I have a question about units placement in my split level house. One unit will be in the living room and the other unit will be in the master bedroom. I am wondering if the cooling/heating from the bedroom unit will help with the adjust bedroom which is a home theater. Due to cost concern (3rd unit in downstairs) I currently don't plan to add another unit in bedroom 2. Please see the picture attached.

I am wondering if the cooling/heating from the bedroom unit will help with the adjust bedroom which is a home theater.

Very unlikely. Your normal flow pattern would be from the MBR into the Master Bath, primarily because of the exhaust issues. It just won't go from corner to corner like that unless you had a superinsulated home and possibly, vented the common wall. It might even take some mild power assist. You haven't told us where you live. You might get it to work during the daytime by opening all the doors and blocking the hallway with that closet door, but if you didn't have better than average insulation or live in a mild climate, you could be out of luck there, too.

consider putting the unit above the door to BR2 where it will blow into the hallway and into all the bedrooms and the bath

Someday someone will make a mini-split that vents to both sides of a wall. Hopefully with some kind of hi/low design that blocks sound.

How are you going to deal with heat in the media room and kitchen? Whats going to happen when you shut a door where no mini split is present? If you have a computer or big screen TV and stereo equipment in the media room its going to be like a sauna room...

Or will you just deal with Hot spots in your home?

So if the indoor unit is not installed on a wall facing outside, should the pipes run in the attic or inside the room along the corner of the ceiling? I think it's not wise to run it in the attic because it can get super hot in summer. By the way, I live in upstate NY so I will actually use it for heating much more often than cooling, lol! The attic has about R50 cellulose, not sure if that's above average, but walls are just regular 2x4 w/ fiberglass. Luckily the window in BD2 is facing north. I have a separate boiler which will be the main heating source, the mini split can assist when the outside is above or at freezing, this will be my first time using it so I will see how to best balance the two heat sources out. Any tips for using two heating sources in terms of the indoor units placement? I know next winter is still some months away but it never hurts to plan ahead. :D

The attic has about R50 cellulose, not sure if that's above average, but walls are just regular 2x4 w/ fiberglass.

The "tightness" of the home is even more important than the insulation values. If you have a leaky home, or windows that aren't so good, it just isn't going to work well. North facing windows are difficult for heating, but can help with cooling. You have to get the heat loads down in the rooms if you want them to be without a point source of heat or cooling.

I just did some measurement, the ceiling is not high enough to mount indoor unit in the hallway above the bedroom door. The closest place to the bedrooms would be in the hallway facing the bathroom door, so maybe I will just focus on one room and deal with the other one with a fan or something.

The "tightness" of the home is even more important than the insulation values.

Generally not, although it can be true is some very mild climates or extreme cases.

You must think of a single-head mini-split like a window mounted air conditioner i.e. one head one room, don't over-size and expect more.

We have a single Mitsubishi unit placed at the highest point in an open three story farm house. All is good until you shut a door.

All is good until you shut a door.

Maybe this is the "common sense" a certain splashy poster is talking about. If you are counting on a room-mounted head to condition adjacent areas, you either have to keep the door open or design additional considerations in. Some of these might be to leave larger gaps under doors or provide ceiling level venting to effect transference from one room to another. Simple heat loss engineering can also help tell you if a room will gain enough heat through adjacent walls to make up for the loss elsewhere.

And, it appears as if it will be necessary to repeat this over and over, but having a tight home, good windows and proper insulation is key to using ductless minis in new construction. I am beginning to doubt that people understand what those simple standards mean. I recently visited a half dozen new homes offered for sale. Not a single one was tight or well sealed, despite new energy codes.

those "simple standards" are new and pretty complicated to someone unused to thinking in those terms. Once you've done some of that it becomes much easier, but it is a hurdle that must be overcome.

Once you've done some of that it becomes much easier, but it is a hurdle that must be overcome.

More and more people seem to be able to talk the talk, but I think the hurdle that must be overcome is what's happening in the heads and hands of the people doing the actual work. I recently oversaw the installation of two exterior doors by two tradesmen. I explained to them that two simple things were necessary here; thermal break and air sealing. They simply couldn't do it. Therefore, I formulated the plan for them and let them go to town, but I had to inspect and correct about every 40 minutes for the entire day. The problem appeared to be that they simply couldn't understand air sealing or thermal transfer.

Precisely, using mini splits in old or new buildings NOT constructed to the new standards can be problematic. Using mini splits in buildings actually constructed or to modified to the new standards (e.g., well insulated/sealed envelope with adequate internal air flow) will work very well. Unfortunately not many GCs or subcontractors have stepped up to the new standards yet and building authorities have not become vigorous about enforcing these new standards yet.

Right. At the risk of beating a dead horse, I don't see any of these tight, well insulated homes being completed, and I can't find tradesmen who know how to do it. Conclusion: It ain't being done.

State and local Governments have a propose, but in most cases they work against us but one way they could help to solve some of the labor problems concerning green building construction and methods, is for states or on a federal level make it mandatory that contractors and employees go through a general green building courses to become familiar with the requirements and become certified. If you have no certifications for the work being performed, you simply are not allowed to work.

The building inspectors not going to watch over your job and make sure its done perfectly to code .... there are many examples of failures on the city's part in that arena. And most builders could care less about how tight a home is unless its a custom home with tight specification which he is bound to by contract even than you still have to watch him like a hawk.

And I certainly don't have the time or patience to hold a sub-contractors hand which is in business cause he thinks he know whats going on, and still have to tell him how to do his own job.

those "simple standards" are new and pretty complicated to someone unused to thinking in those terms.

Agreed, the average hvac installer is going to need software to predict exactly how much colder a back bedroom will be under what circumstances. Then the homeowner can decide if xx degrees is too much of a drop and requires another mini-split.

There are to many cons involved to be using mini splits in newly constructed American size homes.

I have very much come to the conclusion and classify Mini splits as an Mid-End efficient product with major comfort design issues.

Great for room additions and such ect .... but for a large new home using strictly mini spits, would be a major mistake from a High end perspective.

At the Northeast Sustainable Energy Association meeting last week some of the top scientists and GB experts came together to discuss numerous topics including on how ductless mini-splits can and are used to heat/cool an entire home.