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Under stair void used as return air?


Brandon Whitmore
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This home was built in 1991. I can't say I've ever seen a return air set up like this. They are using the area beneath the stairs for their return air duct. To make matters worse, this is on an exterior wall, so there is exposed fiberglass insulation in the walls.

Anyone know whether this could have been allowed in 1991? My concerns are the fire spread issue (enclosed stairs require drywall). A fire could be pulled right in under the stairs. Also, there is the dirt/ fiberglass concern.

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IRC 2003, Section M1601 Duct Construction, M1601.1.1

Above-Ground Duct Systems: Item #7 Stud wall cavities and the spaces between solid floor joists to be utilized as air plenums shall comply with the following conditions: 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.

Common sense would indicate that you should recommend an insulated flex retun install as an upgrade because I am only seeing the fire blocking in the code section. It looks like they used the loophole to their wallets advantage.

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Common Sense?

I dunno,

If we started writing stud cavity and floor joist return plenums out here we'd have to write them up on about 95% of new construction. That doesn't seem to make any sense, let alone be common sense.

I can understand recommending upgrades that will fix stuff that's a violation of the code that we'd consider dangerous; but I don't understand why we'd want to start trying to impose our own quality standards on stuff that complies with the codes - no matter how loopy we think the thing they've done is. As long as there is blocking there and it's in compliance, it's allowed and I wouldn't call it.

ONE TEAM - ONE FIGHT!!!

Mike

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This home was built in 1991. I can't say I've ever seen a return air set up like this. They are using the area beneath the stairs for their return air duct. To make matters worse, this is on an exterior wall, so there is exposed fiberglass insulation in the walls.

Anyone know whether this could have been allowed in 1991? My concerns are the fire spread issue (enclosed stairs require drywall). A fire could be pulled right in under the stairs. Also, there is the dirt/ fiberglass concern.

I don't see a problem with it from the perspective of the HVAC system. However, I think that space is certainly enclosed and accessible. As such, it should be lined with GWB.

- Jim Katen, Oregon

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IRC 2003, Section M1601 Duct Construction, M1601.1.1

Above-Ground Duct Systems: Item #7 Stud wall cavities and the spaces between solid floor joists to be utilized as air plenums shall comply with the following conditions: 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.

Common sense would indicate that you should recommend an insulated flex retun install as an upgrade because I am only seeing the fire blocking in the code section. It looks like they used the loophole to their wallets advantage.

Thanks Wayne,

The above references and R311.2.2 in the 2003 IRC/ 2005 ORSC is what I am basing my opinion on right now. R311.2.2 requires 1/2" drywall for under stair protection. This is not a stud wall or joist bay-- the entire under stair closet void is open right now.

I'm still looking for one that says it's allowed and just dumb to use an insulated wall for return air. I could always nail them on the fact that the paper is not allowed to be exposed on the fiberglass batts in the return air stairwell closet.

I can understand recommending upgrades that will fix stuff that's a violation of the code that we'd consider dangerous; but I don't understand why we'd want to start trying to impose our own quality standards on stuff that complies with the codes - no matter how loopy we think the thing they've done is. As long as there is blocking there and it's in compliance, it's allowed and I wouldn't call it.

Hi Mike,

I'm not trying to make up my own standards. I'm just trying to figure out when the code started requiring the enclosed areas of stairwells to be drywalled/ protected-- I consider using the underside of the stairs to be a violation, at least according to current code.

What seems strange to me is that they did not have to use this entire space for return air. There side of the stairwell closet backs up to the garage, and that's where metal return air ducting starts-- they could have easily extended the sheet metal a few more feet.

I don't see a problem with it from the perspective of the HVAC system. However, I think that space is certainly enclosed and accessible. As such, it should be lined with GWB.

I completely agree. In this case, I think it would be easier just to run the return air duct right to the grille-- it just needs to be extended over a few more feet. Then they don't have to install all of the drywall, which would require removal of the outer wall to get in under the stairs.

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