Central Air vs. Mini-Split for Cabin HVAC?

So, we had been planning from the beginning of the cabin build to go with a traditional ducted central heating/air conditioning system for the cabin, but with having to stop and re-assess and adjust the plans with changing builders it has been suggested that we more seriously consider a mini-split systems (or systems) for heating and cooling the cabin.

The initial reason this was suggested was one of the potential builder's concerns that we would be having a rather long run of the refrigerant line from the compressor given the likely placement of it relative to the main cabin (on the ground at the bottom of the structure, some 25 feet below the floor of the cabin) and the potential efficiency loss over that distance as well as the similar issues with ducting for the system for both heating and cooling. We've been trying to make smart decisions in designing and outfitting the cabin to minimize utility costs (since we intend to own this for the long run) and had from the get-go budgeted for a more efficient HVAC system.

The advantage of using a mini-split would be that it should be more efficient than the traditional system, and also has the advantage- if we use multiple smaller systems- of being able to control the individual temperatures of different rooms/spaces. The downside I've heard is that they are initially more expensive, and that it can be challenging to heat and cool rooms like the bathrooms in the cabin without an exterior wall to attach a unit to.

We've only really ever seen mini-splits in a few other cabins we've stayed in and when abroad... what experiences have you guys had with them, good or bad? Thanks!

In reply to Ashyukun (Robert) :

See if you can hear the mini ones you are planning on trying.  We have those in my in-law's home, and they are so loud that it's hard to sleep.  Maybe newer ones alleviate that problem, but we also rented a place that had one, and it was loud, too.

Central air is quiet.

Every hotel room has a mini split or something similar.

I love the idea, but agree the buy in for nice ones is rough.

What about a geothermal well and heat pump?

Robbie said:

Every hotel room has a mini split or something similar.

I love the idea, but agree the buy in for nice ones is rough.

What about a geothermal well and heat pump?

If you think buy-in for a mini split is high, you don't want to be shopping for geothermal.

My folks have 3 mini splits on one end of their house.  There's a "game room" addition over the car port, it's kind of huge by most standards, around 2300 sqf.  This is a large mostly open space, 2 bedrooms, a full bath, a kitchenette, loft over the bedrooms all on the north end and the rest is a large open space.  The house has a 26' peak, it's post & beam with SIPS, so there's a lot of air space to condition.

I don't know how many BTUs their mini splits put out, but the two in the bedrooms work very well, and their condensers are outside at ground level on the east wall.  The farthest run from a condenser to the evaporator is in one of the bedrooms, it's a ~35' horizontal run and a cumulative ~18' vertical run, I'd guess there's ~60' between the heat exchanger and evaporator.  I don't think I'd get too hung up on the distance.

Now as good as the smaller units work, the larger unit for the main room isn't that great in the heat of the Arkansas summer, it does adequate heating in the winter, though we have pretty mild winters.  I can't say that the mini split is 100% to blame though.  When building the addition to their house, my dad got a few quotes for the custom trapezoidal windows in the gable ends, and then decided that would be a good DIY project...  He made his own gable windows, they're made out of lexan/plexi and they're even double pane, but they're not sealed that great just caulked, there's no vacuum or inert gas between the panes, and I don't think they do much for UV rays.  Needless to say you don't want to sleep in the loft over the bedrooms in August.

I believe my folks have Mitsubishi units now.  They started out with Carrier ~15 years ago.  The original larger unit had issues with its condensation drain, and maybe some other issues.  Sometime in the past 5-ish years they replaced the Carriers with Mitsubishis and have been much happier.  Actually the two bedroom units may still be the original Carriers, I know the big unit has been replaced.  I can find out if you'd like to know for sure.

They also have geothermal in the other end of the house, if its not your "forever home," I don't think you'll see a return on the up front investment, even with tax credits.  My folk's experience has further soured me on it, as one of their 4 wells developed a leak.  There's really no way to fix it once it's capped.  They now have a 5th well, and a dead loop buried out in the west pasture.

