Heat Pump Retrofit Options for Pacific Northwest Homes
I’m one of a few hundred thousand homeowners in the Pacific NW (Climate zone 4C) currently getting quotes to add air-conditioning to my house now that prolonged wildfire smoke and heat waves have set in. I’m eager to use this opportunity to switch from gas furnace heating to heat pump heating for carbon’s sake. I haven’t been able to find a recent article on GBA that provides a lay of the land here (inverter vs hyper heat vs not?), and includes major pros/cons of adding a central HP vs minisplits.
My main question is why we can’t get the low price, high efficiency and wide working temperature range of a mini-split system in a central system? Based on the first quotes I’ve received, it seems the domestic suppliers of central HP systems can’t make their heat pumps work below freezing. I thought we solved that problem decades ago. Mitsubishi offers a hyper-heat central system, but it’s twice the price of anything else. So for my two-bedroom 1950 ranch in Eugene, Oregon, which I’d love to make fully electric, I’m contemplating (3) wall hung mini-splits in order to ensure I’m using a high-efficiency heat pump for all my heating, and tossing my 15 year old high-efficiency gas furnace and ductwork.
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Do you know if your ductwork is well sealed? Where is it located? Did you get a quote on a ducted Mitsubishi unit, if so which one?
For domestic brands, try Enertech or SpacePak. If Canada is okay, Artic and Nordic are good cold climate heat pumps. Chiltrix is also popular. I am hoping that Veissman enters the North American market.
Personally, I would look into replacing your air handler with one designed for either VRF or hydronic coils. That alllows you to use most of your ductwork.
“My main question is why we can’t get the low price, high efficiency and wide working temperature range of a mini-split system in a central system? “
With so many people all looking to replace their systems this year the contractors have no reason to work cheap. If a low price is the most important part of your buying decision you will need to wait for supply to increase and demand to decease so prices will fall.
“It seems the domestic suppliers of central HP systems can’t make their heat pumps work below freezing.”
I agree if you select the lowest cost low efficiency models. I disagree if you select a 17+ seer model with variable speed compressor, 2 electronic TXVs, ECM fan motors and commutating thermostat. I think every brand has a model that fit my description. My Rheem HP heats my house down to 6°F with the strips locked out.
It seems to be a common bait and switch sales tactic to offer very high quote for a mini split and switch you back to domestic brand at a lower price point.
Consider the DIY friendly MR COOL brand equipment from Home Depot.
Thanks Walta. The HVAC guy who provided my walk-through didn't offer such an option when I asked about this, except for the Mitsubishi unit. Do you know if Trane offers a 17SEER option like this which I can ask him about?
I suppose it depends on what you mean by affordable. Just comparing equipment costs, it looks like you can get a 2-ton Fujitsu ducted split system for around $3,500 plus shipping. A 2-ton Goodman 95% efficient gas furnace with AC is around $2,900 plus shipping.
Maybe the question is more rhetorical, like “why aren’t these things more ubiquitous and therefore cheaper?!”, which is the reaction I had when I got a $15,000 quote for a 2-ton Daikin ducted system for my 3-bedroom ranch. In that case, I’m with you.
If it’s pragmatic though, I get that a Mitsubishi Hyper Heat is much higher in price and performance, but it does seem like there are options that are more affordable that get you to the same all-electric point for a price that isn’t much greater than traditional equipment costs. I lived in Roseburg for 20 years, and Eugene for 6, and can’t recall a time when I’d really need the full capacity of that hyper heat, you know?
Thanks all for the feedback. For better context, here is what the HVAC guy gave me for ballpark pricing during the walkthrough (includes electrical):
Central Heat Pumps:
Trane unit that won't work below freezing: $6k - $9k, HSPF 8.5
Side discharge option of above: $10K, HSPF 9.0
Central Mitsubishi hyper heat that will allow 100% HP heating: $20K (!!!)
