Greetings folks... We have a lovely two-story brick house in Central Illinois, built in 1923. It has an Ideal #7 cast iron boiler, originally coal (I still have a few bushels in the cellar if anyone needs some!) and converted to natural gas at some point. It's a two-pipe steam system. The footprint of the house is 25ft x 33ft. The basement is unheated... so heated sq footage is about 1650. The attic is insulated with 6-8" of cellulose, but I don't think there's anything in the walls except plaster, lath, and 4" of brick. We've upgraded the upstairs windows with high efficiency marvin inserts, and intend to do the downstairs as soon as we can. They're original single pane w/ storms now.
As you can imagine, the bills this year have just about killed us... so I don't think I can put off the upgrade any longer. Something more efficient is going in as soon as the heating season is over... the only questions are 1) what and 2) how big.
I'm trying to do my homework in advance of talking to a bunch of contractors, to make sure we make the best decision possible. First things I've been trying to do are to ballpark the heat loss of the house, and the installed radiation. That will (hopefully) help me to decide how large of a boiler to put in, and whether to convert from steam to hot water.
I met with one contractor today, who took a look at the system and rec'd a boiler "sized the same" as what we have now. He took his figures from the plate on the gas burner, which is spec'd at min=60,000 Btu/h, max=200,000 Btu/h. So he's thinking our house needs 200,000 Btu/h.
That seemed way oversized to me. According to my math, we have no more than 120,000 btu/hour of installed radiation. (I can write up the size and style of our 9 radiators if anyone's interested in double-checking this.)
I've run through heat loss calcs with the SlantFin Hydronic Explorer software, and several other ballpark estimates, and by some gas bill shenanigans, and I can't get any estimate above 70,000 Btu/hour.
So my thought has been that we should convert the system to hot water, reducing the installed radiation to a max output of 75,000 Btu/hour.
So I guess the main questions are
1) Am I nuts to think 200,000 Btu/hour is waaaay oversized for our house?
2) Do you agree that converting to hot water would be a good idea? I know it's going to cost a little bit more to do the conversion, but I'm willing to wait 10-15 years for a payoff. We're not going anywhere -- we love the house, and they're going to bury us in the back yard.
Thanks for the help!