It's not as efficient as a well system, but if you've got the acreage, it might be worth looking into shallow loops instead of wells.  It's a lot cheaper to run a trencher, and if you have a leak you can actually get to it.

I don't think that geothermal is likely to be a good choice for us, if you get more than 5-6' down on the hill you hit rock so I don't know how well that would work plus the fact that it's a massively difficult terrain to get any kind of equipment around on (like heavily wooded 40-degree incline). And in addition to the costs we've stayed at places with geothermal when it's been down around or under zero F and it has NOT been fun...

Hopefully the cabin will be reasonably well insulated... the walls will be R19 as is code and we're working on getting the roof better than what it is by default while still keeping the exposed beam aesthetic with some foam board insulation covered with wood. We're still working out what is going to be done under the floors... the airspace under the cabin will be enclosed and its likely the hot water heater will be down there (and if we have a conventional central system that's where the furnace will be as well)

The difficulty would be figuring out just where to place the units- the bedroom is a given, and it would be a fairly small one given it's only like 10'x12', but the majority of the rest of the cabin is open and making sure that the loft area was adequately cooled (and to a lesser degree, heated) would be interesting as will be the bathrooms which don't have exterior walls.

In reply to Ashyukun (Robert) :

I have mini splits. I like them. But not as much as I liked my window A/C in the walls.  The mini Splits were a lot more expensive.  

My house is 5500 sq ft.  I used to have 3 window A/C up high in the walls.  It worked wonderfully they cost me about $150 each I just cut an opening in the wall and slid them in place. In the fall I’d pull them out and replace them with plugs covered with shutters similar to the outside and a false cabinet front.  

I doubt my A/C Bill was $150 for the whole summer. Plus as soon as more efficient A/ C  became available it was only $450 for the more efficient units. A Mini split system is much, much, more expensive to replace  so that unit will likely stay in place for decades.  

We had an lg mini split installed in our bungalow almost a year ago. It’s mounted on rubber pads that are on L brackets into the foundation. It’s very quiet, it was able to keep me from burning oil this past winter (although I still went through a few cord of wood) and the Ac last summer had us spoiled. I think it was just shy of 4000$ Canadian installed.

That sounds like a sales pitch but really I’m just very pleased with having spent the extra 500$ to go with the lg.

Where is your build site? Heat pumps dont work well in the single digits and below. There are some options to help in colder weather, though.

Mini splits are a tool to get some cooling in a spot that cant be done with a ducted system. 

If you are building a cabin, build room for duct work and give yourself a forced air system. You will lose out on some individual control ability per room, but with a well engineered ducted system every room can be at the same temperature as the thermostat.

As for efficiency, there is nothing indicative of a minisplit that is more efficient than a forced air unit. It uses the same process to cool the air, and there are multiple efficiency levels to chose for both ducted and non-ducted equipment.

I am a hvac engineer and I would select a forced air unit for a client and for myself for a new cabin.

Minisplits are cheap to install and cheap to keep on a shelf at the installers shop. 

In reply to Ashyukun (Robert) :

25 feet isn't long for a lineset at all. All it means is whoever installed it would get a 50 foot lineset instead of a 30 to make sure there was enough.

What's the climate like where the cabin is? What are electrical costs there? Is natural gas or propane an option, and if so how do those costs compare to electricity? Is the electricity provided consistently, or is it prone to frequent outages? No electricity means no heat/cooling with minisplits. You can always get a fire going with NG. I've used a gas stovetop and matches to stay warm during a power outage in sub zero temps.

Mini splits are basically a heat pump right? So in cold weather they work well until temps reach a certain point, and then they have to resort to electric backup heat sources which are less efficient. A ducted HVAC system won't have that same drop off in performance/efficiency at lower temps. If it gets cold frequently there, and/or electrical costs more than NG/LP then it might make more financial sense to go with the traditional ducted setup.

I'm also not sure how they're going to use shorter linesets than traditional HVAC unless you have condensers hanging all over the outside of your house, directly outside the rooms they condition. That's not usually the case as it's unsightly. Chances are that the outdoor unit(s) will be placed someplace more discrete and out of sight for aesthetic reasons, and then you'd have long linesets running to the various heads anyway. And the heads can provide some aesthetic challenges themselves from the inside.

