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  1. #14
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    Quote Originally Posted by rglasgow View Post
    You stated that the plenum sweats where it attaches to evaporator coil. The best I can tell there is access if the flue pipe is removed. Have them open the plenum and make sure this area is insulated and sealed. Even the back of the plenum could be sealed from the inside. What part of Texas are you located?
    Here is a photo of what the coils looked like before they sealed up the plenum. Today they cut a hole in the plenum to make sure no mold in there (I didn't get a peek, but they said no). They feel they've done an adequate job of sealing the closet from attic heat/humidity, but it is far from it in my estimation, and as long as those flex metal vent tubes dangle there allowing attic air into the closet, I don't see how we can control the humidity. Can those be "disabled" for the summer? Very frustrating for the company to take such a short sighted approach to what is clearly a bigger problem of installation/insulating. We are in central Texas, humid but not outrageously so.
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  2. #15
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    Quote Originally Posted by Shophound View Post
    Do not seal those tubes up. That is not the source of the problem; only a bit player.

    Do you live in the DFW area? If so I know some folks who can likely fix this problem.

    Also remember Rule Number One: no water, no mold. Cold surfaces attract water. Where there is mold, there is or has been water.
    No, we are in Austin. If I knew what to ask them to do and understood why/how it would fix the problem, I feel like the company would make good on this. But the crew today was told to plug up the access to attic (which they did with some badly cut chunks of fiberglass board stuff that fits poorly) and cap a drain line clean-out on top of the unit that was left open. And clean up the mold (I did the painting myself as an addt'l measure). Heat is of course still pouring down that vent. We are about to leave town for several weeks and have housesitters who can't deal w/this kind of thing. I'm wondering if putting a bucket of Damprid in there would help in the very short term, at least until we can get back home and ask them to more fully assess the situation and correct it.

  3. #16
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    that bucket of mastic they put on is adding to the humidity.

    did they go into the attic & use the insulation...ductboard I'm
    assuming..to seal at the top of the closet?

    the duct boards reflective surface should face into the top of
    the closet. between the ductboard & the framing of the top of the
    closet there has to be a seal. caulk...mastic...something that will
    allow for expansion & contraction while still retaining the seal.

    holes in db for combustion air should be tight and the venting sealed
    tightly at the penetration.
    opening for supply plenum sealed air tight.
    then...still from inside the attic...
    more insulation can be installed on top of the ductboard.

    that seals the top of the closet air tight.
    no hot air entering lessens chances of condensation.

    the unknown is if the seal between the supply plenum
    and the equipment is air tight.
    I like a nice roomy heating closet so that air can move around
    the system. but itrw....it isn't always an option.

    the return air below the unit should also be
    sealed air tight. any openings into the walls...
    air tight seal between platform system rests upon &
    the door of the closet.

    remainder of the ductboard can be used to insulate
    the door on the inside (with foil facing into the closet)
    or to make r/a air tight.

    best of luck
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  4. #17
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    Quote Originally Posted by energy_rater_La View Post
    that bucket of mastic they put on is adding to the humidity.

    did they go into the attic & use the insulation...ductboard I'm
    assuming..to seal at the top of the closet?

    the duct boards reflective surface should face into the top of
    the closet. between the ductboard & the framing of the top of the
    closet there has to be a seal. caulk...mastic...something that will
    allow for expansion & contraction while still retaining the seal.

    holes in db for combustion air should be tight and the venting sealed
    tightly at the penetration.
    opening for supply plenum sealed air tight.
    then...still from inside the attic...
    more insulation can be installed on top of the ductboard.

    that seals the top of the closet air tight.
    no hot air entering lessens chances of condensation.

    the unknown is if the seal between the supply plenum
    and the equipment is air tight.
    I like a nice roomy heating closet so that air can move around
    the system. but itrw....it isn't always an option.

    the return air below the unit should also be
    sealed air tight. any openings into the walls...
    air tight seal between platform system rests upon &
    the door of the closet.

    remainder of the ductboard can be used to insulate
    the door on the inside (with foil facing into the closet)
    or to make r/a air tight.

