[Strawbale] OSB or Not? (rendering versus sheeting) (dirk witvrouwen)

Max Vittrup Jensen max at permalot...
Sun Dec 5 21:09:05 CET 2010

Hi Dirk,

If you'll join the ESBG 2011, you'll see my approach, which I believe is 
fairly generic:
Earth plaster straight on vertical bales, sloped ceiling made from beams 
with rough wooden boards with about 10 cm spacing to hold the bales 
above; the boards covered with reeds below and plastered. (The bales are 
also plastered on top, and ventilated below a vapor barrier, which again 
is covered with roof tiles, after another ventilation space.
I don't usually consider myself 'conservative', but in this respect I 
suppose I am; it's a fairly old proven approach. I'm still waiting to 
hear from people who'd gone in and inspected OSB boards after 5-10 years 
use above a kitchen (used by a family with children in a country with 
plenty of wet and cold days outside). I'd like to see what's hidden 
behind the nice plaster below and covered with straw etc. above.  
Perhaps it's my simple pragmatic mind, however I can't grasp why the OSB 
don't turn black with fungi...

I'm aware of a CZ-Austrian funded project which made such insulations 
about 5 years ago, but apart from the architects showing they could do 
it (and profiling themselves at conferences and media), then there's 
never been a follow up research about the long term effect...

As we also reside in a forested part of Eastern Europe, where rough cut 
wooden boards from local forests/mills are still significantly cheaper 
(despite the export to Austria!!!), then it makes a lot more economical 
sense than OSB.
There's been enough well articulated points about several other 
downfalls to OSB, especially from Derryl and Rob Tom, so I'll simply 
summarize it with Rob's statement: "OSB Stinks!"
[Which might be why, at the ESBG, you're only likely to find OSB used 
for the composting toilets ;o)  (We were given some which had been water 
damaged in a flood)]



I read people objecting agains using sheet material instead of rendering the bales directly. The reasoning seems to be mainly relating fire protection and sealing air leaks. Yet, lot's of people use bales in their roofs. I'm assuming none of them would render the underside of these bales. So why do it for wall's if it's not done for the roof?  Any thoughts?


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