very weary of groups or especially group courses said the same.  It was a very mentally healthy space (and physically too - lots of scrumptious but healthy food.  Scrumptious and healthy people too), and was indeed a generally lovely place to be.  Ridiculously good fun as well.  It's years since I've spent so much time with one bunch of people, living in the same house, working together and eating together.  Possibly 5 days is the right length of time to still enjoy that intense experience, really enjoy the company without starting to get irritable or crave a bit of space.  I'd like to to it again though, and hope that future builds by anyone from the group will provide an opportunity.

The minor downside of such an intensely enjoyable, creative and enthusiasm-feeding experience is the inevitable bump of returning to normality.  I think staying at CAT exaggerates this effect.  It's a brilliant place conceptually, it's a beautiful place in gorgeous landscape, everyone is passionate about what they're doing there (both students on courses and CAT staff), and it starts to feel like a bit of a lovely bubble, isolated from pressures and stress of the outside world.  Which is, while you're there, absolutely brilliant if you don't think about it too much, but makes for more of a bump when returning to the outside world.

A brief dip though, I think.  On the more positive side, the skills and experience gleaned from the course have left me feeling that building a straw-bale home is more possible than ever, really very do-able.  Then I have slightly contradictory feelings of impatience to get on and do it and do it now, and desire to get experience on other peoples' builds first.  Practicality should thankfully ensure that experience happens first in this case...

I was planning to extol the virtues of clay plaster and lime render too, but perhaps it time to wrap this one up.  For the time being I'll just say that clay plastering is a revelation to me, especially the very straightforward (but effective and long-lasting) method practised by Amazonails.  A whole new way to enjoy using clay, very beautiful, and very beneficial (breathable, humidity control, thermal mass/heat stabiliser).  Very low embodied energy too.  And lime's not bad either.

(1) http://www.thenbs.com/topics/environment/articles/StrawBaleConstruction.asp
(2) http://www.rockwool.co.uk/thermal/u+values+england+-c12-+wales/new+buildings+-+dwellings+l1a

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