New construction in Hawaii, exhaust fan routing

Discussion in 'HVAC Heating & Cooling' started by kalanikaau, Apr 20, 2008.

  1. kalanikaau

    kalanikaau New Member

    Messages:
    12
    I am building a new residence on the island of Oahu, on the west end in particular. It gets very warm here, with humidity averaging between 50-90 %, depending on the time of year. Of course, freezing temperatures or snow are not concerns here, however it can and does rain heavily in the spring.
    One of the bathrooms (approx. 60 sq, ft.) requires an exhaust fan to the outdoors.
    The 2 venting options are either roof or wall, as much as possible I'd rather not vent through the roof for leakage considerations.
    Roof construction is a simple hip design, with a 5/12 slope, exposed eaves with 2ft. on center 2X4 trusses.
    I would like to vent out of the eave blocking, which is of 2X6 const. and searched high and low for a vent cap in which I can mount in this blocking area.
    Normal rectangular wall caps are just as tall as the 2X6 blocking, 4" round caps even larger. The total duct run is approx. 12 ft., not including an elbow.
    Other than having a custom wall cap fabricated from sheet metal, I am at a dead end, can anyone offer suggestions?
    Thanks in advance !
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,006
    Location:
    New England
    I'd look into a through-the-wall fan. An alternative might be something like Fantec's central exhaust system. It can hook up multiple bathrooms and I think there's one version that can also hook up to your stove hood.

    With a good roof cap, leaking normally isn't an issue. Just make sure it has a good damper and is installed properly.

    I'd avoid sofits or eaves.
  3. gear junkie

    gear junkie Plumber

    Messages:
    67
    Location:
    Virginia Beach, IPC country
    See how others are doing this. Most problems are not isolated.
    BTW. I used to stay on Ohi St. in Wahiawa.
  4. kalanikaau

    kalanikaau New Member

    Messages:
    12
    Aloha gear junkie,
    Did you mean Ohai St?
  5. gear junkie

    gear junkie Plumber

    Messages:
    67
    Location:
    Virginia Beach, IPC country
    Can't remember, it was 15 years ago.
  6. BigLou

    BigLou New Member

    Messages:
    138
    a fire fighter with a truss roof WOW.
    http://www.youtube.com/watch?v=Jo5ZtBXJiHo

    anyhow I would still go through the roof i think its a cleaner look and if the vent is well installed it won't leak. A side wall is really a much easier place for it to leak and you to not know it untill its too late

    Lou
  7. kalanikaau

    kalanikaau New Member

    Messages:
    12
    Yeah, I know

    Thanks Lou for the interesting and sobering video, but because of cost and logistic considerations, a truss roof was the only way to go.
    For those interested, I've decided to use a roof cap in this vent application, a wall vent is not an option.........
  8. kalanikaau

    kalanikaau New Member

    Messages:
    12
    Hmmmm

    From what I gather gearjunkie, it seems as though you were in the Army back then and stationed @ Schofield?
    If I am correct on the street name (Ohai), it's still the ghettos of Wahiawa....:eek:
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