Central A/C or mini-split heat pump?
November 7, 2021 4:19 PM   Subscribe

We have a Seattle house with a gas furnace and would like to get it air conditioned . I have some questions.

(We currently have two rooms with window A/Cs and two with portables, but would like to improve our A/C)

Our house is two stories, about 2000 square feet total. Downstairs is a great room, bathroom and family room. Upstairs are three bedrooms and a bathroom. With the furnace, the downstairs is heated fine. But the upstairs, when it gets below freezing, the furnace doesn't deliver enough heat to the bedrooms. A previous owner installed auxiliary electric baseboard heaters to handle it. Those bedrooms are have large windows and high ceilings. I don't know if the issue is the ductwork, the sizing of the furnace (it was installed new before we moved in 10 years ago), or something else.

Normally, I'd think central A/C would make sense, but with the heating issue upstairs, I worry that an A/C would have problems keeping the upstairs cool enough (that is, if the issue is the ductwork).

If we go with mini-split, I think we'd have two downstairs (in the great room and family room), and at least one for each of the three bedrooms. And we'd be able to use them instead of the more-expensive-to-run electric baseboard heaters when it gets too cold for the furnace to keep up.

• Does central A/C seem like a bad idea with the issue we have heating upstairs with the current furnace and ductwork?

• If we go with mini-split, would it make sense to have one in the upstairs hallway as well to keep the space outside the rooms cool as well (that is, the bathroom, halls and stairwell)?

• Any recommendations for Seattle HVAC contractors? I'll be calling some soon to get estimates.
posted by ShooBoo to Home & Garden (9 answers total) 8 users marked this as a favorite
If you have ductwork already I think you should use it. You can get a ducted heat pump that is just like a central A/C except it also heats in the winter. You can then use the money you save by not installing a split system to fix whatever the underlying issue is with the upstairs.
posted by goingonit at 4:45 PM on November 7, 2021 [1 favorite]

We swapped our gas furnace with a split heat pump. We put the split unit upstairs in the kitchen, which is already noisy and hot in the summer. The vent work upstairs did not have much capacity, so that's where having the split unit made sense. Having AC has made a world of difference as Seattle has warmed up somewhat the last five years. We went with Ballard Natural Gas, but I'd shop around for quotes. We had some problems with faulty electrical installation and subsequent service has not been great. The rewiring that was done by them needed a $1000 repair by a separate electrician.
posted by They sucked his brains out! at 4:49 PM on November 7, 2021

Best answer: We got minisplit AC in our old Seattle home a couple years ago and it has been absolutely fantastic. I would absolutely go with that if you are dealing with a combination of different heating technologies and odd old house issues.

We got just one pump and two units, one in the downstairs bedroom and one in the upstairs bedroom, and they actually cool our entire house in summer as long as we leave our bedroom doors open and use light blocking curtains on the south side of the house. The downstairs unit is a bigger one, and the upstairs one is smaller. I was worried the smaller unit couldn’t handle the trapped heat upstairs but it effectively cools the whole floor and even the stairs up. The downstairs unit just needs have been running during the day steadily to cool the whole floor, though if I had unlimited money I would have installed another small unit on the other side of the house and put a small one in the bedroom too.

The one problem we have is that in my room I want it about five degrees warmer than the other bedroom, but since they are on the same pump we can’t do heating in one while cooling in the other. We are learning to compromise in spring and fall, and mostly we want air circulation rather than a specific temperature so a little fan makes a big difference.

The company we worked with is actually Beacon Plumbing. They were the only folks who actually responded to and returned our calls. It is hard to find skilled people with open slots for this kind of job right now! They were solid and had the inspection, electrical, and installation done quickly once they confirmed they had the units, and we took their suggestions on placement and size and it’s been great. I suspect it was maybe a little expensive but as nobody else even got back to us with a quote I don’t have much to compare it to.

