[Greenbuilding] CONDITIONED crawlspace ventilation

[Michael McHugh]

Dan,

With no forced air in the addition and hydronic tubes in the wood 
floor, it sounds like you are trying to save heating energy. I don't 
see how heating more space is going to save energy. I don't believe 
Sonoma County has a hot, humid climate that will cause problems in a 
vented crawl space. On the contrary, the cooling sea breezes should 
allow for natural ventilation. A sealed crawl space that has vents 
into the living space should also have a "rat" slab which will just 
use more resources unnecessarily. I still believe an insulated floor 
(weatherproofed as if it was an exterior wall) above a vented crawl 
space would be better in your climate. I've never been to Sonoma 
County unfortunately so I would recommend talking it over with the 
locals or giving  Building Science Corp. a call and asking about your 
particular situation. Conventional practice isn't necessarily bad but 
let me know if you find that I'm wrong on this. Good luck.

Mike


>Just to clarify,
>Building Science Corp (http://www.buildingscience.com) has advocated
>that crawlspaces be moisture-sealed, perimeter-insulated, and
>mechanically ventilated as part of the conditioned space of the
>building. (See their site for more information.) This results in
>better moisture control and energy savings. Conventional practice was
>to insulate the floor with batts between joists and vent the
>crawlspace passively with screened holes. I've read that codes allow
>a conditioned crawlspace if it is mechanically ventilated from the
>conditioned space above.
>
>I was asking about an addition to a house right on the ocean in
>Sonoma County, California.  I think I'll have energy savings if I
>condition the crawlspace below the addition, but I need to link the
>air volumes somehow, and since I have no forced air in the addition,
>how do I do this? (The addition will have hydronic tubes in a wood
>floor.)
>
>Thanks again,
>--Dan
>
>--- Michael McHugh <mmchugh at vernerjohnson.com> wrote:
>
>>  Dan,
>>
>>  You don't indicate what climate you are in or what code you are
>>  designing to meet. Could you insulate the addition floor and leave
>>  the crawlspace unheated with screened vents only?  Is there
>>  plumbing
>>  and/or ductwork in the crawlspace?
>>
>>  Mike
>>
>>  >I am designing an addition to be built on a crawlspace foundation.
>>  >I'd like to seal and insulate the crawlspace for energy
>>  conservation,
>>  >but I think codes require some kind of mechanical ventilation of
>>  the
>>  >crawlspace.  Since my addition has no mechanical ventilation, I
>>  don't
>>  >want to add a fan just for the crawlspace. Is there any way to
>>  ensure
>>  >an air change by passive means?
>>  >
>>  >If we put a heat recovery ventilator on the house, can I just link
>>  >the crawlspace using air transfer grilles?
>>  >
>>  >Thanks,
>  > >Dan Johnson

-- 
*****************************************************************
Michael McHugh AIA, LEED AP
LEED Program Director
E. Verner Johnson and Associates
Museum Architects and Planners
222 Berkeley Street,  Suite 1350
Boston, MA 02116
tel:   617-437-6262
fax:  617-437-1272
http://www.vernerjohnson.com