Heat loss from exterior chimney?

[bluefrier]

A past thread reported a 10 - 20% heat loss from exterior fireplaces with inserts or stoves installed. I can't come around
to agree with these numbers because even when my stove is blasting for hours the bricks outside (directly behind the stove) are stone cold. The mass of the fireplace will radiate a soft heat for hours after the fire dies down. Also, aren't firebricks (in an existing fireplace) suppose to reflect heat and not absorb it? I know some heat is loss to the outdoors and every house is different but come on...10 - 20 percent?

 

[begreen]

There are a lot of variations on exterior fireplaces depending on what the mason was paid to do in the original installation. Installing a chimney or fireplace that is not central and interior is a bad idea, but that hasn't stopped a lot of people from doing it. Perhaps your flue has an insulation or air barrier between the inner and outer brick layers to mitigate the cold chimney effect?