thanks, bonnie.

Better have a "lot of extra money." LOL

This is a project that we just had bidded. For our house, a 2 story 1870s Queen Anne, these are the numbers:

New duct work for 1st floor $1000

Central AC unit 1st floor only $1700 (regular efficiency--high efficiency more)

Separate air handler, duct work, heat pump/AC for small 2nd floor since it does not currently have duct work or heat/AC $4000-5000

Of course, your numbers will vary, but that's just what we were told we would need to spend. Our house is about 2200 square feet, 1200 down and 1000 up.

Maddiemom

I guess I have a little more than a little extra. I could go to 10k to get it done properly. Is it feasable to have a good central air system for that piece? My house is a 4 bedroom, 3 story, 1.5 bath victorian with 10 foot ceilings.

The Unico system mentioned is a "high velocity" system, and uses small 2" tubes to deliver the cold air. The tubes can be snaked in the walls, and you can install it practically anywhere. I've heard good things about it from friends who had it installed, and it's certainly less messy to install.

The Mini split system is ductless. It has a compressor unit outside, like a central ac system, and a 3" refrigerant tube connecting inside to a wall-mounted air-handler unit. So, no ducts necessary. It's like having a large window AC unit, but without the noise and vibrations, or the need to haul it in and out of the window every year.

The cost of the Unico system will probably be in the range of $10,000-15,000. If they can do a standard system, it could be cheaper, but usually the cost of building and running the ducts makes it about the same price as the Unico.

The mini-split system would probably cost half that, maybe $3000-5,000 or so, depending on the setup.

Here's a good link for information on a mini split system:

maddie

I'll stick with my window A/C's. They cost so little to run (we run 2, 6000BTU's for a cost of $40/month, and a 8000BTU and a 6000BTU for $50/month) that it would take more than our lifetime to make the expense pay off...

As far as noise goes, the mini-splits are very quiet. You can stand next to one and almost not realize it's running. Much quieter than a window unit.

I don't regret a penny of the cost. I do regret not getting the vent locations in writing. The boss had told me that all vents would be in the walls (where I wanted them) but the installers put 3 of them in the ceilings, which was easier for them, before I caught them and raised h*ll.

Ductless, mini split-system air-conditioners and heat pumps (mini splits) have numerous potential applications in residential, commercial, and institutional buildings. The most common applications are in multifamily housing or as retrofit add-ons to houses with "non-ducted" heating systems, such as hydronic (hot water heat), radiant panels, and space heaters (wood, kerosene, propane). They can also be a good choice for room additions and small apartments, where extending or installing distribution ductwork (for a central air-conditioner or heating systems) is not feasible. Applications in other types of buildings include: school classrooms; perimeter cooling for office buildings; additional cooling for restaurant kitchens; and cooling for small offices within larger spaces, such as arenas, warehouses, and auditoriums.

Like central systems, mini splits have two main components: an outdoor compressor/condenser, and an indoor air-handling unit. A conduit, which houses the power cable, refrigerant tubing, suction tubing, and a condensate drain, links the outdoor and indoor units.

Advantages
The main advantages of mini splits are their small size and flexibility for zoning or heating and cooling individual rooms. Many models can have as many as four indoor air handling units (for four zones or rooms) connected to one outdoor unit. The number depends on how much heating or cooling is required for the building or each zone (which in turn is affected by how well the building is insulated). Since each of the zones will have it's own thermostat, you only need to condition that place when someone is there. This will save energy and money.

Ductless mini split systems are also often easier to install than other types of space conditioning systems. For example, the hook-up between the outdoor and indoor units generally requires only a three inch (~8 centimeter [cm]) hole through a wall for the conduit. Also, most manufacturers of this type of system can provide a variety of lengths of connecting conduits. So, if necessary, you can locate the outdoor unit as far away as 50 feet (~15 meters [m]) from the indoor evaporator. This makes it possible to cool rooms on the front side of a building house with the compressor in a more advantageous or inconspicuous place on the outside of the building.

Since mini splits have no ducts, they avoid the energy losses associated with ductwork of central forced air systems. Duct losses can account for more than 30% of energy consumption for space conditioning, especially if the ducts are in a unconditioned space such as an attic.

In comparison to other add-on systems, mini splits offer more flexibility in interior design options. The indoor air handlers can be suspended from a ceiling, mounted flush into a drop ceiling, or hung on a wall. Floor-standing models are also available. Most indoor units have profiles of about seven inches (~18 cm) deep and usually come with sleek, high tech-looking jackets. Many also offer a remote control to make it easier to turn the system on and off when it's positioned high on a wall or suspended from a ceiling.

Split-systems can also help to keep your home safer since there is only a small hole in the wall. Through-the-wall and window mounted room air-conditioners can provide an easy entrance for intruders.

