Air Through a non load bearing header

[Greatwhitewing]

Have a header for a 6 ft wide non-load bearing opening for an interior wall between two areas. Having a HVAC drop added on one side of the header through a closet on second floor but wanted to know how large an opening(s) through the header I can have to let "some or about 1/2" of the air from the 8 or 9" drop into the adjacent (living) room on the other side of the header. Living room gets pretty warm in the summer. Separate drop is not possible.

I was thinking of adding a plenum to accumulate and direct air to both sides of the header into the two rooms, the living room and kitchen. I have about 9" of drywall showing between the trim of the opening and the ceiling of what I think is a 12" header. Perhaps two 4" holes, a 6" hole or more smaller holes?

Long story but the AC is really for upstairs but with a new system being added soon by a reputable Bryant contractor I have an option to add a drop to the first floor but trying to get the air into two rooms separated by the 6' opening better. The drop would come out near the middle of the opening but I am not sure I will get enough cooling into the living room without an obnoxious and loud fan.

Very long story of my AC problems, suffice it say I got screwed by a contractor and have to replace it with another drop to first floor. Whole story would make post obnoxiously long. Just wanted to know how much the header can be drilled.

Thanks

 

[fitter30]

Amazon sells combo thermometer and humidity some also have another remote sensor for a few $ more. See what your Rh is. Previously set my stats at 74° running 49-50%. With a dehumidifier temp 77° 38% Rh house feels so much better.

 

[Greatwhitewing]

Amazon sells combo thermometer and humidity some also have another remote sensor for a few $ more. See what your Rh is. Previously set my stats at 74° running 49-50%. With a dehumidifier temp 77° 38% Rh house feels so much better.

Have plenty of temp humidity monitoring devices, some remote but my question was more about going through a header to get air directed where I need it.

 

[chinboys]

You don't need to modify the header.
Cold air is dense and would drop towards the floor from the drop's (ceiling vent) vent.
And if you didn't have this first floor drop, I would know for a fact that cold air from the upstairs volume would sink to the lower floor in time.
Make sure the air handler's blower is moving 400 cubic feet of air per cooling tonage in all of the duct work which includes this drop's duct.
Being able to segregate the upstairs vents and or duct system to force more volume of cooling air to the first floor drop means more cooling volume per minute to the first floor while the second floor suffers. And placing a 18 inch fan on a stand right below this drop would circulate the cool air into the second room.

 

[Greatwhitewing]

You don't need to modify the header.
Cold air is dense and would drop towards the floor from the drop's (ceiling vent) vent.
And if you didn't have this first floor drop, I would know for a fact that cold air from the upstairs volume would sink to the lower floor in time.
Make sure the air handler's blower is moving 400 cubic feet of air per cooling tonage in all of the duct work which includes this drop's duct.
Being able to segregate the upstairs vents and or duct system to force more volume of cooling air to the first floor drop means more cooling volume per minute to the first floor while the second floor suffers. And placing a 18 inch fan on a stand right below this drop would circulate the cool air into the second room.

So stairs are in living at one end of the house with two 6" drops at the far end of the lower floor and it's better than nothing but not at all adequate to cool the living room. Looking to ensure enough air from the "soon to be added" drop get into living room and not stay in kitchen area. Get a small amount of cool air coming down the stairs.

I will likely see if just the added vent in kitchen is enough or if I need to something more proactive. This post is looking at the option if it proves inadequate. By installing this upgraded equipment and drop in the fall I may not know till next year cooling season.