Anyone ever experienced what appears to be much (and loud) thermal
noise from polyiso nail base panels? We are involved in a
recently-completed office bldg in St. Louis. The sloped part of the
roof system is comprised of acoustical `F' deck attached via puddle
welds to open web bar joists, atop which is polyiso nail base (R-30)
and standing seam metal panels. There is an ice and water shield below
the standing seam panels, on top of the nail base OSB. There is,
however, no separation layer or vapor barrier between the metal deck
and the bottom of the polyiso. The building was designed so that the
top floor has a "loft" look, i.e. the roof structure is fully exposed.
The noise sounds like thermal expansion, but is very loud, and
widespread. Seems to be more prevalent in the morning on a sunny day
or, given the current climate in St. Louis, when the heat kicks either
`on' or `off'. Diagnostics to-date have included removing some of the
standing seam metal panels, as it was thought the standing seam metal
was the source of the noise, perhaps the clips were binding. However,
after removing the metal panels the noise still persists and, as the
cold weather has really set in, we also now hear much `popping' on a
flat section of the roof that has solid (non acoustical) metal deck,
topped with polyiso panels and a white colored TPO membrane (no metal
panels). On the sloped portions of the roof, besides "popping" it
sounds almost like a `tarp flopping in the breeze', rolling across the
entire roof, even on calm days with no breeze. This noise (the
"rolling" widespread variety) also existed in the summer when weather
was warm. We are now focusing on the nail base insulation. Tentatively
we are planning to remove some of the nail base panels to see how they
look. The noise is so great the upper floor is untenable for
professional office space. I had thought polyiso was relatively stable,
inert stuff that should not be subject to thermal expansion. Almost
seems like the polyiso is binding to the metal deck and then releasing
itself. Any advice/history anyone can offer much appreciated.
Tom, thanks for the reply, it is the first one we rec'd.
I will post what we ultimately (hopefully) find out to be the cause.
At this point I suppose possibilities may include the need for a
separation layer (thermal break) or vapor barrier between the metal
deck and the bottom of the iso; perhaps the iso was installed too
quickly after manufacture, i.e. foam not fully cured/conditioned; lack
of separation (gap) between the iso panels; loss of bond between OSB
and foam; improper or inconsistent fastening of the iso panels to the
deck; some reason that thermal bridging is occuring down to the metal
deck proper, etc.
In NJ do you ever install a vapor barrier or separation layer atop the
metal deck when it is used in a situation where it is left exposed to
After this problem became apparent, time was spent going around to
other buildings in the area with exposed metal deck, notably the bigger
box retail structures, and similar noise was heard, to varying degrees,
although in those installations (much higher ceilings, relatively noisy
interior simply based on usage) it is not as problematic as for office
space, where a quieter environment is needed.
In a school (gymnasium, cafeteria, etc.) for example, perhaps the noise
does exist, but is not as noticeable? If this type of roof cross
section were ever used in classrooms, or a library, the noise likely
would be more of an issue.
Tom Cular wrote:
I'd really like to see the design/erection/detail drawings for this setup.
I'd also really like to hear if you reach a conclusion for the noise. I've
never heard of a deal like this before. Personally I can only 'suspect'
thermal expansion. On a stupid note, any chance the building itself is
transferring noise from the walls to the roof? As in does the noise start on
one side of the building and transfer across the roof? Radiant
heating/cooling on 1 side 1st?
I don't know. I can tell you this, according to the CRC Handbook of
Chemistry and Physics, the only substance in which carbon is soluable is
molten iron (that's how they make steel), so searching for a chemical
solution is probably futile.
I find the following extremely interesting;
One reply in another group (science - acoustics) mentioned the
possibility of a "stick-slip" phenomenon between the lower iso panel
and metal deck interface. Maybe the interface between the two panels of
The above I've experienced. Not after installation but during install. You
can get some vicious noises by rubbing the iso over clean, dry, metal deck.
And as I believe you mentioned, some serious popping noise. This possibility
could be tested by applying a talc/dry lubricant or similar material between
the iso and the metal deck in a test section. Heaven only knows what that
would take to accomplish..........................
On a side note, we do have one section of flat roof that is "green"
(vegetated atop a membrane), and I've yet to hear any large noises from
This "green" somewhat validates the above "stick-slip" phenomenon. It would
seem you've introduced enough added weight to increase the friction
coefficient between the iso and the F deck. Hence, less movement in a given
amount of time.
As an external test, use a section of F deck and a section of iso and
""drag"" the 2 pieces across each other, with different weights/surface
pressure (in comparison to the real application/including roof pitch-temp &
humidity) to see if you can generate the same kinds of noises you're getting
from the existing roof. This could run as much as 20 lf or more with a full
width sheet of F deck including the joist supports. I'd highly suspect
you're going to experience some 'squealing'/shudder when the iso drags over
the deck. Especially so if both are clean of dust. I'd also suspect you will
generate more noise where the iso drags over the joists (or very close to)
than the free space between the joists. I'd almost bet you'll get a faster
repetative rate of 'shudder' over the joist with a lesser rate progressively
further from the essential pinch point of the joist. Think of it like a high
frequency noise transcending to a lower frequency.
From your added info to your original post, I'm still seeing a thermal
problem here. I'm also seeing it as internallay generated as opposed to
external. IE: The SSR But I worry about the following from you;
I just can't see the SSR transmitting the kind of noises you describe
through the iso. Irrespective of that, an SSR can and will grow/shrink
phenomenoly and in quick time.
Keep me informed directly if you want. This certainly has my curiosity
piqued. IF at all possible, can you send a cad dwg. of the roof design? I
can read any ACAD or Sketchup dwg.
Any chance the polyiso or other panel products are maybe too tight? If
there's some compression on the panel edges, maybe the panels are
acting like a diaphragm, jumping from concave to convex with slight
If you have a way to get negative or positive pressure in the building, the
noise may stop. If so, I don't know what comes next, but at least you'd
have something to go on.
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