Mini-split air conditioner

[marathonwmn]

Hi all,

I own a duplex, live in one side and rent the other. These are two story units each with central air and heat; the thermostat and air return for both units are downstairs. The upstairs is OK in winter but really warm in summer.

The rental side upstairs is one LARGE bedroom with a bath and walk-in closet. The side I live in has two LARGE bedrooms with a hall and bathroom in between. I don't expect the unit to cool the entire upstairs on my side, just my bedroom.

After living in the house for 20 years and I'm tired of dealing with the discomfort. I'm thinking about installing a mini-split air conditioner for each side and wonder what these will do to the resale value of the property.

Any comments on the resale and any other aspect of these systems will be appreciated.

[VLADIN01]

Have you looked into the Ecobee thermostat? It allows for "multiple zones", I put "multiple zones" in parentheses because it is not a true multi zone setup. The thermostat allows for multiple remote temperature sensors to be placed in the house. The thermostat then runs the HVAC system until the temperature in the remote zone (your upstairs) reaches the desired temperature. However, it would likely result in your lower level being rather cold.

I was contemplating putting one of these thermostats in my old house as the upstairs had vaulted ceilings and a skylight that would roast the whole upstairs.

It may not be an ideal solution, but probably a cheaper solution to at least make your upstairs habitable.

[jbuzolich]

We installed a four zone mini split ductless at our cabin the first year after we bought it and love them. We picked the Fujitsu system but I have also used Mitsubishi at my parents house and both are great. For our cabin we did not have any central heating or cooling so it really made sense. I can't imagine installing these in a house that already had central air but if you're really wanting it just to have one room be different then I think it could work well. That's often what I do at our cabin. It will be a warm day and the family is fine but I get overheated so just head off to read a book in the bedroom for a bit and get the AC going just in that one room.

[UpstateNY86]

Very nice units. Get the heat pump instead of just cooling as well . You won't regret it with the inverter compressor. The main drawback to these units is flared fittings( more prone to leaks), and serviceability. They are still a niche market and parts sometimes can be hard to locate verse a conventional AC. They will definitely make you extremely comfortable though.

[Ged]

I put one in my garage which is actually a shop now. It was a huge improvement during the summer. Love it.

[magellan]

Perhaps this isn't an option, but have you considered installing booster fans inside the ductwork to increase airflow to the second floor?

[stonerolled]

I cant comment on mini split ac's but we had to give up on a 2 unit 3 level townhouse layout and add a window unit to the 3rd level. 2 story homes with one unit have always been a challenge. In summer the return air should be in the second floor ceiling, in winter on the first level floor. This way the system works with the thermal currents and the hottest and coldest air is always entering the coil or heat exchanger.

[Runaway]

As far as resale, a Mini-split would not add a lot of value IMO. Most home buyers expect a home that has adequate HVAC and are not going to pay a premium for it. For some a mini-split might be a negative due to the increased electrical bill. You stated you have lived in the home 20 years, have you had the insulation in the attic checked, that could make a big difference in the comfort level.

[Leesbro63]

Have you looked into the Ecobee thermostat? It allows for "multiple zones", I put "multiple zones" in parentheses because it is not a true multi zone setup. The thermostat allows for multiple remote temperature sensors to be placed in the house. The thermostat then runs the HVAC system until the temperature in the remote zone (your upstairs) reaches the desired temperature. However, it would likely result in your lower level being rather cold.

I was contemplating putting one of these thermostats in my old house as the upstairs had vaulted ceilings and a skylight that would roast the whole upstairs.

It may not be an ideal solution, but probably a cheaper solution to at least make your upstairs habitable.

How is this any different than just turning down the old-style thermostat, usually on the first floor, and tolerating it colder on that (first floor) level?

[veena9111]

What about a small portable airconditioner

[just frank]

Hot upper stories in summer indicate a readily fixed problem with the house....lack of attic air sealing.

For years, people have known about the importance of insulating the attic, but little attention was paid to open pathways for airflow between the house and attic. My 60s house had over 10 square feet (!!) of such openings and this is typical of older construction.

In the winter, your warm house works like a chimney, and the warm house air flows into the attic, replaced by air pouring into windows, the basement, etc. This causes cold drafts, frozen pipes in the basement, and ice dams from the excess attic heat.

In the summer, the reverse happens (your AC air is denser than the outside air), sucking superheated attic air THROUGH your attic insulation and into the walls and interior of your upper story.

In most states you can get a home energy audit for <$500, and a simple attic airseal process from a trained pro for less than the price of a minisplit. The result will save you energy year-round, AND make your house more comfortable in summer and winter (reduced drafts, dry air, ice dams, etc).

My house was a mess when I bought it, huge energy and AC bills, drafts, nosebleeds, ice dams. After some thorough airsealing work, my heating bills dropped 50% and my AC bills have dropped 75% and my house is totally comfortable year round.

http://www.greenbuildingadvisor.com/blo ... ling-attic

[Lacrocious]

Have you looked into the Ecobee thermostat? It allows for "multiple zones", I put "multiple zones" in parentheses because it is not a true multi zone setup. The thermostat allows for multiple remote temperature sensors to be placed in the house. The thermostat then runs the HVAC system until the temperature in the remote zone (your upstairs) reaches the desired temperature. However, it would likely result in your lower level being rather cold.

