Re: [Strawbale] Air tightness and earth plastering

2011/4/21 Carina Simons <carina.simons@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@amper....muni.cz [mailto:strawbale-bounces@amper....muni.cz] Im Auftrag von Sebastien Hubert
Gesendet: Mittwoch, 20. April 2011 22:53
An: strawbale@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 n₅₀ 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 (n₅₀ ≤ 0.6 / hour) at 50Pa (N/m²) as tested by a blower door.

He obtained n₅₀ = 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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