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

Fri Mar 15 01:15:09 UTC 2013

Graeme 

Thanks for your comments

Unfortunately there are too many "Energy Blings" out there to provide what
is good design detailing.

Always look forward to your comments

Bohdan

From: GSBN-bounces at sustainablesources.com
[mailto:GSBN-bounces at sustainablesources.com] On Behalf Of Paula
Baker-Laporte
Sent: Friday, 15 March 2013 9:35 AM
To: Global Straw Building Network
Subject: Re: [GSBN] Can bale buildings be air tight?- How to ventilate

Thank you Graeme for expressing my sentiments so well!

On Thu, Mar 14, 2013 at 3:51 PM, Graeme North <graeme at ecodesign.co.nz>
wrote:

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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-- 
Paula Baker-Laporte FAIA,BBP
Econest Architecture Inc.
www.EcoNest.com
paula at econest.com
Phone: 541.488.9508

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