Here’s a few examples of how a whole house fan could work for your Seattle home:

1)  Install a direct-vent whole house fan such as the HV1000 from Tamarack Technologies.  To install these units, you will cut a hole in the ceiling of a central hallway/staircase (in this example about 14×22 inches).   After hole is cut and debris/insulation removed, you create a box from 2×6 or 2×8 timber (whatever matches your existing joists).  It will look something like this:

At which point you can drop in the fan unit — looking something like the picture below:

Next wire up the unit, and run a switch to a convenient location within your home to turn unit on/off.   You will also want to examine venting within the attic to ensure that it conforms with the device’s needs.

Here’s a link to a good DIY article on fan install.

Here’s a link to the install guide for this particular unit:  HV1000 install guide.

Bottom line:

These units will provide you with a cost efficient way of cooling your home with low energy consumption.  This unit uses the same amount of energy as two incandescent light bulbs!   Another benefit is to use it as an air exchanger, to help keep the air fresh and healthy in your home.   I hope you find this info helpful!

Brian