Probably not a good idea. The minisplits are designed/engineered to be used as is. If the 600 sq ft reno is more than one room, I'd go for a standard 1.5 ton ducted split system heatpump.

It needs to be a whole house system 1600 sq ft downstairs with the 800 sq ft upstairs in the former attic.

There isn’t any cooling in the house except old window units which will be discards. and finding space for ducts will be challenging. Can use knee wall space in the 800 sq ft attic as we finish it but can’t add soffits etc in the downstairs 1600sq ft without disfiguring the rooms. Also with temps of 6F for lows this week here in VA and in the 20’s at night for most of Nov and Dec and now January at night we need to add a new furnace for heat and rely on it not a heat pump for the heat except on mild nights with this cold. Thank you for any suggestions of how to duct a house!

Attic space so far by previous owner.

Beautiful doorways in downstairs with 8 ft ceilings.

I have a house slightly older with open attic space.  My longterm plan is to remove the chimney and use the chase for supply and return ducts. The return will be an open grate dormer side of the space. The supply will run under the floor and come up back side of the knee wall to branch off for three or four wall registers.

Maybe they're referring to a low wall/floor standing minisplit unit? They look not unlike traditional radiators with covers. You need to be careful about any further covering because doing so could diminish their effectiveness.

I'd guess they're suggesting a minisplit approach because it's less work with a retrofit to run the required pipes than to run ducts - the pipes are often placed along exterior walls or simply along (and not inside) interior walls. You may want to check on that.

Rather than speaking with just a contractor and a plumber, I'd call in an HVAC contractor or two to get their views. Exposed ducting, or those covered in soffits, can be installed too.

Good luck

yes low wall / floor standing exactly! thanks i am definitely getting hvac folks involved but want to get info first about options. I have had to get hvac in an 1890 remodel and then in our current 1910 remodel now the 1956 remodel. This current house has no duct work anywhere unlike the last two remodels so all new territory. We have a studio in our back garden for DH and he had a minisplit put in . It works great and he loves it but its a 150 sq ft not a whole house and the equipment sticks out and is unsightly … JMHO!

@Elmer J Fudd thank you will post when I get more answers than questions 😊

I agree with more research i realize its the only solution. I appreciate everyone’s patience with me. I like the look of the floor mount and that is likely what we will do. We will use a well ventilated custom cover so as to disguise as much as is possible without interfering with the air flow. I shall post back with pictures of the application and pricing . It will be Spring /Summer before we get underway with the extensive remodel. thanks again c

I put a floor mini-split unit in my house a couple of years ago because I hate the look of the wall mounted ones, plus I have very little wall space in my home that is not windows, so limited places to hang art. I didn't want that space used for a mini split. I recently decided to add a 2nd unit and noticed they now sell ceiling mounts, too, which would have worked great for me as they would be hidden behind large beams - post and beam construction. But since I have a two story home, he said it would be very difficult to install on the first floor, that they work best in the top floor where access to the ceiling is unfettered. I was looking at Mitsubishi. eta: I was worried about how it would look, but it's low enough that it's easy to arrange the furniture so it's behind the arrangement, which doesn't interfere with the flow. They have vents that rotate to adjust the air flow, so I'm not sure how a cover could work.

Do you have a picture you could post of your unit in your room? You have only had one for your whole house ? Any further info you can share about the sq ft that it conditions etc would be great! Thank you @Olychick.

My DH has a wall mounted one in his studio in our back garden. He loves how quiet it is. I see the louvers moving slowly but a cover would not touch those. Have you seen radiator covers? They can be any size or design . I’d love to see your unit.

Trailrunner, I live in the PNW where air conditioning has traditionally been rare because we so seldom need it. The nights always cool off, so open windows usually do the trick. With climate change that is probably all going to change. My bedroom is upstairs and is a large open room with 3 full walls of windows, so it's like sleeping on a screened porch in the summer. I am right on the saltwater, so get a nice breeze in the summer evenings. But, several years ago, when forest fires caused the air to be choked with smoke, there was no way to have the windows open. I have air purifiers, but on hot summer nights, if I couldn't open the windows, it was stifling. So I had a mini split installed upstairs solely for those few weeks each year that I might need to keep the windows closed. This past year, when the temps rose (for the first time into the 115 range), it saved my life! The downstairs is all windows, too, but the summer sun does not reach any of them, so it remains cool, barring those extreme temps. I seldom use the mini split for heat, because I like it cold in my room but have a few times when I was chilled.
It is so quiet and unobtrusive and has lots of features I can't seem to figure out, lol, like a sleep timer and scheduling. But I love the remote that I can use from bed. I'll take a pic tomorrow morning and post it here. Be sure to check out the ceiling units. My outside unit is not too large and definitely not too ugly. It sits on the side of the house that isn't really seen from the garden or the house and is tucked up against the house. I don't think it's noisy - but I only would have it running when the windows are closed so wouldn't hear it anyway.

Thank you! my DH’s sister lives in Bellingham WA out on Lake Whatcom right on the water. A few years ago when they had 100 degrees every day they got central a/c!! They get very very cold wet weather in the Winter and a fair amount of snow as well .You are lucky that your weather sounds more moderate.

The ceiling units are 27” square opening and with a 1956 house with 8 ft ceiling they would be very intrusive visually. We will do well with just one unit for the attic room which is one long area the depth of the house front to back 34’x 11’. Then we can decide how to do the downstairs . I have a 1910 house and we have radiators which I will never remove. They are the best heat.

I look forward to seeing the unit. Your home sounds amazing. Thank you for the info. I really appreciate it. c

I finally remembered to take pics of my floor unit; hope it helps.

this was the mini split ceiling unit I was considering...it doesn't appear to hang down much at all:

@Olychick thank you so much. After thinking about it one floor mount would be what we would have in the attic space. It would easily cool and heat the area as it will be all open except a bathroom door and we can put an electric wall heater in there. As far as the downstairs it would be as your installer said a problem to put ceiling mounts in that old 8 ft ceiling with no access from above. So we will have to get professional advice and see what will work . I thank you for all your help ! c

c- I thought this might interest you. I just had a rep from a local company do a bid to add a second Mitsubishi MUF-ZKJ12NAHZ Single Indoor unit ductless HeatPump - this one on my main floor living area (the other is upstairs in the bedroom). We recently had quite a frigid spell with temps down into the single digits, teens and low 20s. Unusual, but not unheard of for us. I posted on this site my worries about the heat pump being used (or even probs if I turned it off) during such a cold spell). The company that installed it was closed for the holidays then for the terrible snow storm we had, so I tried to get info on the internet. I saw things that said below 40f heat pumps aren't really energy efficient and recommended using auxiliary heat sources. Some nice people here answered my questions and allayed my fears about damage to the unit from extreme cold - even if I didn't use it.

But today when I talked to the Mitsubishi rep, he said that the mini-splits are (at least these models - which he termed Hyper Heat) designed for more extreme cold than regular heat pumps and are efficient down to about 5f. I'm sure your pros will cover all that with you, but I thought I'd pass this along.

Thank yyou for the info. I have had a heat pump in our 1890 house in AL. We had extremely cold weather there on occasion over the 15 yrs in that house. He is correct they are terrible in cold weather and have a strip heater that comes on and defrosts it in cycles and uses huge electricity. I hate the things.

I had looked up whether mini splits were ok in very cold weather when DH was getting one installed outside in his music studio. It does great but its too big for the tiny space so in Summer he has to use a dehumidifier . That is their big failing they cant make a really small unit . But it does great for heat.

I am glad to hear him verify that info. I will report back when we get the reno started. Thsnk you! c