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

[Chris Magwood]

Hi Lars,

We've used two different approaches, and both have worked well.

If we're trying to stay in the realm of all natural materials, we have 
used hempcrete to insulate and seal the gap between window and whatever 
other material it's set in. We use a mix with a finer grind of hemp than 
for insulating walls/roofs, and we up the binder content a bit too. 
Ideally, we actually use the hempcrete to also form a trim detail on the 
interior and exterior of the wall too, and this provides a really good 
seal, looks good, and takes care of several steps with one process.

We also use the tapes from ProClima or Siga. Both make excellent 
products that are meant for sealing windows to any other material, and 
come with split back peels to make it really easy to do a good job. If 
we're using tape, we will typically tape one side, stuff with wool 
insulation, then tape the other side. Both companies make tapes that are 
meant for plastering onto, so if the plaster is finishing right to the 
window these tapes work really well as we don't have to add mesh.

We've been able to hit Passive House air tightness targets with both 
these methods.

Happy sealing!

Chris


On 2018-06-28 12:30 AM, 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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-- 
Chris Magwood
Director, Endeavour Centre
www.endeavourcentre.org

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