[Strawbale] [SB-r-us] Re: Moisture sensor redux (was Re: cement stucco problems?)

[Mark Bigland-Pritchard]

Rob Tom wrote:

>And the fact that there has not been much moisture-monitoring data would  
>not seem to offer much in the way of fact for this discussion.
>  
>
Yes, I would love to see moisture monitoring in every building that goes 
up, especially in places with a challenging climate.  And, yes, my 
feeling is that the jury will still be out until this is done.  But it 
needs to be accurate monitoring - and, specifically, accurate at higher 
humidity levels - if it is to be of any use.

So how about an international monitoring programme specifically for 
temperate maritime climates, using a standardised methodology.  The 
Honeywell HiH series sensors seem to be available worldwide, they are 
reliable, and they are made to a common standard.  Compared to the cost 
of building a house, they cost peanuts (even if you include the 
thermistor you need to measure the temperature and the small bit of 
electronics you need to convert either mains or battery power to a 
consistent 5V dc input).  They can be read reliably using any cheap 
digital multimeter.  Humidity changes in the straw are so slow that they 
only need to be read once a week or maybe only once a month (though some 
people might want to do more than that, and some data on diurnal 
variation would be helpful too).

Anyone interested?

And we also need a lot more pinning down of straw properties - 
mycological growth thresholds, thermal capacity, enthalpy of sorption, 
vapour permeability, air permeability, etc.  Most of these need the work 
of professional laboratories with professional equipment, but I think 
amateurs could handle the first one, and it's something on which we need 
a lot of datasets before we can be fully confident of the data.

So, anyone interested in getting together to watch mould growth?

It would be really nice if we could cut down the amount of guesswork in 
the whole process.

But until then we just have to make informed guesses, and work the best 
we can with the data we have.  And my reading of that data is that a 
well-built, well-designed strawbale building with sensible thicknesses 
of low vapour resistivity plaster should be able to avoid straw mould 
growth in nearly all temperate maritime locations.

I'm sure there is plenty of innovation yet to be done to make the 
"well-built, well-designed" bit easier.  In fact, I think that Mr Tom, 
with his attention to detail, should be sent out to a humid west coast 
for a couple of years, charged with first learning about the climate and 
the challenges it poses, and then developing superior strategies for 
coping with it.

Mark