AC/HVAC replacement for house with gas radiant heat and partial AC
I can use some help to decide on my HVAC replacement.
We bought the house last June. I’m a first time homeowner. The 1920 house is in Zone 5a, 2500 sq ft in two floors, plus a basement. The house is heated with a gas burning boiler and hot water radiators. The basement has two radiators.
Cooling on the second floor is handled by an air handler in the attic sending air via duct work. There is no duct work on the first floor. The first floor living room has a wall air conditioner.
Both the air conditioners are old. Probably 20 years. Last summer we were happy with the cooling on the second floor. But the first floor felt warm on 100 degree days. I would spend $4000 to $5000 to add cooling to the first floor.
We plan to live in the house for 7 years. This is an aspirational goal. As renters we moved every 3 years. I want to electrify the house to reduce my carbon footprint. Over the 7 year period, I’m willing to spend $5000 more to heat the house using electricity.
A local HVAC contractor assessed my house and performed a load calculation. They gave the following quotes. (Attaching the quotes and load calculations)
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A 48,000BTU mini split heat pump to heat and cool the house. Replace air handler in attic with 28,000 BTU, with a blower coil. Add two mini split heads (12k BTU and 7K BTU)on the first floor. This would cost $26,000. The contractor said I would need the blower coil for the really cold days.
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Keep the boiler heating system. Replace the second floor air conditioner with a 29,000 BTU unit for $11,000.(Another HVAC contractor who didn’t do any load calculations gave a quote for a 18000 BTU / 1.5 ton unit for $8000). Add a mini split unit for the first floor for $5000.
The house is very leaky. A blower door test was .75. I’m air sealing the rim joists and whatever I can. But with the age of the house, I don’t have high hopes for making it tight.
I’m leaning towards option 2. But I’m sad that it is so uneconomical to electrify the heating of the house. Do you have any suggestions to electrify my heating for less? Or is it better to invest the money in tightening the house?
Thank you reading this. I hope you and your loved ones are doing well.
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Replies
Silk purse from a sow's ear. Don't drink the Kool-aide. Air seal and insulate. Run the equipment you have until it fails. Add some ac to the first floor. Window ac are much better than they were in the past, lighter weight and durable, also much less expensive. Put in some mini-splits if you must, much more expensive. Get you home comfortable, save your money, plan your move to the house you really want.
Double check the heat loss using this: https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new.
Most bottom up heat loss calculations are total junk and are wildly oversized. However, your boiler’s usage is based in reality.
I think you’re mixing two purchases here, which is confusing things. On one hand, you’re considering electrifying using a heat pump (I did the same, zero regrets). On the other, you’re replacing an old AC unit. Now, you can replace the AC with that American Standard - however it doesn’t cost another $15k to electrify because that American standard unit isn’t in the same league as a modulating cold climate heat pump - it’s a single stage unit. The apples-to-apples comparison would be comparing against the AS Silver 16 Heat pump, which id expect to come in much closer in price. That’d get you probably 80% of the way to electrification. You’ll have to decide if the other benefits of modulation are worth more.
Next, you’ll decide on low temperature heating - that could be that Mitsubishi (double check if you need resistance backup), an AS with resistance or the AS with the boiler as backup. Either way, the current AC won’t last forever, so you’re dealing with a minor upcharge for a heat pump.
The first floor is more subjective - either adding ductwork or a ductless minisplit will be expensive. It may or may not be worth it to you to ditch the window units. Much of the $15k difference comes from the two downstairs units.