Picked up one of these the other day on sale as a new version just came out with Apple HomeKit compatibility. Since we don't really need Siri to control our heat, I took the one on sale, although it still wasn't cheap.

I purchased it for a similar reason. We have a split ranch, bedrooms at either end. The thermostat is in the middle hallway. At night, the bedroom temp's don't match the hall temp - especially if the bedroom doors are shut. The Ecobee3 comes with one remote sensor, you can purchase additional ones. We put the sensor in our bedroom and have it use only the remote sensor for temp at night and average both the remote sensor and the thermostat during the day.

It works great and for the techie person, you get all sorts of stats graphing your amount of heating and cooling, indoor temp, outdoor temp, humidity, current heat and cool setpoints, schedule, etc. After a month, it is supposed to give you some overall efficiency stats, but we haven't had it a month yet.

LIke VLADIN01 stated, it doesn't zone your heating system in the general sense of the term, but it does let you choose to use any or all of the remote sensors to determine if the heating/cooling should come on. You could put the sensor in the coldest room in winter, and have your that room drive the temp in the rest of the house.

So far it has been what we expected when we bought it.
- L

[marathonwmn]

Thanks to everyone for your thoughtful answers. I'm leaning towards installing a mini-split in the renter's side and waiting to do it on my side.

[forevernaive]

Thanks to everyone for your thoughtful answers. I'm leaning towards installing a mini-split in the renter's side and waiting to do it on my side.

I think you should do it all at once. You won't get a huge price break, but there is brain damage from the hassle of getting bid and then meeting the installers and the inspections. Always minimize brain damage when planning home improvement projects. Plus, your real motivation is that you are tired of the discomfort.

I installed a mini-split AC/heat pump system for the MBR suite upstairs in my old Victorian home. It makes for a huge comfort difference in the summer. Electric usage went down compared to my old window unit.

As to valuation, AC (whether central or splits) is a line item on the appraisers sheet here in CO. If there is no AC and a comparable home has it, it's a deduction from yours against the comparable. If you put it in, it might work to your advantage. My experience is that AC is about a $3000 line item.

[shanefairman]

HI,

You didn't mention the area you are planning on installing the units. For each zip code there is usually data available for the degree days for both heating and cooling. This information will help with determine what will best fit your needs.

Talking to a good HVAC contractor could be very helpful. Unfortunately the market demands most HVAC contractors to be poor to mediocre at best. To properly install and heating and cooling systems you need to take a lot of measurements and inspect the building including a blower door test for air leakage. Once the data is gathered there is a lot of complicated math required to properly design a system.

First a Manual J calculation needs to be run to determine the total heating and cooling loads based on your house and location. It includes breaking the required loads down to each individual room.

Next comes the Manual S to determine the proper sizing of equipment. This is where most contractors screw up. During the coldest day of a very cold year your furnace should be running non stop and not quite reach your desired temperature. If your furnace or AC sort cycles by running in small time periods then shuts off there is a good chance your equipment is over-sized. contractors would rather play it safe and over size the equipment because they didn't do the math.

Next comes the Manual T. Based on the individual heating or cooling loads for each room the required amount of conditioned air must enter the room. If using forced air it requires picking the right register size and locations for properly mixing the air. The velocity of the air and the register selection are very important.

Last comes Manual D that is used for properly sizing the duct system to be efficient and deliver air to each location at the right velocity with minimal pressure drop.

All this measuring and math takes a lot of time and knowledge. Both of these can be expensive. Due to this many people just shop for a low price and end up with an over sized poorly designed system. Most people will sacrifice efficiency and comfort at the cost of a low initial purchase price.

The units are getting more efficient as time goes on. As far as things go I really like them as a product. They are highly engineered and require very little in terms of installation compared to forced air.

If you live in a cold climate a few brands carry models that can run as heat even when the outdoor temperature is -15 F.

The single head models tend to be the most efficient. The models that can have multiple heads or short duct runs typically cost more to run.

The best bang for the buck for comfort is likely air sealing and more insulation in the attic. A couple cases of great stuff foam and a few hundred dollars in blown cellulose insulation go a long way to lowering your HVAC bills and increasing comfort. It's a low hanging fruit so go pick it.

Several energy efficient houses are now heating and cooling the whole house with one or two mini split units. In two story houses the 2nd floor unit it primarily used for cooling and the first floor unit for heating.

If in a cold environment I would likely go with a single head unit from Fujitsu or maybe Mitsubishi from their extra heat or hyper heat lines.

Sorry I could likely go on for another hour but I need to grab some sleep.

Thanks,

[just frank]

I think the thing that is notable is that the house has central heating and AC already! The fact that it has central AC and there are uncomfortable rooms means there is a problem with the existing configuration (albeit, one that has been tolerated for 20 years). Just adding another cooling system to augment is a bandaid and a kludge. IF I was shopping for a house with central AC and I saw a mini in one room, it would be a red flag for me that the house was improperly maintained, or operated poorly or both.

That problem is attic airsealing. I was astonished that three previous families suffered the drafty hot/cold discomforts of my house for 50 years (!), and a couple days work by a couple guys in the attic made it seem like a whole new house comfort wise, and saved me $1000/yr on heating and cooling bills. Such a sad waste for 5 decades. Maybe I should have put some window units in instead.