|
Posted by Martin Clark on March 7, 2009, 7:02 pm
89fe-2f3cba78c5a3@r27g2000vbp.googlegroups.com:
show/hide quoted text
> I'm doing a grant application. There are two separate requirements.
> One requirement is that we "weatherization" to homes including all of
> the normal stuff -- fix leaks around windows, blow in insulation, etc.
> etc. Basically we need to wrap the house up a good as possible within
> budget constraints.
>
> The second requirement is for "green" which wants 15 cubic feet per
> minute of fresh air per occupant. To me that seems like a lot. For a
> family of 5, it would be the equivalent of running a 80 cf exhaust fan
> 24/7. Just how "green" is it if you have to heat that much air -- and
> air-to-air heat exchangers are pretty much out of the budget.
>
> Then when we're done rehabbing the house we are supposed to test for
> the right air flow. If we don't have sufficient air I don't know what
> we are supposed to do: Drill holes in the walls to let in more air?
>
> So my question is: Does 15 c.f./minute/person of fresh air in a
> northern climate seem excessive?
>
> (BTW, the answer to all of your questions is "I don't know". I have
> the same questions you have. Why are we doing this? How do we
> determine the number of occupants? Does the air flow have to change
> when the number of occupants change? How do you add more air into the
> unit if it is needed? How was 15 cf/min picked?)
>
Assuming that "northern climate" means that cold is more of a problem
than heat, then its a bit odd, yes. Long time since I had to do any of
this, but the answer used to derive from the heat source. If it involves
any form of flued combustion, then there needs to be a fixed air-intake
vent of at least the same cross-sectional area as the flue, or you start
running out of oxygen if the sealing of the building envelope is too
effective. If there's no combustion then it never used to matter, but
with excessive sealing it would depend on the system. Reverse cycle A/C
includes an amount of air replacement, but a lot less than 15 c.f. /
minute. And it can't measure the number of persons can it?
So probably the question is "how long is a piece of string?". There are
infinite variations for "person". Adults? children? Don't forget the
family dog(s) :-)
It may not be politically correct, but you cannot entirely eliminate user
interaction: "Can you open the window a touch? it's a bit stuffy in here
... "
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap
> One requirement is that we "weatherization" to homes including all of
> the normal stuff -- fix leaks around windows, blow in insulation, etc.
> etc. Basically we need to wrap the house up a good as possible within
> budget constraints.
>
> The second requirement is for "green" which wants 15 cubic feet per
> minute of fresh air per occupant. To me that seems like a lot. For a
> family of 5, it would be the equivalent of running a 80 cf exhaust fan
> 24/7. Just how "green" is it if you have to heat that much air -- and
> air-to-air heat exchangers are pretty much out of the budget.
>
> Then when we're done rehabbing the house we are supposed to test for
> the right air flow. If we don't have sufficient air I don't know what
> we are supposed to do: Drill holes in the walls to let in more air?
>
> So my question is: Does 15 c.f./minute/person of fresh air in a
> northern climate seem excessive?
>
> (BTW, the answer to all of your questions is "I don't know". I have
> the same questions you have. Why are we doing this? How do we
> determine the number of occupants? Does the air flow have to change
> when the number of occupants change? How do you add more air into the
> unit if it is needed? How was 15 cf/min picked?)
>