NO! In fact that's the stupidest thing that I've ever heard concerning BTU's.

I would have a Heat Loss Calculation performed to see what you really need. I'm not a HVAC pro(you might contact NRT.Rob), but the info you've been given is not correct.

anin,

These contractors were certainly NOT well educated in the application and replacement of heating boilers. Get a real heating contractor out there to give you an estimate based upon his math. Not SWAG. (stupid wild ass guess)

The “square foot method” is a rule-of-thumb. Nothing short of a dumb ass guess. The guy that actually counted “the rungs” of your radiators was getting there, but he too falls far short of knowing how many BTUs are required for a replacement boiler. Measuring the rungs, counting the number of columns in each rung, and comparing the info to the MFG’s output chart will only tell us what your connected load is. I doubt he even went that far!

What any knowlegable heating contractor would have done is to evaluate the house on a room-by-room basis and perform a heat loss analyis based on how much heat is required to heat the house on the coldest day of the year. The new boiler is sized by that and that alone. Then, and only then should he take the EDR of the existing radiation to simply calculate the water temperature your system now reqires.

As most heating systems of that era were WAY oversized, a high-efficiency Mod/Con boiler can really work wonders for your fuel bills, carbon footprint and NOS output if sized and installed properly. High efficiency boilers (known as Mod/Cons) are a GREAT choice for old gravity system conversions that used large cast iron radiators and huge distribution piping. We’ve seen efficiencies up to 96% on our combustion analyzer in old gravity systems converted to forced circulation using Mod/Con technology.

You may have enough radiation to put out X # of BTUH using 180ºF degree Fº water, but as your heat loss after any added insulation and improvements over the years gets smaller, you may run much lower water temps through those big radiators. You might even get away with 135º-140ºF water temperature.

Don’t settle for anything less than a Mod/Con if you decide to go with gas. It will save you boat loads of cash over home heating oil, but only if your heating contractor is capable of getting your water temps down below 140ºF and is familiar with the technology.

That contractor does seem to be a couple classes short of a degree. When replacing a boiler, calculating the heat loss of your home is very important. With that in mind, it's a good time to look into reducing the amount of heat loss. The lower the amount of heat loss, the smaller the boiler required which saves some money up front and a lot of money over time.

You should contact your utility company about a home energy audit before you commit to a new boiler. You may be able to make energy saving improvements to your house like having the outer walls filled with foam insulation or replacing old windows with more energy efficient ones.

Your utility company is more likely to give you an unbiased report rather than try to sell you something you don't need like some private energy contractors.