Attic Heat Recovery System

HEAT  RECOVERY DUCTS & DAMPERS
This idea came from the amazing Bob Martin of Reddi-wall, but Andy Stack took on the job of actually engineering and installing the system.
The house has a metal roof and the attic can heat up to over 120 degrees even during the winter. The goal was to pull warm air from the attic when it was available and when the house thermostat called for heat, but still be able to supple the ventilation system with cooler outside air when it needed it. 
A 7” (1) metal heat duct was run through the utility room ceiling and into the attic. An electric damper was then installed on the end of the duct in the attic. A second damper (2) was installed on the duct (3) that brings fresh from outside to supply the ventilation systems. Two thermostats and a couple of relays control the two dampers and turn on the ventilation system when the correct circumstance are met.
Under normal circumstances the ventilation system will pull fresh air from the out side., but if the homes thermostat calls for heat and the heat sensor in the attic says that heat is available, the attic damper will open, the outside damper will close and the ventilation system will turn on and pull hot air from the attic, through the HEPA filters and distributed to each room.