OK I have a customer here who is complaining about his plumber. This affects a kitchen installation. I have no knowledge of boiler types but need to advise him. His currently boiler is very old and is gravity system that has a simple timer and thermostat with a flue running through the ceiling and out the roof. The boiler is in a small room with a 4" air vent pipe running from the outside of the house under the floor in to the boiler room. His plumber insists on a combination boiler and that it is placed on an outside wall, preferably in the loft. That is not acceptable to him. He does not want the boiler in a different place ( certainly not in the loft ) and he does not want a combination boiler. He does not want to change his radiators and he does not want to pressurise them either. However the plumber will not give him any other options. My question is, given that the boiler in in the middle of the house, what arrangements for ventilation are possible for a heat only boiler? It's a bungalow so the flue is pretty short.