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  1. #1
    Join Date
    Jul 2009
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    Default Mildew associated with Radiant ceiling heat

    I did an inspection today the attic has black mildew on the underside of the roof sheathing. There is a power ventilator installed through the roof but I was unable to make it respond. The homes heating system has recently been updated with a gas furnace installed in the attic. The previous and still active heating system is an electric radiant heating system installed in the ceilings. I was unable to inspect the system as it was covered with insulation. The 4 in 12 roof pitch made access difficult. I'm trying to determine the cause of the mildew. Does anyone know if radiant ceiling heat is directly associated with high humidity or mildew problems in an attic. The ventilation in the attic is being achieved by a power ventalator, soffit vents, roof vents and a ridge vent. I would think there is adequate ventilation but the mildew suggests otherwise. I know very little about radiant ceiling heat and this is the first home I've inspected that has one. Any insight on this subject would be greatly appreciated. The mildew is throughout the attic almost every inch.

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  2. #2
    Join Date
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    Ormond Beach, Florida
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    Default Re: Mildew associated with Radiant ceiling heat

    Just curious, is that a double wide or a two-piece modular?

    Jerry Peck, Construction / Litigation Consultant
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  3. #3
    Jon mackay's Avatar
    Jon mackay Guest

    Default Re: Mildew associated with Radiant ceiling heat

    Bill, this is not likely related to the heat system.
    If the house was built in the 70s or 80s, it may be from over tight construction where the house can't breath well.

    Were there any moisture issues in the basement?
    Were the soffit areas free of insulation or blocked?

    The power vent suggests that there has been ventilation problems but these often do nothing for the winter months and as a result, moisture can not escape from the attic and condensates on the sheathing which will get moldy over time..


  4. #4
    Join Date
    Sep 2007
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    Fredericksburg, VA
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    885

    Default Re: Mildew associated with Radiant ceiling heat

    To me, the odd thing is the discoloring looks like it is only on the roof decking.
    Questions: Was the roof sheathing damp? How did you determine the stain was mold? Was there any other evidence of moisture in the attic or ceilings below?

    The above statements are expressed solely as my opinion and in all probability will conflict with someone else's.
    Stu, Fredericksburg VA

  5. #5
    Join Date
    Jul 2009
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    Spokane, WA
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    Default Re: Mildew associated with Radiant ceiling heat

    It's a 2 piece modular, built in 1983. I didn't test the material for moisture and my analysis of mildew is solely based on what was seen. The top portion of the sheathing is plywood and the lower half is OSB. The mildew on the OSB is more circular. I don't know if it is active or from a previous condition. No other signs of moisture in the interior.

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  6. #6
    Join Date
    Feb 2009
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    Southern Vancouver Island
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    Default Re: Mildew associated with Radiant ceiling heat

    Quote Originally Posted by Bill Anglin View Post
    It's a 2 piece modular, built in 1983. I didn't test the material for moisture and my analysis of mildew is solely based on what was seen. The top portion of the sheathing is plywood and the lower half is OSB. The mildew on the OSB is more circular. I don't know if it is active or from a previous condition. No other signs of moisture in the interior.
    I would go ahead and call it mould or mold, but that's just me. And it appears to be active, just from the pics. If it's 3 dimensional and wipes off easily, it's probably alive.

    It's possible the soffit vents are blocked by the blown-in insulation. Multiple roof vents can sometimes short-circuit the air flow, so that no air is drawn thru the soffit vents.

    Look for indoor air leaking into the attic. Possibly past the ceiling fixtures or the seam where the halves were joined? Leaking ductwork? bath fans? Attic hatch? Just a few ideas. It can get complicated, but usually, there's indoor air leaking into the attic, and insufficient venting.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  7. #7
    Terry Moore's Avatar
    Terry Moore Guest

    Default Re: Mildew associated with Radiant ceiling heat

    Could be some plywood sheathing that was use for concrete forms and then set outside for a while. Then later used as the decking


  8. #8
    Join Date
    Feb 2009
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    Default Re: Mildew associated with Radiant ceiling heat

    Quote Originally Posted by Terry Moore View Post
    Could be some plywood sheathing that was use for concrete forms and then set outside for a while. Then later used as the decking
    Nope. It's a modular home, so they likely used clean new wood for the sheathing. Up here, it would all be built under cover as well. There's a bit of staining on the 3rd truss in the pic. There's moist air leaking into the attic, and it is not properly ventilated.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  9. #9
    Join Date
    Mar 2009
    Location
    Utah
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    15

    Default Re: Mildew associated with Radiant ceiling heat

    I have seen this type of radiant heat and you can't see it from the attic. The lines are run on the inside of the sheet rock and then plaster is floated and coated over the wires or tubes. Makes the ceilings really heavy. A lot of homes in my area that were built in this time frame had the bathroom fans vented to the attic and mostly they are covered with insulation so that the air moves through the insulation. They have changed that and the newer codes require the fans to be vented out of the house but there are still thousands of homes out there that were built with the bath fans vented inside. That is where I would look.

    Quote Originally Posted by Bill Anglin View Post
    I did an inspection today the attic has black mildew on the underside of the roof sheathing. There is a power ventilator installed through the roof but I was unable to make it respond. The homes heating system has recently been updated with a gas furnace installed in the attic. The previous and still active heating system is an electric radiant heating system installed in the ceilings. I was unable to inspect the system as it was covered with insulation. The 4 in 12 roof pitch made access difficult. I'm trying to determine the cause of the mildew. Does anyone know if radiant ceiling heat is directly associated with high humidity or mildew problems in an attic. The ventilation in the attic is being achieved by a power ventalator, soffit vents, roof vents and a ridge vent. I would think there is adequate ventilation but the mildew suggests otherwise. I know very little about radiant ceiling heat and this is the first home I've inspected that has one. Any insight on this subject would be greatly appreciated. The mildew is throughout the attic almost every inch.



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