I'm just jealous that it cools down for you guys at night. I wanted to put in an attic fan but the cost outweighed the few nights a year it can be used.

My ac runs from around noon till 10 pm pretty much non stop because it was sized "correctly". New system will end up being around a ton or so bigger due to real world conditions. Also doesn't help that the returns are on the floor and the supply registers are all on interior walls...

dew point calculator
 

Dew Point Calculator
It's optimized to show mold growth potential.

it's not a controller, but with current humidity and temperature
forecast, you can make some guesses.
Arduino boards are below $5 these days. Shouldn't be
too hard to automate it.

I have a psychrometric chart on the fridge with some boundary
lines to predict condensation events.

Yep, that is exactly what I had in mind ham789. I'd imagine a quick google search would even find someone who has done something similar already making it a very easy project.

arduino temp/humidity
 

There you go.

Wiring up DHT11 Temp & Humidity sensor to the Arduino | www.hobbyist.co.nz

Looks like the hard part is done.

One thing that concerns me is the accuracy of the sensors
as you approach 100% RH. Might have to calculate the dewpoint
before the RH gets too near the 100% and rely on temperature
readings...but, if a front rolls thru, that may mess up the
estimate...

I did buy an arduino board and actually made it download
a demo program and spit data out the serial port.

A serial to bluetooth converter can interface it to your smartphone for monitoring.

I've been so caught up with
windows 10 that I haven't had a chance to go any further.

Don't remember if I mentioned it before.
I have a 24" box fan that can do 3500 CFM.
I open the patio door and set the fan in front of it.
I made a "filler" for the space above using 1/2" low density
white insulation board. If you put a plastic U-channel around
the perimeter, it's surprisingly durable.
Stick a handle in the middle and some tabs to hold it in
place when you slam the patio door on it.
I turn it on around midnight when the outside temp gets
low enough.
I just use a wind-up timer to set the run time.
Not very elegant, but effective.
I live alone, so nobody else will criticize my work. ;-)

Do you have a bug screen on the window?. Just wondering if that would restrict the airflow too much.
Bug screens are essential here unless you enjoy being eaten alive :D

Yep, standard patio door with standard patio screen.
Not too restrictive.

Not too much chance of a bug flying against the wind
and getting thru the fan anyway.
This fan was made 40 years ago when fans were real fans.
Not the cheap plastic Chinese crap you get today.

Thanks for the link ham789! That is pretty much perfect. I'd imagine you're probably going to stop your fans well before 100% humidity, so that shouldn't be too much of a problem. :)

I too use a box fan, but in a window upstairs. I stuff a pillow in the window beside it to seal it up.