Greetings. Sorry for the long post. Everyone has had nightmare home repair stories. We've been lucky with painters, electricians, roofers, etc but HVAC is the millstone around our neck.

Some background... We own a 125 year old home with many cast iron radiators across 3 floors. We are comepletely remodeling our kitchen (Philadelphia area) and thought to put in radiant underfloor (hydronic). I was going to install the PEX and plates, insulate, etc myself based on designs received online. I was going to hire a HVAC contractor to hook it all into my boiler.

Here's where it gets interesting...12 years ago our 40 year old oil boiler failed and we were sold a double boiler gas system (Weil Mclain which I believe are 82%AFUE) and a domestic water tank that supposedly would save us money. But it really doesn't seem to, my heat bills are still high to my liking. Calling a few local supply houses for references to a contractor who is up on radiant, the same name kept coming up. He came over and spent 2 hours in our basement and aside from the radiant project came up with the following issues regarding our primary heat system.

1. The two boilers are not controlled by anything more exotic than some relays. There is no boiler controller, no external temperature sensor, no alternating of boilers. It appears that one boiler heats the house and I paid a couple thousand to have a second 150K BTU boiler serve as a hot water heater.

2. He says the piping is all wrong. The boilers are set up in series, i.e. no manifolds, the output of one is the input to the second, there are areas where new pipe (1.5" copper) transitions into the original 3" cast iron, and back, and forth.

So, originally I was looking for someone to hook up the radiant system and take a look at our system for efficiency improvements, this is turning into him proposing, (actually I haven't received the proposal yet, but am nervously awaiting) repiping both boilers and the domestic water tank, installing a control system with outdoor temperature sensor, alternating boilers, domestic water priority and repiping the the main distribution and return lines that alternate between 1.5", 3" and 2" pipe, etc.

So I am expecting the worst and that I'm facing paying for my heating system all over again and am wondering if there is a middle ground. Can this be looked at as separate projects that could be prioritized in terms of increased efficiency and heating cost payback such as:

1. Control module with outdoor temperature sensing, boiler scheduling, domestic hot water, etc.

2. Repiping the boilers and the domestic water tank

3. Repiping the mail supply and return lines to single size pipe.

OR is all of this so dependent on each other that I am wasting my money on one aspect of this without doing the whole thing. Actually his last question was whether I would consider replacing the boilers with a single, higher efficiency boiler. WHen I got off the floor, I told him we'd have to wait on that, now I understand that this would have an impact on the piping. So I am wondering how far to go?

Any and all advice would be appreciated.