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| Greenbuilding Archive for December 2001 |
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| 229 messages, last added Tue Nov 26 17:26:14 2002 |
[Date Index][Thread Index]
Re: [GBlist] Mold question and beyond
Hi Robert
so much for a reflective tone on the new year.
Actually my concern with engineered wood stems from I joist usage or truss
components and long term deflection. Under ideal circumstances the material
would seem to perform well however in out of envelope or 'cross envelope'
where moisture levels can be high there is a basis for concern especially
with long term creep or deflection under dead load with levels considerably
greater than provided for. If the moisture is cyclical the creep can
accelerate with the deflection becoming 'set' in the joist. Eng. wood also
becomes saturated at a fairly low moisture level compared to most solid wood
material and can retain that moisture for longer periods of time allowing
both structural and biological deterioration to occur within a timeframe
that wood might normally recover without deficit. In this sense it requires
'ideal conditions' to perform. Also and more typically I'm not seeing the
installation follow the specifications which can be quite complex for some
loading and which in the case of engineered wood is a little more crucial
and this can exacerbate the problems.
These problems can be countered in design by considering the conditions that
a joist will endure or limit the joist use to conditioned environments only
(interior floors) - but in practice I've found few developers interested in
pursuing such design considerations and it usually makes sense to use a
material consistently through a project. Right now I'm favouring truss
joist (solid sawn material) over I-joist - partially because of the above
concerns but also because most engineered wood material is still being
produced from virgin wood often of structural dimension and once ground up
and pressed together has little potential for further recyclability. Small
and probably biased considerations I would allow.
----- Original Message -----
From: "Robert Jordan" <rwjordan@charter.net>
To: "John Salmen" <terrain@shaw.ca>; "David Seth Melchert"
<dmelchert@earthlink.net>; "Steven Shepard" <sbtdesigns@earthlink.net>;
<greenbuilding@crest.org>
Sent: Friday, December 28, 2001 8:01 PM
Subject: Re: [GBlist] Mold question and beyond
> John,
> I agree that a lot of the questioning, although I grant you is well
intended
> and are questions worth asking and answering, pretty much comes down to
the
> question of how many angels can fit on the head of a pin. I believe that
> the larger question is can 6 billion people ever be sustainable and upon
no
> scientific basis have answered for myself at least in the negative.
> In spite of the nihilism of this view, I do believe that this earth and
all
> of its creatures, animate and otherwise, are sacred. Consequently I try
to
> act in a way that honors our and their existence.
> It seems to me that when we argue over the cost- benefit analysis of the
> preservation of another endangered species, that we are missing the larger
> issue about stewardship of this planet. So the LCA of fiberglass vs.
> cellulose seems relatively unimportant, to me anyways.
>
> Actually what provoked my response was your comment that engineered wood
> products are not designed for durability. Do you have reason to believe
> that I-joists, say, are likely to fail in 30 years or so? If there is a
> problem, I would appreciate more information.
> Thanks,
> Bob Jordan
>
> Original Message -----
> From: "John Salmen" <terrain@shaw.ca>
> To: "David Seth Melchert" <dmelchert@earthlink.net>; "Steven Shepard"
> <sbtdesigns@earthlink.net>; <greenbuilding@crest.org>
> Sent: Friday, December 28, 2001 10:04 PM
> Subject: Re: [GBlist] Mold question and beyond
>
>
> > thanks Seth for continuing the thread a little more. Perhaps it is a
good
> > beginning for a new year thread. I can't quite remember how long I've
been
> > contributing to this list but over the years the consistent base for the
> > conversations has been building products, and the technology or building
> > science behind them. We have had to relegate the 'problems' to the more
> > speculative threads that dwindle quickly.
> >
> > The GBlist focus on products however is appropriate in perspective as
much
> > of the last decade has been a development of product within an economy
> that
> > could afford to build upon all the available technology - and find a
> > marketplace (however slim.) In other words it has been a bit of an
> > entrepreneurial decade which has been a boon for green building
products.
> > Some of these products have been inspired by improving IAQ standards or
> > energy concerns, some by the increased availability of recycled
> components,
> > and still more by the diminishing availability of virgin materials,
> whether
> > wood or water.
> >
> > In this rush to get products, materials, and even concepts into the
> > marketplace I think there has been a bit of loss of perspective or
perhaps
> > foresight . LCA's are a wonderful theoretical tool but in a more vulgar
> > perspective I'm starting to consider simple basic questions like - can
we
> > afford to replace our Pella or equiv. windows every 15-25 years. Can we
> > afford the repainting of an exterior every 5-10 yrs., the compressor on
a
> > heat pump every 8 or so yrs., the surfacing of a driveway, etc. When you
> > look at the mortgage structures on most buildings they generally don't
> > suffice to cover the replacement of the wearable components. It is a
> > speculative nightmare and not to an 'owners' advantage.
> >
> > When I look at public or lower income 'housing solutions' the nightmare
> > grows worse as I'm looking at designs and material usages that are hard
> > pressed to survive a single occupancy much less a generations. Our
> > engineered wood products are not designed for long term durability, our
> > composite finishing products are very suspect. Our VOC finishing
> > alternatives are a chemical soup, and our mechanical contraptions are
> simply
> > that, often or potentially appropriate but more often not.
> >
> > I'm not meaning to sound negative, and generally view most developments
in
> a
> > positive sense but am curious how other building professionals have
viewed
> > the developments of the last decade.
> >
> > best
> > John Salmen
> > TERRAIN E.D.S.
> >
> >
> > ----- Original Message -----
> > From: "David Seth Melchert" <dmelchert@earthlink.net>
> > To: "Steven Shepard" <sbtdesigns@earthlink.net>;
<greenbuilding@crest.org>
> > Sent: Friday, December 28, 2001 4:32 PM
> > Subject: Re: [GBlist] Mold question
> >
> >
> > > Steve:
> > >
> > > Indeed there is a message here to consider.
> > >
> >
> >
> >
> > ______________________________________________________________________
> > This greenbuilding dialogue is sponsored by REPP/CREST, creator of
> > Solstice http://www.crest.org, and BuildingGreen, Inc., publisher of
> > Environmental Building News and GreenSpec http://www.BuildingGreen.com
> > ______________________________________________________________________
> >
> >
>
>
______________________________________________________________________
This greenbuilding dialogue is sponsored by REPP/CREST, creator of
Solstice http://www.crest.org, and BuildingGreen, Inc., publisher of
Environmental Building News and GreenSpec http://www.BuildingGreen.com
______________________________________________________________________
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