Overview
Not sure how much interest there will be in this project but I thought I'd post it in case there are any other people out there that want to make a whole house fan. This projects is for an insulated (R30), automated (using MySensors of course) whole house fan. The purpose of the fan is to vent the hot air in your house out of the attic while drawing cooler air from outside into the house. I live in a climate with hot days and cool nights so this works great for me. The problem is most attic fans that aren't $1,000+ don't have any insulation so during the hot days they allow your house to heat up much faster than it should. So, I decided to see if I could build one, and automate it of course. :)
Here is a short video going over the functionality:
Wiring diagram
I ended up not having enough space in the code for the SD card but this is how to wire it up if you did want to use it. You can also just leave it wired like this even if you don't use the SD card. Alternately you can use the yellow pins on the other side with the same connections and resistors (except for the SD wiring). 
Code Notes
The code is available from the "Source Code" section.
- Most things that may need to be customized (motor stall values, close timing etc.) are at the top
- The LCD uses the Adafruit_GFX & Adafruit_ST7735 libraries. You will need to download these and add them to your libraries folder (or use the Library Manager).
- The code is too large to have debugging enabled and the LCD. Comment out debugging after you are finished testing.
Parts List
Click on the BOM tab at the top Note: Some of these things are probably only sold in the USA but hopefully it will give you something to base it on if you're in another country
Building
Here are some pictures from the build. I have also created the box as a 3D rendering in SketchUp (.skp) so you can get the dimensions of the box or if you want to make any customizations. The file is available on the "Design Files" tab.
It's important to get the box and drawer slides as square and level as possible so the cover operates as smooth as possible (then you don't need a big motor).
I cut 1/2" strips of wood at 45 degree angles that will be used to help seal the slide. Install these perfectly level otherwise the cover won't close properly. 
Making the slide cover: Glue the foam board for the cover 
The wood on the sides will be used to attach the drawer slides 
Make sure everything is square and level 
Glue and clamp 
Attach V-Seal weather stripping 
Install drawer slides. These need to be installed as level as possible. 
The cover installed. Notice the space between the top of the wood. This is for the starting collar. 
The cover should fit tight and square in the back of the box. 
Install the starting collar for the duct work. 
Hollow out a slot in the foam so a piece of wood can be inserted. This will be used to attach the wood used for the threaded rod. 
Make sure to use glue 
Screw in a piece of wood that will be used for the threaded rod. 
Screw in threaded insert 
The threaded rod was slightly smaller than the bearing hole so I used a plastic wall anchor as a shim. 
Install cover and limit switches 
Here is what the motor, Arduino, etc looks like 
I shimmed the motor and board so if they heat up there won't be a fire :) 
The relay and current sensor in the fan electrical box 
A blurry picture of the final install 
The LCD 