Sealaing material around a dryer duct

Discussion in 'Remodel Forum & Blog' started by dabiz7, Jun 16, 2010.

  1. dabiz7

    dabiz7 New Member

    Messages:
    42
    Going to move my dryer duct outlet over a few inches, it passes thru the interior wall and thru the brick exterior to a standard dryer vent/flange. Was thinking about sealing up the gap around the 4" metal dryer duct with some kind of uretahne spray foam in a can. I see that Dow makes the Great Stuff Fireblock. Any ideas whether this stuff would be ok in contact with the hot dryer vent? Or is the regular stuff ok to use? Or just stuff the hole with regular fiberglass insulation?

    Anybody have a better idea?
    Thanks!
  2. Dana

    Dana In the trades

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    Polyurethane foams have an upper operating temp of ~175F, well above the exit-air temp of your dryer unless it's already on fire. Even under fault conditions the temp at the exit is unlikely to exceed 70C/158F (source.)

    Fireblock versions have the same operating temp, but are treated to limit flame spread & smoke (primarily between floors) when the house is already on fire. Since the vent is on an exterior wall, that feature isn't necessary.

    Fiberglass insulation is nearly useless in this type of application and results in yet another air infiltration leak into the house. (Fiberglass is an air-filter, not an air-barrier. Stuffing wads of paper in there would be a more effective air-block.) The dryer vent itself is also a big leak, but some of the better vent backflow preventers reduce that air leak almost entirely (when the dryer isn't in use.):

    [​IMG][​IMG]

    (There are multiple vendors of similar units.)

    These are far more effective than standard dryer vents, and are designed to be easily cleaned of lint, unlike some of their less-effective cousins.
  3. Lowell

    Lowell New Member

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    Dana

    Would you be so nice as to provide a link for this nice Vent?

    Thanks
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Don't know if they still carry it, but I've seen that model (or a knockoff) in HD.
  5. nukeman

    nukeman Nuclear Engineer

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  6. Dana

    Dana In the trades

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  7. Lowell

    Lowell New Member

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    Location:
    Central Ohio
    Thanks to all for your response to source for vent.
  8. CarlH

    CarlH New Member

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    175
    Location:
    Northern VA
    I don't know how this vent (wall cap) comes out in the balance of things. Are you more worried about cold air infiltration or the efficiency of your dryer? That fancy wall cap has a 90 deg elbow followed by 180 degree direction change which is going to have a negative impact on air flow. FWIW, ASHI recommends the use of the louvred type wall cap.

    Source:http://www.ashireporter.org/articles/articles.aspx?id=161
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