SUB-ZERO Mini Split + Spray Foam Report

[duluthUPLAND]

Checking in after my garage build out last summer with a report on my heating and insulation performance. I had made some inquires about mini splits and spray foam on the forum and got a lot of great information from people so I'm sharing this in hopes that it may help someone else.

My garage is 24x24, located in Duluth, MN.

I opted to go with spray foam and paid for 2.5" on walls and 3" on the ceiling. As others had suggested I might, I feel I got more than I paid for. More like 3"+ on the walls and 3.5"+ on the rafters. I do not have a ceiling in, so it's just open rafters.

There's a 16 foot heavy wood garage door. I was looking at replacing it but thought I would wait and see through the first winter. I did have someone come out and look at it and he said it might do just fine, he said sometimes these doors even have styrofoam in the panels... not sure about that.

For heat, I purchased this two-ton cold climate mini split from Senville which has rated heating performance down to -22. I bought the vacuum pump and additional tools to install this myself and successfully complete the job, which is a miracle in itself, seriously.

Heating capability was a huge question mark for me and we'd had a pretty mild winter up until the past week. About November I set the mini split to 69 in the garage and it's been there ever since. We've been subzero here for over a week straight now and definitely below -22 overnight and I can happily report the Senville mini split, has not wavered. It continues to heat and occasionally defrost. I guess I was bracing myself for the worst and am now pleasantly surprised at it's capabilities.

I don't have a lot of technical information to report, just my casual observance as I'm in and out of the garage a few times a day, but anyone questioning the cold weather performance of these things can take this for what it is. A pretty solid report from a mini split working in a pretty cold climate.

No doubt, the spray foam is helping. The building is sealed up tight and I do not open the main garage door at all. It's a totally spare garage with no vehicle usage. It's essentially a storage area for my hunting gear and a kennel for the dogs and it will soon become my home office and general workshop/man cave.

Hope this helps someone, happy answer any specific questions that folks have.

 

[mobetta]

That's good news.

I have a new build w/ a24k Mr cool Olympus hyper heat (rated to-20) and am also pleasantly surprised by the abilities of this unit to operate at these temps. I am maintaining 46F using the freeze protection mode.

 

[Bosscobra]

Congrats on the self install, how are the dog doors at keeping the heat in?

 

[duluthUPLAND]

Congrats on the self install, how are the dog doors at keeping the heat in?

The dog doors are closed off for now. I didn't have time to build the outdoor kennel before hunting season last fall so that's on the agenda this summer. Either that or a fenced in yard.

They are double doors and I have the metal shield in place on the outside so there's really no air flow coming through. I thought I was going to have to put foam in there this winter but I didn't get around to that and whenever I put my hands around there to check, there's no cold coming in. The air bubble between the doors and the lack of air flow seems to be working well enough.

I don't necessarily need the dog door functionality as my dogs aren't out there all day, but I just put them in while I was doing all the insulation and finishing last summer. They might be sealed off every winter, I'm not sure.

There was a triple door option for cold weather environments but I opted not to get that.

 

[casmurbax]

I appreciate you taking the time and letting us now how this unit is working out for you.

There has been some decent write ups recently about mini splits on GJ and it's really steering me into getting one for my garage.

Nice looking dog and kennel.

 

[Jackfre]

Taht is a nice looking install, and congrats on the low temp operation. When the 410a inverters first came out and I was repping Fujitsu contractors would ask how it was supposed to work at the low temps. I had just the right explanation. Magic. Funny now, but it seems to be just that when you look at the experience of the single stage r-22 units. I elevate all of my condensing units. it keeps them cleaner and allows them to drain better in that defrost mode. Keeps the snakes out of them too. Does yours have a base pan heater? I think it must. Good on you man! Nice work.

 

[duluthUPLAND]

Taht is a nice looking install, and congrats on the low temp operation. When the 410a inverters first came out and I was repping Fujitsu contractors would ask how it was supposed to work at the low temps. I had just the right explanation. Magic. Funny now, but it seems to be just that when you look at the experience of the single stage r-22 units. I elevate all of my condensing units. it keeps them cleaner and allows them to drain better in that defrost mode. Keeps the snakes out of them too. Does yours have a base pan heater? I think it must. Good on you man! Nice work.

Thanks! Yes the wall mount was really simple and I like that it's up off the ground. Yes, the specs on mine list "PTC Heat Belt and Pan".

 

[yeldogt]

People mix up how low they will work and the BTU's they produce at a given temp.

Many hyper heat units will work down to -20 .. but will fall off someplace starting around 5 degrees.

So it's a question of understanding what the heat load of the building is .... this will have the historic low temp in the area built in. Then looking at the heating curve of the heat pump.

24x24 is under 600sf. That unit would have no trouble doing my 1600sf studio in PA -- but we never see -20. If I bought a unit that gave me 24k at 5 degrees -- I would be fine as the fall off at zero degree F -- is still above my 15k load.

People are always amazed at how low the load for a spray foamed building can be -- with AC in PA I never worry about 1T per 1000sf. The heat on the other hand can throw it off -- where you need more heat vs AC -- in this case you often need something to supplement the heat pump so you don't oversize the AC

 

[h0und10]

Seems like we are almost at the point of mini splits heating (and cooling) entire houses here in the northland.

 

[walrus]

The rule of thumb in Maine is, 10 days in the winter where you will need supplemental heat if using mini splits for your primary heat source. I use wood in the dead of winter . I will be building less fires and using heat pump more now that March is almost here. I have a walk out basement and really need another 12k unit down there to really cover my heat load in spring and fall.

 

[yeldogt]

Seems like we are almost at the point of mini splits heating (and cooling) entire houses here in the northland.

Mini .. is just a heat pump.

 

[fdizzle]

Looks like a nice setup and a good dog you got there. What was your last electric bill roughly? I like the idea of not having to run a natural gas line to my garage but it is very efficient for heating. I also like the idea of cooling the space in the summer.

 

[mgbbob]

That is where I am at. We are outside of KC and the few days when it is really cold I can supplement with why propane heater or my 5K electric. Yes it costs $.60 per hour to run but $13 or $14 dollars a day for a few days is manageable. We just got done with 12 days below freezing with one day the low of -15 and the high of -1 and for the month my electric was about equal to a July AC month. I did do some heating with propane but it is more expensive than electric but when it is that cold I needed some help.

 

[dcg9381]

People mix up how low they will work and the BTU's they produce at a given temp.

Many hyper heat units will work down to -20 .. but will fall off someplace starting around 5 degrees.

Texas. Have who Daikin units, 24k each. Have heat functions, but not "cold weather" rated or "hyper heat". Can tell you that below 40 degrees they start to fall off, below 30, more fall off, and below 20, they spend a LOT of time in defrost mode and produce what seems like 25% of normal heat capacity. Building was in the 50s with temps in the 20s and I was burning a ton of energy.

Never planned for "real cold" in Texas for more than a day or two. That was a mistake... My power usage was 300% more than average. If I was to "prep" for that last round of weather again, I'd be adding a propane heater.

 

[mgbbob]

I have a $100 5000 watt electric furnace that kept me at about 40 degrees when it was sub zero. The -15 night I think I was 35 in the morning. The 35000 BTU propane Mr. Heater torpedo heater with quiet technology had me up to 60 pretty quick during the day. That is a great little heater.

 

[pfettig77]

I realize this is an older post, but any updates on this system? Still happy? How's your electric bill? I'm just a little south of you and want to do the same thing with my detached garage.