[Greenbuilding] Chase Fan and Differential Thermostat

[Eli]

I am looking for information on a reversible fan to go into a 26"x26" chase
that takes hot air from solar gains that stratify in the attic (heat chamber
I call it) and pulls it to the crawl space, where Main Level Floor is a
composite concrete slab for thermal mass.  I would like the fan to be
reversible so I can also pull cool air in during the summer night to vent
out the cupola and cool the slab.  For my solar clients, I am using a
composite slab for floor instead of framing, because it is very affective as
a thermal mass with air on both sides.  Hot air delivered then spills up to
bottom of slab looking for opening through floor across from where air is
delivered to allow air to rise into the house.  However, I need a strong
reversible fan that is fairly quiet.  I also need an air differential
thermostat to turn fan on when crawl space is 15 degrees +- less than heat
chamber.  It would also open an automated vent that would close when fan
cuts off, when a low heat difference is reached, thereby preventing the heat
from rising back into the heat chamber.

The slab works without the active components.  However, it will work much
better when those features are operating.  If you have any suggestions, I
would appreciate it.

This is on a new addition.  However, I see potential to apply this to
retrofits with redesigned attic (foam insulation along sloped sheathing to
create a heat chamber) and created chase to go to basement or crawl space.
On retrofits, I would be looking for ways of adding thermal mass.  Perhaps
in a crawl space this could be racks of water jugs supported by ground.  I
want to determine the appropriate amount of thermal mass to avoid
overheating from solar components added.

Eli Fishpaw Architect
Lexington, VA