I'd probably lean toward installing ducts in new construction. Minisplits are neat, but they seem like they're best suited for additions, retrofitting homes that never had HVAC and situations where a ducted setup couldn't be implemented well.

RossD said:

 

Minisplits are cheap to install and cheap to keep on a shelf at the installers shop. 

This is exactly what I read from the original post.

RossD said:

Where is your build site? Heat pumps dont work well in the single digits and below. There are some options to help in colder weather, though.

Mini splits are a tool to get some cooling in a spot that cant be done with a ducted system. 

If you are building a cabin, build room for duct work and give yourself a forced air system. You will lose out on some individual control ability per room, but with a well engineered ducted system every room can be at the same temperature as the thermostat.

As for efficiency, there is nothing indicative of a minisplit that is more efficient than a forced air unit. It uses the same process to cool the air, and there are multiple efficiency levels to chose for both ducted and non-ducted equipment.

I am a hvac engineer and I would select a forced air unit for a client and for myself for a new cabin.

Minisplits are cheap to install and cheap to keep on a shelf at the installers shop. 

The savings in mini splits is the adjustable nature of individual units.  We have one up on the third floor and turn it on to cool the wife's office ( and the whole third floor) and when she’s done we turn it off. 

The two units downstairs  serve different functions one cools the great room  and  kitchen. The other cools the master bedroom and lake side of the house. The only time all three are on is when we have a house full of guests.  

Effectively we can cool different zones.   There is a handy remote by all three units located on the way out/ in. Lights off, A/C off.  

While it’s not as efficient as the three A/C window units were ( they had individual remotes too! )  it’s much more efficient than cooling the whole house which is what ducted A/C would do. 

In reply to 1SlowVW :

I too went with the LG and found it very easy to install.  The white head unit is one reason our walls are white. It’s quiet and painted white Tucked between timbers, up near the ceiling  it virtually disappears. Simply cooling the house when guests are running in and out  on hot summer days.  

Thanks for all the good info and experiences!

The cabin is located in central-ish Kentucky, which does on occasion get down into sub-zero temps over the winter but is usually more mild. The cabin's location is such that it is fairly well insulated from getting too swelteringly hot in the summer so hopefully the cooling won't be too bad- but given it will be rented out part of the time we won't have full control over what temps the system is set to.

We did initially plan to have a propane furnace (no natural gas lines nearby), but eventually decided to stick with all electric both because of the additional concern of getting the propane tank refilled and the Dancer's overriding paranoia about fire (specifically that her concerns nixed a gas fireplace & stove, and just having the propane furnace didn't seem worth the added cost of the tank and hassle of having it refilled and the potential that a refill truck might not make it up the road in the dead of winter...).

Going to be revisiting this soon as we're coming up on when they'll need to get started, so I've been doing some searching around trying to figure out what the costs will likely be for the HVAC install. Since all I can really price is the hardware I've been looking into that. So far from what I've found, a traditional AC unit will likely cost about $2500 and a furnace $1000 or so plus the ducting and such to install them.

It looks like I can get 2 mini splits that put out the same heating/cooling for the cost of just the AC unit itself (if not less)- and I would imagine they cost a LOT less to install with not having to worry about ducting.

Going to be interesting talking with the HVAC guy and seeing what we can figure out...

In reply to Ashyukun (Robert) :

What you are likely to find is contractors/ installers who are familiar with one system and unwilling to tackle something they have no experience with. 

They may bad mouth or give you all sorts of dire warnings that sound extremely credible.  That’s when I stopped listening. 

If you’ve done your due diligence stick to your guns. You’ll find someone willing, heck- eager to do things your way.  

Worst case, buy your units on line and ship them to your site. They really aren’t that hard to hang but you will need to figure out where to route the refrigerant lines, the drain line, and the power line.  

Nice thing is most modern units are remote control so you can put the remotes anyplace they are handy. 

