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automatic mechanical return dampers
27 apr 2001
i just visited an old 8 unit apartment house with a gas hot air furnace
and separate 6" supply and return ducts to each apartment, but it only has
a single thermostat. the warmer apartments had open windows... built in
the 1800s, not much insulation, lots of air leaks. about 4000 ft^2 on 3
stories, with a complicated outline and roofline using 550 ccf of gas in
march, with an average outdoor temp of 47 f. 

of course it needs air sealing and insulation, which will make the interior
temp more uniform, but does anyone make a damper with a bimetallic spring and
temperature control that would fit inside the old round floor return grills?
something like an $12 leslie-locke automatic foundation vent, but with more
accurate temp control. close louvers on temperature rise. the air-equivalent
of a danfoss mechanical thermostat for radiators...

nick