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Thread: Condensation on ceiling in one bedroom after equipment change

  1. #21
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    Quote Originally Posted by Mr Bill View Post
    Are you saying that your ducts are covered in insulation? If so, I’ve always heard condensation can form on the exterior side of the duct during the summer, causing the ceilings to become wet.


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    I am saying the metal ducts are wrapped in foil faced insulation with all the seams taped, and then everything is buried in 1.5ft of blown in insulation. This is what I specified as I was told this would prevent exactly what has happened, and I also paid a small fortune to do so. And it seemed to work until the equipment was swapped out for the identical, but newer, equipment and the house was now being kept cooler than before.

    I am hoping it is something simple like the insulation rubbed through, a seam came untaped, or a drywall screw made it all the way to the duct and not something worse. And in any case it looks we are going to have to have part of the ceiling opened up, again, as there doesn't seem to be any other way to diagnose it.

    I am going to check the moisture (its 78 in the house right now) and then turn it to 72 and try to recreated the condition, and if moisture reappears, have it cut open at that moment.

  2. #22
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    Quote Originally Posted by boca View Post
    I am saying the metal ducts are wrapped in foil faced insulation with all the seams taped, and then everything is buried in 1.5ft of blown in insulation.
    I understand, but regardless of the duct material, I've always been told never bury your ducts under the attic insulation, hang them. Now I live in Houston, maybe it because we have high heat and humidity, and most ducts are in our attics here, maybe others will key in, I'm always open to learn.
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  3. #23
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    This youtube video explains it all. It is titled Conductsation.
    Note it is 2 hours long but very thorough.

    https://www.youtube.com/watch?v=LYKq...nel=HVACSchool
    *********
    https://www.hvac20.com/ High efficiency equipment alone does not provide home comfort and efficiency. HVAC2.0 is a process for finding the real needs of the house and the occupants. Offer the customer a menu of work to address their problems and give them a probability of success.

    Find contractors with specialized training in combustion analysis, residential system performance, air flow, and duct optimization https://www.myhomecomfort.org/


    Site member map HERE!

  4. #24
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    Quote Originally Posted by Mr Bill View Post
    I understand, but regardless of the duct material, I've always been told never bury your ducts under the attic insulation, hang them. Now I live in Houston, maybe it because we have high heat and humidity, and most ducts are in our attics here, maybe others will key in, I'm always open to learn.
    Oh I see what you're saying now. I think they were hung in over 3/4 of the house, everything was strapped up, but this is the last bedroom and as you can see from the clearances there just was no other way to do it, they couldn't get any "higher" to come in the top of the supply box. Maybe if they thought it out a little better there were a few inches above (but below the cross bracing in the truss) where they could have ordered a special "tall" supply box and go the side entrance a little higher...but they didn't, and maybe there wasn't (looking at it there is that cross bracing above it too.) It was a really tight fit there as I recall. And I wasn't going to not insulate the room to avoid burying the duct. However I could tell them to leave it unburied after whatever repair is necessary I guess if everyone thinks it will help.

  5. #25
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    Quote Originally Posted by kdean1 View Post
    This youtube video explains it all. It is titled Conductsation.
    Note it is 2 hours long but very thorough.

    https://www.youtube.com/watch?v=LYKq...nel=HVACSchool
    I started watching that video and when he said that you can't change the dewpoint but you can change the outside temp based on amount of insulation, i started thinking the only thing that could be causing this is broken/missing insulation, it has to be. So I ordered a FLIR camera off amazon and got it delivered and stuck it in the vent as close to the distance of the dripping, and this is what I found:




    So I am hoping they just missed an overlap in a seam. However, the house was 78 today and there was no moisture. So I put it down to 70 and we will see if we can develop some moisture overnight.

    My question is this: given the tight area, should I insist they use closed cell foam (higher R per inch), have them rewrap (double wrap) with foil faced duct insulation and inspect the work more thoroughly this time, or just do whichever they recommend? Also, the original company that put in the ducts has gone out of business, so now I have to find a new company.

  6. #26
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    How high are the ceilings in this house?

    PHM
    --------


    Quote Originally Posted by boca View Post
    I will list everything that has been done to the house (all were done by licensed professionals, but 2 separate companies):

    This is all in Boca Raton, FL in a 1900 sqft single family home with the air handler in an interior closet and ductwork in the (low slope roof) attic.

    Approx. 4 years ago ceilings were pulled down and all ductwork was pulled out. New ductwork was installed, all rigid metal round ductwork, every joint mastic'd and everything wrapped on the outside (including metal supply boxes) with I *believe* R-8 insulation. The air handler was not changed at this point, but everything from the plenum and beyond was. I personally inspected between each step to ensure nothing was missed, every joint mastic'd and every seam taped and made them go back over whatever was missed. They did not like me.

    After that the whole attic was re-insulated and 1-2ft of blown in pink insulation (unsure if fiberglass or cellulose) buried all the ductwork which mostly ran exactly 3.5" over the drywall (because of joists.) The thickness varied with the height of the attic at a given point (max 2.5ft at ridge) but at the point in question later, it is at the higher end of the range (parallel, directly under ridge).

