+ Reply to Thread
Results 1 to 4 of 4
  1. #1
    Join Date
    Jul 2008
    Posts
    7

    Default Geothermal in an old house?

    Does anyone have experience with sizing a geothermal system for an old house? Arriving at a realistic heat loss figure seems to be a problem, because most people seem to want to oversize systems on a "better safe than sorry"--or maybe that should be CYA--principle.

    Our take is that we could install a reasonably large system--probably 4 tons--in the cellar with ductwork to the first floor, then go through an actual year with our existing oil-fired boiler and steam radiators as a backup and see how the house actually performs after adding insulation in the attic and cellar and doing something about the windows. Then we could add an additional 1 or 2 ton system in the attic with ductwork the the second floor if we think it is necessary.

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Geothermal in an old house?

    It's going to cost at least $15k or more for the geothermal system.

    In my mind I would invest a portion of that up front with tightening the house with air sealing , insulating , and windows first.

    Then you would a better value for calculating any future HVAC system.


    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Jul 2008
    Posts
    7

    Default Re: Geothermal in an old house?

    Quote Originally Posted by canuk View Post
    It's going to cost at least $15k or more for the geothermal system.

    In my mind I would invest a portion of that up front with tightening the house with air sealing , insulating , and windows first.

    Then you would a better value for calculating any future HVAC system.


    Just a thought.
    A geothermal system looks like it will cost more like $10K per ton. So revise your figure to $40K.

    We would certainly agree on the tightening issue. That needs to be done just to make it even faintly feasible to put geothermal in a 3,000 sq ft house with 35 over-sized old windows and 9 or 10 foot ceilings. That's why we've just invested in additional attic insulation (6" of cellulose blown in under the floorboards on top of the already-present-but-settled rockwool), cellar insulation (foaming the sill perimeter and the chases to the first floor, cut foamboard to insulate the single-pane windows and bulkhead, foaming perimeter and walls of crawlspace under kitchen), and why we are presently deciding whether to go with replacement windows (unlikely) or--currently more likely-- renovating the original windows (replacing weights with spring balances and insulating the pockets, weather-stripping) and adding high-quality new storms with low-e coating.

    The insulation and the renovation/storm approach will cost every penny of that $15K, by the way.

    The problem I have is trying to get a reasonably accurate BTU figure for the house AFTER we do these things. I'm wondering whether anyone has any experience with this.

  4. #4
    Join Date
    Jul 2008
    Posts
    7

    Default Re: Geothermal in an old house?

    When you have a system that uses 2,000 gallons of oil, at over $4 per gallon, $8000 per year in fuel cost, the economics of geothermal add up rapidly. Our alternatives are a $26K conversion to a forced hot water oil-fired system that uses 700 gallons of oil per year (at today's price $2800 per year), an $8000 new steam boiler which will bring us down to about 1300 gallons of oil (at today's prices, $5200, or a $43000 geothermal system that will use no oil at all, but about $2000 worth of electricity. What do you expect the price of oil to be 10 years from now? Electricity in our area is increasingly diversifying to wind and solar, and nuclear is possible down the road (especially if they get smart and build the kind of idiot-proof reactor that was available when they fell for the Westinghouse con job instead). THe price of oil has nowhere to go but up. PLUS, with the geothermal system we get air conditioning at a very low cost, plus free hot water when we run the a/c.

    There's a lot to be said for it.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •