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  1. #1

    Duct material questions

    I am resealing and inspecting the ducting on my ranch crawl space house. It has ductboard fiberglass for the trunk and flexduct from the trunk to the registers. This is all new as house is 2 years old...but its all crap stuff. I want to replace the flexduct with 6inch pvc sdr35. Then next year I want to replace the trunk with metal ducting. Currently I am getting good airflow from all registers I just want to upgrade it and do some overkill. My question is can I use pvc rigid pipe and if not why?? I plan to wrap pvc in 1inch insulation. It seems I would have less air restriction and less air leaks with pvc. Thanks for any replies, advice.

  2. #2
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    PVC will not meet the code for class1 duct,flame and smoke developed rating.

    A fire could be deadly.

    If you feel you have good air flow,why the thoughts to change it??

  3. #3
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    Even if you could do it, you're "getting good airflow form all registers" now. Why on earth would you want to mess with it, unless it's absolutely the only thing in the house you can find to do. Didn't you ever hear the saying "leave well-enough alone".

  4. #4
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    Generally speaking I agree with the leave well enough alone sentiment. However, I also don't blame anyone for wanting to get rid of duct board. I'm sure it's great stuff for some. I just don't like the idea of matted fiberglass as my interior duct surface.

    If you want the absolute best, go with sheet metal and prepare to give up your first born. If you want super airtight and clean (no fiberglass), go with R-8 insulated wire flex. It may seem cheap. But it's quiet, inexpensive, airtight when installed right (and much easier to make airtight than sheet metal), and works like a champ when designed and installed right. It’s also resists the unintentional pressure of fat service men (it bounces back). The only thing it lacks is rodent resistance, which is certainly important in some applications.

  5. #5
    I have many house projects...I just like to do the challenging ones that may not be seen but are core functions to the home. I am very interested as to why pvc cant be used or has not been developed as a viable duct material. I reference this article http://www.eere.energy.gov/buildings...b_georgia.html It seems the SpacePak has developed a pvc ducting but is used in HV systems only i think. As far as class1 and fire and smoke are concerned...guess I wait and let the pex in the home melt and kill me.

  6. #6
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  7. #7
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    Quote Originally Posted by letsfixit View Post
    I have many house projects...I just like to do the challenging ones that may not be seen but are core functions to the home. I am very interested as to why pvc cant be used or has not been developed as a viable duct material. I reference this article http://www.eere.energy.gov/buildings...b_georgia.html It seems the SpacePak has developed a pvc ducting but is used in HV systems only i think. As far as class1 and fire and smoke are concerned...guess I wait and let the pex in the home melt and kill me.
    They also insulated them with spray foam after they were installed, which is probably what you'd have to do. Any other insulation would most likely fall down. You need to find another project. Don't you have an addition or something else you can build?

  8. #8
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    Quote Originally Posted by letsfixit View Post
    I have many house projects...I just like to do the challenging ones that may not be seen but are core functions to the home. I am very interested as to why pvc cant be used or has not been developed as a viable duct material. I reference this article http://www.eere.energy.gov/buildings...b_georgia.html It seems the SpacePak has developed a pvc ducting but is used in HV systems only i think. As far as class1 and fire and smoke are concerned...guess I wait and let the pex in the home melt and kill me.
    Don't know what they use, but PVC type duct can be made to meet the code,just costs more.

  9. #9
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    you cannot use pvc. It does not carry a 25/50 rating and is not allowed in open plenum space for drain lines either. The underground pipe we use such as k-27 and pvc coated spiral has a "UL" listing and is a coating on the "outside" of the pipe where it touches the earth, not the inside where the air will be passing through.


    matt

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