[Strawbale]Re: Strawbale]straw woof insulation??

[Rene Dalmeijer]

Dear Dee,

On Jun 2, 2005, at 07:36, strawbale-request at amper....muni.cz wrote:

> Dear Duncan
> thanx for your reply  and questions. this is our situation:
>
> * if you take the tiles off, put straw beneath and the tiles back on, 
> the
> space is skyhigh so thats no limitation
Putting in loose straw is a serious fire risk. You need to use bales if 
you do. As it is a refit the trusses (roof frames) are most probably 
not at a suitable bale distance apart. This means cutting bales to fit 
(no looses stiffing of straw.) The bales can be quite a serious load. 
personally I would prefer using a blown in insulation Like cellulose or 
Rice husks if they are available.

> * about moisture, the attick is dry. Of course when putting the tiles 
> back
> on, one has to be very carefull to do a good job and perhaps one may 
> want a
> 2nd backup layer. my first thought is a plastic foil but that of course
> doesnt breath. Perhaps a milk treatment on top of the top plaster?
With bales you need some form of drip barrier above the bales This 
should prevent water dripping into the bales. Preferably the drip 
barrier should have an air cavity between it and the bales. A good, 
also fire proof, drip barrier is a closed layer (with very few  bits of 
straw poking through) of earth plaster. Below the bales you need a 
really good moisture barrier sheets of osb is not good enough you also 
need to close all seems. A continuos lapped seems foil is very 
important there should be absolutely no interior air leakage into the 
bales.
> * With what i told about the sandwich idea i think the roof only gets
> stronger when aplying the strawbales. IFFFF the interconnection 
> between the
> upper and lower layer are strong and stiff. the old roof has survived 
> many
> winters with a meter of snow or more on the roof so to start with, it 
> seems
> pretty rigid.
I can not fully comment on the structural merits of this construction 
but I suppose you are thinking of creating a box with OSB sheeting 
above and below the bales? This will make the outer roof surface 
stiffer but not substantially increase the strength of the roof 
trusses. This can only happen if the sheeting is joined along the edges 
(nailing) and the sheeting is placed on the upper and lower (the bottom 
horizontal or lowest member) surfaces of the truss ie not sandwiching 
the bales.
>
> about your alternatives like the popcorn (new to me, gr8 idea!) what 
> do you
> do to keep rodents away?
> by the way at the moment the roof has no box structure between which 
> we can
> blow in stuff. we have to do carpentry anyhow it seems.....
>
> many thanx for all your thougths
>
Rene