Aug 14, 2019 10:56 pm
Trying to build a high performance house where product of choice for wall construction lists "breathability" as one of the major advantages. So, to keep the entire wall system "breathing active" have been told to steer away from standard acrylic paints, as they're "film forming" and not breathable.
Just wondering if anyone here has encountered mineral (silicate/limewash), or clay, or silicone resin emulsion paints?
These other paints are so rarely used, it's really hard to get any direct comparison between them...
Appreciate any input into this.
Re: Non-standard (acrylic) "breathable" paints2
Aug 21, 2019 12:11 pm
I had some dealings with the Victorian Keim Agent many years ago. A sample was given to me and applied on a house I was working on. Don't know the outcome from there.
After examining a variety of the products Porters, Keim etc it was my conclusion that they still have acrylic in them. A recent project used a Porters product and to me it was just an acrylic paint probably at a low % in can. Porter's owned by Dulux since 2015.
Is your building a non cavity construction?
Re: Non-standard (acrylic) "breathable" paints3
Aug 22, 2019 10:49 pm
Thanks for the reply. Anyway, yes the build is non-cavity construction using Durisol blocks.
It claims to be "vapour active" (allows adsorption / release of moisture), therefore I'm after a finishing product that does not impede the movement of moisture into/out of the walls.
Hopefully, someone else with more experience can chime in too.
Re: Non-standard (acrylic) "breathable" paints4
Aug 23, 2019 1:18 am
One way is to consider silicon render which already has paint in it.
For internal, you can go with clay paints or Keim breathable paint, but a lot will depend on the breathability of your internal render though. Remember, that paint is relatively very thin layer (few microns), so doesn't really have much impact on "breathability".
From the scientific article I was e-mailing to you the other day:
"As regards hygroscopic qualities, these are not really relevant as regards the paints themselves as
they are so thin. However it is assumed by many people that a paint’s vapour permeability
seriously affects the hygroscopic performance of the rest of the wall. In practice this may not
actually the case. This was the surprising result that Minke obtained, when he was looking at
how finishes affected the hygroscopicity of an unfired clay wall. He tested a number of finishes
including standard emulsions and distempers. The only products that significantly reduced the
hygroscopic performance were double boiled linseed oil and pure latex. These both have an
extremely high vapour resistance. Most standard wall paints, according to this research will,
therefore, have relatively little effect on substrate hygroscopic performance. However these
results are countered elsewhere, and this is one area that certainly requires further research."
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