Bonus room above Garage Mini-Split

[M-technik-3]

So I think i made an uneducated decision on a min split with heat for my bonus room- mother in law apartment. Temps today are hovering about 10 degrees with wind chill about -15 and the unit is struggling to bring space up to 60 degrees. It is attached via a newly constructed staircase, that needs more insulation and rerouting a heat duct to the area.

It's a mitshubushi msz-ge12na and I probably should have gotten a unit with two blowers for one at each end. Farmer's almanac was correct about this year but they sure were off last year.

 

[theoldwizard1]

So I think i made an uneducated decision on a min split with heat for my bonus room- mother in law apartment. Temps today are hovering about 10 degrees with wind chill about -15 and the unit is struggling to bring space up to 60 degrees. It is attached via a newly constructed staircase, that needs more insulation and rerouting a heat duct to the area.

It's a mitshubushi msz-ge12na and I probably should have gotten a unit with two blowers for one at each end. Farmer's almanac was correct about this year but they sure were off last year.

It might be worse than you think ! More insulation would help. A second interior air handler would help.

I do not believe that unit has the Mitsubishi Hyper-Heat technology. That is what allows them to work well in cold. Here are some specs from your unit.



Heating performance is dropping off quickly even at 17F

 

[M-technik-3]

Yeah, I know I have to close all the gaps in the garage below, the nice thing is the doors are decent and seem to keep it above freezing in the garage last year. We will see about this year. She has not moved in yet which is a big plus as her house has not sold.

Well with luck I can always move this unit to my barn for cooling next year and put in a more efficient unit with more btu and hyper heat to work better in the sub zero weather.

I imagine keeping it going would be the smarter thing than chasing the temps up and down as we have been, It has plumbing so we want to prevent the plumbing from freezing of course.

Oh the space is 24x36 with 10 foot ceiling so it's about 780 square feet.

 

[bzinsky]

Space is on the large side for 12k btu's

Would probably be fine if you insulated better

There's a whole tier of mini splits that provide heat down to -5, then there's another tier that provides heat at like -25/-30 degrees, mitsu hyperheat and fujitsu 9/12rls are in that tier.

I can get away with the -5 variants as the sole source of heat in NJ, but MA, VT, NH, ME probably should go with the next tier.

 

[HoosierBuddy]

I don't have a minisplit, but I do have a small ventless gas spaceheater in my bonus room above my garage. It has a wireless remote thermostat that is set 2 degrees under the t-stat for the hydronic system that heats the floor.

It's especially helpful when we get a very sudden drop in temperatures as it can provide heat for a little while until the hydronic loop has time to heat the floor up. Also, it serves as backup heat in case of power failure.

I bought it on closeout 10 years ago for around $100.

It had not run at all this fall until this morning when we saw single digits for the first time. It's like 30,000 btu and was made by Comfort Glow. Not sure if they are even still in business.

Phil

 

[tab2]

I stole a circuit from my electric baseboard heat for a Mitsubishi dual zone mini split for the two bedrooms. I left the electric baseboard in the main living area. If I ever get rid of that it will be replaced with a hyper heat.

It is the first winter with it but our mini split is keeping up for now. I hope I can say that in 8 more hours!

 

[Jackfre]

You should be ok for cooling with that unit. Another option would be to add a direct vent wall furnace. For 750 sq ft in WMA I'd look at a Rinnai EX22.

 

[M-technik-3]

Well this morning it was a whopping -2 when I got up, went out to garage and it was 34 degrees as I had the pellet stove running in the den that abuts the garage, the stairs that enter second for are in this room so I moved box fan in to keep warm airflow into the space.

Artic blast is ending today we hope with more snow tomorrow followed by 50 degree weather Sunday.

I need to add more insulation to the stairwell and the put some foam board under the shiplap that I plan to use. When the previous homeowner buly the place he did it out of 2x4 walls grr you can never get the R factor in with such skinny cavities.

 

[Gerald O]

Did you ever get the garage below insulated and drywalled, including the ceiling/loft floor?

 

[M-technik-3]

I have not finished so I know I'm fight a loosing battle there. Had some financial set backs last month with well issues. Resolved one of the issues working the other one come spring time.

Wanted to do closed cell but both companies I spoke with gave estimates of over 6K dollars and felt that was a bit steep. Thinking of taking down R13 bats that are on two walls and doing blown in insulation with sheetrock that would improve the space imensely and putting R38 in the ceiling and then putting a fume barrior with some proper fire resistant sheet rock

 

[kj_mustang]

Spend the money for blown dense pack cellulose insulation. It is not expensive and will be much better than fiberglass.