    best of luck
    The bandaid they put on it yesterday was to try to plug up the ceiling of the closet with bits of ductboard (they got the direction right!) that are pieced together very inexpertly with mastic, w/gaps, lumps, holes. They did not go into the attic at all, which is not navigable because of the blown-in-insulation (my husb went up there and can't even see where to step, it's like a grey snowdrift). They made no attempt to cut the ductboard to fit tightly into the corners, nor around the flex metal vent tubes---I insisted they plug the gaps btw those up, so they jammed some scraps up in there. They said the "seals" on the sides were fine b'c it wasn't wide open to attic, but there is no insulation whatsoever at the sides, and you can see the original framing. You nailed it: they use mastic like a lounge lizard uses cologne. The hole they cut in the plenum y'day to check for mold was sealed back up with yet more mastic. The door seems nicely sealed, with foiled backed sheets on the louvers and good weatherstripping on the door. But those vent tubes hanging down are next to the plenum and walls (though far wall molded as bad as the near wall to them) and a constant source of hot attic air against the coils. You couldn't design a worst thing, but we didn't understand the first thing about any of this last year when they installed. This has been an education, and now we can see how poorly it was done. If only they will make good on it. Do you think using Damprid tubs in there until we can get them to come back out after we return from an absence of several weeks (leaving the temp set fairly high will help some, no?) is useless?

  5. #18
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    The only way to gain any confidence with the mold concern is to determine if the walls surrounding the plenum in the closet are getting cold, and if they are, what is making them cold (by "cold" I mean cooler than the surrounding air).

    I hate to say this, but insulatingmthe closet ceiling could potentially make this problem more likely to continue. How? By slowing heat gain from the attic, the walls can get colder, and closer to the dew point temperature of the air surrounding the walls. It is the dew point that drives mold...if the walls get cold enough to begin collecting beads of water on them, that is a sure fire way to grow mold. Even if you see no visible moisture on the walls, if they have an elevated moisture content due to being chilled below surrounding humid air, mold growth is favorable.

    The plenum is the likely culprit in all of this, not so much air from the attic entering the tubes. The plenum should be thoroughly insulated anywhere it can get cold.

    Central Texas...how near Austin or Georgetown? I have HVAC friends there.
    Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.

  6. #19
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    dampered combustion vents?

    you don't need the combustion air until the furnace runs...
    but there is a lot of liability for anyone to tell you to close them off.
    there is the possibility that you would use the furnace without
    opening. I can't imagine any hvac company recommending this.

    you have to seal the top of the closet.
    not gobs of mastic & by no means expanding foam.
    with the hot attic air meeting the cool/cold coil housing &
    start of the supply plenum mold will grow.

    the attic insulation can be moved aside, the top of the
    closet sealed, and insulation swept back into place.
    shame that they blew the insulation so quickly...
    and is it cellulose? ugh...dust making stuff.
    missed the perfect opportunity to air seal & mastic
    seal ductwork.
    makes it a real pita for anyone to do the necessary work,
    which sometimes is the point.

    I'd like to see the top of the closet if you have one more
    picture in you...
    would there be room to wrap some R-6 or R-8 duct wrap around
    the sides & rear of the coil & extend the wrap onto the
    supply plenum?
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  7. #20
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    Quote Originally Posted by Shophound View Post
    The only way to gain any confidence with the mold concern is to determine if the walls surrounding the plenum in the closet are getting cold, and if they are, what is making them cold (by "cold" I mean cooler than the surrounding air).

    I hate to say this, but insulating the closet ceiling could potentially make this problem more likely to continue. How? By slowing heat gain from the attic, the walls can get colder, and closer to the dew point temperature of the air surrounding the walls. It is the dew point that drives mold...if the walls get cold enough to begin collecting beads of water on them, that is a sure fire way to grow mold. Even if you see no visible moisture on the walls, if they have an elevated moisture content due to being chilled below surrounding humid air, mold growth is favorable.

    The plenum is the likely culprit in all of this, not so much air from the attic entering the tubes. The plenum should be thoroughly insulated anywhere it can get cold.

    Central Texas...how near Austin or Georgetown? I have HVAC friends there.
    We're in Austin, and the company has agreed they didn't send their best guys out to address this, and will do so once we return in August. Surely mold won't grow over again in a few weeks, and we can get a bead on how to best fix it. Whether the main culprit for humidity/dew point is heat from the attic or improper insulation to the plenum, doing both won't hurt, will it? See my reply to next guy's suggestions. I really appreciate everyone's help here!

