On Sun, 24 May 2009 09:29:41 -0400, 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


There is no simple answer to the question because you are
missing so many parts of the calculation.

You don't know:

* The delta (the change) of the outside air temperature or the outside
humidity, it will be changing
* How quickly your home will absorb the moisture out of the air, or
release it into the air
* How quickly your home will absorb the heat out of the air, or
release it into the air.
* Exactly how long you are going to be in the home and for what
times.
* How tolerant you are to changes in humidity and temperature and
since this will change with how active you are, we will also need to
factor that in
* Other sources of heat or moisture into your home (this would include
heat gain via insulation etc.
* Other people who might visit and how often you might open a door or
window.

I'm sure I could find a few more issues like sun light clean
or cloudy skies (day and night) etc.

It really is a difficult task to properly measure it which is
why so many sellers of this or that gadget can make all kinds of
claims that don't seem to make much sense.