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re: energy efficiency - window units
19 jun 1997
"harlan hendricks" wrote:
>my office building is up for a new central system, but management has placed
>window units in our offices in the meantime. my office is approximately 1000
>cubic feet
like, about 12x12x8' tall, with 384ft^2 of wall area?
>and on the shadeless east side.
hanging a piece of greenhouse shadecloth outside near the wall would help
to some extent. a large banner, painted with some company slogan, like
"i love the director of asset management."
>the building itself (ca. 100 yrs. old) has masonry walls throughout.
foot-thick walls have about 384ft^2x1ftx20btu/ft^3-f = 7680 btu/f of thermal
capacitance, which could help keep your office cool overnight, but it sounds
like this old building does not have much insulation, and it may have lots
of air leaks. caulking your office, or somehow insulating the brick walls
on the outside (dri-vit, etc.) could help keep it cooler.
r20 exterior insulation might give it a time constant rc = 20/384x7680
= 400 hours, so if the initial indoor office temperature were 70 f, and
it were 100 f outdoors, after 24 hours the office temperature would be
100-(100-70)exp(-24/400) = 71.7 f.
r20 insulation inside the walls would work equally well with 7680 btu/f of
thermal mass inside that, eg 17 brightly-painted 55 gallon "accent drums"
or 1,828 2 liter soda bottles full of water around the office, or 384 ft^3
of concrete office furniture. someone important might notice this office
decor, and try to help.
>i was always taught that it required more energy (and $$) to turn a unit
>off and recool the space the next day, rather than leaving it set at a low
>setting overnight.
i think that's incorrect, as are similar myths that a setback thermostat
wastes heating energy, and turning off lights wastes electrical energy.
>the "director of asset managment" (who is questionably in charge of
>buildings and grounds) has never heard of this recommendation
good.
>and has directed us to shut the units down when leaving for the day.
good for electrical energy conservation, but...
>needless to say, my office is a sauna the following work day.
you might open the windows at night, or install a window fan with a
differential thermostat, or wear a bikini...
nick
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