Mini Splits in New England

17 Replies

Hello guys and gals,

I am currently in the process of purchasing a 7 unit complex (built in late 1800s). The building consist of 4 studio units and 3 single bedroom units. Each Unit ranges from roughly 500Sf-650SF max. The issue lies that all the units have baseboard hot water heat, however, it is through one older boiler that I am responsible. The same lies with the hot water boilers, it presently has 2 large water tanks that the landlord is responsible for payment of the natural gas. The electric is also only on one meter, where I am responsible for the payment. The units are all currently occupied. My goal is to rehab as each tenant leaves, mostly focusing on lowering my expenses (utilities). I will be looking to have each unit sub metered with electric and to clean up the co-mingling. But when it comes to heat solutions, I am a little bit lost. I had stumbled upon the idea of AC mini-splits, that would sub meter these units as well as offer A/C, which would make the units more marketable. I am curious if anyone has had experience with these units in the New England area? I would like to avoid purchasing 7 brand new boilers if possible. The thought with mini-splits is it would allow me to lower my expenses, and keep the renovations more or less isolated so I'm not having to redo plumbing or ductwork etc etc to other units that are currently occupied. My other concern that I recently just thought of was what do landlords due if there are any power outages and tenants are left with no electric, what are landlords doing that run into this same problem?

Any questions, suggestions or thoughts are much appreciated. Thank you!

@Nicholas Davila I know that when it gets very cold outside that mini splits don't really work so great. I would guess that in those times you would see a spike in the electricity as the units struggle to heat. I am no hvac guy so my comments are based more on what I've seen in the area when it gets closer to 0. I guess you'd still be using the boiler at those times as well.

@Nicholas Davila

Ductless split heat pumps are an option but they can be problematic in the northeast. Heat pumps work on the premise that no matter how cold it is outside, it can always get colder. In other words, there is some heat that can be used. The outdoor section of a heat pump extracts that heat from outside and transfers it inside. With older heat pumps, they would only work down until it got down into the 40's outside before they lost most of their ability to extract that heat and would then switch over to electric resistance heating. The newer ductless units are much more efficient and most are rated down to about 5 degrees outdoor temperature while still producing about 60 percent of their maximum rated capacity. That's the good news.

The bad news is that the colder it gets, the more these units need to defrost themselves. Ice builds up on them as a part of normal operation. When they go into defrost mode they stop producing heat. This might not be a big deal when outdoor temperatures are in the upper 30's but when it drops down to the teens or single digits for extended periods of time it can be problematic. The temperature indoors may drop faster than the unit is able to recover it because of multiple or extended defrost cycles per hour. In other words they will be producing less heat at the times when it is needed the most. When you add in additional factors like deep snow drifts around the outdoor unit, the problems begin to compound.

A better solution for you may be to go with gas fired "combi" boilers, one for each apartment as you renovate. A combi-boiler is a small, wall mounted, high efficiency unit that will produce hot water for both heating and domestic hot water. For the small square footage that you have indicated you're probably going to be looking for smaller units that are relatively less expensive. Air conditioning could then be provided by either window units or, depending on your budget, ductless split cooling only units.

If you go with minisplits you may need backup electric baseboard and in all instances it sounds like you may need an upgraded electric for minisplit or electric heat. If you have natural gas see what is available there and if electric or gas costs less. If you are paying electric think about what it costs when they install window ac.... In any event they are using high performance minisplits in canada @Roy N. has mentioned using them and I imagine that is at least as cold as Ma. If you are at risk with electric install a generator, if you instal it that gaurantees the power wont go out!

@Alfred Edmonds , that was my concern, was whether they would be able to keep up with some of the colder days, as well as occasional massive snow build up and whether I should be attempting to cover these outside units somehow. Thank you for your input

@Tom W. Thank you for the information, I figured with newer units they would be more efficient and understand that obviously the colder it is the harder the unit is working, so not as efficient at that specific time. I guess I would relate this to a car and MPGs on how hard it is working etc. I had never considered the defrosting process, and that is another concern of mine, with sometimes colder days turning into a week, would these units have sufficient time to defrost? I don't want to be eliminating one problem (single meter gas) to create multiple upkeep issues. I like this idea of "combi" boilers, I'm all about two birds with one stone. And if the plumbing can be easily separated at the boiler, then this could work. The thought of AC wasn't a real necessity, but rather an added bonus. Do you have any recommendations of companies or models for the combi units? Have you used any of these yourself?

