Thread: Supply duct through joist cavity

Hi guys,

I inspected a condo built in 1973 that utilizes the cavity between joists for a supply trunk line. The cavity is not lined with sheet metal. I know returns can be built this way, but does anyone know if supply lines could be run this way back in the early 70's?

Thanks,
Ron

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Not to be a jerk but who the hell cares whether it was allowed or not. If you are writing your report or recommendations based on whether or not it was allowed 40 years ago you are NOT serving your clients best interest. I suggest you look at it from a health, safety and utility cost standpoint.

Markus...Thank you for your kind reply. The inspection was done 6 months ago and I did write it up. My client just contacted me asking if I knew if that type of installation was acceptable in the early 1970's. I'm just trying to respond to a clients questions.

Ron, I think there was a thread on this not too long ago, do a search in HVAC. Found it. Read #7.



- M1601.1.1 Above-ground duct systems. Above-ground duct systems shall conform to the following:

- - 1. Equipment connected to duct systems shall be designed to limit discharge air temperature to a maximum of 250°F (121°C).
- - 2. Factory-made air ducts shall be constructed of Class 0 or Class 1 materials as designated in Table M1601.1.1(1).
- - 3. Fibrous duct construction shall conform to the SMACNA

Fibrous Glass Duct Construction Standards or NAIMA Fibrous Glass Duct Construction Standards.
- - 4. Minimum thickness of metal duct material shall be as listed in Table M1601.1.1(2). Galvanized steel shall conform to ASTM A 653.
- - 5. Use of gypsum products to construct return air ducts or plenums is permitted, provided that the air temperature does not exceed 125°F (52°C) and exposed surfaces are not subject to condensation.
- - 6. Duct systems shall be constructed of materials having a flame spread index not greater than 200.
- - 7. Stud wall cavities and the spaces between solid floor joists to be used as air plenums shall comply with the following conditions:
- - - 7.1. These cavities or spaces shall not be used as a plenum for supply air.
- - - 7.2. These cavities or spaces shall not be part of a required fire-resistance-rated assembly.
- - - 7.3. Stud wall cavities shall not convey air from more than one floor level.
- - - 7.4. Stud wall cavities and joist-space plenums shall be isolated from adjacent concealed spaces by tight-fitting fire blocking in accordance with Section R602.8.

Originally Posted by Ron Tipton

Markus...Thank you for your kind reply. The inspection was done 6 months ago and I did write it up. My client just contacted me asking if I knew if that type of installation was acceptable in the early 1970's. I'm just trying to respond to a clients questions.

Hi Ron,

Fill your profile out so we know your location. This can help folks with an answer if they know your location.

I have never known of this type of supply to be OK. No insulation and the wood is a perfect breeding ground for all types of little nasty things.

hey ron

welcome aboard. click on the heat subject title and go down to unlined retun thread dated 10/13/09--half way down page. you will get your info there

see you on the 17th

charlie

Thanks. I need to learn how to use the search better. This condominium complex utilizes exterior closets for the furnace and water heater. The trunk run on the supply side travels into the unit between joists. Apparently the interior of the joist cavity was painted silver. From what I'm hearing, this installation was never acceptable. Apparently the entire complex was built this way.

Ron