I put a mini split in our rental apartment. It’s just under 500 square feet in west palm beach, it is very hot here for most of the year. We really like ours. I paid $650 for the unit and I installed myself. The unit runs off of a 20 amp breaker. It is very quiet and seems to be very efficient. It is much much quieter than the central a/c in our home. As for heat- I have no experience. I’m willing to bet 2 mini splits would work great for you. 

In reply to grover :

Where did you buy your unit? That sounds like a great deal and a worthwhile DIY project.

In reply to nderwater :

Craigslist believe it or not! It was a really nice guy running a business selling daizuki units in Miami. The guy had hundreds. He said he used to own an a/c business but likes this better. He was pretty helpful. 

In reply to frenchyd :

Yeah, it is a concern that the AC guy that the current contractor wants to use may not know his way around them- but I can't remember whether it was the contractor we went with or the one who decided to not bid who had recommended looking into the mini splits in the first place. If necessary I can talk with the other contractor about who he'd recommend to get a good quote on installing the mini splits.

As you said- worst case, we have the contractor cut the necessary openings (probably very similar in concept to windows) and mount the units and the electrician hook them up. With not having to run ducting I would imagine that it's infinitely easier to install than a 'traditional' system.

When I discussed this with the Dancer last night the only concern is figuring out exactly where to put things- there isn't a HUGE amount of wall space to mount things, especially in the bedroom, though a ceiling-mounted interior unit might work. The idea of having the bedroom on its own small unit though is VERY appealing as we'd likely only worry about it keeping the bedroom where we wanted the temperature (likely in the summer, we like it on the cooler side in the winter) and the rest of the place wouldn't have to be dragged down to quite that cool so would cost less. Of course, there's little guarantee that people renting the place would do anything similar, but at least there would be the option...

In reply to Ashyukun (Robert) : OK the unit itself is mounted inside on the wall near the ceiling.  The hole in the wall to fit the coolant lines. The drain line, and the power line goes in a smallish hole roughly 4x4  near the upper right hand corner of the unit.  

The compressor is mounted outside like a normal A/C unit.  One compressor can supply up to 4 zones.  ( or  head units) You’ll get a remote for each unit.  I made a bracket and put the remote by the light switch.  

I’ll be home tonight and get you exact dimensions of my brackets and send you a picture of everything.  

In reply to frenchyd :

Cool, thanks! I was thinking that the whole unit stuck through like a window A/C unit, good to know it only requires the small cutout- that will help. 

The bedroom may be a challenge because of the window above the bed on the wall where I think the unit would go best but there should be enough space to the side of it to install a normal unit. If not, as I said a ceiling cassette might work or one of the floor ones. The other unit(s) should be much easier- might want to put another smaller one up in the loft area to specifically cool around the bed there and a bigger one to cover the main living area- or could just put the one big one where it should also hit the loft area well to cool it in the summer.

In reply to Ashyukun (Robert) :

The head unit is roughly 10 inches high, 36-38 inches wide and sticks out from the wall 6-8 inches.  

I could be a little off on those so wait until I get home  but roughly that is the size of each unit.  Normally the coolant lines, drain line, and power are run up in the wall cavity before the Sheetrock is put on. In one case I made a fake beam  and ran them inside that.

The drain lines I just ran over a Basement drain  and let the condensation drop right into the drain. At first there is a steady drip if the house has been open and the humidity is high.  But as the cooling takes effect the drippings slows way down.   Nice thing is the water that comes out is distilled water.   You could put it into your waste line but then you need to put a trap in.  

nderwater said:

In reply to grover :

Where did you buy your unit? That sounds like a great deal and a worthwhile DIY project.

I just bought my LG units on the internet.Google mini splits.   An outfit in Florida was the lowest cost selling them. And I got three zones ( head units)  all the insulated coolant line, three remote control units. And the outside compressor shipped up to Minnesota  for something like $1500 

There were cheaper units but with our experience with LG. ( very positive, no trouble in a decade on anything we got from them). We spent the few extra bucks.  

Mitsubishi  also made them but they didn’t have as glowing praise as LG did.