I really blew it!

[thammel]

My garage is 32x28 with 12' ceilings and a 32 x 12 x 7 man cave attic room above - with an open staircase to the attic. This is the problem area.

The place is very well insulated - R19 in all walls and r30+ in the ceilings.

I put in 2 mini splits (Mitsubishi) - an 18k in the garage and a 9k in the attic. This is where I blew it. The 9k simply can't keep up in the summer when all the cool air goes down the stairway and the warmer air from below comes up the stairway.

I'm thinking of biting the bullet and replacing the 9k with either an 18 or 24 k unit. Can any of you offer any suggestions? Any reason to not go with the 24K one?

Thanks,
Tom

 

[Streetbu]

Why not swap the position of the the two current mini spits. Since cold air drops and all.... just a thought

 

[Showkey]

Install a Door on the stair way...........

 

[James-W]

Install a Door on the stair way...........

That would be suggestion as well. The top part needs to be closed off and once that is done, it should make a world of difference.

 

[Texsun]

I use one of these strip doors in the stair way between my garage and upstairs game room, still looks good after 14 years and keeps the AC where it belongs.

 

[polizei1]

Yep, I third the door option. Easy to do, and probably the most effective.

 

[justinjoyal]

Yep, the door would be best.

You keep the room upstairs colder than the garage I supose?

 

[soob]

Man, that's wimpy. Don't replace the 9k, though, just put in another unit next to it.

 

[ford33]

Another vote for the door. A door would prevent the movement of cold air out of the upstairs room.

 

[thammel]

A door is an obvious possible solution but not easy to install. There is only a half wall up top and a window which makes placing a door up there not possible. I had tacked up plastic sheeting last summer which didn't seem to help all that much. And no, I don't keep the upstairs cooler than the garage.

I have a half wall over the bottom half of the stairway also so a door isn't really feasible there either. The reason for the half walls is to make it a lot easier to move items up and down between floors.

and yep, I though about adding another unit but that does seem to get crazy....more things to fail, but then more redundancy is good when considering single point failures and reliability analysis... (the engineer in me speaking).

Oh well... lesson learned.

Tom

 

[TheEquineFencer]

Install a Door on the stair way...........

 

[bobbyjean]

hmmm...hot air rise's......how bout ...well it isn't efficient but keeping the lower garage setpoint dropped way down will eat the load up some..then add a dehumidfier of some sort...it may help

 

[drs3317]

If the half wall is for ease of moving large items up or down, why not add removable or sliding shutters? Even the door could be made with a removable jamb. Design it to your liking and it could add style to the room. Wood shutters or even a heavy insulated curtain.
I think there would be many ways to do this. You could even make removable insulated panels to set on the half wall.

 

[dave89iroc]

grab a couple sheets of rigid foam insulation, cover the opening, just to see if it has any effect

 

[OccupantRJ]

Put a $200 window unit in the window for backup, or close the hole.

 

[Trey T]

There are two main things to consider when we heat/cool our space, capacity and air distribution.

W/o doing some math, I can't say if the units installed has the capacity for the spaces. However, I can guess in most cases for mini-splits, they have an inherit issue with air distribution, which I believe many people do not think about during the planning phase. The issue can be compounded when the two system is not ran in tandem to provide adequate capacity. Ultimately, you have three choices:

1. go back to planning phase and figure out the issue is either capacity or air distribution
2. put a door and/or add ceiling fans
3. play the guessing game of upgrading the units to higher capacity

 

[BillK]

Any way to install a small air duct from bottom to top and have a fan in it to circulate the cold air from the garage up to the attic room ?

 

[ripperd]

It is not just the hot air rising that is the problem. Even though you have R30 in the ceiling, there is still some heat gain through the ceiling, especailly since the roof is so much warmer when heated by the sun than the walls. So you may find that just adding a door doesn't make quite as large of a difference as one would hope.

 

[old__man]

How is the roof vented if at all?

 

[yeldogt]

I have done 1k sf per ton w/ foam.

If the upstairs is not cooling with the downstairs units operating -- you have a heat gain problem or leaking ......... or the unit is not working correctly

 

[justinjoyal]

9kbtu should easily take care of a 380 sq ft space with the insulation you have, I’m sure a door would fix your problem. (Unless there are other unmentionned issues.)

 

[mtref]

Instead of a door, put up a quilt or blanket to block the air movement. We did that in our house to keep the heat downstairs instead of going up the stairs to a spare room above the garage. Now the upstairs stays around 40 degrees while downstairs it is 66 degrees. you can then remove it when you aren't heating.