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  1. #1
    Join Date
    Jun 2012
    Location
    Louisville, KY
    Posts
    141

    Exposed flex ducts - Any tips?

    Good evening!

    I live in a manufactured home set on a slope, built circa 1995. The builder installed all the supply ductwork underneath the house, exposed to outside air, and it's all flex. The return is indoors just above the AHU. The heat in the house is uneven, it's several degrees warmer (or cooler in the summer) in the rooms closest to the AHU.

    I have a feeling that a lot of heat is lost on the ductwork along the way, and possibly have leaks in it due to small animals as we live out in the country. I'm trying to think of ways this could be improved and was wondering if (after I patch any holes and looking for obstructions) there is a way to insulate flex ducts to reduce the amount of heat transferred to (or from) the outside air. If this is too DIY just let me know. Not planning on touching the equipment itself.

    Thanks all!

  2. #2
    Join Date
    Nov 2007
    Location
    Mississippi
    Posts
    1,307
    I would suggest you replace the whole duct system with hardpipe and size properly for even airflow velocity. It will probably be cheaper and have better results in the end if you pay for a duct contractor to do this for you. You WILL continue to have problems with flex. I have never seen flex underneath a house last long.

  3. #3
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,704
    Flex duct is not intended for exterior use.

  4. #4
    Join Date
    Jun 2012
    Location
    Louisville, KY
    Posts
    141
    Quote Originally Posted by kdean1 View Post
    Flex duct is not intended for exterior use.
    Looks like mfg housing builders like to cut corner don't they. Know anyone in the Southern Indiana area? I'm guessing any licensed contractor could handle this comfortably?

  5. #5
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    518
    also a good start is to shore up the skirting ,insulate it and isolate it as to keep out both the critters and old man winter
    I do agree that the duct should be redone also though it is what all of them use those who dont know or maybe care about your comfort after the sale$$$$

  6. #6
    Join Date
    Apr 2012
    Location
    Louisiana
    Posts
    657
    Get it done right with hard pipe. I have relatives that had flex under a manufactured home. They had to replace most of the first floor floor and spent tens of thousands of dollars on repairs due to supply leakage under their home.

  7. #7
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,426
    We replace a lot of "cross over" pipes under double wide homes with metal round pipe, covered with a slightly larger piece of insulated "flex pipe". Using the flex to insulate the metal inside is much simplier than trying to "wrap" that pipe! Even if the flex get torn, you'll still have heat or cool. And sealing up and insulating the skirting is a very good idea. Most homes have vinyl skirting which is totally useless except it covers up the mess underneath!

  8. #8
    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 11-14-2012 at 04:15 PM. Reason: non AOP member

  9. #9
    Join Date
    Jun 2012
    Location
    Louisville, KY
    Posts
    141
    Quote Originally Posted by wahoo View Post
    We replace a lot of "cross over" pipes under double wide homes with metal round pipe, covered with a slightly larger piece of insulated "flex pipe". Using the flex to insulate the metal inside is much simplier than trying to "wrap" that pipe! Even if the flex get torn, you'll still have heat or cool. And sealing up and insulating the skirting is a very good idea. Most homes have vinyl skirting which is totally useless except it covers up the mess underneath!
    Makes sense. Yeah the skirting is vinyl, I'll give that some thought. A coworker of mine who is in the field suggested I look into insulated flex, he said that would keep the expense minimal and pretty easy to do yourself. I haven't noticed what the crossover pipe is made of, I'll check on that later. Think this would yield some results?

    Any suggestion on materials for the skirting?

  10. #10
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,426
    If you replace this flex pipe cross-over with flex by itself, then it will last about as long as it takes you to crawl out from under home. Waste of time to do flex only. On most manufactuered homes, the main ductwork is built into the floor and only the cross over is the flex. Is your home different?

  11. #11
    Join Date
    May 2008
    Location
    Central Fla.
    Posts
    311
    What color is the exhisting flex? If it is shiney silver that is for attics and basements only,if it is black that is for crawl spaces and designed for exterior use.If you can seal the crawl off completely,insulate it and put a vapor barrier down on the ground and add a dehumidifier in the crawl that will protect it and keep it dry.Just my $.02 ,PS I have done this in Ga. to my old home and it worked like a dream.

  12. #12
    Join Date
    Jun 2012
    Location
    Louisville, KY
    Posts
    141
    Quote Originally Posted by TwincamDave View Post
    What color is the exhisting flex? If it is shiney silver that is for attics and basements only,if it is black that is for crawl spaces and designed for exterior use.If you can seal the crawl off completely,insulate it and put a vapor barrier down on the ground and add a dehumidifier in the crawl that will protect it and keep it dry.Just my $.02 ,PS I have done this in Ga. to my old home and it worked like a dream.
    I'll check on all that tonight

  13. #13
    Join Date
    Jun 2012
    Location
    Louisville, KY
    Posts
    141
    Quote Originally Posted by wahoo View Post
    We replace a lot of "cross over" pipes under double wide homes with metal round pipe, covered with a slightly larger piece of insulated "flex pipe". Using the flex to insulate the metal inside is much simplier than trying to "wrap" that pipe! Even if the flex get torn, you'll still have heat or cool. And sealing up and insulating the skirting is a very good idea. Most homes have vinyl skirting which is totally useless except it covers up the mess underneath!
    Wahoo, it looks like you were right on target. I crawled down there tonight and to my surprise I found the crossover pipe to have... one of our cats, laying there nonchalantly among some mangled insulation. I went back inside and turned on the blower, and went by each register. All those on the furnace side of the home blow fine, but those across have barely any air coming out. Any suggestion on replacement crossover materials? Got Lowes & THD nearby but not sure if they carry that. Also got a Johnstone Supply and Berkheimer pretty close by.

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