@Colleen F. The idea of the mini splits was to reduce the renovations and back up heat source, I have a 4 unit that I had to do your very suggestion to and although it works out, that building went through a full renovation and am trying to attempt a more isolated 1 by 1 unit renovation with vacancy. I have space heaters in my 2 of my 4 units, and because of this put baseboard electric in each bedroom for a back up or additional source, if they decide to close their doors. But I am also concerned with power issues, I definitely don't want to be getting phone calls regarding 7 tenants without heat due to loss of power, and although a generator would suffice, I ideally would not want to spend the money and also have the maintenance and concern of it. I have noticed that @Roy N. has mentioned these mini splits before, and thought I would piggy back off his posts.  Thank you for your input.

@Nicholas Davila

I have installed several different manufacturer's brands of combi boilers. I recommend and have installed the Navien NCB series unit in my own personal projects. TriAngle Tube and Weil-McLain are two other manufacturers that provide reliable products

@Tom W. thanks for the input and recommendations! Do you have any suggestions when it comes to size? with roughly the above stated dimensions in each unit etc. Or is that something that I should get someone out there to specify and will depend on many different other factors? Was just looking for a rough estimate, so I can began some further research on my part for costs etc.

@Nicholas Davila

Based on the square footage per unit that you provided, I would estimate that you would need less than 40,000 BTU of heating output for each. This is just an estimate and should be verified by heat loss calculations but it should suffice for budget purposes. You can also do a close estimate by adding up the linear footage of radiation in the space and calculating total required BTU's. Standard hot water baseboard produces approximately 500 BTU's per foot.

Based on the above numbers, the smallest Navien boiler would do well for you. It has a heating input range of 12,000 to 60,000 BTU's with a maximum output of 56,000 BTU's. The input is regulated by the boilers internal controls based on water temperature in and out so they are very efficient. They will only produce as much heat as is required based on outdoor temperatures. The same boiler will increase it's input as high as 120,000 BTU's for domestic hot water so there is always plenty of hot water for showers and sinks.

Another nice feature for you as the owner is the ability to monitor and and make adjustments to these boilers via a smart phone app. 

@Nicholas Davila

We just deployed another Fujitsu Halcyon mini-split last month - those and the Mitsubishi Mr. Slim remain my favourite, but I am tempted to try one of the Gree (they manufacture house brands for several of the "traditional" HVAC companies who have recently introduced heat pumps) as their specs are impressive as is their price. 

We also use heat pumps in buildings (predominately houses) with central air handlers.  Traditionally these central systems lag the mini-splits in ultimate performance (COP, HSPF), especially in cold climates, but there is a new Canadian designed unit being commercialized by EcoLogix which has the compressor indoors, allowing it to retain efficiency down to -25C (or lower) without the energy costs of frequent defrost cycles.

In the dead of winter when we have a week or two of temperatures below -30C, auxiliary heat is still required, but we realize benefit from the heat pumps most of the winter and particularly in the shoulder heating seasons.

Heat pumps or not, the first order of business is to improve the air sealing and insulation of the building envelope - you receive less benefit of producing heat more efficiently/cheaply if it is going straight to the outdoors.

My $0.02 would be the Aurora series with Daikin. These too are the high heat output as mentioned above.

We have done a few hundred of these with little issues in Condos here in Moncton NB (Above Maine)

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Originally posted by @Cameron Brioux :

My $0.02 would be the Aurora series with Daikin. These too are the high heat output as mentioned above.

We have done a few hundred of these with little issues in Condos here in Moncton NB (Above Maine)


We have Daikin installed for *real world* comparison. 

Specification-wise, the Aurora's HSPF and COP ratings are on par with the Mitsubishi Mr. Slim (which have been around longer) and a about 15% less than the Fujitsu Halcyon.

My reply may not be the typical: I own or manage 49 units over 11 buildings in Central Maine (Waterville and Winslow) 

I like to think about OVERALL EFFICIENCY when it comes to heating solutions. When I started out, I always automatically thought "shift utilities to tenant whenever possible". Frankly that's far from always the best solution. For example, we have a duplex with TWO boilers and TWO electric hot water heaters. Sounds great...each tenant pays own oil and having two single family houses. BUT ... overall the BUILDING uses much more oil & electricity than it would it it had ONE boiler with an indirect hot water heater. So overall, the units cost the tenants more than if we supplied heat. If we supplied heat and hot water, I would be able to charge about $100 per unit more per month that would go straight to the bottom line. I'd have slightly more risk but a lot would have to go wrong, and often, to outweigh the math. 

