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GSBN:Interior RH in China



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<blockquote type=cite class=cite cite><font size=3>Hi
All,</font></blockquote>Thanks for all the thoughts and ideas on the
higher humidity in straw-bale houses than in brick houses. To expand on
what Paul said, there are three typical heating systems and they are
found in both brick houses and straw-bale houses, all radiant: 
1. Kangs - raised masonry bed platforms, about 3m x 4m, heated by hot
flue gases traveling from the kitchen to the chimney. 
2. "Fire walls" - brick cavity walls, heated by hot flue gasses
traveling from the kitchen to the chimney 
3. Hydronic radiator systems that work on the natural flow of hot water
and gravity  
Almost every house has a kang, some have firewalls and very few have
radiators. The fire which heats the kang and firewall comes from the
kitchen cooking stove (in the next room on an adjacent wall). It consists
of hollow brick box on the floor on an interior corner, about 1m x 1.5m x
0.4m high. It has one or two round openings on the top (for a wok) and an
opening 15cm w x 20 cm high on the side through which the fire is fed.
The whole system is a like a masonry stove, but <b>not</b> air tight.
Sometimes the kang has a small air damper in front, but not always, it
seems to depend on the size of the system. I'm always amazed that these
systems draw well, but there's rarely any dark smoke marks on the
ceilings. Crop residue is generally used as fuel for cooking (rather than
coal) and as owners get used to their straw-bale houses they're generally
heating primarily with cooking fires (more crop residue and less coal).
This is especially true during a warm winter like last year. 
 
The water for the radiator systems is heated by coal in a metal firebox.
Most folks are finding that with the high insulation provided by
straw-bale, they don't need a radiator system (which is good as it is
relative expensive).  
 
The window and doors are the same for brick and straw-bale houses .
Windows a double set of single pane windows, about 20-25cm apart, usually
in-swinging casements. Double pane vinyl windows are becoming available
in more developed regions and some owners use them, but we've had reports
that they don't perform as well as the double, single pane style (in
spite of all the convective currents in the wide air space). Double solid
doors - one in-swinging and one out-swinging. Most houses are designed
with an unheated entryway that acts as a buffering "airlock"
between the outside and heated interior rooms. Neither brick houses or
straw-bale houses are air tight which is good since their heating systems
need combustion air. 
 
After hearing your comments and thinking them through, it seems there are
at least four explanations for the drier air in brick houses (arranged in
order from greatest effect to least effect). 
1. Because brick houses burn more fuel, they draw in more dry outside air
thereby lowering the indoor RH. 
2.The cold interior surface temperature of exterior brick walls,
condenses water out of the interior air, thereby lowering indoor 
RH. 
3. Straw-bale houses in the study, by virtue of their younger age, may be
slightly more airtight than brick houses in the study. 
4. Since half the straw-bale houses in the study were completed in the
fall just before study began, the new plaster harbored significant
moisture that tempered the interior RH to some degree throughout the
winter. (a one time effect, but since the sample is so small, 12 SBH and
12 BH, it could skew the data significantly). I will have CESTT look at
the RH in the new SBH compared to the old SBH and also if the interior RH
in the decreased i the new SBH over the course of the winter.  
 
Thanks for reminding me about dry, cold winter air! Living as I do now in
the balmy bay area, I forget about my childhood winters scooting around
the carpet with wool socks to make hair raising sparks and filling the
kettle on the back of the wood burner every night before bed. 
 
Kelly 
 
 
 
 
 
<blockquote type=cite class=cite cite><font size=3>Date: 28 Jun 2002
17:39:41 -0500 
From: Paul Lacinski paul@... 
Subject: Re: GSBN:More from Kelly about China 
 
Hello All, 
 
One of the reasons the straw bale houses are succeeding in China is 
 
because they are so very similar to the brick houses.  Both are
 
plastered inside and out.  The windows vary from location to
location  
and house to house, but not according to whether the walls are of  
bales or bricks.  The heating systems are the same, a coal-burning
 
steel firebox (leaky) hooked to a kang (raised platform with stove  
exhaust snaking through it) or firewall (brick wall with exhaust  
snaking through it) or both.  I do not recall any intake or exhaust
 
dampers, but I'm not sure.  Ceiling insulation is usually bagged
 
sawdust in both cases, and roofs and ceilings are the same.  Floors
 
are slabs.  We're introducing the idea of coal slag as floor  
insulation, but it hasn't caught on yet. 
 
The stoves do draw from the interior (as does the separate cooking  
stove), and so the fact that the bale houses use alot less coal  
points in the direction of Derek's conclusion as the major reason for
 
moister interior air.  The other factor at work is that the brick
 
walls are acting as de-facto dehumidifiers in the winter- their  
interior surfaces are apparently quite cold- so much so that frost is
 
common in the corners of the buildings.  When people don't have this
 
problem in the bale houses (thanks as much to the exterior insulation
 
in the bond beams as to the bales) they are surprised and very
happy. 
 
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Kelly Lerner 
One World Design 
<a href="http://www.one-world-design.com/"; eudora="autourl">http</a>://www.one-world-design.<a href="http://www.one-world-design.com/"; eudora="autourl">com 
</a>510-525-8582</font></html>

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