Whole house fan
 

Most mornings the inside temp of my house is around 80 and the outside is about 68. Starting at 4am when I get up, I'm opening every window in the house and I can drop the temperature a few degree's, but only a few, may get it to around 78 if I'm lucky, so I started looking at whole house fans to give the hot inside air an added impetus to leave allowing the nice cool air in.
Looking at what's on offer there seems to be the box fan on it's side type

http://www.homedepot.com/catalog/pro...compressed.jpg

and the blower motor connected by ducting to a vent in the ceiling type.

http://www.homedepot.com/catalog/pro...compressed.jpg
I'm leaning towards the second one but rather than cutting another hole in my ceiling I was wondering about adding a junction duct to the outlet of my attic furnace and pulling the air out of the existing feed and return vents. I would of course add insulation and motorized gates so it only operates when there is a temperature difference (Arduino). May even help pull some of the dust out of the ductwork :thumbup:
Any input on overlooked potential disasters?

If you're pulling suction on both inlet and outlet ducts without the furnace blower running, aren't you likely to pull dust in from the outlets and deposit it in the ducts only to get launched when you go into heating mode with the furnace in the fall?

I built an economizer into my new (at the time) house 15 years ago. A forced air system with a damper in the return air duct, a duct from the outside with a damper, and a switch (normal / economizer). In normal mode, the heating and central air worked normally. In economizer mode, the return air damper closed, the outside air damper opened, the AC was shut off, and the furnace blower ran until room temperature met the cooling setpoint.

When we first started it up, no air came out of the registers. Tried to open an outside door. It did not open. A two handed pull got it open. Then we got air out of the registers. Then closed the door and opened a window. Less than several inches open, the window howled. Fully open, everything was was good. It ran until the house got down to setpoint, then the blower shut off. Everything worked as planned.

EXCEPT, Wisconsin is humid during the summer. And the relative humidity is highest at night. We woke up to a house at setpoint, about 72 degrees, and very high humidity. It was a swamp inside.

Then I thought "what will happen if the outside air damper fails open in winter at -20 degrees F outside". So I removed the outside air duct and put in a dehumidifier.

Also, the house is so well insulated that the central AC gets very little use.

In dry climate with large day to night temperature swings, an economizer system can work extremely well. When I was in the Air Force at March AFB, CA in the 1970's, our barracks air conditioner failed one summer. We kept the barracks comfortable by running the ventilation fan all night and shutting it down during the day. Typical night low temperature 60 to 70 deg F, typical day high temperature 100 to 110 deg F.

Not sure, my thinking was that it would almost clean the ducts with the reverse air flow and dump the dust into the attic, not that I don't have enough up there already:D
I may get an initial shower of dust when the furnace first starts up but that will be nothing new. Sort of like when you turn on your cars AC for the first time in the summer and all you get is hot air, dust and dead bugs out of the vents

Your system sounds exactly like the one I had in mind.
Here in SE New Mexico the day and night temperatures are about the same as your summer temps, but no humidity.
My house is well insulated, doubled the wall thickness then put in R30 fiberglass batts and a separate plastic vapor barrier. When the outside and inside temps are the same we close all the windows and turn on the AC, let it run for an hour then it's turned off and we don't need it until early afternoon.
I'm hoping that by using your example to extend that time to late afternoon or ideally, not need the AC until morning.

Did you get a fan yet Neil?

I have a 10" inline centrifugal fan that is rated at 650 CFM, just need to sort out the ductwork and controls etc. But as we are still in triple digits or close to every day, I'm staying out of my attic until it gets to a reasonable temp to work in.

You should go on with the professionals help for installing this whole house fan.

Insulation of walls or full house cooling fan is a good idea to control your house temperature. You can also use some little alternative fan to deal with restricted ventilation at home and all around places. It can be operated at your convenience anytime. There are too many models of battery operated portable fans. Here you can get a comprehensive information about the different latest model of portable fans with defining their features and guide, so that you can select the best one to use when you feel its need at the time when the temperature goes high.