Re: GBlist: Ventilation per John Bower

Mike O'Brien (
Tue, 11 Mar 97 14:19 PST

Hi, John--

You wrote--

>Comfort, other than your basic thermal kind, is a factor of health and
>we have been sadly inundated with studies linking deteriorating health
>to air-tight structures and the materials and processes used to create
>them. This is an unalterable byproduct of the initial design regardless
>of the amount of source control in material specification. Healthy
>materials may have a lot of resilient properties but at this point there
>usage is token or cosmetic. Our code structures in an attempt to achieve
>and enforce some of the measurable efficiency goals or to offset their
>drawbacks, or simply to accomodate problems of affordability are
>increasingly dependent on manufactured components - the net effects of
>which we simply cannot predict in day to day usage and these are the
>components that will be used in the bulk of affordable structures.
>My biggest concern with air-tight design is that it has become the god
>to which all our time and resources are given - and in turn it has
>created the specifications that drive the industry leaving little room,
>resources or even vocabulary for the development of more applicable
>design models that tamper less with the health of the end occupant.

I wonder if we should single out building tightness as the main reason for
indoor air quality and health problems.

When people say "today's tightly built buildings trap indoor air
pollutants" the implied meaning is, "yesterday's loosely built buildings
didn't have an IAQ problem". But, is that true? Probably all of us can
think of examples of air pollution in older buildings.

Loose buildings really do not "breathe",as the builders say; they do not
provide good ventilation for the occupants, they are prone to discomfort,
and they waste energy--and, sometimes "loose" buildings are actually built
tight unintentionally. How many builders actually check envelope tightness
with a blower door? They don't have any idea how tight or loose their
buildings are, yet still say they don't want buildings that are too tight.

The pollutant loading from building products sometimes seems almost
casually criminal. For example, what would the actual manufacturing cost be
to switch particleboard from urea to phenol formaldehyde glues? Maybe 25
cents per sheet? Why does the gas industry promote unvented fireplaces?
But, would these sources be less of a problem in a loose envelope?

It seems to me that ventilation systems could be much better--standardized,
durable, quiet, easy to use, and redundant, the fresh-air equivalent of an
auto air bag. Maybe the biggest hurdle, as Dave Brook points out, is that
consumers don't understand ventilation equipment, but it isn't designed to
be understood. For example, when the Super Good Cents program tried
requiring humidistat controls, the control cover plates were marked with
numbers in increments of 10 from 30 to 70--so occupants logically assumed
they were thermostats and turned them up to 70. Things are getting
better--a big national home appliance company that 10 years ago only sold
cheesy bath fans, now carries a line of good quality fans, controls,
registers, HRVs and filter boxes.

Designers and builders end up feeling frustrated, because they recognise
the problems and try to do something about them. There are so many
pollutants that it's impossible to deal with all of them in any single
project, or, as Hal points out, to educate everyone who could pollute the
building, like the maintenance staff. And, it doesn't take many experiences
like the moths in the Audubon building's wool carpets to discourage

However, I think John Bower is right: tight envelopes are the way to go,
because we can get a handle on pollutant loading and ventilation in that
envelope; whereas we probably never would in a loose one--it's too much out
of control. Joe Lstiburek once described a breathing wall, an idea of Gus
Haandegord's, where the wall would have fiberglass cladding that would
allow air to diffuse into a slightly depressurized building--kind of
"controlled looseness". Maybe there's potential in such ideas--I'm just
saying, follow the loose path if you want, but be prepared for a different
set of frustrations.


O'Brien & Associates
Environmental Building Consultants
Portland General Electric Earth Smart program

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