Duct Board to Register connection

[JD Johnson]

While I am on checking the Board for feedback for the question I had about screens, I have another quick question.

Recently while inspecting a new construction condo unit, I discovered that the majority of the HVAC supply registers were simply supplied with an air hole cut in the duct board.

This doesn't look correct at all, especially since there is no template as to the size of the cut out - - it is simply a hole cut in the duct board. I attached a few sample photos, but I am not sure they provide a clear illustration of the condition.

Can y'all tell me if this is an acceptable practice? (Jerry Peck - I found some Code Citations in the FMC 603.4.2 and 603.1.2 but I am not sure those cover this issue.)

ALSO...Guess what - the HVAC contractor who did the installation says it is fine, but I don't think my Buyer's who are paying $1m plus per unit will accept it, and I don't think it is correct.

Thanks for any feedback / advice.

Inspect safely -

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[Gunnar Alquist]

JD,

Seems to me that the moving air in the duct is just going to "breeze" right by that opening. Using the venturi principle, that would likely pull air from the room into the duct system. Normally, ducts use a wye connection that directs the air to where you want it to go. Did you test the system? I suppose that if the duct tapered down where the register is, it would force some of the air out of the register. It may not be a code violation, but it also may not work adequately.

[Ted Menelly]

Very common practice in the old metal duct and the duct board. Even in the older homes that had the ducts in soffits they would just cut a hole in the side of bottom of the duct and hook a vent up to it. Plenty of air blows out of them and almost all have some type of design to follow for placement and air flow.

[Edward Loughran]

The area I am in would allow this if it could be demonstrated that the "R" value was 6 or higher.

[Jerry Peck]

Recently while inspecting a new construction condo unit, I discovered that the majority of the HVAC supply registers were simply supplied with an air hole cut in the duct board.

JD,

What is up inside those, beyond the hole?

In one photo, it looks like the inside of a duct board duct, the other photo looks like it is just going up into the space above the supply register ceiling box.

No, all duct connections are required to be two things: 1) mechanically attached together; 2) sealed with proper sealant.

I do no see any means that 1) was even attempted, and no means with which to proper attempt 2).

I am suspect that there is a duct above those holes, otherwise it would be a supply plenum, not good. A return air plenum, okay, but not supply.

That said, what you 'might' be looking at is a template cut and fit into a properly attached and sealed duct board ceiling box and duct work, where the duct board template you are seeing is just 'stuck up inside' the ceiling box.

The reason for the template would be to reduce air flow and balance the systems to a good basic level, after which the adjustable vanes would be used for 'final tuning' of the balancing.

The reason for using the duct board template instead of just using the adjustable vanes for the initial balancing is noise. Using the adjustable vanes causes whistling noises, using the duct board for the first reduction eliminates that noise.

The irregular cut hole is because it was cut out with a duct board knife, cutting out just enough to make it balance better, then just a little bit more, then a little bit more, ...

Thus, the final answer is ... It depends on what is really up there.