    Fast forward 3 years and the air handler and outdoor unit was replaced with the *identical* updated rheem model (same exact size in interior closet, almost identical model number except the year.) 3.5 ton, 1200cfm i believe, etc.

    A month later a water spot appeared on the ceiling going into one of the bedrooms right at the intersection of the wall and ceiling, about 1 ft before the supply register in this room (I recall this being a tight fit over the top plate and then there was a truss of some sort that ran the opposite way so they couldn't go any further into the room with the supply. I also recall making them re-do the insulation in this area because the supply branch was so close to the top plate and they did a poor job but I thought it was taken care of.)

    So, why would an air handler equipment change cause this? I remember the first time the new unit was turned on, I thought it was defective because the old unit, by my hand, "felt" like the air blowing out of the ducts was colder than the new unit. And it took forever to cool the house, but the old unit would only cool the house to 76 by the time it perished (it was 20 years old) even if it ran 24/7, and the new one will cool the house to 72, eventually, and cycle on and off - it clearly works better. Also, this duct seems to have been undersized from the plenum, the velocity of the air coming out of the 3 supplies on this side of the house is slower than the velocity coming out of the supplies on the other side of the house, though this did not seem to change with the equipment change, and this room seems to be consistently 1-2 degrees hotter than the other rooms of the house.

    What's the theory behind what could be the cause of this, other than "something is below the dewpoint of the air touching it"? What would change with an equipment change to the identical (but obviously newer) equipment? Should this be examined with a thermal camera "inside" the duct or should the ceiling be cut out (again) or?
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  7. #27
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    Quote Originally Posted by Poodle Head Mikey View Post
    How high are the ceilings in this house?

    PHM
    --------
    8ft, normal, but the trusses are only like 2.5ft, it has a 2.5:12 slope roof, and at that point it is really tight with the cross bracing in the attic. Like you can't crawl over there, the ceiling is going to have to be cut out no matter what.

  8. #28
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    I came to Florida and found the same things you found - it is maddening. <g>

    One of the compensating methods I came up with is that of building a soffit along the length of the house - in the corner where the center wall and the ceiling meet. I install the air duct inside of it. That way the air ducts are inside the conditioned space rather than in the attic. And an 8' ceiling is plenty high enough for that.

    Something else I do, although the cost is higher, is to use a high velocity system - such as Unico. The supply ducts are either 2" in diameter.

    PHM
    ---------


    Quote Originally Posted by boca View Post
    8ft, normal, but the trusses are only like 2.5ft, it has a 2.5:12 slope roof, and at that point it is really tight with the cross bracing in the attic. Like you can't crawl over there, the ceiling is going to have to be cut out no matter what.
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  9. Likes kdean1 liked this post.
  10. #29
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    Quote Originally Posted by Poodle Head Mikey View Post
    I came to Florida and found the same things you found - it is maddening. <g>

    One of the compensating methods I came up with is that of building a soffit along the length of the house - in the corner where the center wall and the ceiling meet. I install the air duct inside of it. That way the air ducts are inside the conditioned space rather than in the attic. And an 8' ceiling is plenty high enough for that.

    Something else I do, although the cost is higher, is to use a high velocity system - such as Unico. The supply ducts are either 2" in diameter.

    PHM
    ---------
    Why does the high velocity help? I think mine isn't set on high so I could have a company do that I think? I know it won't be the system you are talking about, but would it help?

    All the ducts in the entire house were replaced 3 years ago with rigid metal ducts and wrapped with insulation but they had to stay in the attic, there was no way to bring them into conditioned space. And the way this house is built "lengthwise" is directly under the middle of the ridge, it would be exactly in the middle of a 26ft x 26ft wide room. If I ever design a house (lol) I will have them do so though, believe me.

  11. #30
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    Quote Originally Posted by boca View Post
    RBHP21J11SH2 and RA1636AJ1NA

    I promise you there were no reports done before or after work down here. I don't think anyone realizes that no one in South Florida is going to do any reports no matter how much you ask.

    They just eyeball up your house and oversize the equipment.

    It took an act of god to get even one company to use rigid metal ducts
    as opposed to flex ducts
    and we paid over double to have that done
    and we had to tear out the ceilings.

    99% want to use flex, poorly.
    I would have to drive to the house to look at the dipswitch settings
    (we live in a condo 40 miles south and rent our house out) so I will do so tomorrow.

    I also promise no temperature readings were taken, they got out of there as fast as possible after changing the equipment, I wasn't sure it even worked until 24 hours later it took so long to cool the house down (but once it was cool it stayed, unlike before.) I got so many quotes on both of these jobs its ridiculous. No one will spend one extra minute on any of those things you ask and I have no idea of how to get them for you. The ductwork people didn't even pull a permit.
    When you refer to South FL, you actually mean south EAST Florida.

    There are MANY COMPETENT Residential HVAC Mechanical Contractors
    in South WEST Florida.
    However, the number of qualified, competent firms may be a very low percentage
    of the overall, enormous total of HVAC contractors.

