I can’t comment on price but if you want control with all these zones, then mini splits seem the way to go. I suppose HPs if you will need heating. Of course I would want the old system decommissioned and removed. Electric service will need to be reviewed if any upgrades are required.

TD

Does the duct work have easy access from the attic, basement, or crawl space? If it does then I would lean towards replacing the ducts and installing a central system with a heat pump. A total of 5 zones for a 1600 sq. foot house is not practical. The zones become too small. You may be able to create two zones, and possibly three. You have to find an installer who is good a zoning, which in some areas is difficult to find.

I highly doubt you will be able to install 5 zones with mini splits for under 20K in your area. You won't know until you get some quotes.

Ductless is not going to offer “air purification” or lower noise. With ductless, you have a blower in each “head.” The air filtration is just the basic dust-filter like is on a portable AC. As others have said, 1600ft ranch is too small for 5 zones. Probably you’re looking at bedrooms on one zone and living areas on the other. But you shouldn’t really think of it like that - orientation matters most. Consider the heat gain at various times of day. If one bedroom is on the East side and one on the north side, the East bedroom is getting cooked while the north bedroom is experiencing little heat gain.

Mini-split doesn’t necessarily mean ductless. They can be hooked up to small or full-size air handlers. You could do two separate mini-split ducted systems - one for the bedrooms and one for the living areas for example. This will likely give you the best efficiency and comfort. Mini-splits don’t modulate nearly as well when multiple heads are connected to one compressor.

A central air system is tougher to install but since you've got the ducts, it may be cheaper than installing mini-splits. Mini-splits are great for efficiency though, especially because you can use them in specific rooms on an as-needed basis as you specified. Best to talk to your HVAC contractor and see if they can give you tips/quotes to give you more specific info!

Twintech Heating & Cooling

https://twintechheating.ca/

Thanks for the comments everyone!

Based on the comments and what we've read, we are leaning toward ductless split with 5 zones now. We got our first quote for a system like this and it came in at $21K.

We also found the old system is trashed and would cost about 17K to replace. It still wouldn't support multiple zoning at that price.

Looking at websites like this https://www.acwholesalers.com/LG-LMU600HV-5-PT-UQC-5-LCN128HV4-NG/p68160.html or https://www.acwholesalers.com/Mitsubishi-MXZ-8C60NA-U1-5-MLZ-KP12NA-5-MLP-444W-AD/p82840.html it seems like the units themselves can be bought for cheaper online at ~$6-10K. Anyone have experience buying the AC system online and having it installed by an HVAC person?

Insist on a manual J heat gain/loss calc. The smallest size head I’ve ever seen is 7,000 btu. In the size rooms in a 1600dt ranch that will be grossly oversized and you will end up with poor efficiency and poor humidity control. With multi-split systems the condenser modulates but the heads don’t. They are either on or off. You could easily end up with 70-80% humidity at night which means cold and clammy.

Ask about slim-ducted mini-split. You could get 2-3 zones that way with much better load matching and comfort. Multiple small air handlers that each serve multiple rooms attached to one outdoor unit. This would also let you serve the bathrooms. Total cost should be similar to 5 heads.

If your aim is for zone control, then a ductless system is better as central system is for an entire building as the name implies.