Is this Duct Modification Acceptable?

[john_ertw]

I have hired a contractor to renovate my basement. One of the tasks involves relocating a low section of HVAC duct work to give more head room. Currently the duct is directly below the joists, but it bends down to clear a structural steel beam. At this point it is less than 6 feet off the floor. It is also in the middle of the room so I think it is a safety issue as someone can walk right into it.

The contractor's proposed solution is to use the joist space as a duct for a portion of the supply line to allow it to be routed over the steel beam. I believe the contractor will do something similar to what is done for returns (the joists and subfloor are boxed using sheet metal). Is this ok for supply or does it need to be an actual metal duct?

Unfortunately, due to the layout, none of the proposed solutions I have been given sound ideal to me. I spent an hour or so last night looking at it and I can't come up with any better ideas either.

[openclasspro]

Not the right way,only way I would even consider it ,no plumbing or electrical goes through that portion,joints are sealed tight.

[heaterman]

No supply air should be directed through a wooden chase or joist space using that space as the sole conveyance. In other words, sheetmetal ducting IS required, period.

[openclasspro]

Forgot to note,line with tin.

[john_ertw]

I will discuss with the contractor tonight and suggest that the wooden space must be lined with metal and sealed to create a duct.

One other thought that occurred to me is that perhaps making the duct wider and not as high as well as having more efficient framing for the bulkhead will provide acceptable headroom. Currently it is a 16"x8" duct with multiple bends. The bends would stay the same, but I may be able to accept it if I can reduce the height from 8" to maybe 4" or 5".

If this is possible how do I know if the new duct dimensions are acceptable? How can I make sure the contractor is using adequatly sized ducting to make sure I get enough air in that section of the house?

Thanks for the help.

[openclasspro]

Have a Hvac contractor do it,not a general contractor.

[skippedover]

At a duct height of 4 or 5 inches, you might just as well not run it at all for all the air you'd ever get out of it. As you can see, you're encroaching on the mechanical space in an attempt to make a living space out of it. Bad idea in my books as I've seen many, many "finished" basements that are in ruin from lack of use. JMO. Perhaps you'd consider hiring a qualified company to do a Manual "J" and Manual "D" to help solve your problem, if it's solvable. The might find an alternative, like making the 18x8 smaller (it could be over sized) or breaking it into two trunks that can travel differently than the current trunk. Or not. I would not recommend just modifying ducts willy-nilly. If there was a Man 'D' design to it originally, you'll ruin that and likely end up with less than stellar results. And if there was no design (most likely case) then you'll just make it worse.

Since you're making living space in the utility space, then you could likely sacrifice a little space upstairs. So to save you head from nasty dents, why not raise the floor joists as necessary and go over the beam. It might create a bump in the floor above but you won't notice if you're in the basement.

[john_ertw]

Perhaps you'd consider hiring a qualified company to do a Manual "J" and Manual "D" to help solve your problem, if it's solvable. The might find an alternative, like making the 18x8 smaller (it could be over sized) or breaking it into two trunks that can travel differently than the current trunk. Or not.

Great thoughts. I would consider hiring a professional HVAC company, but when I was on the search for one 3 years ago to replace my furnace and AC I was unable to find a single company who would perform a load calculation. It is actually pretty pathetic. I would call the 20 or so HVAC companies I spoke to “equipment installers/parts changers” and not true professionals.

As for your suggestions, we already gave them thought. The configuration of the house framing really doesn’t leave many options.

[tinner73]

http://img340.imageshack.us/img340/5540/27572d123466538309herit.jpg

[skippedover]

Great thoughts. I would consider hiring a professional HVAC company, but when I was on the search for one 3 years ago to replace my furnace and AC I was unable to find a single company who would perform a load calculation. It is actually pretty pathetic. I would call the 20 or so HVAC companies I spoke to “equipment installers/parts changers” and not true professionals.

As for your suggestions, we already gave them thought. The configuration of the house framing really doesn’t leave many options.

That's a sad truth for our industry and the worse truth is that those of us who try to do it correctly are constantly getting beat up on the price of the jobs. Once it's in and 60% uncomfortable, the customer has already made the investment, knows they've screwed up and doesn't even call us back to try and remedy the issue. That said, the easy way is to either duck under the space, or wait until your grow old and bent (you'll be shorter) or is there any possibility of moving the main trunk to one extreme side of the space? (Ducking or shrinking are the cheapest options).

[john_ertw]

I think we came up with a solution. We will use the joist space, but slide a metal duct inside. It requires reducing a return chase slightly (it currently is 32" wide and will be reduced by a couple inches). Not an ideal solution, but I think it's better than other options.

Thanks for all the suggestions skipped over. We did consider moving the ducts to extreme ends of the house, but it only move the low portion to other unacceptable areas. If I have any more questions on the detailed proposal I'll be sure to post here as this is a forum filled with top techs that know their field and care about it.

[jpsmith1cm]

Nods

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