[GSBN] Air tight window sealing - ideas and experiences.

[Feile Butler]

Hi Lars

I remember asking this question a good while back and, if I remember 
rightly, it was Graeme North who suggested hemp rope. He recommended 
purposely over-sizing the gap (i.e. leave closer to 10 or 12mm, rather 
than only have 2 or 3mm) around the windows so that it would be possible 
to stuff the rope in there (and of course, the rope would have a bigger 
diameter than the designed gap).

I think it is a really elegant solution and don't see why it wouldn't 
work. I tried specifying it for a job recently, but having fought hard 
to get the mainstream contractor to cope with hempcrete and clay 
plaster, I had to let some other stuff go .... the window sealant being 
one of them.

We have a self-build house (cob and timber-frame/straw bale hybrid) 
about to start on site with a very environmentally-conscious client, so 
I am hopeful that we might be able to try it out on this project. I am 
providing architectural services only, not carrying out the physical 
work. However, as he is a true self-builder ... building the house in 
his own time while juggling work, family, etc., and he does not intend 
putting himself under any time pressure, it may be a few years before I 
can report back!

Regards from sunny Ireland .... experiencing our hottest summer since 1976!

*Féile Butler*
B.Arch MRIAI Conservation Grade III
Executive Board Member of Earth Building UK and Ireland (EBUKI)

*Mud and Wood / Roots Architecture*
Grange Beg, Skreen, Co. Sligo

*T:*  +353 (0) 71 930 0488
*M:* +353 (0) 86 806 8382
*E:*  feile at mudandwood.com
*W:* www.mudandwood.com

On 28/06/2018 05:30, Lars Keller wrote:
> Hi Derek,
> Yes, it is based on the heated floor area. Tested at 50 pascal over- 
> and underpressure, and then an average hereof.
> The test conditions are defined by EN 13829 Thermal performance of 
> building - Determination of air permeability of buildings - Fan 
> pressurization method (ISO 9972:1996, modified) - This standard is 
> intended for the measurement of the air permeability of buildings or 
> parts of buildings in the field. It specifies the use of mechanical 
> pressurization or depressurization of a building or part of a 
> building. It describes the measurement of the resulting air flow rates 
> over a range of indoor-outdoor static pressure differences. This 
> standard is intended for the measurement of the air leakage of 
> building envelopes of single-zone buildings.
>
> Yes, it is exactly the areas you mention that most often cause the 
> leaks here in Denmark as well.
> What I mentioned was the traditional method to seal the joint between 
> a wooden frame window and a brick wall in Denmark before modern big 
> scale building systems arose from around maybe the 1950ies.
> As far as I understand, the big building segments proved to have 
> expansion rates which the traditional mortar method could not deal 
> with, and thus “plastic” sealants where developed.
> And what is happening today is what we know so well: due to speed, 
> lack of knowledge, advertising etc the “modern” sealing method has 
> taken over.
>
> What I am wondering is, if anyone know of modern sustainable products 
> for sealing the joint between the window and the wall, be that wood or 
> brick or straw...
> Best, Lars
> -- 
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