I have a wood burning fireplace insert with a 2 speed blower. It makes a HUGE difference in how effectively it heats our home.
It has a thermostat that allows it to come on once the firebox reaches 150˚.
The only thing I'd like to see different would be to use a Stirling engine to power the blower instead of electric which requires a cord to run across a portion of the hearth. Since you need 150˚ air for the blower anyway, the Stirling engine would come on when you need it and shut off when it cooled down enough.
I have to look into upgrading my unit this way.
