I have seen several homes with an inadequate air gap usually the result is the doors close themselves when the furnace turns on and as a result the room is usually colder than the rest.
Gap under interior door.
But for finished conditions bedroom closets area with w to w carpeting ect 1 2 max.
The other thing neglected by the building science conventional wisdom is the other air flow.
I think it is too big and think a 1 4 1 2 gap would accommodate any unevenness in our floors and allow us to use area rugs.
Look at the gaps on the sides and top.
Door gaps especially on exterior doors can be serious energy wasters.
This is what i particularly suggest for the front door to keep our.
This is the alternative to using a door sweep.
When you close a bedroom door the undercut isn t the only pathway for return air.
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This is a simple solution to your problem.
You are unlikely to find and direct plain english codes or technical health safety standards written for this in washington however if you have a modern central heating system with centrally located return air grills no return air in small rooms with doors then the hvac calculations will be relying on a 1 minimum gap under the door.
My contractor just hung our fancy dancy un painted solid wood door slabs in my 100 year old house with solid hardwood floors throughout.
Gap under interior doors let me get more specific if the conditions will likely end up with a door mat like a front entry door 3 4 is more appropriate.
Walk over to a bedroom or other interior door and close it.
4 2 out of 5 stars 1 027.
There is an approximately 1 5 gap at the bottom of the doors.
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Grab the handle and see how much movement there is.
How to fix a gap under a door.