Open the door, and look for weatherstripping around the perimeter. Do you see areas that might be missing?

If you're not sure, attach a photo and maybe we can help more.

Weather stripping is certainly important and easy to verify if it's missing or damaged.

Air sealing around windows and doors will go a long way to minimizing air infiltration. You'd need to remove the interior trim to see if the space between the jamb and stud is sealed. If not, I'd use a low pressure spray foam to insulate it and then reinstall the trim.

Hello @Ripped Jeans Construction @Charles Ross Homes Please find attached photos of the weatherstripping and french door problem areas. I have a few questions:

1. Based on looking at it, I can't tell whether I need to replace entire OR fix some weatherstripping. Is there a telltale sign? looks like it is q-lon brand.

2. Is this kerf based weatherstripping? I am a new condo owner so not sure about this.

3. Is there anything that can be done to the space between threshold and weatherstripping on both hinge sides, and space where the doors meet?

4. Is there anything that needs to be fixed that I missed from the pictures?

Also please let me know if you want me to retake some of the pictures. Black seal is the weatherstripping.

I really appreciate all your time and help on this!

Thanks a lot!

Below is the capture from inside when we close the door. This is just an example but there is always space between doors when they are closed. I applied fixes using adhesive seals but they are not working completely.

Below is the picture of the bottom of the door (sideview) where two doors meet.

Below picture from inside where hinge side cold draft is coming in...

General view of the weatherstripping:

Below picture (it is not clear) but the space where top and side weatherstripping meets there is a small gap and I don't know how to fix this.

Below is the side view of the hinge side with door open:

General view of weatherstripping. How can I tell if the stripping is worn out and need to be replaced?

It's difficult to tell the condition of the weather stripping from the photos. It would need to be replaced if it's torn, or friable or doesn't meet up against other weather stripping at the corners.

Would you consider hanging heavy curtains, then draw them closed in the evening? That will block the draft. Keep them over the sides of the French doors during the day then draw together to block the middle at night.

We already have heavy curtains but they seem to be not protecting from the cold drafts. Temperature in that room is at least 5 degrees colder than other rooms. I am running out of clues on what I can fix. Do you have any ideas for corner areas of the door?

If I had to guess from those photos, I would say your door is not the root cause of your 5 degree room temp difference (contributing factor? - sure).

Do a test: plastic/tape over the entirety of the doors for a day, and see whether it helps.

Other things to check: do you have a heat register/return somewhere in the room? Are they open? Is the room well insulated? Is the slab/crawl/basement different than the rest of the house?

We had a sinilar problem but ours was where the doors meet at the top and bottom so i put a corner seal on each spots and its helped so far. bought them at the local hardware store

Oh i was thinking maybe you need a larger weather stripping. they do come in different widths etc

Thank you @Ripped Jeans Construction and @JANE HESTER.

There is no return vent in the room. Heat register is open. Since it is a condo, it must be insulated because there is a unit upstairs. Am I correct in assuming that?

How about pictures of the entire door from both the inside and the outside? How old is the unit? Does it operate properly? What type of locking mechanism? Tough to tell anything from your pics.