PP here, the problem is that room is too small with very little air circulation due to closed door. You have to control the temperature of that room at night either by passively control the opening of the AC vent or actively using the smart room sensors as I did.
Google sleeping room temperature for kids/adults. They will tell you it's between 65-70 (or 68-72 degrees). It's hard to breathe when it's hot.
My 3 years old used to be in that room, and now it's the 16 months old one. The room is by the stairs, so it's closed during nap and sleep time.
The solution is, keep the temperature low and bundled up.

Anonymous wrote:

Anonymous wrote:I had similar problem with my kid's (10x10) room, and here're what I did,
- Check AC vent flow and buy the biggest opening AC vent, like this one
https://www.homedepot.com/p/Everbilt-10-in-x-6-in-1-Way-Steel-Adjustable-Wall-Ceiling-Register-in-White-E210VM-10X06/300539449

- Have room sensor in the room, set 70 degrees as average temperature for 3 bedrooms, dress her warm for sleep.
- Keep her door open for air circulation (crack is OK.)

What is room sensor? We set temperature at 73 or 74 degree 24/7 in the house, and both 2 kids have sleeper sack on. The other kid room is a bit chilly with humidifier room in the middle of night. Her room is a bit too warm & suffocated with the Same humidifier on in the middle of night. Thoth rooms are next to each other.

We cannot have her door cracked open for circulation because she is a light sleeper. Any sounds will alert her. And one more thing, I do notice that her room is loudest whenever heater kick in with air blowing from the vent. The return vent is right behind one of the wall (the wall behind her closet walk in closet), not sure if it matters or not.

Ecobee with smart sensor
https://www.amazon.com/Thermostat-Ecobee4-with-2-Sensors/dp/B08KHFTX3G/ref=sr_1_2?crid=3RUSUJWLDFK53&dchild=1&keywords=ecobee+smart+sensor&qid=1611628311&s=home-garden&sprefix=ecobee+smart+se%2Cgarden%2C157&sr=1-2

I have 3 of them, one in each of the kid's rooms. During sleep hours, the thermostat is set at an average of 70 of those 3 sensors, so the room temperature is stable for all 3 rooms (the coldest room would be 69 and the hottest room would be 71). We use gas for heating, and 73-74 degrees would be too hot and too dry for us even during the day. We don't use humidifiers anymore. They are too loud. We just moisturize ourselves with a thick layer of lotion/cream every night. Sleepwear includes one layer underneath a one-piece fleece footies. That's how we solved that particular room's heating problem. In the summer, we have to use a small fan in that room but that's another story.

Good luck.

Probably bad vent duct or bad insulation

Anonymous wrote:

Anonymous wrote:Have you checked that the vent blows air out?
We had poor ventilation in a basement bedroom and it turned out that the vent was actually a return and not sending fresh air to the room.
For now, put a gentle fan in the doorway to help circulate the air.

Her room is the warmest in summer and winter, and I hear vent blows out air loud. It is weird that her room is not cool in summer while other 2 rooms are cooler. And, her room is the hottest in winter while other rooms are a bit chilly.

How could that be possible? How did you find out? Is there a trick to test?

Anonymous wrote:I had similar problem with my kid's (10x10) room, and here're what I did,
- Check AC vent flow and buy the biggest opening AC vent, like this one
https://www.homedepot.com/p/Everbilt-10-in-x-6-in-1-Way-Steel-Adjustable-Wall-Ceiling-Register-in-White-E210VM-10X06/300539449

- Have room sensor in the room, set 70 degrees as average temperature for 3 bedrooms, dress her warm for sleep.
- Keep her door open for air circulation (crack is OK.)

What is room sensor? We set temperature at 73 or 74 degree 24/7 in the house, and both 2 kids have sleeper sack on. The other kid room is a bit chilly with humidifier room in the middle of night. Her room is a bit too warm & suffocated with the Same humidifier on in the middle of night. Thoth rooms are next to each other.

