Re: [Strawbale] Alternative tightening materials

[Jan Hollan <jhollan@amper....muni.cz>]

Sara,

clay plaster as a good and reparable airtight layer can be connected to 
wooden parts (window frames, beamers penetrating the wall) by felt strips 
from flax filled with clay -- as I remember, this is the way Roland 
Meingast used in his natur & lehm Lehm-Passivhaus Bürogebäude (Tattendorf/ 
NÖ), see http://lehm.at/?591

Otherwise, a vapour barrier made using any polyethylene foil (an old used 
one suffices) might be another reasonable element, provided it can be 
employed within the construction and fixed mechanically there. There is no 
advantage letting the vapour diffuse from interior to those parts of the 
construction which become cold in winter.

For green roofs lying on straw, a good aluminium-covered vapour barrier 
beneath the straw is a must, as no relevant moisture from the interior can 
diffuse through the roof membrane below the soil -- it has to diffuse to 
the walls instead and away to exterior from them. We do have such an 
aluminium-covered PE foil on the dormitory part of the Hostetin Centre in 
Czechia.

(The only possible advantage of a construction without a vapour barrier 
near to the interior warm side of the construction might be for a bad, 
damaged wet construction in winter, in case of a non-inhabited but 
_heated_and_ventilated_ building which has no internal sources of vapour 
-- I doubt that such cases exist in good building practice.)

best regards,
 Jenik

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                             Jan Hollan, Ph.D.
                                CzechGlobe

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