What's the Best Way to Convert from Oil to Gas Heat?

JDel83 asks,

Help! I have a two-family home with an oil-fired furnace that heats and provides hot water to the apartment on the 2nd floor. The system is currently costing me approx. $3,500 a year for a 1,100 square foor apartment and its killing me. The system consists of a single pipe steam system and I’m really not sure how old the current furnace is. I do have two gas meters in the house and the gas is going up to the second floor for the stove. I’ve had a few HVAC contractors come in and give me estimates on converting from oil to gas and it seems like putting in a natural gas warm air furnace in the attic is the least invasive and my best bet but I’m getting conflicting information.

Contractor A quoted me on a Carrier 80% AFUE Natural Gas furnace with evaporator coil and a 40 gallon hot water heater. He states that 80% AFUE is the best efficiency I can put in my unheated attic (I live in Rhode Island) because of the condensation in more efficient units create. Contractor B quoted me on a Tempstar 92% AFUE and a 40 gallon hot water heater. When I questioned him on the condensation issue he stated that he will insulate and heat trace the drain line along the gas line he runs into the attic.

I like both contractors and they both rate well with the BBB, but who do I believe? I’d like to get as energy efficient as possible. Just in case your wondering about the insulation in the attic, I currently have 12″ of older batt insulation and will be blowing more in once the heating system is in place.

Thanks for any advice!

Our Answer

I don’t quite follow Contractor A’s concern about condensation. High efficiency furnaces are known as condensing furnaces because they take so much heat out of combustible gases, and much of what’s left is water. That water is expected, though, and is drained out with a gravity drain, if conditions allow, or with a condensate pump that pumps it away.
The same is true in warmer months. Condensation forms as the AC runs, and it also has to be pumped out. It’s managed by the system.
This really comes down to cost benefit analysis. If the 92% AFUE is grossly more expensive, it might not be worth it. But if it's only slightly more, it might be worth it.