> There are a variety of parameters to control ventilation: CFM
per person,
> Air Changes, CO2, and RH. If you had to pick one, which one
would you pick
> and why?
For residences I would pick CFM per occupant in most every case. After all
it's people that need the fresh air. The problem with ACH is that a big
house with 2 people in it involves lots of air exchange while a small
dwelling (under 1000 s.f., such as 2 bedroom apartment) may not have enough
air exchange for 3+ people that might be living there. My example of the 2
bedroom apt is intentional since the number of common walls will probably
reduce air exchange significantly. As others have observed CO2 control is
probably not effective for residences.
In all of this discussion no one has mentioned the importance of insuring
that the fresh air is evenly distributed. What good is all the CFM or ACH in
the world if it's not being delivered to the areas where people are living -
hence the ultimate problem with "natural" ventilation (ie uncontrolled
ventilation which depends on air leakage).
It's ironic, I think, that right now the only place you reliably find whole
house ventilation systems is in new manufacturered homes. Windows inlet
vents, transom grilles over bedroom doors and a central fan (even quiet
Panasonic fans in some homes)! Admittedly, they may be reacting to problems
caused by 20 years of building tighter homes notorious for high initial
formaldehyde levels.
Dave Brook
__________________________________________________________________
This greenbuilding dialogue is sponsored by Oikos (www.oikos.com)
and Environmental Building News (www.ebuild.com). For instructions
send e-mail to greenbuilding-request@crest.org.
__________________________________________________________________