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GSBN: Digest for 7/1/02

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-> Re: GSBN:Interior RH in China
     by Maurice Bennett mbenn1035@...


Date: 30 Jun 2002 23:46:06 -0500
From: Maurice Bennett mbenn1035@...
Subject: Re: GSBN:Interior RH in China

Thanks so much & welcome home!  We miss you!  Just had
a great CASBA Class & wk. shop here in Angels!  Kelly,
you should  use what u sent here as a dessertation 7
go for your PHD!  go. girl, go!  Come on up!  Joy
- --- Kelly Lerner klerner@... wrote:
> >Hi All,
> 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 not 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
> >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.
> >
> Kelly Lerner
> One World Design
> http://www.one-world-design.com
> 510-525-8582

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