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

[Graeme North]

Well my 2c worth is that in NZ we have a long history of cold damp houses, in a very humid mostly temperate climate.  (As it is at the moment we are in the grip of the worst drought for over 70 years so any hint of damp would be welcome.)

That aside - the best strategy I have found for drying out damp houses is to use hygroscopic materials in the fabric of the house - and the best and easiest is earthen walls or at least earthen plasters on any suitable substrate such as dry wall.  Of course to help get over cold we insulate and that's where sheep's wool, or strawbale,  or low density earthen materials, come into their own.  Condensation on windows and the accompanying wet window sill syndrome simply vanishes.  Needless to say we don't have several cm of snow lying around but we do get some pretty good frosts.  Then reducing the size of houses and the size of windows in them also helps. Lets face it, oversized badly orientated triple or quadruple glazed self ventilating thermally broken windows are still not nearly as good as a bit of well insulated wall at keeping heat in or out.  

I suggest that the approach of using more and more of the earth's resources to sort out these building issues  may not be a good primary design strategy, especially when it leads to oversize buildings, with oversized windows needing mechanical ventilation systems etc., -  mechanical systems that are only as good as their energy supply.  I don't want to wake up dead of asphyxiation in an air tight building because the electricity failed while I slept.

This is not to dismiss some very good building science and its associated research, but I am finding this conversation on interior air quality in air tight buildings a bit disturbing when we end up with buildings so tightly sealed that the occupants are at risk from either the building fabric itself, or even more alarming, from their own breathing!   People would be much healthier outside the building under these circumstances.  Interesting, isn't it, how, if a person feels ill we often take them outside, where they usually feel much better?  We really do need protection from the built environment.  

I prefer a design approach that minimises the use of expensive, resource gobbling, and complicated materials and systems.  A colleague of mine sums it up thus:
The.... division is between those who fling open their doors to embrace the day, and those who huddle behind triple glazing worrying whether they are going to be comfortable.   Tony Watkins FNZIA 



Graeme "Stirrer"

Graeme North Architects
49 Matthew Road
RD1
Warkworth 0981

www.ecodesign.co.nz


 






On 13/03/2013, at 5:04 AM, RT <ArchiLogic at yahoo.ca> wrote:

