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Re: GSBN:HRVs and SB
- To: "GSBN" GSBN@...
- Subject: Re: GSBN:HRVs and SB
- From: Paul Lacinski paul@...
- Date: Fri, 24 Jan 2003 07:54:42 -0500
- Reply-to: "GSBN" GSBN@...
- Sender: "GSBN" GSBN@...
I would agree with what Derek and others have said about indoor air
quality, etc. I would even go so far as to say that I wish our codes
would follow yours and require HRV's, because then I could actually
get people to use them, instead of cutting them at the last minute,
as is generally the case. I say "almost" wish because requiring them
flat-out would be an excessive expense for some people who are
building small houses on a very tight budget. (So now we come back
to the heart of your question.) I assume that the generally
enlightened Canadian codes make provision for use of energy modelling
software, so that if you can show that a given design will meet the
overall intention of the code with the use of exhaust-only
ventilation (bathroom fans with timers) rather than an HRV, I would
imagine that you would be OK. Of course, it may turn out that an HRV
is a less expensive way to meet the code than having to bump up to
(for example) those Canadian triple-paned fiberglass windows. (Which
we have only used once so far, but which work supremely well, in
terms of both heat loss and noise reduction.) Such provisions
sometimes also account for size, allowing a slightly less efficient
envolpe and sysstems for small houses, since small houses use so much
less heating energy than large ones.
So now that I've gone in a bit of a circle about that, I will
disagress with Derek's assertion that "current heat recovery
ventilation systems are primitive and expensive." They are somewhat
expensive, but I would certainly not call them primitive. They
ventilate an entire house with only a 30% heat loss, using 1 moving
part- a very high quality fan. They have filters for incoming and
outgoing air which can be specified to remove pollen, dust, urban
pollutants, and other matters of concern to allergy sufferers,
chemically sensitive people, children, etc. They replace the
bathroom fans, so there is no noise in the bathrooms. They provide
some circulation of interior air. And they lead to houses in which
the air is warm but also always fresh and clean. Regardlesss of
building materials, I have never been in a house with an HRV that
didn't have sparkling air quality. So given all of that, and
considering that they are built to last indefinately, I don't think
they're very expensive.
Lacking comments from Rob Tom and Paula Baker Laporte, here is what
I think about indoor air quality. Moisture buildup is not the only
problem. It may be the most serious issue for the physical
structure of the home, but it is probably secondary for the health
of the inhabitants.
For good indoor air quality, a home needs significant, continuous
air exchange in all rooms. This is hard to achieve. If a building
has lots of air infiltration, it wastes energy and can lead to
invisible moistuure problems in the walls. A loose home is also
likely to have very uneven air exchange. If a building is tight,
then air exchange needs to be designed in, in order to have healthy
air quality in all rooms, regardless of moisture levels.
Current heat recovery ventilation systems are primitive and
expensive, which is why we don't want to use them. But to ignore
the problem and subject ourselves, our families and our clients to
unhealthy indoor air is irresponsible.
--On Thursday, January 23, 2003 10:03 AM +0200 Evgeny Shirokov
From my experience with straw-clay houses: moisture is not a problem
in bathroom, if you use clay stucco and protect walls from "direct
water flow" by ceramic or other with ordinary system of ventilation.
And Chris Magwood relayed:
Has anyone with a strawbale home NOT installed a heat recovery
sytem (HRV) and if so do you have a problem with condensation?
I'm trying to decide whether to install one before my interior
walls are closed in.
Now that HRVs are part of our building code, it seems
inspectors are not giving owners any options other than
installing the full systems ($3-6000 and require constant fan
noise and energy, plus ductwork everywhere). Does anybody know
of an indoor air quality expert who might have options/opinions
other than the installation of full HRVs? My own home was built
without one, and we don't have any moisture problems, which I
attribute to the amount of porous, unsealed natural materials in
the house (barn board, beams, unpainted gypsum plaster, etc)
which are capable of a lot of storage when conditions are
humid, and release when conditions are dry.
Language Learning Center, Ortega Hall Rm 129, University of New Mexico
Albuquerque, NM 87131 505/277-7368, fax 505/277-3885
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