We cannot have her door cracked open for circulation because she is a light sleeper. Any sounds will alert her. And one more thing, I do notice that her room is loudest whenever heater kick in with air blowing from the vent. The return vent is right behind one of the wall (the wall behind her closet walk in closet), not sure if it matters or not.

Anonymous wrote:Have you checked that the vent blows air out?
We had poor ventilation in a basement bedroom and it turned out that the vent was actually a return and not sending fresh air to the room.
For now, put a gentle fan in the doorway to help circulate the air.

Her room is the warmest in summer and winter, and I hear vent blows out air loud. It is weird that her room is not cool in summer while other 2 rooms are cooler. And, her room is the hottest in winter while other rooms are a bit chilly.

Anonymous wrote:We have the exact problem. We keep the heating vent closed in there too, and we have a ceiling fan and keep the window cracked sometimes. I finally just moved my son into the adjacent room this weekend; it has 2 windows and doesn't seem to have the same stuffiness. I'm so curious as to what the problem is with this one room. Thought maybe it has something to do with the attic. But our "hot" room also has one window and is the smallest, so it must have something to do with that.

This is op. That is interesting, and I never think of the reason could be attic because I never go up there. I will try to close the vent to see, but unfortunately we don’t have ceiling fan installed in our house. Is there another better alternative than having ceiling fan installed, like is there any cool looking wall mounted air circulator that I can easily mount high on one of the wall?

I had similar problem with my kid's (10x10) room, and here're what I did,
- Check AC vent flow and buy the biggest opening AC vent, like this one
https://www.homedepot.com/p/Everbilt-10-in-x-6-in-1-Way-Steel-Adjustable-Wall-Ceiling-Register-in-White-E210VM-10X06/300539449

- Have room sensor in the room, set 70 degrees as average temperature for 3 bedrooms, dress her warm for sleep.
- Keep her door open for air circulation (crack is OK.)

We have the exact problem. We keep the heating vent closed in there too, and we have a ceiling fan and keep the window cracked sometimes. I finally just moved my son into the adjacent room this weekend; it has 2 windows and doesn't seem to have the same stuffiness. I'm so curious as to what the problem is with this one room. Thought maybe it has something to do with the attic. But our "hot" room also has one window and is the smallest, so it must have something to do with that.

it also may be that it's the first room on the way from the heater. You may need to close the vents a little bit in her room. That will reduce the amount of heat coming in, and increase the amount of heat in the other rooms.

Have you checked that the vent blows air out?
We had poor ventilation in a basement bedroom and it turned out that the vent was actually a return and not sending fresh air to the room.
For now, put a gentle fan in the doorway to help circulate the air.

Can you install a ceiling fan? And also I’d recommend hiring an HVAC technician.

You need to get an HVAC person out to evaluate the problem.

Op here, I have slept in my toddler girl bedroom even with humidifier on. I wake up in the middle of night feeling kind of suffocated and throat drying and lips chapped. I don’t have those feelings when I sleep in my master bedroom or my another kid room. There is something weird about my toddler girl small bedroom and it has 1 window, 1 vent and a humidifier.

We have 3 bedrooms on second floor of end unit townhouse. Two bedrooms with walls located on the end unit side each have two windows have no problem with air circulation. There is one bedroom with only one window with one wall adjoining to next bedroom & one wall adjourning to neighbor wall has poor air circulation. It has vents on the floor, but it feels so dry and sweaty sleeping there overnight, and unfortunately that’s my toddler girl bedroom. She has been crying in the middle of sleep because she gets so sweaty & uncomfortable even we have humidifier on in her bedroom. We have windows closed all the time with hvac/heater on 24/7. My toddler girl has been coming to our bedroom to sleep or afternoon nap b3cause it feels so comfortable sleeping in our bedroom.

My question is how do we fix the poor air circulation problem in that bedroom? Is there a good and quiet wall mounted air circulator machine that acts like a fan I can buy to simply to fix the problem? Her bedroom is the smallest, probably 8’ x 8’ something like that. Thank you.