I'll be installing a new boiler soon in my 1835 2,000 sq ft farmhouse in CT. House has another uninsulated two story sheep barn attached to kitchen which I plan to finish a few years down the road. (about another 500 sq ft). I'm trying to weigh my options in considering sizing the new boiler which needs to be replaced soon. On the one hand, I'm trying to gain efficiency now, but by planning for the future expansion project, I want to make sure I have enough in reserve without oversizing too much.

Based on some online heat loss calculators, I've come up with a figure of around 75,000. So, I'm looking at the Burnham MPO IQ115 at 85,000 BTU, or going one size higher to the MPO 147 with 112,000, and adding the Alliance 35 gallon indirect HW heater.

I've spoken to a couple of installers over the phone, met with another, and all have said based on sq feet and length of baseboard I need at least 125,000-140,000 btu's, just for my current needs????

Figured I'd check in here to get some advice.

It's an old house, so it's pretty loose. Was insulated during a renovation in the 60's where PO's tore out all plaster, insulated all outside walls with R11 rolls, and re-sheetrocked. Saw some of it when I replaced some clapboards a few years ago. Not too bad. I actually found corncobs in the attic soffits too. Also insulated the ceillings in 2nd floor under the floor of an uninsulated walk-up attic. Unused Center Chimney with three fireplaces, all sealed with r16 glued to plywood jammed up into the flue. Fieldstone foundation and dirt basement. 17 windows, all with storms, 6 original single pane still original to the house with wavy glass, the other 11 replaced during the 60's renovation. Two zones, 100 ft of baseboard on the upstairs zone, and 80 ft downstairs.