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Replacing oil fired to natural gas

Jeff Mark | Posted in Energy Efficiency and Durability on

I currently have hydronic heat via oli fired boiler to basboards (single zone to two floors). Contemplating converting to natural gas and splitting zones via hot water coils to existing central air system. There is an air handler in the basement and another in the attic. The question is…is it more efficient to remain with a single zone via baseboards or split the zones via existing ducting?

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    Jeff,
    Q. "Is it more efficient to remain with a single zone via baseboards or split the zones via existing ducting?"

    A. The system efficiency depends on the heating appliance efficiency and the heat distribution system efficiency. If your proposed forced-air system includes an air handler in the attic, the distribution efficiency of that forced-air system is probably quite low, unless you have an unvented conditioned attic (making the attic included in your conditioned space).

    Your hydronic distribution system is likely to be much more efficient than your forced-air distribution system.

    You also need to compare the efficiency of your existing boiler with the efficiency of the natural gas boiler you hope to purchase.

    Remember, zoning your house won't really save any energy unless you keep one zone at a much lower thermostat setting than you would with a single-zone system.

  2. Jeff Mark | | #2

    The natural gas boiler would have an AFUE of >95%. Current oil fired has an AFUE of 82.8%. The central air system handlers air rated at 16 SEER. The upstairs houses the bedrooms and main bathroom. Upstairs gets very warm when trying to heat the downstairs. The attic is fully insulated and vented. The price of oil is what is driving the decision.

  3. Jeff Mark | | #3

    the house is over 100 years old, plaster walls....big deal to open walls

  4. Keith Gustafson | | #4

    It is probably cheaper to dig open a wall and rerun some pipes[to add a zone] than add a hydro air.

    Could be either the downstairs is 'lossy' for some reason or under-radiated compared to the upstairs.

    [edit] I cannot even think of how they ran pipes without bringing two loops to the basement, you probably just
    need to add a pump or zone valve
    Oh how I wish I had gas in the street...........

  5. Keith Gustafson | | #5

    gimme 15 minutes and a sawzall................

    see my edit in the last post

  6. User avatar GBA Editor
    Martin Holladay | | #6

    Jeff,
    Keith is right -- it's much easier to zone a hydronic system than a forced-air system. Most people with hydronic heat prefer it to forced-air heat, and would consider a switch to forced air to be a step downward in convenience, comfort, and noise.

    Cut one or two pipes in the basement, put in a new circulator and a new thermostat, and you're done.

    If your attic is vented, that means it is outside the thermal envelope of your house -- and it's a lousy place for ductwork and air handlers.

  7. Jeff Mark | | #7

    SIngle zone means single copper loop - all supply and returns flow to basement. Contractor runs pex to attic along side existing chimney, coil to air handler. Cutting and mapping the pipes for five rooms is the labor intensive side of this equation. Quoting $1700 for the added work.

  8. Aj Builder, Upstate NY Zone 6a | | #8

    Close off upstairs baseboards, remove some fins upstairs... Or...

    Really, should be very easy to split to two zones. We remodelers love our sawzalls.

    Ultimately it's your call.

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