Message Board Thread - "Ice over membrane"

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Ice over membrane Ben10 12/4/2008
What do you think of that...
The thermo was taken in may. It shows an area arond the skylight were there is water in the insulation under the roof membrane.
The picture of the same roof was taken this weekin december. How do you explain that the ice forming over the roof membrane is exactly the same shape as on the thermograme...
Re:Ice over membrane Ben10 12/4/2008
here is the thermo
Re:Ice over membrane Tucan73 12/10/2008
The answer is not very simple. When was the scan was done what did the control look like? The fact that the ice is the same as the thremal anomolie is directly against the lwas of thermal conduction. With wet insulation the heat should move throught he system with less resistance and therefore prevent ice from forming.How cold was it when the ice was photographed? That would allow me to make a better anaylsis.
Re:Ice over membrane Ben10 12/10/2008
I tucan 73
The ice was photographe in december at -1 deg. cel. The scan was don in mai at 7 geg. cel.
Like you said, there is no thermal conduction. Could it be that there is only water IN the 12mm base board under the roof membrane. The base board beeing over ther thermal insulation cannot beneficiate from thermal transfer throught the systeme.
Thanks for your time.
Re:Ice over membrane SLR 12/11/2008
A curious situation. This is a slightly wild guess, but this may be due to additional insulation placed to provide slope to drain. The higher r-value prevents the snow/ice melting. The additional r-value would also cause the area to maintain a higher surface temperature during the day and may have not cooled before the IR image was taken. Had the roof sufficient time to cool and was the anomoly cored to verify there was indeed wet insulation? Again, a slightly wild guess.
Re:Ice over membrane beaware 12/24/2008
Isn't the pattern on the thermo actually slightly warmer than the remainder of the roof, which is darker. The wet insulation is allowing more heat to escape. The ice may be the residue from fallen or blown snow, melted by the escaping heat. Often where you have the bottom layer of snow form into ice, it is more presistent, resists melting, then the snow itself.
Re:Ice over membrane StecGuy 1/15/2010
Sorry guys, but i'm going to resurrect this one. My interpretations:

1. The span of this IR image of just the roof is too large.

2. Typically, you see a coverboard of either wood fiber or perlite installed below a modified system. Ponding water adds a lot of weight to the roof system. the additional weight could have actually compressed the wet insulation (especially the aformentioned types), thus creating additional ponding that would follow the outline of the wet insulation, since these areas could now be a little more recessed as compared to the remainder of the roof surface.

3. A foam layer of a urethane or iso based insulation is likely to be installed below the coverboard, these layers do not draw in moisture as fast, and may be providing some r-value yet not allowing the interior temps to conduct through well enough to melt the ice.
Re:Ice over membrane B. Boyd 2/9/2010
I agree with StecGuy. However if you look closely at the patterning in the the thermal image and the ice formation of the surface there appears to be some distinguishing lines the might indicate insulation boards.

Also look closely at what appears to be thermal bridging at the fasteners in the photo. These do not appear in the the thermal image.
Re:Ice over membrane TexasHomeInspector 3/8/2010
I’m guessing the berm at the left is providing reflective heat; the ice closer to the berm appears warmer and is cooler the further from the berm.
Re:Ice over membrane drleak 4/13/2010
Ben10 wrote:
the thermo
I noticed the skylight as well as the flare along the wall where there appear to be roof top units on curbs. It has been my experience that often roofers do not seal the vapour barrier around penetrations or wall perimeters and warm air can exfiltrate into the roof assembly under interior pressures. Often discoloration of the roofing membrane, from ponding water, can also affect infrared images.
Jim Jennings
Canadian Academy of Building Sciences Inc.

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