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Re: GSBN:More from Kelly about China



Hi all

This is a really interesting question - about the relative relative 
humidity. It is important to find out about the heating systems in the 
two house types - brick and straw.  I tend to agree with Derek's 
speculation that it has to do with less heating being done in the straw 
house, because that is an obvious significant difference between the two 
building types affecting the amount of air exchange at a large level, and 
possibly introducing or removing moisture into the houses depending on 
the heating system and configuration.

There are a lot of climate specific things to consider, as well as a few 
time/materials comparisons to check out. It is pretty much a certainty 
(barring some unusual circumstance bringing moisture into the building), 
however, that  unless there is something creating negative pressure in 
the house, in the winter there is no significant amount of moisture 
entering the building from outside. Moisture in buildings in the winter 
typically is coming from internal sources, since the physics require 
moisture to migrate from warm to cold and moist to dry -and when it is 
really cold, the outside air is usually drier than the interior. 

I wonder about the interior finishing in the brick houses. Are they also 
plastered?  Is there anything like the quantity of plaster in them as in 
the sb houses?  We shouldn't underestimate the amount of moisture that 
could be initially in the building from construction. Do the readings 
show variation of RH over time? Is there a trend - toward drying or 
increased humidity? And are there sensors in the walls themselves? Do we 
only know about the room RH or do we know about the moisture content in 
the bales too?

I'm thinking, like Derek, that if the straw houses turn out to be 
tighter, and there is less heating and ventilation going on, that this 
could be both a source of increased RH in the house and lowered indoor 
air quality. It would be interesting to do some sort of blower door test 
or air infiltration test on these houses to know just how much air 
exchange they have. I am remembering also the stories from the first sb 
houses in Mongolia, that they needed to leave a window open in the dead 
of winter - well below zero - because the heat from cooking overheated 
the spaces.  Of course those first two houses had bales in the floor and 
in the ceiling and I don't know what the floors or roof insulation is in 
the houses in question.

Well, there are just some thoughts from here. I think the one thing we do 
know is that we need more information to know what is actually going on 
in these houses. But isn't it great to this work going on in China and to 
have some monitoring and observations, and to know just how well these 
houses are outperforming their brick counterparts. Now if we had some 
stick houses to compare them to, we could invite the big bad wolf over 
and listen to him huff and puff and blow a few myths down.

David


David Eisenberg
Director
Development Center for Appropriate Technology
P.O. Box 27513
Tucson, Arizona 85726-7513 USA
(520) 624-6628
(520) 798-3701 Fax
David@...
strawnet@...(direct personal e-mail)
www.dcat.net

"When I despair, I remember that all through history
the ways of truth and love have always won. There have
been tyrants, and murderers, and for a time they can 
seem invincible, but in the end they always fall. 
Think of it ... Always."    --  Mohatma Gandhi