Air return … using joists framing?
I’m replacing the floor of my 1/2 bath. Upon removing the floor, I see that the air return is using a portion of the joist framing. I don’t understand why.
In the pics, you’ll see the main return duct running towards the furnace/blower in the basement. However, between the joists, there is a square cutout. The square cutout opens into a section where the HVAC had sealed a section of the joist framing with sheetmetal.
Questions:
What does the cutout and sealed section of the joists do?
Could it have led to previous return duct that has since been removed (and sealing the joist framing was the HVAC’s way of closing this old duct off?)
Should I seal the square cutout?
I need to add some blocking between the joists where the cutout is so I can have something to support the ends of the new and existing floor. The old floor had been rotted away over the years due to a leaking toilet.
Replies
I should also mentioned that the "joist air return" is only about 5 feet long and doesn't open up into any other framing or floors.
Are you certain that that joist /duct doesn't have an opening into the heat duct below it? Is it possible that it is actually a heat duct not an air return , or is the duct below it an air return. It is not uncommon to use a joist space as either a heat duct or an air return. You need to be certain that the "sealed off" area is actually sealed and doesn't have an opening to another duct somehow."Poor is not the person who has too little, but the person who craves more."...Seneca
It's definitely the air return. In pic "pict9941.jpg", the big rectangular duct is the air return and it goes right into the air return filter. The sheet metal attached to the joists is the underside of "sealed cavity" that I was referring to.
The square opening in pict9937 is a cutout in the air return. The entire cavity between the joist is not well sealed at all.
I don't see how such a small cavity could provide any kind of quality air return. The other concern is that it's right near the flue for the hot water heater.
Any chance of it sucking in fumes and sending it thru the houes? I have carbon monoxide detectors in all the bedrooms, hallways, and living rooms and non have ever gone off.
I'm thinking I will seal it. Any suggestions has to how?
I am not an HVAC person. Best make a call to someone who may understand the system or hope my replies serve as a bump and get someone who does know to reply here. Closing off an air return can cause imbalance in the system , that much I do know."Poor is not the person who has too little, but the person who craves more."...Seneca