  8. #21
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    Name:  IMG_0549.JPG
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    Quote Originally Posted by energy_rater_La View Post
    dampered combustion vents?

    you don't need the combustion air until the furnace runs...
    but there is a lot of liability for anyone to tell you to close them off.
    there is the possibility that you would use the furnace without
    opening. I can't imagine any hvac company recommending this.

    you have to seal the top of the closet.
    not gobs of mastic & by no means expanding foam.
    with the hot attic air meeting the cool/cold coil housing &
    start of the supply plenum mold will grow.

    the attic insulation can be moved aside, the top of the
    closet sealed, and insulation swept back into place.
    shame that they blew the insulation so quickly...
    and is it cellulose? ugh...dust making stuff.
    missed the perfect opportunity to air seal & mastic
    seal ductwork.
    makes it a real pita for anyone to do the necessary work,
    which sometimes is the point.

    I'd like to see the top of the closet if you have one more
    picture in you...
    would there be room to wrap some R-6 or R-8 duct wrap around
    the sides & rear of the coil & extend the wrap onto the
    supply plenum?
    Thanks again for all the help here! To be clear, no HVAC tech recommended sealing up the vents, we just wondered if it could be done as a temporary solution to the heat in the closet until we can get them out here again (we are about to leave all in the hands of housesitters for several weeks).

    One of my pictures (this website turns it sideways, sorry) shows how close to the coil housing the nearest combustion vent is, and that is the one you can feel heat radiating from (the one that hangs lower in the closet, almost to the floor, doesn't feel so warm). Would extending that upper vent help, to get it from breathing hot air onto the coils/plenum? You can also see in the other pic that the whole shebang is close to the walls on both sides, and apparently mounted against the back wall (which we can only hope was properly insulated, as no way to see back there. There's about the space of man's hand between the drywall sides of the closet and the unit/plenum.

  9. #22
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    Am I missing something here?
    to me it seems like one vent goes to the return?
    granted Austin is miles ahead of La. in terms of energy
    efficiency...but if I put an open vent from attic into return air...
    I'd be introducing dirty hot humidity laden air...past the filter
    & into the return. it would be like a return air leak...??
    Shophound...your thoughts?

    I've never added combustion air in this manner.
    to the top of the closet for the gas burning furnace...
    but not to the return below...
    in my area, the one combustion vent would be added..
    with a bug screen on the attic side.
    but codes & code enforcement changes from state to state.
    (town to town!)

    in addition to the proper air tight insulated top of the
    ceiling (with venting sealed into cuts)
    I'd wrap the coil & as much of the plenum as possible
    with R-8 duct wrap & seal it. at seams, top and bottom or wrap.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  10. #23
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    Thanks Louisiana. My pictures must not show that the second vent does not extend thru the floor of the closet to the return air space--it just hangs down about four feet in the closet from the ceiling (and doesn't feel like it's emanating as much heat). The second shorter vent, zip tied to it, extends only about two feet into the closet and breathes hot air right next to the coil. Our old unit didn't have tubes hanging down for combustion at all. It relied on the louvered door vents for air. I have no idea whether either one has a bug screen on the attic side, as that's a blown-in insulation no-man's land up there now! But I'm not clear AT ALL why there are two tubes. ??? Any ideas, anyone?

  11. #24
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    Your furnace installation configuration in a closet of a house is a very common older house method of install in Texas. The two tubes that come down from the attic are to provide combustion air for the furnace now that the closet louvers are sealed. One extends lower than the other as code states so if one is blocked for whatever reason the other can still provide air (unless it also gets blocked). Neither of these tubes connect to the return air path for the furnace. Or at least neither one should.
    Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.

  12. #25
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    Thanks Shophound. So code probably dictates the "backup" vent tube. All in all, the energy savings on this pricey new system aren't enough to make up for the problems occurring in that closet due to their jack-leg installation or lack of understanding of simplest formulas of heat + cold + moisture. We appreciate everyone's explanations here, it's made it much easier to talk to them about what's needed and not sound like pure idiots.

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