urnace in a pantry off the kitchen. She wants to replace it with a high eff= iciency furnace, taking her from 80% efficiency to 95% efficiency,for the f= uel savings.
gh efficiency unit in that space but didn't give a good reason, at least no= t one that she understood. One complicating factor is that she thiks that t= here is just one chimney outlet on the roof which is shared by the two adjo= ining condos but I haven't actually seen the unit as it's hundreds of miles= away.
le to just remove the old unit and put in a new one unless the high efficie= ncy units are somehow larger, hotter or whatever.
Well in the UK gas appliances can't share a flue with other fuels, probably the same in the USA. If your friend wants a high efficiency heating system it will have to be wet (ie recirculating water and radiators). No chimney is necessary, most boilers are room sealed. ie air is drawn from outside into the boiler. Exhaust gases are just piped to the nearest point outside, usually the wall the boiler is fixed to via a plastic pipe.
Read up about it here:-