Heat loss?

Last wood burner I was around was a fireplace with a brick/mortar chimney outside the house. Thinking about adding a wood stove to our future house with a simple stove pipe but I am concerned with potential heat loss when you run the pipe thru the ceiling, the unconditioned attic and out the roof. Can you insulate right up to a box similar to this one? Or is there still clearance needed around the box? Either way heat will escape out the top of the box, will it not? Heat loss is not my real concern, it is where the heat will be escaping to that concerns me. The barn style building we are living in right now gets gigantic ice damns on the roof if we get any snow that accumulates on the roof. Will be using a metal roof on the new house, just like we have now but the ice damns and the gigantic ice bergs hanging off the roof concern me a bit. Or am I just being paranoid?

Like I said, not real worried about the actual heat loss, just where it will be going.....and the potential for ice damns that it will create. The counties building inspector informed me of the issue of snapped pipes...and then mentioned using a diverter of sorts to prevent it form happening. Have seen them on several local roofs, they are similar to this, sorry for the terrible picture, it is all I could find. But it is a simple steel wedge that bolts to the roof, in front of the pipe. There is small home not to far form us that has PVC vents thru the roof, at the edge. Even with the monster storm we had in 08 he had no troubles....