Whole wall as duct

[csnydermvpsoft]

I've been doing a lot of poking around in my recently purchased house in preparation for some major wiring work (the house has the original

1948 wiring, and I'm going to be adding a lot of up-to-code circuits). The house is a 1.5 story with a finished attic. When I took off one of the floor heating vents in the attic (forced-air heat) and shone a light down the opening, I discovered quite a bit of electrical wiring, including a junction box, visible below. As far as I can tell, attached to the box is a wall light fixture in a room on the main floor.

I haven't done a lot of further investigating yet (I didn't have a powerful enough flashlight), but it looks like it might be the case that the ducting is not continuous from the basement to the upper floor

- the whole section of wall between the two joists is being used as the duct. This is obviously very bad - especially considering the electrical wiring in the space. I'm planning to replace the wiring anyways, so it won't be a problem, but I should do something about the duct. What options, short of ripping up a section of wall on the main floor, do I have? My fiancee is not going to be happy if I tell her that we have to rip out a section of wall, though if that's the only option, I guess I'll do it (at least that wall only has paneling, not drywall).

It looks like the wiring is original, so that means that either someone was careless at the time of construction, or some HVAC person did a crappy job when adding a vent to the upstairs.

Any tips on how I should handle this? Thanks in advance.

[Doug Kanter]

My 1945 house had the same thing, but ONLY for the cold air returns. Still an odd thing, though.

Before I'd start ripping walls down, call a local heating contractor and ask about flexible ducting material. They use this stuff when updating really old homes and they don't want to mess with the walls.

[RayV]

Are you sure this is not a return vent? It is fairly standard to just use the space between the studs to return air to basement. I have a center wall in my two story house with several returns and the bulkhead in the kitchen is open to the floor joists. System works fine.

[Edwin Pawlowski]

Are you sure it is a supply and not a return? In the 40's and 50's, it was common to have an unlined air return and even fairly common to use it for wiring. Returns have no heat to speak of, no pressures or things that will cause problems.

[PipeDown]

You could install a few fire dampers where the space transects the floor or other places that make sense.

Aside from the fire issue, leakage of the hot air out of the cavity might be a concern for efficiency. Use of wall space for cold air return is common. The under stair space in my prevoius 1973 home was used for cold air return but a seperate return was used for the second floor.

There is nothing requiring you to change anything.

[louie]

I agree with others in making sure this isn't just a return that you're looking at. It's very much ok and normal to use a wall cavity for cold air return, and not unusual to find electrical wiring running through it. J-boxes are ok, but I think they have to be accessible and not hidden in the wall, so that may be against code (you'll have to check your local codes to be sure).

[hallerb]

Technically wiring shouldnt be in any ducts because the air flow will spread fire fast, and be hard to put out. But its common to find in cavitys, because it was easy and probably isnt a code issue on a existing home

[Pete C.]

I believe BX, EMT and similar are ok to pass through plenums.

Pete C.

[csnydermvpsoft]

I'm pretty sure it's not a cold air return (IIRC, there was hot air coming out of it last time the heat was on). I agree that it's not a problem if it's a cold air return, especially if I remove the wiring that's there. I'll check next time I'm over at the house (I'm not living there yet).

[PipeDown]

I would guess; The attic was probably finished as a remodel and someone took a shortcut routing the heating connection. Is there even a cold air return for the attic or did they just assume it would flow down the stairs?

If it was an unpermitted remodel of the attic, make sure the joists are built sufficient for a floor before you load that room with too much stuff (might not make a good home gym)

[Goedjn]

Don't they make wire that's specifically rated for use in plenums?

[Pete C.]

Yes, for comm. type wire like cat 5. It's not commonly found in power type electrical wire though, the norm there is to use metal armored wire like BX or metal conduit.

Pete C.