[GSBN] Can bale buildings be air tight?- How to ventilate discussion

Mon Mar 11 17:00:58 UTC 2013

All-

First my bias: we engineer mechanical and structural systems for buildings. So it goes without saying see better results from adding a level of control and predictability. With that bias comes a lot of experience looking at under ventilated homes. The discussion about building and occupant related pollutants is a big factor, but misses another crucial component- condensation due to moisture. The building envelope may be permeable enough to survive, but in cold climates condensation on windows is unavoidable without controlling moisture in the home. In cold climates what we see time and time again for a remotely tight home (homes with 2 or 3 times the air leakage we are talking about here) is significant condensation build-up resulting in damaged materials and mold growth on surfaces. This primarily at windows due to the cold temps, but if there is any other location were the insulation detail isn't right problems will happen there as well. 

We have had a number clients/friends decide to skip the ventilation system over the years, and every time what ends up happening is they are either forced to run bathroom fans continuously in the winter (heat loss) or find a way to retrofit an HRV or ERV in. That applies to standard construction, bales, anything you build that is somewhat well sealed. We all know retrofits are expensive and to be avoided, so why leave it to chance?

This probably is not too much of a surprise in the high-mountains of Crested Butte, Colorado, I assume the effect is worse in Chris' backyard. I was however surprised to see it is a big problem even in Moab. Moab is where we go to thaw our bones out in the middle of winter, it isn't cold right? We have been involved in the Community Rebuilds project happening there (If you aren't familiar, make sure and check out what Emily Niehaus has started over there, we are now starting one in our valley as well) and 3 homes had significant condensation on windows this winter resulting in a mold problem and damaged finishes. The result is that all future CR homes will have HRV's. 

From my perspective there is no debate: build it tight, and ventilate right. Relaxing the tightness of the home just leaves it up to chance- did I make it leaky enough for the building envelope to dry? enough to get the moisture out of the air? enough to get the result of cooking (gas combustion and lots of other pollutants)? It isn't' worth the risk to building occupants or to the building. Do we want to have a realization 10 years from now about health problems from a homes that seemed leaky enough, but oops not quite… Daily life makes pollutants, even if we are all watching everything we do (breathing, showering, cooking). So now I have a choice of how to ventilate: crack a window? exhaust fan? or HRV/ERV? Only the heat/energy recovery ventilator allows for exchanging air efficiently. The others are fighting against all the great work you put into the building envelope. 

My 5 cents-

August

_________________________

August Hasz, PE, Principal
LEED AP
Resource Engineering Group, Inc.
Mail: Box 3725
Delivery: 502 Whiterock Ave., Suite 102
Crested Butte, CO 81224 USA
Tel: 970-349-1216
hasz at reginc.com 
www.reginc.com
_________________________

On Mar 11, 2013, at 10:02 AM, Chris Magwood <chris at endeavourcentre.org> wrote:

> Hi Tony,
> 
> I share some of your concerns about the quest for air tightness. The energy savings side of being air tight is undeniable. In our projects, we make sure that there are absolutely no toxic materials going into the house (which can take a lot of research and sourcing effort), so try to alleviate some of those concerns in that way. You are right though about post construction toxins... people love their bathroom sprays and cleaning products.
> 
> I have a lot of questions about moisture loading in a building that is both air tight and vapour permeable. We use a lot of materials that are highly moisture absorbent within the house (untreated wood ceilings and sometimes walls, permeable plasters, etc), as well as permeable exterior wall systems. I don't know that anybody has studied the difference in moisture loading between an air tight building with non-permeable surfaces and one with very permeable surfaces, but anecdotal evidence suggests that there is way less problematic moisture build up in the permeable building. Otherwise, every sauna in the world would be rotten very quickly.
> 
> When I lived off-grid, I was very opposed to mechanical ventilation systems due to the constant energy use of the fans. There are much more efficient systems now, and they really do a good job. The new ERVs exchange the heat and humidity of the outgoing air to the incoming air. Definitely keeps things fresh, especially with good filters.
> 
> I would love to experiment with some less high-tech solutions, but it's difficult to do that under our current codes. Earth tube systems are kind of hit and miss, with some performing really well and some being the source of major air quality problems. We did a solar hot air system once that worked really well... provided great exchange and heated incoming air whenever it was sunny in the winter. More than enough to keep the building at comfortable moisture/temp levels, but it doesn't work at night or when it's not sunny. HVAC design is always about control... and maybe we have to give up some of that control to use more passive systems.
> 
> This is definitely an area for more research. Now that we know our bale buildings stand up under loads and don't turn into mush at a problematic rate, it would be great to move into some more detailed testing around performance, air quality, air exchange, etc. I'd be glad to jump on board anybody's efforts to move in this direction!
> 
> Chris
> 
> On 13-03-10 2:20 PM, Anthony Novelli wrote:
>> Just a comment and a correction (sic)....
>> 
>> Comment: Kudos for such great strides in achieving these numbers, and thanks EJ for compiling the data. I always have running questions in my mind about the quest for air-tightness, with off-gassing and such. Perhaps less need for air-change systems if this quest is partnered with close attention to materials in construction, though post-CofO purchasing could load any tight building with noxious vapors it seems.
>> 
>> It also seems useful to show where infiltration occurs, and perhaps adapt systems for the "point loads" of moisture to occur at those points?
>> 
>> Correction: I believe the .88 refers to Patrick Kane, in this wondrous season ;) - at least from my Windy City upbringing!
>> 
>> best to you all,
>> Tony
>> 
>>> Chris wrote:
>>> 
>>> Hi ej,
>>> 
>>> Our last test on the house was 0.88 (for hockey fans among you, you may
>>> notice that our two scores are the jersey numbers of Wayne Gretzky and
>>> Eric Lindros... coincidence?).
>> Anthony Novelli
>> Assistant Director
>> Development Center for
>> Appropriate Technology - California Office
>> 2101 Wellmar Dr. Ukiah, CA 95482
>> (520) 360-8858 • www.dcat.net
>> anthony.novelli at gmail.com
>> 
>> 
>> 
>> 
>> 
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>> 
> 
> -- 
> Chris Magwood
> Director, Endeavour Centre
> www.endeavourcentre.org
> 
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