[GSBN] Air tight bale buildings and ventilation

[Chris Magwood]

Thanks John, for your input. I agree wholeheartedly, even more so now 
that I've built an extremely air tight (final inspection 0.63ACH/50... 
finish clay plaster over the rough, straw-rich plaster brought us down 
from 0.88, for those who still think this thread is about air tight bale 
buildings!) bale home with a full mechanical ventilation system. It is 
hands-down the freshest, cleanest and healthiest indoor environment I've 
ever experienced. Even the construction dudes who've come on site have 
commented on this, including the smokers!

For me, the question is not whether to build appropriately air-tight and 
well insulated buildings, or whether to ventilate them. The question is 
how much ventilation is required and can it be done in a more passive 
manner.

I definitely have reservations about having made a building that is so 
reliant on generated energy (the house has 5kw of solar, but is still 
grid-tied) in order to function as designed. I certainly understand the 
hesitation of those who would rather not have the "mechanical lung" 
running in their homes. I'm not sure I do either.

What seems to be needed is a look at how much ventilation is required. 
Right now, this particular home is designed to Ontario Building Code 
standards for "required" ventilation to each designated room in the 
house. These standards, I'm assuming, were developed for homes that have 
little or no moisture storage capacity in the building materials and a 
certain amount of offgassing from materials in the home. I'm sure that 
our "vapour-open" home with the large storage capacity of timber 
subflooring, clay plasters and wood ceilings in the bathrooms, and no 
impermeable paints even on the drywall sections, does not need the 
prescribed amount of ventilation to ensure that there is no moisture 
condensing on the walls or windows. And given that no material in the 
home contains toxins (or at least identifiable toxins), we probably 
don't need code levels of ventilation to flush the poisons.

So the question I have is this: Can we figure out ways to passively (or 
with gentle mechanical persuasion) ventilate such a home adequately? 
Solar hot air collectors? Earth tube ventilation? Vent tubing in trombe 
walls? Solar exhaust fans? Air intake through heated slabs? Gerbil 
propelled fans in each room?

Just as we've started to see that there is a reasonable meeting ground 
between 100% natural (a la cave or mud hut) buildings and those that use 
lots of assembled natural materials used wisely along with sparing and 
thoughtful use of manufactured materials (nobody seems to think that 
good windows are a bad idea), I think our next collective objective is 
to figure out how to service such buildings with a blend of assembled 
natural principles and materials and sparing use of manufactured systems 
(little, hard-wired PV with DC motors).

It's hard to imagine that the acres of ductwork, wiring, computer chips, 
blower motors and other equipment used to heat/ventilate our buildings 
can really be the end point on this continuum. Those systems work very 
well and meet one key objective of keeping the IAQ way up. In the same 
way that we've collectively figured out how to make high performance 
structures with the lowest possible impacts, I think the next frontier 
for those looking to move forward is high performance mechanical systems 
with the lowest possible impacts.

The good news is that our collective knowledge of how to make efficient 
buildings makes the next task of figuring out high performance, low 
energy mechanicals so much easier. The bad news is that I don't think 
we're going to get the infusion of research cash that helped the 
building industry figure out the air tightness, insulation and 
mechanical strategies that are now becoming current. The next round of 
arguments with code officials will not be around straw bale walls, but 
around passive and low-energy ventilation and heating strategies, use of 
rainwater in buildings, composting toilets and grey water recycling, etc.

Here's to hoping that the creative energy that we collectively displayed 
in learning how to make high performance natural buildings can now be 
directed toward the operational systems of these buildings. Then we'll 
have really kicked some ass.

Chris

On 13-03-20 11:53 AM, John Straube wrote:
> The claim that "airtightness = unhealthy" is simply not true.
>
>
-- 
Chris Magwood
Director, Endeavour Centre
www.endeavourcentre.org