Old, leaky home needs new heating system
I have an energy audit scheduled (although likely pushed out now due to the current state of things), and over time hope to upgrade the envelope, but a failed recent oil tank inspection has pushed needing to replace my heating system to the forefront.
Here’s the info: Central Vermont 1890’s home, with only few envelope updates over time. An addition in 2003 with batt, not super well installed, insulation. It’s a duplex and has been for a number of years, with tenants on second floor, and I reside on the 1st floor. 1425sf footprint. I’ve owned it since 2013. Current heating for the first floor is forced hot air from an oil fired Williamson furnace with leaky duct work in the uninsulated basement. Other parts of the house (including one room on the 1st floor) are heated by propane fired hot water systems, and a Rinnai. I have plans to insulate the not-livable-space basement as a first step after the future energy audit. The oil tank is leaking, and so I’ve decided to get off oil and convert all the systems to propane. On site solar isn’t an option.
A mechanical installer friend has suggested two different systems. 1. Installing another Navien boiler fired by propane (he recently installed another to separate out the hot water system for the apartment upstairs), that will connect to a pin up radiant system for the full first floor heat. I would do a bunch of the pin up install and insulating to keep costs low.
2. Using the existing ductwork and furnace fan, install a hydro coil which would also be fed by a new Navien boiler. This option is quite a bit less expensive (and less work on my part).
I’ve read a bit here and elsewhere on how pin up radiant may be a good option for old, drafty homes. I haven’t heard so much about the hydro coil option and whether that would make more sense. I do plan to upgrade the envelope over time, but it will be a slow process, and won’t happen for a while. I’m a self-employed architect, and finances are an issue, but I want to keep energy efficiency in mind as I upgrade, so I’m willing to pay a bit more for a more efficient system…of course, understanding that I do need to get some of the worst case drafty areas fixed asap. One concern I have is with the constant energy needed for the circulator in a pin up install, but maybe I’m not seeing the forest for the trees. Any input would be appreciated.
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Replies
Re: changing from oil to propane: Per gallon, burning oil produces about 40% more btus than propane (135,000 vs. 93,000). Here in Maine, a gallon of oil is about the same price as a gallon of propane.
Prices look to be close to each other in VT as well but as you pointed out you get substantially more btus from oil.
https://publicservice.vermont.gov/content/retail-prices-heating-fuels
$3/gallon propane works out clost to $0.10/kWh electric equivalent.
If your electricity cost is near that, heating with resistance heaters would be similar cost but MUCH cheaper install.
Your lower operating cost option is to replace the existing air handler with a heat pump.
Something like a Mitsubish SVZ-KP18NA mated to a MXZ-3C24NA2 with a wall mount head in the basement for heat, should get you much lower operating cost and for a slightly more expensive install.
Make sure to do a heat load calculation on your space post insulation upgrades, for these multi splits, you need to get them closely matched otherwise the efficiency will suffer. My feeling is the MXZ-3C24NA2 is already over sized.
If you have winter time fill up data, you can check your existing heat load by following the steps here:
https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new
You don't need to wait for the energy audit to know that you need to air seal and insulate the basement. Read the articles here if you haven't already, and start taking on that task. At least start the design, specification and finding contractors part of the process so you're ready to go. If you do a good job here, you can save 15% or more on your heating loads (and costs).