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Redo entire HVAC or work with what's installed.

I'm in a '97 two-storey house with finished basement, 2100sq feet, 2x6 wall construction. I've updated the windows to all triple pane and the house is generally comfortable except master bedroom/ bath which takes up the back half of the house (not enough air through the vents), but it has an original 80% furnace at 100k btu (which is very overkill and I'm sure it's short cycling) that's on it's way out, there's no AC, and no ventilation outside of the furnace fresh air line.

I'm in zone 6/7a so it can go down to -30C or lower for 1-2 weeks at a time. So a heat-pump doesn't seem like a great choice since I'd still need natural gas for a back-up.

Geothermal seems like a great option but I got a quote for 40-60k depending on certain variables, (50k most likely) and there is the possibility of a 0% loan over 10 years to cover the cost of install. Not sure if this is worth it.

Thinking possibly of doing a hydronic floor retrofit and combi-boiler (would also solve wasted natural gas for a really old water heater that needs replacing) or combi boiler with 95% efficient hydronic furnace.

If I went with heated floors, I'm assuming I would need a dedicated ducted HRV or ERV for the whole house, if I went with hydronic furnace then is it worth getting the ducted HRV/ERV or just hooking it up to the existing ductwork.

If I keep the existing ductwork it will either need to be retrofit zoned, or possibly aerosealed (probably 4k).

It's a lot of options to consider and not really sure what's best. Any help would be appreciated so I know what further questions to ask installers and what options I really should be looking at.


  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
    edited February 2023
    I think you need to decide what problem you’re solving for. If a bedroom is a few degrees cold, you can add an electric baseboard and solve that for a few hundred bucks. Why not start there? If it works, you’ve just saved tens of thousands. Likewise, I wouldn’t let a water heater dictate a huge purchase either - the annual energy usage gap between a bad water heater and a good one is pretty small. 

    With existing ductwork, a furnace with or without a heat pump is the simplest option - a heat pump could work just fine depending on your rates.
  • Jamie Hall
    Jamie Hall Member Posts: 23,649
    At -30C? Heat pump? Not yet. A furnace or boiler backup is needed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
    @Jamie Hall

    With existing ductwork, a furnace with or without a heat pump is the simplest option…

    It’s not a binary. They pair well together. 
  • retiredguy
    retiredguy Member Posts: 930
    edited March 2023
    My neighbor has (had) a Geothermal HVAC system that heats and cools his one level home. His basement has 2 discharge vents and 1 return vent that he can open just to add a little heat in the winter. The house is approximately 1800 sq ft, well insulated, and built in 1997. He installed an insulation system in the basement that has a 1/2" Styrofoam board held in place by a metal beam style device that was purchased at a local store.

    My house, built by the same builder, is approximately 2000 sq ft, built one year later, has a single stage Goodman high efficiency gas furnace and a standard seer 3 ton A/C system. I insulated and finished the basement in 1999 and it is heated and cooled by the same system. So, my total conditioned space is about 4000 sq ft.

    We keep our house temps about the same; 72F in the winter and 76F in the summer. Last year, he wanted to up grade his HVAC system so we compared our total gas and electric bills. My totals were lower than his and I condition more than twice the sq ft. Last summer he had the Geo system disconnected and had a new Lennox system installed. We have to wait at least a year to compare $ but the early estimates look pretty good. He did say that the home was more comfortable this winter than in the past.

    If I were a younger man, I would seriously consider a Solar system to offset the high electric rates that I see coming, and maybe even a passive Solar constructed home.

    @ Primevega, I would have a couple good HVAC contractors look at your system and make recommendations. Adding to the system and correcting a few problems would be more cost effective and cause a lot less disruption in your daily life.
  • primevega
    primevega Member Posts: 2
    Thanks for the responses thus far.

    Yeah based on replies, there are probably easier ways of solving the heating issues in the house without breaking the bank and chasing every last efficiency.

    I like the idea of having electric heated flooring in the master since it will be used only on the coldest days of the year the usage wouldn't be super high and install would make more sense.

    Thinking then as well in the short term I can get an ERV and just hook it up to the existing ductwork.

    Still very tempting to do the hydronic floors/boiler though :D