    Dipswitch settings information by itself is
    definitely NOT a Complete set of operating data.
    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  12. #31
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    Quote Originally Posted by boca View Post
    Why does the high velocity help? I think mine isn't set on high so I could have a company do that I think? I know it won't be the system you are talking about, but would it help?

    All the ducts in the entire house were replaced 3 years ago with rigid metal ducts and wrapped with insulation but they had to stay in the attic,
    there was no way to bring them into conditioned space.

    And the way this house is built "lengthwise" is directly under the middle of the ridge, it would be exactly in the middle of a 26ft x 26ft wide room. If I ever design a house (lol) I will have them do so though, believe me.
    High velocity system ( i.e. Unico or Spacepak) addresses humidity issues by
    installing an air handler
    with a strong blower and several rows of coils.

    The differential temperature across the coil may be > 26'F with a 6 + row
    versus 18- 'F in a 2 or 3-row coil.

    Duct-in-an-attic with spray foam on the roof deck underside
    brings the duct work into a SEMI-CONDITIONED Space.
    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  13. #32
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    Quote Originally Posted by dan sw fl View Post
    When you refer to South FL, you actually mean south EAST Florida.

    There are MANY COMPETENT Residential HVAC Mechanical Contractors
    in South WEST Florida.
    However, the number of specific competent firms may be a very low percentage
    of the overall, enormous total of HVAC contractors.

    Dipswitch settings information by itself is
    definitely NOT a Complete set of operating data.
    Lol I forgot that the people in the center west side of the state say they are in "south" florida. But yes I am in actual south florida, the miami/ft lauderdale/west palm metro area.

  14. #33
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    The problem is that the cold air flowing through the duct cools the duct, duct insulation, and vapor barrier below the attic dew point. The 12-18" of insulation with out a vapor barriers allows attic moisture to migrate to the duct vapor barrier because the vapor barrier is cooled by cold air blowing through the duct. The attic insulation prevents the vapor barrier from warming by the attic heat. Adding closed cell foam insulation as a vapor barrier may help.

    A tuff little unexpected problem. We see this often. A final fix could be to open the ceiling from the drywall side and thickly wrapping the duct with 2-3"s of closed cell foam like Rubetex or foam. Closed cell spray foam encasing the cold duct on the outside may also work.

    Keep us posted on the fix.

    Regards
    Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  15. #34
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    Quote Originally Posted by boca View Post
    I started watching that video and when he said that you can't change the dewpoint but you can change the outside temp based on amount of insulation, i started thinking the only thing that could be causing this is broken/missing insulation, it has to be. So I ordered a FLIR camera off amazon and got it delivered and stuck it in the vent as close to the distance of the dripping, and this is what I found:

    So I am hoping they just missed an overlap in a seam. However, the house was 78 today and there was no moisture. So I put it down to 70 and we will see if we can develop some moisture overnight.

    My question is this: given the tight area, should I insist they use closed cell foam (higher R per inch), have them rewrap (double wrap) with foil faced duct insulation and inspect the work more thoroughly this time, or just do whichever they recommend? Also, the original company that put in the ducts has gone out of business, so now I have to find a new company.
    You are fixated on insulation alone. You need to watch the ENTIRE video instead of "started watching it."
    He recommends NOT burying the ducts and keeping the ducts high in the attic.
    *********
    https://www.hvac20.com/ High efficiency equipment alone does not provide home comfort and efficiency. HVAC2.0 is a process for finding the real needs of the house and the occupants. Offer the customer a menu of work to address their problems and give them a probability of success.

    Find contractors with specialized training in combustion analysis, residential system performance, air flow, and duct optimization https://www.myhomecomfort.org/


    Site member map HERE!

  16. #35
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    Quote Originally Posted by teddy bear View Post
    The problem is that the cold air flowing through the duct cools the duct, duct insulation, and vapor barrier below the attic dew point. The 12-18" of insulation with out a vapor barriers allows attic moisture to migrate to the duct vapor barrier because the vapor barrier is cooled by cold air blowing through the duct. The attic insulation prevents the vapor barrier from warming by the attic heat. Adding closed cell foam insulation as a vapor barrier may help.

    A tuff little unexpected problem. We see this often. A final fix could be to open the ceiling from the drywall side and thickly wrapping the duct with 2-3"s of closed cell foam like Rubetex or foam. Closed cell spray foam encasing the cold duct on the outside may also work.

    Keep us posted on the fix.

    Regards
    Teddy Bear
    This is what they ended up doing. There was no room there to re-wrap the ducts with more insulation than was already there so they foamed it. They also had to open up the adjoining room ceiling to do a longer section of the duct than I had hoped for. It seems to have worked, I ran the house down to 72 with no drips, and the only thing left to do is paint. In the end I'm not sure I'll ever pay extra for metal ducts again, I'll just have them oversize all the flex ducts to make up for the fact they are never perfect (at least here in Florida I mean.)

    I also am thinking about closing up the attic and installing a dehumidifier up there. The house is 40% humidity and the attic is absurd. The roof that was put on had a layer of self adhesive underlayment that is basically a giant water/air barrier so the thing is probably pretty tight, it was even wrapped down onto the fascia to cover the edge of the decking. All I would have to do is have the vents stuccoed over.

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