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Return air question


Brandon Whitmore
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Did a 2 story house today. The main floor return air grill was located in the ceiling at the NE end of the home, and it passed beneath the Master bathroom located upstairs at the E. end of the home. The furnace was located at the SE end of the home, so the return air ran directly beneath the whirlpool tub.

I opened up the tub access hatch and instantly felt a whoosh of air pulling from the bathroom closet where the access door was located into the area beneath the tub. There was so much air pulling through that it was pulling dust and spider webs pretty well.

I am assuming that the plumbing must run right through that return air location and was not air sealed at the penetration (must be a big opening too). I could not see anything-- the plumbing penetration was on the opposite side of the tub with no access.

Anyone aware of any codes that would apply here?

This is on an outside wall so it is pulling insulation fibers into the home...

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Originally posted by Brandon Whitmore

Did a 2 story house today. The main floor return air grill was located in the ceiling at the NE end of the home, and it passed beneath the Master bathroom located upstairs at the E. end of the home. The furnace was located at the SE end of the home, so the return air ran directly beneath the whirlpool tub.

I opened up the tub access hatch and instantly felt a whoosh of air pulling from the bathroom closet where the access door was located into the area beneath the tub. There was so much air pulling through that it was pulling dust and spider webs pretty well.

I am assuming that the plumbing must run right through that return air location and was not air sealed at the penetration (must be a big opening too). I could not see anything-- the plumbing penetration was on the opposite side of the tub with no access.

Anyone aware of any codes that would apply here?

This is on an outside wall so it is pulling insulation fibers into the home...

If there was that much air being pulled through, it sounds as if they used a panned joist bay as the return air duct. If so, that's been a no no for several years. M1601.1.1, (6).

- Jim Katen, Oregon

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Originally posted by Brandon Whitmore

They were......... but it was a 1989 home. Can't say I've ever seen anything quite like this. Nothing like inhaling insulation fibers when the system is running.

So, in your world, the HVAC guys don't glue sound-deadening panels to the interior of the air plenums?

ONE TEAM - ONE FIGHT!!!

Mike

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The next time you open a furnace, look up or down into the air plenums above and below the furnace to see if there are any black panels about an inch thick attached with glue or rivets to the inside face of the plenums. They have a smooth thin facing; want to guess what the rest of that 1-inch is made from?

ONE TEAM - ONE FIGHT!!!

Mike

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The next time you open a furnace, look up or down into the air plenums above and below the furnace to see if there are any black panels about an inch thick attached with glue or rivets to the inside face of the plenums. They have a smooth thin facing; want to guess what the rest of that 1-inch is made from?

I have a hard time believing that the insulation fiber concern would be the same between a densely packed board material and loose packed fiberglass batt wall insulation material, but could be wrong........

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Originally posted by hausdok

Originally posted by Brandon Whitmore

They were......... but it was a 1989 home. Can't say I've ever seen anything quite like this. Nothing like inhaling insulation fibers when the system is running.

So, in your world, the HVAC guys don't glue sound-deadening panels to the interior of the air plenums?

ONE TEAM - ONE FIGHT!!!

Mike

When I was installing ductwork; we only installed the sound dampers in commercial jobs. (schools and hospitals) Not in most homes.

I have panned out a few joist in my time.

As I see it any opening in the return that letting air in that not filtered needs to be sealed so the coil will not get stopped up from the items getting in.

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Hi Brandon,

No, I'm not talking about duct board I'm talking about 1-inch thick fiberglass batting with a thin hard face that is otherwise nothing more than a 1-inch thick batt. It's not any harder than the stuff in the walls and it shreds the same way. It's in a humongous percentage of systems up here. If it were so hazardous, I'd expect to see lines out the door at the hospitals.

OT - Of!!!

M.

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Originally posted by Jim Katen

Originally posted by Brandon Whitmore

Did a 2 story house today. The main floor return air grill was located in the ceiling at the NE end of the home, and it passed beneath the Master bathroom located upstairs at the E. end of the home. The furnace was located at the SE end of the home, so the return air ran directly beneath the whirlpool tub.

I opened up the tub access hatch and instantly felt a whoosh of air pulling from the bathroom closet where the access door was located into the area beneath the tub. There was so much air pulling through that it was pulling dust and spider webs pretty well.

I am assuming that the plumbing must run right through that return air location and was not air sealed at the penetration (must be a big opening too). I could not see anything-- the plumbing penetration was on the opposite side of the tub with no access.

Anyone aware of any codes that would apply here?

This is on an outside wall so it is pulling insulation fibers into the home...

If there was that much air being pulled through, it sounds as if they used a panned joist bay as the return air duct. If so, that's been a no no for several years. M1601.1.1, (6).

- Jim Katen, Oregon

Jim,

I believe M1601.1.1 prohibits only supply ducts in joist bays. Returns are allowed.

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Originally posted by johnmcda

Jim,

I believe M1601.1.1 prohibits only supply ducts in joist bays. Returns are allowed.

Only in existing buildings.

All heated, cooled, supply or return distribution-air enclosures shall be ducted. Building framing cavities, closets, crawl spaces, and chases shall not be used as heated or cooled supply and return air enclosures. Ductwork may be housed or pass through these spaces.

Exception: Building cavities used as return air ducts in existing buildings.

- Jim Katen, Oregon

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Originally posted by hausdok

Hi Brandon,

No, I'm not talking about duct board I'm talking about 1-inch thick fiberglass batting with a thin hard face that is otherwise nothing more than a 1-inch thick batt. It's not any harder than the stuff in the walls and it shreds the same way. It's in a humongous percentage of systems up here. If it were so hazardous, I'd expect to see lines out the door at the hospitals.

OT - Of!!!

M.

I guess I miss under stood what you are talking about.

It sounds like you are talking about the duct line that installed

inside of the duct. It black on the top and fibers under the

bottom and most of the time it is glued to the metal ductwork

along with a few insulation nails to hold it in place.

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Originally posted by Phillip

Originally posted by hausdok

Hi Brandon,

No, I'm not talking about duct board I'm talking about 1-inch thick fiberglass batting with a thin hard face that is otherwise nothing more than a 1-inch thick batt. It's not any harder than the stuff in the walls and it shreds the same way. It's in a humongous percentage of systems up here. If it were so hazardous, I'd expect to see lines out the door at the hospitals.

OT - Of!!!

M.

I guess I miss under stood what you are talking about.

It sounds like you are talking about the duct line that installed

inside of the duct. It black on the top and fibers under the

bottom and most of the time it is glued to the metal ductwork

along with a few insulation nails to hold it in place.

Yep,

Often damaged by a homeowner that's careless when replacing the filters. Never hear anyone complaining about it though. I remember one lady that claimed to have all sorts of allergies. I ended up doing 4-5 houses for her until she'd finally found one that she claimed didn't irritate her sinuses. That house had a bunch of this stuff inside the furnace plenum all damaged by an owner that was careless when replacing the filters.

OT - OF!!!

M.

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