Question: We have a masonry fireplace with no flue through to the chimney. More specifically, a while back we installed a B-Vent gas unit in an adjoining room using this flue. Of course, now we want to put an insert into this fireplace.I was wondering if with insulated pipe, or double wall pipe and possibly a power vent (such as on a water heater) I could go out a side wall of my house? Answer: There are power vents which allow for B-venting through a side wall. You can usually find these at plumbing and heating supply houses, as they are commonly used for furnaces and hot water heaters.Your other choice would be to B-Vent all the way through the roof or up the side of the house.A third choice which may or may not be legal (check with a professional) would be to line your masonry chimney with B-Vent to hook to the gas unit, and then line it with stainless steel to connect to the insert. This way each fuel has a separate flue.