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Re: GSBN:More from Kelly about China



<x-charset iso-8859-1>Derek, Kelly,

I support the case put by Derek. I would like to add the following.

In the brick houses there is a lot more heating going on. This heating is
effectively drying the air because the surface temperature of the heater has
to be much higher to create the same heating effect then for the better
insulated SB house. In the Netherlands poorly insulated houses with central
heating with radiators have a bad reputation because of the very dry air
during the winter 10%-20%. Simply replacing the single glasing with double
resulted in higher moisture levels. Sometimes to such an extent that
moisture problems cropped up due to previously disguised bad building
practices. For this very reason well insulated and airtight building
practices have had and still have a bad rap here. Offcourse this is due too
the prevailent and persistent belief in old wives tales and other vernacular
superstitions circulating in the building trade. (Its like these building
physicists are banding together to pull an enourmous con job on the poor
builders and other honest people)

There are various reasons for the drying effect in a poorly insulated house.
To compensate for the lower inner wall temperatures a higher heating
temperature is used this causes more air circulation due to convection and
most probably more are leakage. The extra air required for combustion is
also a substantial contributer to the dryness of the interior air in less
insulated buildings. Judging by the relatively high moisture levels in the
brick buildings I suspect that these houses have moisture problems.

I am interested in the heating systems used. What type of stoves and fuel
are used and where does the combustion air come form? What is the surface
temperature of the heating surfaces? (higher temperatures mean more
convection)  Ie drier air.

Kelly
>>> They also observed that the relative humidity (RH) in
>>> the straw-bale houses (SBH) is about 10% higher than in the brick
>>> houses (RH in SB 61%, RH in BH 51%). The RH of the SBH is much
>>> closer to the outdoor RH of 66.5%.

Derek
>I also doubt the "moisture sink" explanation. ...

>My best guess is that the difference has to do with the heating
>cycle, directly and indirectly.  Not knowing the details of the
>heating systems, we can't be sure of anything.  If the heating system
>exhausts air from the living space, as a fireplace or unsealed heater
>does, then an equivalent amount of air must be drawn into the house
>from outside, usually through open windows and/or small leaks and
>holes.  Assuming that the brick house and the SB house are equally
>tight (resistant to air leakage), we could explain the higher
>relative humidity of the SB house by the lower use of the heating
>system

Rene Dalmeijer