Hi Ya'll
I hope you don't mind if I ask all of you an radiant heating question. I was looking for idea's for an answer to my questions and found this forum with many good suggestions and was hoping to get a little insight here too.

I have an offer to buy an old house that was converted into a duplex. I went to see it yesterday and talked with the owner and one of the tenants. The owner explained that the upper level unit and the lower level unit's thermostat's control the pump and heater to kick on for the whole building. So if the upstairs tenant raises the heat, the downstairs unit heats up too. One big issue is if one of the tenant's decides to close the valves on any of the radiant heaters then decides to raise the thermostat's temperature the other unit will become sweltering.

The gas bill from what I've been told is ridicules. Obviously I need to find a way to fix this. One solution I realized from the get go is that they "should" be zoned. I wasn't able to trace everything out while I was there by any mean's, but I think most of the piping is walled in. I'm afraid the upstairs "a separate unit" and the main level are going to have a heating pipe that's on a common header located somewhere on the main floor.

I realize to zone this I'm going to have to find the separation between the 2 zones and if it's walled in separate them and pipe the upper unit's to the basement and install zone valves off a common header to each zone.

My question is does anyone know of any way to control this situation better that doesn't involve zoning? All the radiant heaters have normal manual inlet valves. I guess what I'm wondering is if there is any type of thermostatic valve that can replace these valves and if the boiler circ pump can be operated off pressure of the system above it? Meaning if the pressure drops between the pump and the thermostatic valves "by one opening" the pump kicks on. Then.. can the hot water boiler simply kick on based on temp of its reservoir? I didn't get the make of it, I just know that its 10-15 years old.

Any suggestions you have would be greatly appreciated. Please understand the tenants aren't wealthy, it's not a slum, but were still talking 1000 sq ft 2 bedroom units renting for $550 a month. The gas bill in winter can be $400 as is right now. If I'm going to buy this thing I feel a responsibility to try to make it right for them. I don't want to make it harder than it has to be on them. But at the same time I'm not wealthy either. I need to make every dime I can afford count in a productive way.