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Posted by on July 25, 2005, 9:08 am
Anyone else notice the ad for dehumidifiers on Bob Vila's web site,
which says "Stay a bit cooler with a dehumidifier"?
If it's 75 F and 80% RH indoors and outdoors, 11.8% of people would find
that "too warm," according to the ASHRAE 55-2004 comfort standard.
Dehumidifiers add about 1600 Btu/pint. An average house with 400 Btu/h-F
of conductance and 200 cfm of air leakage would be 79 F with 65% RH with
a dehum removing 1 lb/h of water, and 27.3% would find that "too warm."
OTOH, an AC using the same electricity and removing 1500 Btu/h of heat
and 1.5 lb/h of water would leave the house 71.3 F and 82% RH indoors,
and only 5.1% would find that "too warm." (We can't please everyone--
about 5% of the population will always be dissatisfied.)
Clicking on "How to contact Bob Vila" brings a message saying you can't :-)
Nick
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Posted by Abby Normal on July 25, 2005, 8:26 pm
Try this scenario, almost up your alley. Home without AC.
If you must have weather data, pick Duluth Minnesota. It can get hot
there, well above averages. Assume a somewhat inland from Lake
Superior.
Small place, 900 square foot main floor, 900 square foot basement,
undisturbed R40 blown into ceiling, walls poorly insulated, lathe and
plaster, recovered with vinyl siding, similar to 2x4 framed walls.
67,000 Btu/hr 80% AFUE furnace more than adequate for heat loss, no
cooling load ever sized but would be no bigger than 1.5 ton.
Basement floor 5.5 ft below grade, 8 foot to under side of joists, main
floor 9 foot ceilings.
Basement walls, 10 inch poured concrete, no insulation added.
Windows upgraded to double pane low e. Natural infiltration sufficient
to avoid winter condensation, not high enough to warrant use of
humidifier.
Large picture window facing east, perhaps 8'x5', two at 3x3 windows
west.
North and south walls, two at 3x3 windows. Guessing that eaves overhang
by 2 feet and were typically 2 feet above top of windows
Curtains drawn to keep sun out as best it can.
House with basement, basement tends to be cool, like 66F in summer,
will get warm upstairs.
Run dehumidifier in basement.
Imagine access door on return air drop, open the access door. Run
furnace fan, most return gets drawn from basement, cool thermal storage
of air in basement gets re-distributed upstairs.
Upstairs will cool off a couple degrees, below grade effect takes the
air from upstairs and sensible heat rejected by dehumidifier, basement
temp stabalizes at 68.
End up typically with 78F upstairs humidity less than 60%.
I lived it for a couple summers, dehumidifier made a big difference.
Also helped to have spare bed down in basement.
Need airflow take 67,000 input, 80% afue, 60 degree ATR
nicksanspam@ece.villanova.edu wrote:
> Anyone else notice the ad for dehumidifiers on Bob Vila's web site,
> which says "Stay a bit cooler with a dehumidifier"?
>
> If it's 75 F and 80% RH indoors and outdoors, 11.8% of people would find
> that "too warm," according to the ASHRAE 55-2004 comfort standard.
>
> Dehumidifiers add about 1600 Btu/pint. An average house with 400 Btu/h-F
> of conductance and 200 cfm of air leakage would be 79 F with 65% RH with
> a dehum removing 1 lb/h of water, and 27.3% would find that "too warm."
>
> OTOH, an AC using the same electricity and removing 1500 Btu/h of heat
> and 1.5 lb/h of water would leave the house 71.3 F and 82% RH indoors,
> and only 5.1% would find that "too warm." (We can't please everyone--
> about 5% of the population will always be dissatisfied.)
>
> Clicking on "How to contact Bob Vila" brings a message saying you can't :-)
>
> Nick
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Posted by on July 26, 2005, 6:06 am
>Try this scenario, almost up your alley. Home without AC.
>
>If you must have weather data, pick Duluth Minnesota...
Ah yes... 66.1 F in July, with 55.1 and 77.1 average daily min and max
and w = 0.010 (not very humid.)
It can get hot there, well above averages.
A 30-year record max of 97.0...
>Basement walls, 10 inch poured concrete, no insulation added.
>
>Windows upgraded to double pane low e. Natural infiltration sufficient
>to avoid winter condensation, not high enough to warrant use of humidifier.
>
>Large picture window facing east, perhaps 8'x5', two at 3x3 windows west.
Unshaded...
>Curtains drawn to keep sun out as best it can...
>
>...basement tends to be cool, like 66F in summer, will get warm upstairs.
Average yearly air (and deep ground) temp: 38.5 F.
>Run dehumidifier in basement.
For heat :-)
>Imagine access door on return air drop, open the access door. Run
>furnace fan, most return gets drawn from basement, cool thermal storage
>of air in basement gets re-distributed upstairs.
>
>Upstairs will cool off a couple degrees, below grade effect takes the
>air from upstairs and sensible heat rejected by dehumidifier, basement
>temp stabalizes at 68.
>
>End up typically with 78F upstairs humidity less than 60%.
Warming outdoor air to 78 would make the RH 48%...
>I lived it for a couple summers, dehumidifier made a big difference.
You mighta froze without it.
Nick
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Posted by Abby Normal on July 26, 2005, 5:20 am
I actually grew up north of there. They just had about two weeks of 90.
Heat wave for there.
It just illustrates how you live for averages.
nicksanspam@ece.villanova.edu wrote:
>
> >Try this scenario, almost up your alley. Home without AC.
> >
> >If you must have weather data, pick Duluth Minnesota...
>
> Ah yes... 66.1 F in July, with 55.1 and 77.1 average daily min and max
> and w = 0.010 (not very humid.)
>
> It can get hot there, well above averages.
>
> A 30-year record max of 97.0...
>
> >Basement walls, 10 inch poured concrete, no insulation added.
> >
> >Windows upgraded to double pane low e. Natural infiltration sufficient
> >to avoid winter condensation, not high enough to warrant use of humidifier.
> >
> >Large picture window facing east, perhaps 8'x5', two at 3x3 windows west.
>
> Unshaded...
>
> >Curtains drawn to keep sun out as best it can...
> >
> >...basement tends to be cool, like 66F in summer, will get warm upstairs.
>
> Average yearly air (and deep ground) temp: 38.5 F.
>
> >Run dehumidifier in basement.
>
> For heat :-)
>
> >Imagine access door on return air drop, open the access door. Run
> >furnace fan, most return gets drawn from basement, cool thermal storage
> >of air in basement gets re-distributed upstairs.
> >
> >Upstairs will cool off a couple degrees, below grade effect takes the
> >air from upstairs and sensible heat rejected by dehumidifier, basement
> >temp stabalizes at 68.
> >
> >End up typically with 78F upstairs humidity less than 60%.
>
> Warming outdoor air to 78 would make the RH 48%...
>
> >I lived it for a couple summers, dehumidifier made a big difference.
>
> You mighta froze without it.
>
> Nick
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Posted by on July 26, 2005, 9:01 am
>I actually grew up north of there. They just had about two weeks of 90.
>Heat wave for there.
>
>It just illustrates how you live for averages.
Rational people do, if they pay for air conditioning.
Nick
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