My jotul Oslo is attached to double wall uninsulated to the 8' ceiling the. insulated out the top. My question is what should the flu temp be? I know ....I have a flu thermometer on it and it will be low. I also have a stove top thermometer as well. Do any of you smart guys at math have a conversion? Let's say my stove top says 500. What should the flu temp be with uninsulated double wall?