[Strawbale] Air tightness and earth plastering

Thu Apr 21 22:44:19 CEST 2011

hello,

As I'm not english native speaker I probably made a mistake...  I 
thought render means the last finished earth layer...  It seems this is 
not the case...

Thus to summarize, in our building the earth plastering is done but we 
still need to do the last finish layer...  At the moment we have more or 
less 5cm earth on the straw bale walls.

Regarding the first house where they made the blower door test, on the 
basement walls they only put 1.5cm earth plastering and the finish layer 
is not done yet...

I hope this is clearer now ;-))

Thx

Seb

On 21/04/2011 18:34, paul paul wrote:
> To try and answer your question Carina, it looks like they use the 
> word “render” to mean interior undercoat, before a top or finish coat 
> of plaster is applied. In this case, an undercoat of plaster was not 
> applied first, which is why the total thickness of applied plaster was 
> quite thin. As I said in my first post , sometimes an interior 
> undercoat is called a “render”, possibly because quite often the 
> undercoat would be cement/lime based, like an exterior render, and 
> then finished with a gypsum plaster top coat.
> Paul
> *From:* Carina Simons <mailto:carina.simons at gmx...>
> *Sent:* Thursday, April 21, 2011 6:29 PM
> *To:* 'European strawbale building discussions' 
> <mailto:strawbale at amper....muni.cz>
> *Subject:* Re: [Strawbale] Air tightness and earth plastering
>
> Hallo,
>
> If render and plaster is he same, than what is meant with the problem 
> of the air tightness in the passive house. There was said that the air 
> tightness was not so good because of the failing render but then earth 
> plaster was on it!
>
> Greetings,
>
> Carina
>
> ------------------------------------------------------------------------
>
> *Von:*strawbale-bounces at amper....muni.cz 
> [mailto:strawbale-bounces at amper....muni.cz] *Im Auftrag von *Andrew 
> Morrison
> *Gesendet:* Donnerstag, 21. April 2011 17:46
> *An:* European strawbale building discussions
> *Betreff:* Re: [Strawbale] Air tightness and earth plastering
>
> As far as I know, they are the same. Here in the United States we say 
> plaster. When I was in Australia teaching last month, they spoke of 
> render. I don't know of a difference.
>
> Andrew
>
> 2011/4/21 Carina Simons <carina.simons at gmx... 
> <mailto:carina.simons at gmx...>>
>
> Hallo to everybody,
>
> Since I am not a native English speaker I do not know the differents 
> between a render and a plaster. Can anyone explain that to me?
>
> Many greetings,
>
> Carina
>
> ------------------------------------------------------------------------
>
> *Von:*strawbale-bounces at amper....muni.cz 
> <mailto:strawbale-bounces at amper....muni.cz> 
> [mailto:strawbale-bounces at amper....muni.cz 
> <mailto:strawbale-bounces at amper....muni.cz>] *Im Auftrag von 
> *Sebastien Hubert
> *Gesendet:* Mittwoch, 20. April 2011 22:53
> *An:* strawbale at amper....muni.cz <mailto:strawbale at amper....muni.cz>
> *Betreff:* [Strawbale] Air tightness and earth plastering
>
> Hello everybody,
>
> Till yesterday I was pretty confident that it was possible to make a 
> good air tightness using earth plastering.  Yesterday an other 
> professional  called me regarding air tightness.  His neighbor and him 
> did a blowerdoor test to verify the airtightness of their 2 passive 
> houses (should be passive).  The result was not good.  The n_50 
> leakage rate is supposed to be smaller than 0.6. The building must not 
> leak more air than 0.6 times the house volume per hour (n_50 ≤ 0.6 / 
> hour) at 50Pa (N/m²) as tested by a blower door.
>
> He obtained n_50 = 1.2 and it was 0.95 for the second one.  They 
> worked 2 days trying to find what could be the problem and didn't find 
> any major leakage.  There was 1 point that could be a problem.  A 
> basement wall that is part of the living space get only 1 layer of 
> earth plastering but no render.  The thickness is more or less 1.5cm.  
> They decided to glue a airtightness sheet (1 square meter) on this 
> wall.  They blew the air outside of the building.  Then they saw the 
> sheet (that has been glued) inflating meaning that the earth 
> plastering was not airtight.
>
> Of course, I have to say that it would be better to put the render on 
> this wall.  Airtightness should be probably better.
>
> I'm building a straw bale (this is our house) and we really want a 
> good airtightness.  For the wall, the earth plastering is supposed to 
> do the airtightness.  We are going to make a blower door test before 
> finishing the details.  This means the renders are not ready yet 
> because we will put the last earth layer on the wall and ceiling at 
> the same moment.  This will be done after the blowerdoor test.  This 
> means that the blower door test will perhaps not be successful.
>
> What do you think about it ?
>
> Does anybody already make a blowerdoor test with earth plastering 
> airtightness ?
>
> I would really appreciate a feedback.
>
> Many thanks
>
> Cheers
>
> Sebastien
>
>
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> Send all messages to:
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