2-3 Ductless Units: $8, - $12k, HSPF 9.5-11 (up to 13 if 1:1 indoor/outdoor)
1 Ducted + 1 Ductless: $12k, HSPF 9-10
So my question is why is the central heat pump that works below freezing so much more than the mini-split options? I suppose mini-splits have a global market whereas central force-air systems are more of an American phenomenon?
My house is a pretty average 3BR 50's ranch. Supply ducts (insulated) through the crawlspace. Return (insulated) through the attic.
My guess is the contractor is quoting a large PVA model which is quite expensive (~$8k) and then adding a huge markup because he is not familiar with them and doesn’t want to bother so he is trying to make the other options he is familiar with more attractive. There are much cheaper “slim duct” mini splits out there that are in the $2k range from Mitsubishi, Fujitsu, Carrier etc. However these units have lower flow rates and static pressure, so your existing ducting needs to be evaluated.
The correct way to do this is to hire a third party to do a Manual J, S, and D on your home and have them spec the equipment. Then take that to installers to bid. It can be difficult to find a company to do this and do a good job.
You could also use your winter fuel bills to do your own heat load calculation like outlined here. https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new
My guess is a 1.5 - 2 ton ducted mini split should have you covered. If you can get confident in your heat load you can start challenging contractors that give you bids.
I think Kyle is definitely on to something in terms of there being a 'tax' for unfamiliar equipment. I contacted an installer about getting a ducted split system; when he came to my place to give me a bid, the first thing he said was, "You sure you don't want a gas furnace?". And I should mention that I got a Manual J/S/D done, had a site visit by the mechanical engineer to make sure there wouldn't be large issues with the ducting or anything else that would compromise performance. There was no reason not to go with a split system. The installer still wanted to put in a gas furnace after all of that, so I can really only attribute that to familiarity and the added time it takes to install those types of systems.
The lowest bid I got on that type of system was near $12,000 for the Fujitsu ducted system that I linked to earlier in the thread. The nice thing about that particular unit is that it has a full 1 i.w.c. of static pressure available so if your ducts are a bit lacking—and it seems they almost always are on houses of our vintage—then you don't have to start from scratch necessarily.
And like Kyle mentioned, there are other options that may be more economical if your ducting isn't constrictive (or you're up for reconfiguring your ductwork). Changing the ductwork isn't as challenging as I once thought, so don't let that necessarily scare you off. You may find that the cost of ductwork plus that of a lower static pressure system is equal to a higher pressure split system with no ductwork. And again, in houses of our vintage, it seems like the ductwork is pretty terrible, so that may be a good upgrade.
One thing that helped me narrow down the options was Neep's ASHP list. You can search equipment by load and configuration, such as a 24,000 btu ducted system, and it will give you a nice overview of the options. https://ashp.neep.org/#!/
Kyle and Brian, thank you both for these pointers. Super helpful. Agreed, I need to roll up my sleeves and do a Manual J/S/D and better inform myself on the options. Was just trying to avoid it given that my house is pretty much the same as 100,000 others in Eugene. But you're right about contractors bidding within their comfort zone, especially when the demand is so high.
This will also allow me to consider the potential impact of that future Passive House retrofit I've been dreaming about. ;)
Glad to help out.
And you may be able to avoid that Manual J for sizing the equipment. I'd second Kyle's suggestion of doing the heating fuel calculation that Dana Dorsett outlines in that link. I did one for my house after getting my Manual J done, and they were really, really close to each other.
Awesome, thank you.
Ask for a quote for the following models XV 18 XV19 and XV20.
Note the XV19 looks to be a rebranded mini split that can feed Trane's normal indoor unit and has a much better HDPF rating.
Thanks Walta, will do.
I guess it depends what you mean by "work below freezing." Even the bottom of the line 48K BTU Goodman heat pump my parents have puts out about 30.5K BTUs at the 99% design temperature for where they live in the PNW (25F or so) at a COP of 2.77.
