[GSBN] IAQ (was Can bale buildings be air-tight ?

[RT]

On Thu, 14 Mar 2013 the GSBN Digest tells me that on Date: Wed, 13 Mar 2013
>
> Swiss architect Werner Schmidt says that 90% of the air movement needed  
> for ventilation in a standard home is to clear out the toxins released  
> by conventional building materials and furnishings, while only 10% is  
> related to purely people needs.


Not sure if I'd agree with Herr Schmidt.

The ~20 yr-old NRCan study to which I referred the other day (and I  
mentioned it only because I happened to have it around, not because it's  
an authoritative last word on anything) mentions that in the sample size  
of 128 homes (both "conventional" and R-2000 certified) from which  
monitoring data was acquired,

total volatile organic compounds (TVOCs)   =  558 micrograms/cu metre   
[ug/m^3] (average)

It cites an external study that mentions that for levels below 200 ug/m^3  
no effects can be detected and that most people will experience discomfort  
at levels above 3000 ug/m^3.

OTOH, some simple number-crunching showed that in a master bedroom with  
two occupants at low levels of activity, with the F326  
Standard-recommended 10 l/sec supply air ventilation rate , the CO2  
concentration would be 914 ppm.  (The discomfort level is stated as being  
1000 ppm).

Presumably people who are building SB homes pay some attention to what  
they put into their indoor environments so would hopefully opt for low/no  
VOC choices in building materials, furnishings, day-to-day items so I  
would suspect that the TVOC concentrations would be closer to that of the  
R-2000 homes in the test sample  (388 ug/m^3).

... which is to say, an argument could easily be made that it is the  
"people needs" that govern in determining fresh air supply rates.

-- 
=== * ===
Rob Tom					AOD257
Kanata, Ontario, Canada

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