Underground Concrete Return air Plenum

[Buildtech2]

Dear All,

I would like to know the possibility of using underground concrete plenum as return air plenum for my ongoing factory project without any sheet metal duct work.

Is there any issue related with condensation or formation of mold or any infection related issues which can cause any significant problem. Please advise.

 

[DrRTU]

You may have issues with material and insulation. Chicago only allows metal and approved materials. Energy codes (90.1 & IEEC) may force you into an insulated construction. Concrete has been used before and will be used in the future. Filtration, sealing and moisture must be a concern. If ducts are not big, I like blueduct.

 

[berkshire]

Most common method of producing underground ducting is to use Galvanized drain piping and backfill around with concrete.
B.E.

You are judged not by what you know, but by what you can do.

 

[Buildtech2]

Thanks DrRTU.

Hi Berkshire,
I would like to use underground concrete plenum as return air plenum as I am not using any galvanized duct work. Off course galvanized drain piping will be considered in this concrete plenum.

Do we have any code which says underground concrete plenum can be used as return air plenum. please advise.

 

[willard3]

You will have to read the codes yourself, it's the Engineer's job.

 

[DrRTU]

Most codes prohibit materials & methods but do not state if a design is allowed. I personally have encountered concrete tunnels in theaters, industrial and process related return air paths but was concerned about ground water intrusion. Flooding and floor drains are the issues. Placement of a concrete duct tunnel below grade my require floor drains. An active drain in a duct is prohibited. The ifly facilities being build, utilize large below grade w/o metal walls and have cooling coils installed in the air path. When we design PCD, PVC, fiberglass or Blueduct in a below grade design, we utilize a large slope and a “drop” tee to allow for a sump pump in the advent of water intrusion from above or below. You can get around thermal requirements by insulating the concrete, pressure testing for integrity, filtration for concrete dust & IAQ but moisture will vary with building life and present an ongoing liability. If you are doing a large test cell or wind tunnel, I see no issue with concrete but for a standard commercial building, utilize a conventional smacna construction technique.