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Community and Q&A

Biomass boiler for Climate Zone 5a, CT

jenniferz5 | Posted in Mechanicals on

I am hopeful that I am getting to the final stages of planning my HVAC system.  To recap:  The decision has been made to go all electric with a PV array to be added in the future to offset cost of operation.  My home is 1400 sq ft, 15.7 ACH 50, but will be getting new Alpen double pane casement windows and loads of new insulation in the attic and rim joists.

In addition to the ASHP or AWHP (of the two, I am leaning toward a Chiltrix AWHP), I found in my notes “pellet boiler.”  After additional research, I found that biomass boilers have similar start-up costs, lower running costs, can run at lower temps than HPs, release little to no CO2 into the environment (unlike HPs), can heat DHW and radiant panels, are quieter than HPs, run off of solar (if desired) and have great rebates for every NE state but mine.

Can anyone offer advice about this system, or as it compares to the AWHP?

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  1. jenniferz5 | | #1

    Updating to add: John Siegenthaler recommends that biomass boilers be sized for 60-75% of heating load (closer to 60). My home needs 33k btuh for heating. The brands that I am considering (if I go this route) are and, mainly because they are essentially hands-off and can (I think?) accomodate that lower btuh number that I require (most biomass boilers are 50k btuh and above, if I am correct). Does anyone have experience with either of these; or, have you completed a similar retrofit?

  2. Expert Member
    Michael Maines | | #2

    Jennifer, I can't answer your question, but I hope that as part of your insulation upgrade you will be doing a lot of air-sealing? 15.7 ACH50 is absolutely horrible. You should be able to get down to 3.0 ACH50 or lower without too much effort, save a bunch of money each year, and down-size your mechanical system. For reference, a 3000sf Pretty Good House I'm designing in Maine (zone 6) has a heat load of about 23,000 Btu/hr.

  3. jenniferz5 | | #3

    Yes, it's dreadful (I say as I sit here shivering in several layers of clothing). I have added an attic door box with insulation, ordered SmartBaffles for the attic (where I will also be adding several layers of Roxul ComfortBoard), and am slowly insulating and sealing the rim joists in the basement. The windows will be replaced asap with Alpen double pane casements (and insulated). I have new doors and cedar siding (with a good bit of compacted insulation in the walls). I'm getting there! It is really important to me to get everything done well so that I don't regret whatever system I end up with - I can't afford to be one of those that "throws the thing in the dumpster" because it isn't working.

    1. bwsct | | #4

      Hi Jennifer,
      Not sure if you'll check this but where are you located in CT? I'm in CT also and looking to undergo a similar project.


      1. Expert Member
        Dana Dorsett | | #5

        What is your design heat load?

        At 14kw (48,000 BTU/hr) the very smallest EvoWorld can handle the heat loads of the vast majority of homes in CT and would be "right sized" for homes with 99% design loads in the 30-35,o00 BTU/hr range:

        The EcoBoiler and Effecta Komplett III start at 20kw (68,000 BTU/hr) and would be sub-optimally oversized for most homes, and may need some thermal buffering tank beyond the thermal mass in the boiler.

        Any of the above can be had from EcoHeat Solutions in Walpole MA:

        For homes with design heat loads less than 30K a pellet boiler may not be great solution- they can't make pellet burners arbitrarily small and still have them work reliably. Ideally it would have a decently long minimum burn time, and operate at a ~70% duty cycle at design temperature.

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