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

[RT]

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

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