With electric we have mostly separate meters but we do offer to have electric included. If they skip out on rent, sure we get stuck with an extra $50 but it's only happened once in 3 years. We bill $45 for 1BR, $55 for 2BR, etc. and cap usage at that amount. So we keep the difference if they use less (to compensate for the extra bookeeping and risk) and get paid if they use more. 

So back to heat...yes, mini splits are all the rage. Most that have tried them regret it as a PRIMARY heat source. They're WONDERFUL for cheap cooling and beautiful for heat at 30 degrees and higher, but most have told me even the brand new ones struggle below 10 degrees and they cost more to run than old fashioned electric below a certain temp. (and maine has MANY MANY nights of zero or below). For "in unit" heat, most still stick with monitor (oil or propane or NG). Most experienced Maine landlords will tell you, from a comfort viewpoint, NOTHING beats ONE CENTRAL boiler with HWBB. I wouldn't have anything else in most of my buildings EVEN IF some program came out offering a 50% rebate. It's simple & reliable. 

One thing you can do is to add a heat pump water heater. Assuming you have a central HWBB boiler with boiler mate, you can "join" a heat pump or hybrid water heater and have things setup so that in the winter when the boiler is running anyway, your boiler mate will handle the hot water, but in the spring, summer, early fall when you can shut the boiler down, you use the hybrid, and maybe have the boiler set to kick in if the hybrid is having a hard time keeping up. I've spoken with our local heating contractor and it's a pretty sweet setup. 

@Kenneth LaVoie

Good to see you still here.   I too share a preference for central heating plants as they can be (but are not automatically) more efficient.,  However, I also believe in having tenants be accountable for their resource consumption.

When I worked in Europe, one of the places we rented was on a local (as in neighbourhood) heating plant and every residence had a caloric meter which measured the energy (BTUs) consumed (this was fairly common).    I've been thinking about deploying similar metering in some of our buildings; the catch being that most of our old (i.e. Victorian or Edwardian) buildings were not plumbed with separate zones for each unit (even in those instances where the building is not a conversion, but was built as a multiunit).   Ironically, by the time you re-run the hydronic lines to separate units, it is often more cost effective to replace the central heating system with a distributed (electric) system.


Regardless of the source of heat, the best returns, by far, come from improving the air sealing and insulation of the building envelope.  If you stop the draughts and leaks and wrap the living space in a warm blanket, there is little "regret" associated with the heating system.  We've taken Victorian era buildings from no insulation to R30 (walls) and R50 (roof) reducing the heating costs by more than 50% along the way.

Do not forget the mini splits have to drain for the a/c so they should be on a outside wall. Then the line set is going down from the upper units all over the outside of the house. Also think about the maintenance issues every year were they will need service were they run for both heat and a/c.  And you will have problems with them as primary heat in the exstream cold. 

@Patrick Harrington

These days we typically plan for a ductless heat pump in our renovations and use it as an opportunity to plumb them on an internal wall where it makes more sense w/r to the layout of the unit.

That make sense when you are remodeling the whole building. Around here it is for replacement of equipment not a total gut job. Where they want to remove a oil fired boiler and put in multiple heads off a mini split system for heat and a/c. There is a 2nd problem with them the high of the indoor head on a normal ceiling 7’ 8”. With the return from the top you have to drop them down from the ceiling and the supply is on the bottom and it hits you in the face when you walk by.

Originally posted by @Patrick Harrington :

That make sense when you are remodeling the whole building. Around here it is for replacement of equipment not a total gut job. Where they want to remove a oil fired boiler and put in multiple heads off a mini split system for heat and a/c. There is a 2nd problem with them the high of the indoor head on a normal ceiling 7’ 8”. With the return from the top you have to drop them down from the ceiling and the supply is on the bottom and it hits you in the face when you walk by.


We are fortunate that most of our old buildings have 10' ceilings (8.5 - 9' once you clear the ornamental crown) and we wall heads are high enough.  In situations with lower ceilings you could use a ceiling, wall or floor cassette or, if you have freedom for the flex ducts (say in an attic), a mini air-handler.

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