Results 1 to 9 of 9
  1. #1
    Join Date
    Nov 2019
    Posts
    2
    Post Likes

    PVC/CPVC HVAC ducts

    Can I use PVC or CPVC pipes as HVAC ducts in a residential attic? Would this violate any codes?

    I'm trying to make my AC system as efficient as possible to live through the Louisiana summers. PVC (or CPVC) seems like it would be a perfect choice of material for ducts. PVC is used for water pipes, so I assume it's safe to use for air. It's smooth, easy to seal, insulates better than metal, and I could install it myself. I have found a few articles in favor of it, but nothing from professionals. I figure I'm missing something. Does anyone do this?

    Thanks in advance,

    John

  2. #2
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    3,080
    Post Likes
    Whatever you use for the ducts in your attic it's all about how well you insulate them, not what they're made of.

    To get PVC pipe and fittings of sufficient size to move enough air for the average home would cost you many times than it would save over using metal.

    Insulate your attic and all the existing ductwork to recommended levels for your area and it will be money and time well spent and pay off in more comfort and savings in your energy bills for the life of the home.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  3. #3
    Join Date
    Jun 2014
    Location
    Dover, DE
    Posts
    11,775
    Post Likes
    If you were to price 6-20 PVC pipe and fittings, youd quickly find out why it isnt used for ductwork.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  4. #4
    Join Date
    Sep 2002
    Posts
    27,249
    Post Likes
    Cost would be the primary reason PVC pipe isn't used.

    What style house do you have? Recently I have been building air ducts from sheet rock.

    PHM
    --------


    Quote Originally Posted by John1182 View Post
    Can I use PVC or CPVC pipes as HVAC ducts in a residential attic? Would this violate any codes?

    I'm trying to make my AC system as efficient as possible to live through the Louisiana summers. PVC (or CPVC) seems like it would be a perfect choice of material for ducts. PVC is used for water pipes, so I assume it's safe to use for air. It's smooth, easy to seal, insulates better than metal, and I could install it myself. I have found a few articles in favor of it, but nothing from professionals. I figure I'm missing something. Does anyone do this?

    Thanks in advance,

    John
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  5. #5
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    7,282
    Post Likes
    Can't. Gotta be rated 250 F by code.

  6. #6
    Join Date
    Nov 2019
    Posts
    2
    Post Likes
    Thread Starter
    Thanks for all of the quick responses. The cost of PVC would be a deterrent, but the fire resistance requirement is a definite end that idea.

    I live in a ranch style house, and it currently has flex ducts. I can see bits of insulation coming out of most of the vent covers, so I figure it's time to replace them. There's also very little airflow coming out, so there may be leaks or they may be improperly sized.

    I plan to spray-foam the roof, and I'll go look into the different types of legal rigid ducts.

    I appreciate the help,

    John

  7. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    26,318
    Post Likes
    Find a contractor you can trust (easier said then done)

    They can replace the existing duct and make improvements where needed!

  8. #8
    Join Date
    Nov 2008
    Location
    Piney Flats, Tn.
    Posts
    2,012
    Post Likes
    Quote Originally Posted by hearthman View Post
    Can't. Gotta be rated 250 F by code.
    doesn't that eliminate flexible duct?

  9. #9
    Join Date
    Sep 2002
    Posts
    27,249
    Post Likes
    Flex duct is rated from about 0 to 250 - to meet that code requirement. I have sometimes wondered why it's so high. Maybe somebody here nows and can tell us? <g>

    BOCA says that sheetrock / drywall can be used for air ducts. In Florida I have been exploring it's use for air ducts. Some have been lined with 1/2" polyiso board and two have been just the drywall (to save some height) but so far all are working as intended. Although the application is mostly cooling with smallish electric resistance elements. Generally 5K with a discharge air temp of maybe 100. So nothing very 'high temp.'.

    PHM
    --------



    Quote Originally Posted by DOGBOY View Post
    doesn't that eliminate flexible duct?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •