[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

GSBN:More from Kelly about China



Following is the full text of Kelly's message, which includes the piece about flyash:

Hi all,
Here I am running around northeastern China. 340 houses in 4 provinces this year and all is going well. There are couple of technical issues here that I'd like to bring to the community think-tank.

The first issue is relatively benign, just interesting. We finally have some excellent monitoring data from last winter comparing straw-bale houses and brick houses. The data was collected by the Chinese Centre for Environmentally Sound Technology Transfer (CESTT). They monitored 25 houses (half brick, half SB) using HOBO data loggers for temperature and relative humidity as well as measuring fuel use (both coal and crop residue). The data clearly shows that straw-bale houses are 64 -68% more fuel efficient (MJ/day) than their brick neighbors (not surprising, but still very gratifying). 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 SHB is much closer to the outdoor RH of 66.5%.

I'm postulating that the straw bale walls are more vapor permeable than the brick walls and thus the interior RH follow the exterior RH humidity more closely. It may also be that thicker plaster on the straw bale walls (compared to brick walls) is acting as a moisture sink and working to balance the RH between times of high RH and low RH. Any other thoughts??

FYI, the whole report will be available in early July and CESTT would like to present it at some technical, architectural and/or sustainable development conferences. Any suggestions?

The second issue has to do with plaster. Paul Lacinski and I have been experimenting with plaster mixes here in China using locally available materials. Last year we used flyash in several mixes (both with lime and with cement). I won't go into the detailed mixes, but do any of you have a feeling for the effects of flyash in plaster? Clearly flyash is a pozzolanic material, and in concrete it adds compressive strength and decreases workability. I'm wondering if it also (like cement) makes the plaster less vapor permeable. Does anyone have experience using flyash in lime plasters? There are actually two types of flyash here - one is fine and powdery (very similar to cement) and the other is rough and irregular, up to 3mm diameter. We've used both types. The rough type is actually more like an aggregate though it does seem to have a very weak pozzolanic reaction. Any thoughts on flyash and permeability or suitability for plasters?

Thanks,

Kelly
----------------------------------------------------------------------------------------
Kelly Lerner
One World Design
http://www.one-world-design.com
510-525-8582

----------------------------------------------------------------------------------------
Kelly Lerner
One World Design
http://www.one-world-design.com
510-525-8582


--
Paul Lacinski
Amy Klippenstein
GreenSpace Collaborative
Sidehill Farm
PO Box 107
463 Main St.
Ashfield, MA 01330 USA
01-413-628-3800