Disadvantages
The primary disadvantage of mini splits is their cost. Such systems cost about $1,500-$2,000 per ton (12,000 Btu per hour) of cooling capacity. This is about 30% more than central systems (not including ductwork) and may cost twice as much as window units of similar capacity.

The installer must also correctly size each indoor unit and judge the best location for its installation. Oversized or incorrectly located air-handlers often result in short-cycling, which wastes energy and does not provide proper temperature or humidity control. Too large a system is also more expensive to buy and operate.

Some people may not like the appearance of the indoor part of the system. While less obtrusive than a window room air conditioner, they seldom have the built-in look of a central system. There must also be a place to drain condensate water near the outdoor unit.

Qualified installers and service people for mini splits may not be easy to find. In addition, most conventional heating and cooling contractors have large investments in tools and training for sheet metal duct systems. They need to use (and charge for) these to earn a return on their investment. So they may not recommend ductless systems except where a ducted system would be difficult for them to install.

1) you don't have to cool the whole house, we just cool the bedroom level at night, and the lower level as well during the day

2) you don't lose space to ductwork (even Unico needs a big main duct, although the ducts that branch off of this are small)

3) you don't tear up the house to install ductwork; the minisplits were installed in a few hours

4) they take a lot of humidity out of the air

Disadvantages:

1) noisier than central air; you cannot install one of these in your bedroom

2) they do not come on automatically, you just turn them on when you need them

3) hard to place; practically they have to be on an outside wall, where the compressor line can come in, and where the tube removing water can come out

Although I could easily see my toddler dropping things down those small, open Unico vents. At least my existing floor & wall vents can be closed & have screens behind them. Oh God, I just thought of the cat chasing packing peanuts into those Unico holes!

Nina

http://www.acdirect.com/matrixcs5.php?source=google&group=1&campaign=1 7&keyword=mitsubishiairconditioner

I currently cool each floor of my duplex with an 8000 window unit (1080 s/f each) so this may be within reach.

Look into casment units if you need window units short term.

"Duct losses can account for more than 30% of energy consumption for space conditioning, especially if the ducts are in a unconditioned space such as an attic."

Not in any modern system with insulated ducts. A Unico system typically has about a 5-10% duct loss number for an unconditioned attic depending on what R value ductboard and flex is used.

If you can do separate systems for a 2 story house, an attic system for the second floor and a basement system for the first floor is still a very good option. The attic system should use ductboard, NOT sheet metal. The lower mass of the ductboard and better R value is very beneficial in this application.
If you want a single system a Unico high velocity system will be the least intrusive for building damage and required repairs. The larger diameter flex (higher R insulation) can be used only in the unheated areas, and the smaller (about 4 inch) used inside walls in conditioned space.
In a cape type house, running a loop of ductboard in the attic with the air handler, and dropping flex lines into the second floor rooms is very simple. The first floor rooms can be served by running in the knee walls and closets to reach the first floor ceiling. The return is typically placed in the ceiling at the top of a center located stairwell.
Unico ) and Spacepak) have higher equipment costs, and take more care in design and installation, but typically make up for this by minimizing wall repairs.
While mini-splits are less noisy than window units, I have yet to hear one that I would describe as silent.

Now all of that said..given the size of our house we have one conventional unit ( ducts were in place for the down stairs from the old foreced heat unit ) the Unico upstairs where sir was never added long ago and then we are doing a mini split on the back two rooms of the house since we could nit size up any bigger and adding these two hot rooms ( they get LOTS of sun) would have been a strain on the system. I think we are going to go with a Mr Slim but still on the fence till I talk more with my Ac guy.

Maddiemom

I'm kind of interested in the Unico for our third floor, which is a finished attic with one supply duct for two rooms and a short hallway. The first and second floors can be done with a conventional system using the supply ducts that we use for heat, but the attic rooms, which are not used all the time, could have a separate Unico system that could be turned on when we have guests. (The attic is our guest suite; two rooms and a tiny full bath.) Or get tired of the heat radiating down from the hot attic into our air conditioned bedroom!

I have no choice but live in the old brick house with such system installed, as opposed to all my previous life in the similar houses but with old steam radiators central heating.

1. Noise/ acoustic tunnels.
This is noisy, not as a loud music, but you will have to live in the presence of additional source of noise for years.
You will have to watch out for privacy: ducts transfer sounds (usual speech, for example) from basement to bedroom, and opposite; and doors would be cut at the bottom (2" or 5cm) to allow air return.

2. Smell tunnels: watch for a kitchen and bathroom smells leaking in an intence all-house air circulation. These doors with holes and stairways are very difficult to prevent from transferring the smells, when forced air moves.

