Nate Nagel wrote:
E Z Peaces wrote:
Nate Nagel wrote:
Wondering which would be more efficient in this situation...

A/C is set at 76 degrees. Dehumidifier is set at 55% RH. it's 67
degrees outside, approximately, but the house is right at 76 because
it was hot yesterday. Outside RH is 80+ percent.

Is it more energy efficient to open all the windows and turn on a
fan, and let the outside air cool the house off (thus forcing the
dehumidifier to run,) or just leave the windows shut at let the A/C
do its thing?

no, this isn't actually a hypothetical... this is exactly what I
woke up to this AM. I chose to open the windows because I like fresh
air, but on reflection didn't know which was really more efficient.

nate


http://einstein.atmos.colostate.edu/.../Humidity.html

At 67F and 80% RH, the dew point is 61F. At 76F and 55% RH, the dew
point indoors is 59F. So the absolute humidity is about the same.

As long as it's at least 5F cooler outside than in, I'll probably open
the windows even if the dew point is several degrees higher outside.

I keep a wet/dry bulb thermometer beside my thermostat and turn on my
AC as needed, according to the wet bulb. If the house is humid in the
morning, I can take care of that by running the AC two or three times
for ten minutes or so. The amount I save by letting the house cool at
night is more than I use to reduce the humidity.

I don't try to keep my humidity as low as 55%.

A dehumidifier is an AC that dumps the heat right back in the house.
If it were winter and I wanted to reduce humidity without losing heat,
I'd invest in a heat exchanger, instead.

I don't need to dehumidify in the *winter* - exactly the opposite.

Summer (well, let's be honest, spring and fall too) here, humidity is
silly high though.

nate

I would depend on the AC to control summer humidity. A dehumidifier
warms the house.