I can recall my own visceral reaction against the concept of airtight
housing the first time I worked on one. It seems that the idea of a
mechanically ventilated plastic bag just doesn't do it for most people.
However, I sure changed my mind after the client had a party for all the
workers - there were 20 -30 people, about 10 of them smoking cigarettes
(this was 20 years ago) and a couple of guys smoking cigars. The air in
that "airtight" house was WAY cleaner than if you had opened all of the
doors and windows. This is a 3000 sq. ft. single storey bungalow in an
8800 degree-day climate that heats with an electric furnace for
$200/year.
So, the first, giant, misconception seems to be to assume that there is
some kind of automatic relationship between airtightness and lack of
ventilation.
Secondly, I've noted over the years a gut reaction (including my own)
against HRV's. Well, this (Ottawa) happens to be HRV country now, and,
granted, they may make less sense in other climates where forced air
ductwork is not a standard tract house item (although I personally doubt
it). We've got a client in Missouri, for example, who wants to follow
R-2000 guidelines for his house, and, typically, none of the local
mechanical guys has ever heard of an HRV, much less installed one (I'm
fairly certain, however, that this in no way inhibits them from having
opinions about them).
This could largely be a cultural reaction to change, since the same
thing happened here 20 years ago. As someone who views a lot of this
from the combustion side of things (building scientists tell me that
there is no way that you can put an open fireplace into an airtight
house, for example), I shake my head when I see whole house
depressurization seriously discussed as a ventilation strategy.
I was doing a little research recently on the original airtight house,
The Saskatchewan Conserver House, built in 1978. Notably, it heats with
electricity for $35.00 per annum in a 12,000 degree-day climate. Before
writing HRV's off too soon, based perhaps on emotion, I'd sit down and
do a serious payback analysis, rather than just looking at capital cost.
"Expensive/cheap", as we know, can be loaded terms - as in "I'd like to
build a big, affordable, sustainable house that I can make some money
on".
I'm no economist, but it seems to me that if your ROI on an HRV is
greater than your mortgage interest rate, you are making money on it.
We're making about 30% per annum on our compact fluorescent bulbs, for
example. Yet, most people I talk to would rather invest their money in
mutual funds, and wouldn't dream of spending $25.00 for a lightbulb.
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Norbert Senf email: mheat@mha-net.org
Masonry Stove Builders mheat@hookup.net
RR 5, Shawville website: http://mha-net.org/msb
Quebec J0X 2Y0 fax: 819.647.6082
voice: 819.647.5092
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