3. Drafts (I suppose that unwanted air movement, causing discomfort and sneesing can be called so).
You also will be limited if the furniture placement options because of this, for two reasons: air vents should not be blocked (in order to transfer heat efficiently) and you should be able to sleep not in the intermittent stream of air. Built-in location of vents, doors, closets and windows left me (at least) in almost intolerable situation.

Beware, please.

The air blowing out of the registers is definitely louder than a conventional system, but the comfort it provides far outweighs a little noise.

As previous posters said, go with an experienced installer. I used a guy who puts a video camera into the walls to see where the ducts can go. See other installations and ask those customers lots of questions. My installation took two guys about 6 business days. (The first day and a half were just spent planning and measuring. I remember checking in at the end of Day 2 and they only had one duct run to one room. I didn't question it, which they appreciated.) They didn't make any wrong cuts so no patching was required.

Be sure to talk to the installers about which rooms get hotter than others so they can plan accordingly.

It's expensive, but if you can manage it you should go for it. It's a very elegant solution to a tricky problem.

BreakerOff

maddiemom

I am very intrigued by the unico system. The SpacePak seems to be only an AC set up & I'll need a system that covers both heating & cooling (like the unico). Can anyone give me an idea of what the Unico system costs? We'd be looking at heating/cooling 2 stories, a total of about 2000 sq ft when all is said & done.

Oh, an addendum to the original poster...we did have central air installed in my mom's house about 20 years after it was built. This was in a house with plaster walls. Since the house was a ranch they were able to run all of the ductwork through the attic & place the grids in the ceiling of each room. Since you're lucky enough to be living in a multi floored victorian it sounds like the mini splits or unico type system would be a better option for you.

Nina

The Mr. Slim did its job, but it was unattractive and louder than I would have liked. Ours was suspended from the ceiling (peaked attic ceiling) and cooled the space quickly and well. But it did take away from the charm of the space.

Unfortunately, I don't know that there was really any other option fot that space. The only windows were two small half-rounds in the gable ends. The construction of the house was clay tile block. We lived with it, and the current owners enjoy having it -- they use the room for studio space.

I guess all that leads to this: It wouldn't be my first choice. But if budget means the option is the Mr. Slim or window units, I'd opt for the Mr. Slim. Otherwise, if I had the budget, I'd spring for the Unico/Spacepak.

We have two separate units, a client of mine did it for 15k for the basics (we added a bunch of other things that brought the cost closer to 20k).

I love it, we didn't have a single hole the guys who did ours were absolute artists.

However, it does sound like whoever put in your central forced air system didn't do a very good job of it. You should *not* have smell transfer from bathrooms and kitchens, those rooms should be at a slight negative pressure. If possible, install bathroom vent fans and a kitchen range hood that vents to outside; that should take care of the smells. If you have the space for ductwork, there are central bathroom fans that are silent in the bathroom because the blower is in your basement/attic or on the roof.

2" undercut doors is a mite excessive. Transfer vents above the doors can prevent any need for undercutting at all, and are definitely how I would go with old historic doors if individual room air returns were not practical. Also, it sounds like the supply ductwork was poorly designed and placed if you're feeling the "drafty" blowing on you; they should have positioned the registers to "wash the walls" with conditioned air.

Noise should be minimal with properly sized ductwork. Undersided ducts will be noisy. Noise transfer can also be minimized with proper design.. not eliminated though.

If you have radiators, I would keep them. If your space accomodates full ductwork, a regular central air conditioner can be a great complement.. in the winter run the fan on low for air filtration and humidification with a steam humidifier.

Also, has anyone chosen to use hi velocity ac on upper floors and not for the ground floor? This has been suggested to us because our 1st fl is quite cool (granite stone exterior) and since cold air drops the thought is that might be sufficient. Can one apply this thinking to hi velocity -- or is it meaningless due to the simplicity of snaking flexible hose through your house frame?

I will note that one of my clients did this for me, and the next closest estimate was approximately 28k for about the same system.

Thanks so much for all the info!

Former neighbors of ours, had the Unico system installed in their South End brownstone in Boston. They were very happy with the results, and I was in the house, and it seemed very comfortable and quiet. Here is a link to the dealer that installed theirs.

Unico does not make compressors/condensers, just air handlers.

Repeated failures sounds like an bad design or bad installation.

The only problem we have is that there is a 10 degree difference between downstairs and upstairs (I think this has to do more with hot air rising than the PUSH of the system though)...and we have no return from the 2nd floor, just on the landing of the stairs. It can get a little warm in the summer as we try to go light on the A/C for $$ reasons but since we put in the blown-in insulation in the attic, it's been good.
We've been here 2.5 years and are comfortable. I'm glad we didn't have to install it.

I don't know if just because it works for us it works for everyone... our ducts are large, probably 8-10 inches square, with large louvered grates, and the longest run is probably 40 feet.