DO YOU LIVE WHERE THE WINTERS ARE SUPER COLD?
If you are in northern areas where it gets really cold in the winter you might want to insulate the hole in the ceiling that your whole house fan pulls air from. As you can imagine, the Home Depot type of propeller in your hall ceiling is almost impossible to insulate. There are covers you can find but they do little to stop cold from coming down.
QuietCool and Airscape have very little insulation between your ceiling and their motors. QC uses an insulated duct but it is only about R6. Airscape is about the same. Only Tamarack and Invisco have truly high performance insulated ceiling interfaces. Tamarack has a motorized door system that is rated by them at R38 and they just introduced their new R50 systems. Invisco has patented a dual thermally broken damper assembly that traps air when closed for R ratings that exceed R60. This system is available as both motorized and gravity operated. Invisco says they have excellent performance from the gravity operated doors and they are less costly than motorized doors.
If you research the 2012 IECC International Energy Conservation Code you will discover that the latest recommendations have been changed for Climate Zones 4 and 5. Below is the map. Until this year, zones 4 and 5 were R38. In January 2012 the recommendation was changed to R49.