I am looking into getting a high efficiency furnace. I understand that the furnace can not be vented using the existing chimney. The outside of the wall that the furnace resides on, is underneath an enclosed porch.
My question is, can the pipe used for venting the furnace run underneath the porch to the outside the wall of the enclosed porch? Or would this outside exposure of the vent pipe lead to condensation problems inside the vent pipe during cold weather?