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Thread: Dryer vent question

  1. #1

    Default Dryer vent question

    Great forum!!!
    Not sure if this is the right place for this question, but...

    During re-model of house, went into the attic to check status of dryer vent duct. Laundry area is in middle of houe (concrete slab) so dryer is vented thru 4" duct between back wall, straight up thru attic space to roof vent. Lo and behold, the idiots who built the house never extended the duct to reach the roof vent !!!!! Lint every where !!!!

    So, my question is, after I connect the duct to the vent, I have seen advice that says that the dryer duct that passes thru unheated attic space should be insulated to prevent condensation. I bought some 1/2" aluminum-foil covered fiberglass wrap to wrap around the duct, but (this may seem like a dumb questions), do I wrap the insulation around the duct with the aluminum side out or the aluminum side against the duct?


  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Aluminum side out...you sure you want lint on the roof? Putting the exhaust into the attic is not a good thing - all that heat, lint, and moisture. In the winter, it could cause a big problem - melting snow, creating ice dams, saturating the wood and promoting mold and rot. If the run is within the manufacuter's length specifications, can you get it to a gable end wall instead of the roof?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3


    I wanted to take a picture of what I was faced with before my temporary fix, but forgot. The dryer vent duct (4" duct) came straight up from the laundry room and stopped about 6" from the roof sheathing. Of course, lint was everywhere, I don't think this thing was ever hooked anything. How does this get past building inspectors. Doesn't give me much confidence in my local insopectors. This house is about 13 yrs old.

    Anyway, there was a roof vent installed right above the duct. It looked just like the other regular attic vent cap that you would see in a shingle roof. But, it was not in the same line along the roof as the other vents. I can only assume that this type of vent cap is what they intended to use for the dryer vent. I am positive that this is NOT the correct vent to use for a dryer duct thru the roof.

    Temporary fix was add 6" duct to get to the vent, stuff some foil face insulation around the joint to seal, wrap the duct in 1/2" foil face insulation, wrap ith metal tape. Seems to be working ok. I will probably be replacing the roof this summer, will plan to get the correct type vent and replace it then.


  4. #4

    Default Vent ?

    Is the vent cap the type with small holes to keep bugs out and DRYER LINT IN??
    When you vent to a gable, pick one without a condensing unit nearby. Those critters suckup everything that can clog the coils.


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