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keep me warm

Brain Ross
Brain Ross Member Posts: 20
how should i insulated my insulate my attic hvac heating lines. and how should i insulate those lines in my basement too. what r-value?


  • Brad White_184
    Brad White_184 Member Posts: 135
    Steam or Water?

    Here in MA at least, our energy code (similar to many national model energy codes in this regard) states that ductwork inside the building envelope and subject to a 15 degree or greater differential from the ambient, requires an R value of 5.0. If the same ducts are outside the building insulation envelope, this increases to R-8. By default, this corresponds to 1.5 inches of fiberglass for R-5 and 2.5 inches of fiberglass for R-8. Realistically, this becomes 3.5 inch thickness by availability.

    If you have hot water, most piping sizes in a home (up to 2 inch pipe size) will be well-served by 1-inch fiberglass or Armaflex (same R-value for each essentially). For steam, this would be 1.5 inch thickness for piping up to 1.5-inch pipe size. Use 2-inch thick above that.
  • Brain Ross
    Brain Ross Member Posts: 20
    insulating heating lines

    i understand code is code. but wow a 1" line now jumps to 3" in diameter and 2 at that running down the attic. will i have room to store my x-mas lights?

    so letsa say this i've got 2 hot water coils most of the 1" piping is in the thermal envelope (approx. 50') the balance (50') is in the attic. would you insulate the first 50' with a smaller diameter insulation as not to heat the interior wall of the house(like radiant) and the insulate the attic lines with 1"?

    by the way what is the r-value of 3/8", 1/2" and 1" insulation. armaflex seem really nice to work with even around tight bends!
  • Brad White_184
    Brad White_184 Member Posts: 135
    The energy code is self-policing

    when you are doing it yourself, frankly. But it at least demonstrates a standard.

    In any installation worth insulating at all, I would not use less than one-inch although with Armaflex, the 3/4" seems more readily available. It is as effective as fiberglass thickness to thickness but I agree it is a good seal and easier to work with.

    In the attic or where outside the envelope, I would double it, simply stated. You are not only losing more heat (greater temperature difference) but you will lessen the risk of a freeze should you have a power outage. It can buy you some time.

    And leave your Christmas lights up year round... :)
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