Our power bills have dropped kind of dramatically since getting the minisplits, even when we also ran big air purifiers constantly during smoke season. We have Mitsubishi units and they are pretty easy to keep clean, rather quiet, and clearly efficient.
posted by Mizu at 4:58 PM on November 7, 2021 [1 favorite]

Best answer: Check with Ballard Natural Gas and Glendale Heating. They are both booking a couple months out for sales visits & quotes, so get on their calendars now, and time will come along soon enough. Evergreen and Greenwood Heating & AC were also recommended to me, but beware, they are even more busy and booking sales calls out 6 months in advance last time I checked. The estimate I got from Ballard Natural Gas was for a Mitsubishi heat pump & air handler, and no alternatives, they 100% prefer to install that model. They may advise you to get central AC, and replace your gas furnace with an electric air handler. And even though their business name includes "Natural Gas," it seems they are steering people toward electric these days.
posted by oxisos at 5:04 PM on November 7, 2021 [1 favorite]

Heat pumps are also the best choice in terms of climate change.
posted by pinochiette at 6:14 PM on November 7, 2021

I tend to agree with goingonit: I love mini-splits, but in this situation I'd recommend getting the ductwork checked out first to see whether there's an obvious and fixable issue, and whether it can be reused with a central ducted heat pump / air handler. Less tweakable than multiple indoor units, but also a simpler installation.

If you do go with the mini-split option, five or six units feels a little like overkill, but the pros would be better judges of that.
posted by holgate at 6:25 PM on November 7, 2021

My recommendations are this:

1) You need a pro. Get a good HVAC contractor to assess the entire state and needs of your home. They may also have some other suggestions like blow-in insulation in the attic, etc, to reduce the energy needs of your home.

2) I think your minisplit-only plan has too many indoor units. You don't really need that many. I don't recall the BTU output of the unit in my old office, but it could get the ~200sqft uninsulated room from the 50s to the low 80s soooo fast (if you take a nap and forget it's on TURBO), and same for cooling. I'd arrive in my office at any time of the year in Portland OR and I could get it to 70F in less than 20 minutes.

The two 12k btu units on the ~1000sqft (but vaulted 12-15ft ceilings) main floor of my house get us from 60F up to 70F in under 20 minutes, and then the heat rises to our bedrooms and they follow shortly thereafter. My family in Boston has one head unit for their entire upstairs with about 4 rooms, and it keeps them all very comfortable all year.

A friend has a poorly insulated and highly sun-exposed 3-room upstairs where they sleep, is considering a minisplit, and I recall the calculations we did put us ~12,000btus for the whole floor.

3) One option to consider is a an outdoor heat pump with the evap in the place of your furnace, using your existing ductwork. You *may* be able to have that and several smaller head units upstairs running on the same heat pump.
posted by MonsieurBon at 8:10 PM on November 7, 2021 [1 favorite]

I agree with the comment above that you need a pro (and multiple estimates) to find what would work best in your house.

We used Washington Energy Services for a very similar situation, and learned that the size of our backyard, together with a Seattle noise ordinance, essentially made the decision for us. We ended up with a heat pump and just one strategically placed mini-split unit. It works great for cooling our house in summer, so long as we leave the doors open to the bedrooms. A traditional A/C unit would have violated a city noise ordinance unless we had it installed right in the middle of our backyard.
posted by pril at 2:37 PM on November 8, 2021 [1 favorite]

Response by poster: Thanks all. I've made a few appointments for an estimate, including Glendale and Greenwood (who will do it when they're out to our house for a scheduled furnace maintenance in February). Almost everyone I contacted was booked completely for estimates until February, although I found one (Cardinal) that had a slot open at the end of November.

Someone at my work compiled this Google spreadsheet of a number of HVAC contractors and their ratings on Google/Yelp/Angie's List/Home Advisor.

Also, I have a friend who now works in commercial HVAC, but used to work for Ballard Natural Gas. He does not recommend them (and he doesn't have any recommendations for home A/C installation).
posted by ShooBoo at 9:17 PM on November 10, 2021 [1 favorite]

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