[GSBN] More ventilation...

[Chris Magwood]

This is a very interesting thread.

I had never considered things from John's point of view regarding the 
other - and often more complex - machinery/systems in a typical home 
versus the ventilation equipment. Having been a long-time off-grid, 
fridgeless neo-hippy, I understand the aversion to equating machinery 
with sustaining life. At the same time, I've never questioned the need 
for my car to be fed as much air as it requires to operate... So thanks 
for that kick in the perspective, John.

(As a sidebar... I've often wondered why our ventilation equipment isn't 
coupled with our refrigerators. Use those heating coils on the back of 
the fridge to heat incoming air in the winter. Run the ventilation every 
time the fridge cycles... fridge should perform better if the coils cool 
down more...)

I still have questions (actually, it was the initial question that 
kickstarted this discussion) about /how much/ ventilation is required. I 
still feel that our code requirements are overkill, as they are designed 
for homes with greater need to move moisture and toxins out of the 
building. Seems to me that the ventilation requirements began from a 
need to exhaust first, and the fresh air component was a side-effect of 
needing to exhaust without depressurizing, not to ensure oxygen for 
occupants.

How much of this discussion is really about occupants having enough 
oxygen? To what degree are we really in danger of asphyxiation inside a 
tight home? Just to get inside the home, we open up the door and create 
a bunch of exchange... In a home with no combustion devices inside, do 
people really asphyxiate or even get sick from excessive CO2? What 
amount of trickling fresh air would service a bedroom adequately?

Obviously I'm not really looking for hard answers here... it's all 
highly specific to location, insulation, air tightness, heating 
equipment, etc. I'm just musing on where my own next steps will go in 
order to make tight buildings with adequate ventilation. My search for 
answers to "how much" is in pursuit of designing systems that can 
potentially be run with as little energy as possible in order to be as 
resilient as possible. I guess I'm going down the same path with 
ventilation as Passivhaus does with heating systems... trying to make 
the needs as low as possible and meet them in the least energy intensive 
way.

Where do the numbers the codes use come from? And are there ways to 
calculate and propose our own numbers based on actual needs for oxygen 
and for exhaust? And if you're a person who answers yes to this, do you 
want to talk more off-list?

Thanks all, this group is the best brain trust I can imagine.

Chris

-- 
Chris Magwood
Director, Endeavour Centre
www.endeavourcentre.org

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