Sandra:
>I'm wondering if the trade off between heating fuel and
>energy needed to run ventilation systems is ultimately sustainable.
It does seem inefficient to ventilate with cold outside air and
blow the warm air outside. In the summer the opposite occurs
with hot air being blown into a cold room. Most references don't
talk about closed systems as a good alternative. I think
there are two problems with closed systems:
1. Closed systems are expensive to build.
2. We are not very good at designing closed systems.
Anyway, the open systems rely on nature to provide clean air
and do waste a lot of energy both for fans and for heating and
cooling.
The book "Eco-renovation" suggests lookings at the impact of
four factors first:
1. prevailing winds interacting with the building.
2. stack effect (warm air raises)
3. combustion (furnaces with burn fuel have expanding gases)
4. fans
A designer can easily look up in tables how big a fan needs to
be design the ventilation system in a few minutes. The impact
of winds, stack effect, and combustion are much more difficult
and few bother. They do consider filters sometimes but these
are usually for the outside air entering the house. Closed
systems with filters, plants, and humidity controls are rare.
This whole topic makes me a bit cynical. First we have a
chapter on venting the house and next we have a chapter
on sealing the leaks. No one talks about the seasons
and how the house could interact with its environment.
Some times of the year we might want the windows open
and at others we might want a closed systems for part of
the day.
My solution to all this is to work with whatever house
i'm stuck with. Observe and adjust. Since my memory isn't
very good i use this computer to provide reminders and
have several books on local weather patterns. It becomes
a game of watching the wind shift, opening windows, etc.
It has to be easy and require little thought or it gets
ignored.
----
jeff owens, [EMAIL PROTECTED], http://www.xprt.net/~jko
underground house, solar power, self-reliance, edible landscape
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