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Issues from a new “flat” roof install

alexc927 | Posted in General Questions on

Hope I do a good job explaining myself here:

Early last week we had a new roof installed. The front portion of the house is your typical pitched roof (shingles) but the back portion of the house, which is a new addition (prior owners added on), required a “flat” roof system. The “newer” addition enabled prior owners to move a kitchen back there as well as a larger family room. So the flat roof system is above the kitchen and family room.

I believe the contractor employed a torch down roofing system for the “flat roof”. I cannot confirm if he used modified bitumen. I just know that when I watched a bit of the process, it appeared to be the torch down method.

Everything seemed to go great and the pitched roof looks awesome but the flat roof is rather…unsightly. Fortunately, it can’t be seen from my backyard. Problem now is, during the day (when it’s hot) the kitchen smells pretty badly of what I think is a tar-type smell. Not sure what the smell is but it smells like the stuff they torched down. While the kitchen smells awful there is absolutely no odor in the family room, yet both rooms have the flat roof above it.

The kitchen also has two skylights and my theory is that the odor is seeping in through the skylights.
What do you guys think?

To make matters worse, if I turn on the central air, (only the front portion of the house has central so the kitchen and family room do not. When we remodel the kitchen and family room the plan is to put in mini-split system) the kitchen no longer smells but the air conditioned part of the home now begins to reek. I theorized that when the central is turned in, the hotter air from the kitchen (which smells badly) seeps into the living room.

How plausible does this sound to you guys? I’m generally pretty clueless about this whole thing and somewhat discouraged. I just paid for central air to be installed and then two weeks later had a new roof installed only to find that the flat portion of the roof stinks up the kitchen and turning on the new central air moves the stink to another room. Hope you guys can either validate or invalidate my theories and provide some guidance on how to resolve these issues.

Thank you

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  1. GBA Editor
    Martin Holladay | | #1

    A site visit might prove instructive.

    One possibility is that operation of the range hood exhaust fan in the kitchen is depressurizing that room, and is drawing makeup air from a smelly source.

    Another possibility is that a ventilation system has a "fresh" air intake opening near the new roof.

    This situation calls for good old-fashioned detective work. The key questions are:

    1. Is the forced-air system balanced or unbalanced?

    2. Is the smell better or worse when certain exhaust fans are turned on?

    3. Which rooms are pressurized, and which rooms are depressurized, when the smell is worst?

    4. Are there any air pathways that originate above the roofing?

  2. alexc927 | | #2

    Hi Martin,

    Thank you for your response.

    1) How do I determine if the forced air system is balanced or unbalanced? Also, by "forced air system" are you referring to my central air unit?

    2) If nothing is turned on, the house smells as it normally does. But the kitchen smells like the new flat roof.

    3) The smell moves. If the central air is on, the front portion of the house smells like the flat roof but the kitchen has no odor. If the central air is OFF, only the kitchen smells like flat roof. Every other room in the house smells completely normal when central air is OFF.

    4) Air pathways above the roofing? I do not know. Above the kitchen and the family room is flat roofing. The family room there is NO smell. The kitchen smells like new flat roof and I believe it's coming from the skylights.

  3. GBA Editor
    Martin Holladay | | #3

    You probably need to hire a home performance contractor who is familiar with diagnostics and who owns a blower door and a Duct Blaster. Look for a home energy rater who is certified by RESNET or BPI.

    A technician with a blower door, a Duct Blaster, and a flow hood can perform all kinds of tests, and will be able to determine if your forced air system (used for a central air conditioner, or space heating, or both) is balanced or unbalanced.

    It's possible that there is an air leak near your skylight that pulls exterior air heated by the sun into your kitchen when the kitchen is depressurized. But I'm just guessing.

  4. alexc927 | | #4

    Martin, are you referring to an energy audit or something else?

  5. GBA Editor
    Martin Holladay | | #5

    This might be the same type of contractor who performs energy audits. But in your case, you are looking for something other than an audit. You are looking for an explanation for your smell.

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