It is definitely oversized for the shoulder seasons and the backup heat kicks in occasionally on the very coldest days. But there are no real comfort or short cycling issues and the overall seasonal performance is not bad, at a COP of about 3.25 based on comparisons to pre-heat pump utility bills.
I don't think you really need hyper heat in Climate Zone 4. I have an 8.5 HSPF Trane heat pump north of Spokane (border of zones 5/6). It does fine keeping the house 70 all the way down to about 15 outside by itself (2.5 tons for 2400 sq ft). House is 14 years old with mediocre insulation and air sealing.
The key to keeping the running cost down is having properly sized and staged aux heat so it doesn't come on until you really need it. With PNW electricity prices ($0.065/kWh in Eugene?), I bet it's less expensive to pay a little extra for occasional strip heat use over the life of the equipment than even a few extra thousand for something more efficient. Not sure if your installation costs include strip heat install so that would factor in.
Richard and Ben, thank you for this. I was under the impression the central domestic heat pumps didn't work at all below freezing, but from what you're saying it looks like the may still have quite a bit of capacity in this climate. I will definitely take a closer look at this.
Okay, I've really appreciate everyone's advice. Here's an update. I've calc'd my heat load at 20,000 BTU/hr based on January energy bills using Dorsett's approach. With priorities being: reasonable cost, high-efficiency, and getting rid of my gas furnace, I plan to ask my HVAC guy to quote the following options:
1) Central: Trane XV19 (not sure what indoor equip is best for this), HSPF 11.5 (Also not sure if the XV20i is worth considering).
2) 1:1 Minisplit: (3) 1:1 wall units such as MSZ/MUZ-FS06NA. HSPF 13.5 [Question: I assume it's better to size based on rated capacity at 17F (nearest to our 99% design temp of 27F) rather than max capacity (which is substantially higher).]
3) 3:1 Multizone Minisplit: Something like MXZ-3C24NA2 with MSZ-FS06NA. HSPF 9.8. I really don't like the drop in efficiency with multizone (and the higher carbon footprint of longer refrigerant runs). Not sure this is better than Option 1 or 2 unless it's significantly cheaper.
Given the capacity of the minisplits at 17F, I think I'm okay to go without either hyper heat or backup gas furnace here in Eugene. Sound right?
Note, a ducted mini-split doesn't seem workable, because my attic and crawlspace access points are too small.
Feedback on anything I might be missing?
I wouldn’t abandon your ductwork unless there is a serious issue with it. The Trane can work, but it will cycle and be less efficient compared to a ducted mini split. If you are replacing your furnace I’m not sure why you wouldn’t have room for a ducted mini split, it would go in the same place? If you have a Fujitsu installer near you I would seriously consider an 18RLFCD.
To my knowledge, ducted minisplits are all setup for a horiziontal orientation and don't fit within the tight vertical space my gas furnace currently occupies. So I'm assuming a ducted minisplit would need to live immediately above or below the furnace location in the attic or crawlspace in order to tie into the duct system efficiently. I know Mitsu has air handlers for central systems but I'm told their about twice the price of the Trane system.
I'll check into Fujitsu vendors.
Fujitsu and Carrier both have “slim duct” style ducted mini split air handlers that can be installed vertically. You can check out an example installation here: https://www.greenbuildingadvisor.com/article/getting-the-right-minisplit
Many manufactures make a multi position air handler that looks very close to a furnace. These can be an easy swap in most cases. They are not cheap, but also not much more that expensive.
The nice part about any of these is they are inverter based and fully modulating. Modulating units tend to provide much better comfort as they are always supply an amount of heat instead of cycling on/off. The outdoor units are also pretty much silent. For the extra bit of money, they are worth the cost.
Go to here and select "single zone centrally ducted". You can than use the sliders to match up your heating needs.
For budget friendly, you can look at something like this
Agree with Akos. I was able to do a 1 for 1 replacement with a Goodman HP that was multi-positional from HVACDirect at a reasonable price. I noticed they had a Mitsubishi that looked to fit the same rated for 14 degrees for about $1k more.