Dual fuel heat system for new build??
I’m just starting to build my retirement home here in coastal Maine (zone 6A). House is 1400 sq ft., with a conditioned crawl space. Budget is $350,00. Attic insulation will be R-60, walls likely in the R-32 range. I’m trying to decide on an HVAC system, I do like the benefits of a dual fuel system..and have two quotes. One at $35,000, another at $30,000. My goals are efficiency, air quality, noise, low maintenance. I’m also considering adding solar panels at some point. I’ve also thought about radiant (I’ve had in the past, and very happy) and mini split air conditioners (one each of the two bedrooms and perhaps a ceiling unit in the living/dining room. I would love any feedback on this matter. I’m a home owner, not a builder, so please keep it simple….if possible. Thanks
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Replies
"Please keep it simple."
OK -- use a single fuel (electricity). After all, if the electricity goes out, almost all types of heating and cooling systems won't work (except a wood stove).
Use a combination of ductless and ducted minisplits to provide heating and cooling. Done.
Make the house as tight as possible.
Make sure the installer does what's called a Manual J -- it's a computer model that calculates heating and cooling loads. Don't let him rely on rules of thumb or his experience. It is depressingly common for HVAC systems to be mis-sized, which results in poor economy and poor comfort. If you have to, hire a separate mechanical engineer to do the Manual J.
Post here what the installer recommends.
I’d go with a ducted heat pump! You’re probably in the 24kbtu to 30kbtu range so options are plentiful. Ductless heads in the bedrooms will probably be close in price (I’d expect ~$5k/head) but are less desirable because of noise, air quality and maintenance - exactly what you mentioned as important. I have both because of ductwork constraints in an old house and ducted is so much better.
You’re in a cold climate so you can get a higher end cold climate unit (variable capacity is awesome if you can afford it) or a lower end one paired with a beefier backup.
Radiant would crush your budget and doesn’t include AC or filtration so I’d pass.
I'm not sure I'd go with inverter technology yet. How clean is your electricity? I'm leaning towards multiple single head air source heat pumps, but I want my propane/ng furnace for super cold days and for when they flip the switch on the price again. If you have a unobstructed view to the South, you may want to consider passive solar.
“mikeolder | Jun 26, 2023 07:24am | #4
I'm not sure I'd go with inverter technology yet. How clean is your electricity? I'm leaning towards multiple single head air source heat pumps”
What are you talking about? Every miny split has a variable speed compressor with an inverter running it.
Note inverters are very common in homes today every front load washing machine runs an inverter and many refrigerators even the motors in my dishwasher uses an inverter. The fans in the computer you are sitting next has an inverter. Every electric car has a huge inverter.
You should know the inverter has a kissing cousin called the switch mode power supply SMPS it makes even more electrical noise and is a thousand times more common.
Walta
I don’t see the point of a dual fuel in a new build.
I say pick one horse and ride it.
Fuel prices very by location but generally
City gas is often the low-cost highest comfort option.
If you can’t get city gas air soured heat pump is general next.
Propane and oil are next.
Electric resistance is last.
Ground sourced heat pump would be almost last given it high install costs.
You should do the math with your local numbers.
My air sourced heat pump provides 99% of my heat and the resistance kick in when it is under 6°F as a supplement with the heat pump still doing most of the work with a COP of 2.
Walta
Thanks to all for the replys, it's very helpful!