 

[M-technik-3]

Thinking blown in will give me an R15-17 depending on how dense it is. Machine is free with 10 or more bags of material. Then it's just drywall and a vapor barrier.

 

[BadgerBoilerMN]

A half inch of Thermax on the inside with 1/2" of rock and paint. Real R-value will go up by 5 with the 25% hit from thermal bridging gone. The garage can be heated taking considerable load off the floor, not to mention comfort. A thick pad and wool carpet would help.

We stopped putting ventless gas heaters in decades ago. Even where they are legal. Rare.

 

[kj_mustang]

Dense pack cellulose is blown in with a wetting agent. You can't do that with a rental machine. The R values are very close per inch between loose blown and dense packed cellulose but dense packed is much better at stopping air infiltration.

 

[Warrenator]

Throw an electric space heater to just boost that room heat on the very coldest days. They are expensive to run but might save you from having to do a bunch of extra work just to combat the few cold cold days.

Or at least keep the space livable until you can fix it properly.

 

[M-technik-3]

Thanks guys for ideas. The fortunate thing is she has not moved in so it's a bit low on priority list.

 

[mrpizza]

Spray foam is expensive, but worth it. Are you only doing the walls in the garage? or is it just an apartment above? How many square feet of surface are you wanting to spray foam?

 

[M-technik-3]

about 800 square feet plus or minus a 25 sq ft.

https://www.awarehousefull.com/dow-froth-pak-spray-foam-kits/

This place has it but I would still need to add some blown in. since I would onlly be getting R6.6 for 2 inches of foam which is not enough, add some blown in that would get me to 13 and then some drywall, 2x4 construction should not be done in the North.

 

[kj_mustang]

You will be shocked at how well that 2 inches of cc foam works. I live in a pole building. 2" cc foam on the walls and then a R-8 fiberglass blanket over that. I stay very warm with radiant floor heat. But my foam insulation was sprayed by a professional.

 

[M-technik-3]

Agreed I know the benefits of how well closed cell work the bad is the cost estimates I got for it. That is the only reason I did not get it done. It stops drafts and air leaks which is one of the main losses of heat. I will be needing to replace the two windows in the garage as well since they are single pane glass.

 

[terabitdan]

about 800 square feet plus or minus a 25 sq ft.

https://www.awarehousefull.com/dow-froth-pak-spray-foam-kits/

This place has it but I would still need to add some blown in. since I would onlly be getting R6.6 for 2 inches of foam which is not enough, add some blown in that would get me to 13 and then some drywall, 2x4 construction should not be done in the North.

The spray foam is R6.6 per inch, or R13.2 for two inches.


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[M-technik-3]

Oh yeah was having a brain dump so I could do r13 plus 1" plus drywall and that would roughly give me R20 vs blown in giving me r15 but a significantly less money. But it's about money recouped on the back side.

Wait till summer till nice warm 85 degree day and spray the ****, that will also give me time to swap out the windows.

 

[joe--h]

Dense pack cellulose is blown in with a wetting agent. You can't do that with a rental machine. The R values are very close per inch between loose blown and dense packed cellulose but dense packed is much better at stopping air infiltration.

Dense pack cells are blown dry with a mesh to keep it in place until drywalled, or it can be blown into closed walls through small holes. Either way the rental machine will do it.
The R value per inch of loose blow is nowhere near the same as dense pack, it's only for attics. It settles over time.

Here's one way of doing it http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm

I've done it with and without the strapping, the strapping makes for a better job.

If you've never done it I'd recommend the mesh so you can see what you're doing. If it's not packed enough it will settle and the top of the wall will be cold.
It's a nasty dusty job but worth the effort. If you're anywhere near a celluslose manufacturer you might be able to buy direct, it's marked up about 300% at the box stores.
Joe H

 

[M-technik-3]

Funny, I saw the town of Taunton mentione and realized it was here in New England. My mom used to live in Taunton for sometime. This is how my rental house was insulated and god it was a mess to remove when we remodeled that house. There was so much in the walls that the lathe and plaster was pushing the sheet rock off of the nails.

We did spray foam in that house in certain rooms, If I were to do a remodel again it would have been gut the whole house vs two rooms at time like we did on the last one but budget didn't allow for that.

So If one was to foam a 1" and then dense pack it would be the most ideal way of doing the garage, but a bit messy.