[GSBN] Natural ventilation - a new question

[Frank Tettemer]

Thanks André and Derek,

I'm in agreement with both your comments.  The home owners suggested 
this addition to the wood stove factory-requested combustion air tube.
It went something like, "since we'll only be using that 4" tube during 
the winter, and the manufacturers, (and thus the bldg. inspector), 
require that we go to the expense to put one in, how 'bout we jimmy rig 
it to do a miracle?" or something similar.

Thanks to all on this list for their comments. I can now go back and use 
the same excuse that I used to not place any wiring above the ceiling 
... potential leaking penetrations.

Frank
.......................................................................................................................
I agree with André, especially on the general principle of not putting 
lots of resources into solving small problems.  The corollary is that if 
an issue is important enough to address, then we need to do more that 
make tiny improvements.

My guess is that the 4" ceiling vent will not have a perceptible effect 
on heat, either in the summer or the winter.  Measurable with proper 
instrumentation, perhaps, but not something the homeowner will feel or 
notice.  And anything that the homeowner doesn't notice won't get used 
or maintained. On the downside, is the cost and complexity.  But far 
more important are the risks of an additional ceiling and roof 
penetration.  The chances of moisture leaks into the ceiling cavity are 
worth considering.  The amount of damage that will result if this vent 
allows passage of moist air or water into the ceiling insulation space 
is significant.  Even with the best of intentions, the best materials, 
and the best workmanship, many penetrations leak air.  So we are trading 
a possible minor improvement for a possible major point of damage.

On the inlet side of the equation, Frank mentioned the existence of 
straight cleanouts in the inlet tubes, to handle mildew.  I think there 
are three related problems with the concept.  The first is that this 
idea builds in an additional element of required maintenance by the 
homeowner.  Homeowners are usually overwhelmed by maintenance, and 
adding to their burden is not a kindness.  Owners will become aware of 
an indoor air quality problem only when it gets severe enough to be 
quite noticeable to their noses.  Hence, they will have been exposed to 
excess levels of various airborne microorganisms for some time. 
  Finally, the cleaning procedure for the tubes is likely to knock loose 
and stir up lots of little beasties that will get into the indoor air, 
for a while.  Are the risks worth the reward?  I have my doubts.

Derelict


On Aug 31, 2011, at 7:39 AM, forum at lamaisonenpaille.com 
<mailto:forum at lamaisonenpaille.com> wrote:

> I don't see the logic of going through the trouble of installing such 
> a cooling system for just a few days a year. Often, when adding 
> 'solutions' for problems that do not really exist we introduce 
> problems that we are unaware of. For instance, a downside to this type 
> of natural ventilation (the pipe going through the ground that we call 
> a 'canadian well' in France ;-) is that the warm air cooling down in 
> the tube will deposit condensation, thus creating an environment that 
> fungi just love. Hence, this system needs an airfilter before letting 
> the 'contaminated' air in the house in order to maintain a correct air 
> quality. That is what I've understood from Habib Gonzalez' who has 
> done research on these passive cooling systems for the CMHC. He opened 
> up some of those instalations and, if I remember correctly, all of 
> them had fungi growth inside.
>
> Have a nice day,
>
> André - sniffing arround - de Bouter
> France

-- 
Frank Tettemer
Living Sol ~ Building and Design
www.livingsol.com
613 756 3884