Originally Posted by CtTradArcher
Is an insulated firebox really that much more efficient than uninsulated? I admit I can be a bit simple minded at times, but I just can't imagine it makes a considerable difference.
I can understand an insulated cooking chamber where you are trying to reach and maintain temps.
To me, it seems the heat is leaving the firebox at a rate determined by the dampers and would only be marginally effected by outside temps.
Yes, it makes a difference. The k-value (measure of thermal conductivity) of mineral wool is 0.04 W/(m.K) and the k-value of steel is 43 W/(m.K).
Going from a 1/4" to a 1/2" firebox provides a negligible insulation difference.