I have an upstairs bathroom, it used to be a half bath, but was converted to be a whole bath using an adjacent closet, whole room is maybe 40-50 sqft. The bathroom does have an air vent and I have tested to make sure cool air is coming out of the vent, however the second you walk in the door the whole room is significantly warmer and feels more humid that the game room it is attached to.

Two of the four walls are exposed to attic space. I have been into the attic and it looks like the walls are insulated, but this room still doesn't cool or feel like the rest of the house. Does this seem like I have an insulation problem or an HVAC problem. For the record, I did just replace my whole HVAC system and the system has been working well. On the old system this room did always feel a bit different than the rest of the house, but it seems like more so now. The old system was a Single Stage Zoned system, and now I have a 2 stage zoned system.

Should I call my HVAC company back out (even though the vent is blowing cold air) or should I contact an insulation company to see if there is something I am missing that is making this room hotter than the rest of the house?

A Home Inspector's eyes would give more precise solutions or better guesses since all bathrooms will be more humid/warmer than other rooms ... and more so when used more.

• Open window when possible .... IF any
• Add a 2nd, more effcient ceiling vent (most sold are whimpy and sell on Quiet Factor) then put both on timers to force ON at least 20 minutes after occupancy
• Leave door open when not in use
• Caulk all possible water traps/leaks floors/walls/fixtures - no water hiding to evaporate long term nor cause rot/mildew
• Replace all insulation with thicker rockwool
• Adjust HVAC damper (if any) to force more air supply BUT some might freeze in summer when wet
• Consider a towels/mat drying rack outside the room, perhaps hallway ... a natatorium ploy
• EZ: A very old house's owner/client set up a big box fan in hallway that blows out the bath from open door when not in use. Reports that the hassle solves their problem Presto & 100%

Couple thoughts:
- Is the HVAC register directing air towards the door? Does it need to be turned around to direct more airflow back into the room?
- Does the HVAC system need to be rebalanced to send more air back to the bathroom?
- Is there insulation on the ceiling and/or floor missing?
- Is the insulation tight against the sheetrock?

Ask the HVAC company if a jump duct to the adjacent room would be helpful. We did this in 2 secondary bedrooms to the hallway b/c no returns in those bedrooms and not enough air gap under the doors

Non-HVAC things you can confirm or deny:

Where in the house is the bathroom expansion / former closet? There is a small but non-zero chance that the closet walls were not insulated as well as the rest of the house (or at all) if the closet was set off somehow (e.g., in an outside corner of the house). If you're comfortable with drywall patching, you could check this yourself - cut a few holes in various places to see if there's insulation behind the drywall.

It's also worth checking the attic insulation above the bathroom extension. The original blown fill might not have adequately covered the closet or it may have been kicked around when doing the remodel. You can easily check this yourself, just take a ruler up to the spot above the bathroom and check in a few spots to see how thick the insulation is.

Make sure there is a good check valve in the bathroom exhaust vent.