HVAC / Room Temp Question

add a mini-split AC to the room.

or put a return duct up high to pull the heat out. call an AC company for an estimate.

if you don't want a lot of expense, pain in the butt, add a window unit.

Get a non contact thermometer from Harbor Freight for $10 to figure out where the heat is coming from. My hall was 6-8 degrees warmer than the rest of the house. Interior hall wall where thermostat is mounted was getting up to 89-90 degrees on really hot days. Looked in attic and found blown in insulation had fallen into a 2" gap between two wall partitions allowing 120+ attic air into the wall cavity. 2 cans of spray foam solved my problem.

Harbor Freight

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Neither of the two access doors seal very tightly when closed.

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They should have weather tight seals.

Weather stripping around the attic doors



When the AC is running it is drawing in hot air through the cracks thus making the room warmer.


Also does this room face the afternoon sun more than the others?

After having a mini-split for a small workout room, I'm not enamored with them.

It was a good solution for my situation, but I'd look hard before I did it again.

I taped some Reflectix R21 16-in x 25-ft Unfaced Roll Insulation on the attic door and back side of closet door where HVAC unit is located. Use the aluminum duct tape. I have half a roll I will sell cheap

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Not a good idea. Keep them open.

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Layman's understanding...

It's not a good idea because it increases the static pressure the fan has to work against. For a fixed speed fan, it will reduce its output, while a variable speed fan may use more electricity. If the open ductwork isn't adequate, you'll get less air through it, while if it can handle the increased pressure, the air will move out faster, and it may seem drafty. In extreme cases, the charge might even need to be adjusted.

Closing doors to rooms OTOH is OK, IF they have sufficient return air path. Most don't, relying on an inadequate door undercut, and the system makes up the return air from the attic and outdoors through holes in the building envelope. If you're buying a house, and you see the master suite with a bunch of registers, your question should be, "Where's the fricking dedicated return for this area of the house?" If there isn't one, and there often isn't, closing that bedroom door is going to kill your AC performance and probably be noisy as hell as the air from that pressurized room tries to escape under and around the door. A room with a single register will probably be OK, though.