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Community and Q&A

Philadelphia row home roof

NIGHTNANC | Posted in General Questions on

I have a flat rubber roof installed 9/2015. Today, A contractor doing work on the house next door to me, told me I don’t have any ventilation on my roof.  Why didn’t the roofer who installed roof tell me this or is it not needed? Can a silver coating  do the same as ventilation? I live in a Philadelphia row home.

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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Ty,

    Not all roofs need to be vented, but we'd need to know more about your roof to tell you if it should or shouldn't be vented. Here is an article that will help you understand the different ways flat, or really, low-slope roofs can be detailed: Insulating Low-Slope Residential Roofs

  2. NIGHTNANC | | #2

    What kind of roof doesn’t need to be vented?
    I have included a picture of my roof from google maps . Not that’s easy to tell what my roof is ,but just so u know it is in middle of block, no attic, neighbor just added a third floor on top of a roof like mine. Help! I think the worker wanted me to have him do it ...... is ventilation those whirlybird things?

    1. GBA Editor
      Brian Pontolilo | | #4

      Hi Ty.

      Roofs can be insulated in ways that make venting unnecessary. For example, your low slope roof could have (an appropriate amount) of rigid foam insulation above the roof deck and beneath the roofing membrane (and maybe more insulation in the rafter bays) and not require venting.

      Yes, those "whirlybird things" are part of a roof venting strategy.

      All of this is explained in the article I posted above.

  3. Deleted | | #3


  4. Expert Member
    Dana Dorsett | | #5

    >" Can a silver coating do the same as ventilation? "

    Absolutely not!

    Roof ventilation is primarily about purging moisture. Silvery coatings are about reducing solar gain. They are different things entirely. But reducing the roof deck temperature with reflective coatings increases the need for venting.

    A turbine vent "... whirlybird ..." doesn't work when buried in snow, and would have to be installed on a sufficiently high stack to be effective in winter. Proceed with caution, since they can depressurize the attic space by quite a bit, and unless the attic floor is well sealed can pull conditioned space air into the attic, which then pulls outdoor air into the conditioned space. Don't install one unless you absolutely KNOW it's needed.

  5. NIGHTNANC | | #6

    Dana, I don’t have an attic. I have a flat row home roof.
    Brian, i have a rubber roof, that is all i know. I have lived in this house for 39 years and this is the first time i have heard about ventilation in roof, by neighbors handyman. How do i know i need this?

    1. Expert Member
      Dana Dorsett | | #7

      Some flat row roofs have 10-36" of "micro-attic" space between the ceiling and the roof deck. Is your ceiling actually the roof deck, with open joists?

      If yes, is there any rigid foam or other flat insulation above the roof deck, under the EPDM/rubber roof?

      If no, is there insulation between the joists? If yes, is there an air gap between the insulation and roof deck?

    2. GBA Editor
      Brian Pontolilo | | #8


      You have to be able to answer the questions that Dana and I are asking to know if your roof should have vents. Perhaps it would be best to call a local contractor to take a look at your situation.

  6. jgitman | | #9

    Hey Ty - curious if you ever solved this problem?

    I'm having a similar problem in Philadelphia in my row home. Just bought the place over the summer. Now that winter has rolled around we're seeing an extreme level of condensation accumulating on the underside of our roof and dripping onto the ceiling.

    If anyone on this thread has suggestions, they would be appreciated.

    Extra info: Minimal amount of insulation between joists and not consistent across entire ceiling from what I can see. It's about 12 inches between ceiling and roof. The roof is elevated above the joists with about 1 inch to allow airflow. There are no vents in the "micro-attic" space.

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