[Strawbale] Strawbale roof insulation

Jan Hollan jhollan at amper....muni.cz
Tue Sep 17 23:07:10 CEST 2002

> Moths are insects, arent they.
> Its important not to wash the wool ( if its very dirty use only warm
> water no kind of soap whatsoever, the wooloil ( lanolin) will act as a
> soap and  will stay in the wool)
> Collect shitty parts out by hand, before you wash the wool.  
> The lanolin is a moth prevention by itself but it will also act as a
> "glue" sticking the borax, wich should be applied as a dry salt to the
> wool. This should happen in situ and most of the times this will mean
> from above, so make sure, that the wool is not pressed to densly, before
> the salt can penetrate thorouly.
> Thats the way we did it.
> Harald

Harald, this is a really serious topic. If it would work, it would be a
salvation for so many abandoned pastures (at least here in Czechia).

Up to now, I've always reproduced the view of wool industry experts saying
there is no way to protect unwashed wool reliably for decades (perhaps the
pyrethroid which can stop the moth attack cannot be added in a dry
process). I contributed a bit to the development of an original Czech
technology for building insulations from wool and to using such layers,
but as the price mounted to perhaps thrice the least expensive materials
(as cellulose), practical impact has been almost none. Unlike in Austria,
where the cheapest processed wool has a comparable price to the common
materials as mineral wool or EPS -- they are not so cheap there as here in

As with straw and fire, a standard test on moth resistance is needed with
unwashed wool peppered by borax -- maybe a pre-test could be done in
amateur conditions, before a test in a certified laboratory would be paid
for. I am sure that some union of shepherds would be able to pay for it,
even here in Czechia. They have always asked, if they could not avoid
expensive processing (and transport).

I'd say that if using cheap wool as insulation would explode, it would
promote even its commercial variant, with layers of defined thickness and
guaranty, which can be simply hanged and applied by building industry.
Its use is still too low in most of the world, esp. outside
German-speaking countries. So even wool experts should not object to this
straightforward alternative, after all, they like wool also because they
like sheepherds and sheep in general.


 the price is vital: the cost should not prevent people to insulate
properly, i.e., at least 30 cm thick and with no thermal bridges, like in
case of strawbales. I've recommended processed wool like just an inner
layer in roofspaces, before the vapour barrier to serve as a best moisture
buffer, and a plenty of cheap insulation behind the barrier.

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