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zoning an addition to an old house with hot water

Brad White
Brad White Member Posts: 2,398
Are you sure you have enough radiation in the new addition compared to the heat loss?

What I am getting at is that an older house with a boiler installed 50 years ago tend to have:

1) A generously sized boiler, just the way things were done, and,

2) Energy improvements over the last several decades, reducing the demand.

My thinking is that the new addition could well be accommodated given that it is of newer, more energy-efficient construction and that the older portions are tighter.

Given these possibilities, what is the heat loss of your old house, new addition and the relative amounts of radiation you have in each?

Also, I gather that the "two circulators" you have are each dedicated to the old and new portions, respectively? At least the copper baseboard is zoned separately from the cast iron? If they are combined on one zone and the thermostat is served in a room with a cast iron radiator, grab a blanket and enjoy your addition. Let's say for argument's sake that the copper baseboard and the cast iron radiators can be called on independently.

I am not suggesting that you keep the old boiler, you have gotten your money's worth out of that. But it may not be the boiler.

The question can be answered by you with the following posed by the great John Barba at Taco: Has the boiler ever shut off in cold weather? If it has, I suspect the radiation, either size relative to heat loss or that it is combined in zoning with cast iron.

Take stock of the home's insulation quality, windows and so-on, both new and existing. Perform a detailed heat loss on each. No matter what else you do, start here. The numbers will support you at the point you might change your boiler but in the meantime will help you assess your radiation capacity too.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

-Ernie White, my Dad


  • zoning an addition to an old house with hot water

    I have an old house with newer addition. Hot water heat - radiators in original house, copper baseboard in the addition, 2 circulators. The addition is chilly and will not warm up enough with the boiler alone. Will creating zones + new boiler help by heating either the house or the addition, not necesarily both at the same time? Most of our time is in the addition. Contractors suggest a new boiler (existing boiler is from the 1950's) and new pipe to the addition with a separate thermostat. Looking for better ideas, please. Thanks.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,542

    I've asked that question of customers many times and invariably the answer is "Yes,but we still want a bigger one so it won't have to work so hard" !!!

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