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

Tue Mar 12 13:14:11 UTC 2013

The problem with airflow windows, which have been around for 30 years or more, is that the heat recovery is only as efficient as an HRV during sunny hours.  On a 24 hour basis in winter, the heat recovery (defined as the ratio of the energy content of the incoming temperature and outgoing air, which is leaking out somewhere) is not as good as a good HRV and a triple glazed window.  If you couple these with an heat pump to extract heat from the air you exhaust, these systems can be equal or better than a good HRV.
Of course, you need one such window  in every room to get the air to each room.  
A good HRV with good TG windows seems a lot cheaper and a lot simpler...
On 2013-03-12, at 8:40 AM, Caroline Meyer White <hojtpaastraa at gmail.com> wrote:

> Hi there on the other side of the pond. (Is that a general North American expression, or just my grandmother?)
> 
> In Denmark, a company is selling a "ventilation window". I attached their flyer, it has some drawings, though in Danish) It is developed from an old Russian type of window, where you have two glass panes with space in between - like 3-4 inches. The interior pane is a well insulated double pane, and I believe that the exterior is only a single layer pane. The frame is engineered, both being a very high quality wood for windows, but also with detailing breaking thermal bridges. Now the secret about it, (not kept) is a vent with a phase changing (I believe oil substance) at the top and bottom. These vents do not have any energy supply, but allow air to flow in between the panes FROM the out side, entering at the bottom, when heat is required in the building. The air is pre-heated between the panes and reach a temperature of average 10 Celsius above what it was before it entered - heated by the sun hitting the outer pane and the heat loss going through the inner pane. 
> In summer the flow goes the other way, and the window helps cool down the building. The Technical University of Denmark has made some calculations determining that a window of the standard size (around 1,2 m2) on average of the four corners of the compass, contributes with 425 kWh / year - that is the heat gain, then comes the ventilation supply besides that. 
> 
> We do not have air tightness tests on SB buildings in Denmark yet. But this summer we are building a large residential home with these windows and I am very eager to see, if they will be sufficient to take care of the ventilation demand, as I don't know the air stream I haven't been able to calculate it. 
> 
> Cheers
> Caroline
> 
> 
> 2013/3/11 Anthony Novelli <anthony.novelli at gmail.com>
> Thanks Chris and August...
> 
> August, you bring up a point that might help me clarify my question... I would assume in cold climate situations that very little humidity would be required to develop condensation on exterior glass, unless employing some super efficient triple pane with thermal breaks. Either way those surfaces will be much colder than an earthen plaster or wood that spreads and holds warmth. Part of what I'm considering is not how to eliminate the condensation, but rather what to do with it while it's there? Is there a window sill detail for the interior that could accommodate the inevitable moisture present? Perhaps these are already employed and I'm out of the loop... just seen a lot of attention on moisture on the outside of windows more than inside. Even with excellent venting it seems a good passive fail-safe.
> 
> Best,T
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 11 Mar 2013 11:00:58 -0600
> From: August Hasz <hasz at reginc.com>
> To: Global Straw Building Network <GSBN at sustainablesources.com>
> Subject: Re: [GSBN] Can bale buildings be air tight?- How to ventilate
>         discussion
> Message-ID: <EB70F934-A014-47AA-9BE4-03F8E2FF2884 at reginc.com>
> Content-Type: text/plain; charset="windows-1252"
> 
> 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
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> -- 
> Caroline, Tahir, Noah
> 
> Friland 11, 8410 Rønde, Denmark, tlf. (+45) 40 76 19 80, skypename: caroline.meyer.white
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John Straube
www.JohnStraube.com