Aside from the publication of Steve’s W2 and social security number, this adventure’s biggest surprise to date has been — without a doubt — the complexity around choosing the right mechanical systems for Dash Landing.
Not only are decisions around heat, hot water and air quality critical to “livability,” but recent changes in technology have added far more options into the mix. And as we’ve come to find out, it’s often the consequences of interplay among decisions where the true challenge lies.
We had four basic criteria for our mechanical systems going into the process : 1) We’d like them to be dependable and simple to operate. 2) We’d like to hedge against future financial exposure. 3) We’d like to minimize our energy footprint and fossil fuel consumption and 4) We’d like them to be relatively affordable.
Our first line of offense is the structure itself. We agreed with Rob early in the process that our best investment was going to be a tight, well-insulated exterior shell. And after looking at a number of options including flash & bat and dense pack cellulose, we’ve decided to go with 4″ of closed-cell foam as our primary wall insulation and 8″ in the roof assembly. Barring a last minute change, our window selection is the Anderson “A” series. The “tight” part will come from the two blower door tests required in the construction bid spec :
“Blower Door Testing: Contractor to coordinate, schedule, and perform two (2) certified blower door tests by an independent party. Tests to be scheduled at (1st) post-insulation/pre-drywall, and (2nd) prior to substantial completion. Testing to achieve the following performance ratings: Test (1) pre-drywall = 1.5 air changes per hour at 50 pascals. Test (2) prior to substantial completion = .5 air changes per hour at 50 pascals.”
Maybe not at “passive haus” standard, but definitely a well-insulated structure. So how to heat it?
Option #1 and the “baseline” in the bid is radiant floor heat via a high-efficiency condensing propane boiler. We’d get hot water through a tankless Rinnai, again through propane. We’d maintain air-quality through the use of an HRV system.
Bullet-proof. Cost-effective. Easy to operate. Plenty of people in the area that could do any possible repairs. We already have Viessmann ski swag.
On the other hand, we’re not keen on being overly dependent on propane. Not only a fossil fuel, but a relatively expensive one in Maine. And given our experience with electricity to date, we’re not holding our breadth on getting a natural gas line across Mast Landing any time soon.
Option #2 is a bit of a surprise. We’ve been reading about evolutions in the heat pump industry and Rob introduced us to a local vendor who believes our house is tailor made for a Daiken Altherma. A bit of a “swiss-army knife” unit — not only would it generate heat for the radiant floors, but the same unit would also handle hot water. As an added bonus, the unit will also handle air-conditioning via a ERV system. A portion of the unit would be installed in the basement, another portion would be outside. Early heating load calculations indicate that we’d save $1,200 a year over the propane baseline.
Radiant heat, hot water, air conditioning and save money? Sounds a bit too good to be true, huh? But it’s the references that we find most interesting. These units are used in cold climates all over the world and the feedback is overwhelmingly positive. When someone in northern Sweden raves about the device, it gets your attention. Dependable and reliable. Good to -4F degrees and comes with a back-up heater that kicks on at low temps.
At the same time, it’s a heat pump. And anyone who has grown up in Maine remembers the last time that heat pumps tried to make it here. Let’s just say that it didn’t go well. (Think “noisy tinker-toy.”)
Option #3 is geothermal. This is where the interplay among decisions has an impact. Our philosophy of “insulation first” and resulting low heat requirements make the payback on geothermal’s high upfront fixed costs a challenge. (Drilling those wells isn’t inexpensive.)
But we’re still intrigued. When done right, we can’t help but believe that geo would be the simplest. Everything installed in the basement. Sure, it’s another kind of heat pump, but without the low-temp issues.
We’ll know a lot more about geo’s feasibility when we get pricing back next week. But after talking through a myriad of options including oil, wood pellets and nearly everything else imaginable, it’s going to come down to one of these three choices.
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