> Tony wrote:
> 
>> Is there a window sill detail for the interior that could accommodate the inevitable moisture present?
> 
> Carolyn wrote:
> 
>> "ventilation window" ...two glass panes with space in
>> between - like 3-4 inches.
> 
> Tony;
> 
> Condensation on glass and subsequent puddling on window sills would of course, best be addressed at the source of the problem (in most cases just providing proper ventilation) but for small amounts of water accumulation, a gutter detail can be useful.  In the commercial window industry, the aluminum extrusions (especially with sloped glazing) typically include a condensation gutter.
> 
> For residential windows it would be a matter of bending some corrosion-resistant sheet metal flat stock to mimic the profile of the sash and glass stops of the bottom rails to function as flashing to direct the runoff into a collection gutter which may be integral to the flashing or a separate piece of off-the shelf stock (ie J-trim ).
> 
> Also, for the sills themselves, tile or stone set in a mortar bed rather than a moisture-susceptible material such as wood.
> 
> 
> Carolyn;
> 
> I don't see a file attachment for the windows you mentioned but they sound like the "laminar flow" windows that were marketed over on this side of the pond in the early 1990s.
> 
> My objections to them back then were:
> 
> (1) Solar pre-heating of ventilation supply air by the windows would only be happening when the sun is shining and striking the equator-facing glass.
> 
> In winter, at my latitude here near Ottawa, Ontario Canada that would be be limited to effectively about the 4 hours around 10:00 to 14:00 hrs.
> 
> Problem is, in most normal households, there is no one home during that time.
> 
> "Okay, so we'll just store that fresh air inside until people get home to use it. Right ?"
> 
> I don't know if Denmark has ventilation requirements written into the Code but there are minimal flow volume guidelines in existence intended to ensure good indoor air quality (see handbooks put out by ASHRAE or IHVE etc).  These, like building codes are minimal standards intended to provide a minimum level of health safety. I assume that we on the GSBN list aim higher than the worst buildings allowed by law.
> 
> Here in Canada we've had considerable experience with trying to make well-insulated buildings and learned very early in the process that making such buildings air-tight was an absolute necessity and of course, the corollary being that proving an effective ventilation strategy is also absolutely necessary and the R-2000 program from the early 1980s taught us many lessons that are still valid today.
> 
> The PassivHaus standard utilises most of the same principles (with some variations on targets) but PH strikes me as being confused so I won't talk about it here.
> 
> The CAN/CSA-F326 Standard (first published in 1989 and revised in 1991) is one of most comprehensive available on the subject of ventilation requirements and it lists the following:
> 
> ==============Copied material =================
> Table 1. Ventilation Capacity
> 
> Room					 Capacity, L/s
> Master bedroom 		10
> Other bedrooms 			5
> Living room 				5
> Dining room 				5
> Family room 				5
> Recreation room 			5
> Basement 					10
> Other habitable rooms		 5
> Kitchen 			5
> Bathroom or
> water closet room 			5
> Laundry 			5
> Utility room 				5
> =================== end of copied material =================
> 
> In 1994, a study was done for the Energy Efficiency Div., Residential Program, Energy Technology Branch CANMET, Dept of Natural Resources Canada (now NRCan)
> 
> "Indoor Air Quality and Ventilation Rates in R-200 Houses"
> 
> which found that most owners of R-2000 certified homes were operating their heat recovery ventilators (HRVs) at 75% the rate specified by the F326 Standard with no deterioration in IAQ and recommended that the lower rate be adopted for R-2000 certified homes.
> 
> Recently on the Greenbuilding list in a thread on the topic of ventilation, WatJohn mentioned some similar numbers (ie lower rate than those specified by F326) as a guideline:
> 
>    (per WatJohn)  7.5 cfm (~3.6 L/s) per occupant + 0.1 cfm per sq foot floor area
> 
> ... which, if you crunch the numbers will yield a "NO!" to the question posed (re: storing solar pre-heated fresh air) -- the point being that depending upon the degree of air-tightness of the building, there are certain minimal ventilation requirements that must be met or there will be unacceptably high levels of pollutants which will have deleterious effects on the health of the building's occupants.
> 
> Condensation on windows is just the most visual and most easily-addressed indicator that the house is suffering from poor ventilation.  It is the "invisible" pollutants that are more worrisome -- CO2 and VOCs.
> 
> The other thing that is troubling (to me anyway) is that we're only just now having this discussion on this List when the resources to address these questions have been readily available for the past three decades or so, pretty much pre-dating the current "SB Revival".
> 
> The need for air-tight construction with well-insulated buildings and the need for effective ventilation strategies for air-tight buildings does not have one set of requirements for buildings made of conventional materials and another set for buildings made of natural materials simply because the natural processes involved don't make the distinction.
> 
> That is to say, since the resources to address these issues already exist and these days are quite likely accessible with a few mouse clicks, there is no need for willful naivite or missions to re-invent the wheel. It's okay to transfer that knowledge to SBC and NatBuild.
> 
> No doubt there will be arguments to the effect "We don't want no stinking mechanical ventilation gizmos just so we can breathe ..." but that's a non-starter.
> 
> What's necessary are the ventilation rates to ensure health.
> 
> It doesn't matter how those rates are provided.
> 
> In milder (than Canada) climates and smaller, single-storey homes (ie under 160 sq metres) exhaust-only/passive-inlet ventilation strategies (EOPIVS) are an alternative to HRVs. The downside to EOPIVS is that there will likely be no heat recovery capacity on the exhaust air stream which means that energy consumption for space conditioning will likely be up to 40% higher than it needs to be and for any building aspiring to be "Green" in 2013, is that acceptable ?
> 
> But enough of that (and apologies to those who have had to endure this rant on numerous occasions previously).
> 
> 
> 
> 
> -- 
> === * ===
> Rob Tom					AOD257
> Kanata, Ontario, Canada
> 
> < A r c h i L o g i c  at  Y a h o o  dot  c a  >
> (manually winnow the chaff from my edress if you hit "reply")
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