[GSBN] Natural ventilation - a new question

[Derek Roff]

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 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

Derek Roff
derek at unm.edu



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