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cast iron radiator and geothermal heat

Technically, yes it can work, if you use a constant flow upwards-resetting heating water supply temperature, or simpler yet- use a Euro approach and use some Danfoss style self controlling rad valves on each unit to have a fine modulating flow of the low temperature heating water through them. The high mass radiators would not work very well with any kind of on-off rad valves due to the cycle time of heating up that mass with low temperature heating water.

I'm in Vancouver as well and I can tell you that for every $ you put into really good windows, envelope insulation and air leak sealing, you should be able to provide enough heat with 120F HWS. In Vancouver winters you ought to be able to heat the home with lights and people, and hardly any net energy input from a central heating device IF you use triple (yes, I said triple) low-e glazing in Vancouver with R-20 walls and R30 attic/roof inulation. The lower the heat losses (and heat gains) of the house, the smaller the geo-exchange system needs to be, and the better your geo-exchange yearly energy balance will be, making for a very efficient system.

I'm in a pretty inefficient wood frame townhouse in Richmond, and just swapping the windows out from single glazed to double low-e glass along with sealing cracks, and we find the furnace might need to come on for a couple hours for 3-4 days a week from December to February. If I spent more time to police up the thermal bridging, and add more insulation to the walls, the furnace would never have to run, and the heat from me and the three wimmen here would keep us cozy all winter.


  • Paul Preto
    Paul Preto Member Posts: 2
    cast iron rads for geothermal heat

    I am builder in Vancouver B.C. and I am building an infill development that includes a retained character house from 1930. It has cast iron rads and gas fired boiler (and single glazed windows and not a scrap of insulation).
    The 5 unit project will be using geothermal heat pumps, and the question is how to heat the character house effectively. Could the cast iron rads be used with the low temp water (120 max)? there is some "character appeal" to the old rads but they also likely need to flushed and may cause problems with a GHP with sediment etc... plus they are *heavy* and awkward. I guess my other option is something like warmboard or stadler comfort panel over the existing subfloor, the exisiting floors are being replaced. the basement level will be insulated slab on grade w/ pex piping. Perhaps a combination of retained rads and comfort panel would work?
  • Paul Preto
    Paul Preto Member Posts: 2

    forgot to mention the character house will be totally insulated etc so the rads should be way oversized for boiler temp water.
  • Perry_3
    Perry_3 Member Posts: 498
    Totally possible if...

    You need to do a proper heat loss, then calculate the required radiator sizes for each room (and the house) based on 120 F (max) - and the radiators are at least that big.

    I am a homeowner/engineer and I looked very hard at converting my house (Cast Iron baseboard on a Monoflo T system) to geothermal.

    In my case I actually need 140 F water for design days (and found out that 145 F works really well on extended cold at design day conditions last year). Thus, I was not able to convert to geothermal. So I installed a Vitodens 200 and cut my fuel usage by 45% instead.

    However, I have often thought of my dream heating system - and alternate between geothermal and solar heat using a Cast Iron baseboard system.

    Slantfin was giving out free software for sizing of room radiation and boilers for a while. Goto their website and see if it is still available (it took a week or two to get in the mail after I requested it). I am sure other programs also exist.

    Have a great day,

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