One of the bedrooms in my house has a problem heat in the summer and cold in the winter. It being summer here, it's immediately warmer in the room as soon as you step in from the hallway. The problems has gotten worse with time over the last several years. We've sent people up to check out the AC unit and make sure we're not just venting cold air into the attic, but every one we've sent up has said it's not related to the AC. We then had more insulation blown into the attic, with extra being placed in the back where the bedroom is. Our next step is opening the walls and replacing the insulation there, as the bedroom has three exterior walls. Does anyone have an idea if it could be anything else?

  • it might be your AC duct is not distributing the airflow properly, there is a distribution box attached to the air handler - more or less air will be diverted to any particular area by that distribution box. For me I had one room facing the morning sun [Central Florida] the duct for that room was too small - I enlarged the duct size to fix that. Your problem sounds similar not enough airflow. Getting worse over the years I suspect you also have a fan that is wearing out (going slower) moving less air.
    – Ken
    Commented May 5, 2017 at 23:21
  • We have a ac unit we use during the summers in the bedroom, and once we cool down the room we've noticed it doesn't take very long for the temperature to rise again, which is why we've been led to believe it is an issue with insufficient insulation rather than the unit. I will definitely have someone check that out though!
    – Bev
    Commented May 6, 2017 at 23:57
  • I understand - you should get a different AC person to look and explain the situation to them - installing a window AC to try and get it to cool down on top of using Central AC should never happen. That is a tell tale sign the air flow into that room is too little - insulating the walls will certainly help but that is a more expensive route..
    – Ken
    Commented May 7, 2017 at 4:23
  • One thing to check; since most people have commented on having reduced air flow by some means, I would have to ask if you regularly change the air filter in your air-handler and is it a good quality filter. If the answer is "no" to both then I would buy a better filter and have an HVAC guy check for a dirty coil in the air-handler. Dirty coils reduce the amount of air flow. Also see if you can get more air into the room (another duct , larger duct, adjust dampers, etc.) One last item, more insulation can become a heat sink that dumps heat long after the sun goes down.
    – d.george
    Commented May 7, 2017 at 11:03

2 Answers 2


I would check / change the distribution box next to the Air Handler and the duct size to that particular room.

Engineering wise it was probably sized for the room not for the fact that it has 3 walls to the outside!

Why over time has it become worse ?

Good question now to the second issue you have. Your Fan in the Air handler is not running as fast as it used to, bad bearings, bad capacitor or some other failure. Your system could have a blockage of sorts as well.

  • I would change the duct size and also adjust the distribution box to move more air to that room.
  • Check the Fan, the Fan bearings / check or replace the Fan capacitor.
  • 1
    I had a similar problem where 1 of 2 upstairs bedrooms was hot in summer cold in winter same size duct as the other bedroom but this one was on the south side of the home. Increasing the duct size and the register took care of the problem. Flex ducting is cheap the register to match the others was a bit expensive and this is not hard to do if you don't mind crawling in the attic.
    – Ed Beal
    Commented Sep 22, 2017 at 19:33

If this is the only room with 3 walls then that is probably the reason for the difference temperatures in that room compared to the rest of the house. For example; a room with 1 wall has a heat loss or heat gain from 2 surfaces, the (ceiling and that 1 wall) a room with 2 walls has a heat loss or heat gain from 3 surfaces, (the ceiling and those 2 walls) and so forth. Solutions to this problem are few. In my house just north of Pittsburgh, Pa. I have a bedroom with 1 extra wall and it is the room that is hard to heat and hard to cool. To help this room I run the furnace fan 24 hours a day on a low speed for continuous air circulation. This helps to even out the temperature but there is still a difference from the rest of the house. Nothing I have done in the 18 years we have lived here has corrected the problem. Adding an extra supply duct did the most to correct this problem. When you have a room with extra walls the best solution would be to have a separate heat/cool unit for that room but that is not cost effective. Hope this Information helps. Lastly what type air ducting system do you have and do you have a central return or a return in each room, do the doors stay open in this room. More info will help people make better suggestions.

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