"Skin" on ccf | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

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steve kester Posted: Jan 14, 2010 09:11 PM	"Skin" on ccf I am new to your forum but have been in the "building" industry for 35 years. My question relates to the surface skin that develops on ccf. Does the formation of the skin relate in any way to the development of the vapor/air barrier qualities of the foam? Does a job that has a surface that is VERY irregular necessarily suffer from a lack of vapor/air barrier qualities? I have looked at a job that was done within the last few years with ccf sprayed against a vented roof deck and have found a considerable amount of moisture on the back of the osb. The cavities have approx. 3 1/2" to 4" of a mix of two different product applications of ccf. There are a few spots where water has worked through the foam and stained the surface. If water can get through then water vapor and air can get through. any ideas of what may be going on with the foam to cause this condition?
mason Posted: Jan 15, 2010 07:58 AM	While the foam skin is a higher density than the rest of the foam and will provide some additional moisture vapor retardency, it is not the prime reason for its MVT properties. I would suspect other factors rather than the lack of a skin on the foam. such as 1. off ratio foam 2. poor cell structure (too many open cells) 3. low density foam 4. extremely high interior humidity (greater than 65%) 5. water leak 6. improper venting design
Dennis Davidson Posted: Jan 15, 2010 10:23 AM	Does the foam feel spongy or crunchy? Could be cc installed off-ratio. From your description though it sounds more like it an oc and not a cc foam.
steve kester Posted: Jan 15, 2010 07:54 PM	Thanks for the responses, the foam was definitely cc, although from two manufacturers. Original install was not to spec,(thickness issue). Installer then sprayed a second time with different foam then had to come back again and used same foam as original shoot. Should water be able to permeate properly installed foam? Does the spray technique and the number of lifts influence the quality of a job? If I send a sample to the original manufacturer will they likely be able to pinpoint a deficiency?
Posted: Jan 15, 2010 08:12 PM	???"Does the formation of the skin relate in any way to the development of the vapor/air barrier qualities of the foam?"???? no,,but it does effect the air permience to a minimal degree(of no significance in CC foam out at the depths you describe) ???"Does a job that has a surface that is VERY irregular necessarily suffer from a lack of vapor/air barrier qualities?"??? most cc foams have a perm rating of <1 out at 1.5"...so no on the vapor barrier compromise,,, and air barrier is achieved in the first 1/2" of application of closed cell or open cell foam... they are 2 different properties(vapor/airbarrier),,and can not be used/compared in the same statement,,, so how are you seeing moisture on the osb if the foam was spray to the roof deck????you say it was vented,,do you mean under the vent chutes,,,well go friggin figure,,you dont put vent chutes in a conditioned lid..ever,,,i hear folks doin it thinkin it is "safe" cause they just havent ever "heard of this foam shot right to the lid" and "a roofs got to breath to prevent ice damns" and " a roof need ventilation to prevent shingle damage",,"and it will void the warranty of the roof cladding" and all the other excuses/brilliant thoughts of the uniformed but frequently well intentioned... you cant mix technologies,,,you do not ventilate a conditioned lid...if you do you are now creating a "airspace"...the airspace needed for condensation to lay down on if the dewpoint is met out closer to the cold side of the roof... when hot meets cold condensation occurs,,,and the condensation needs an airspance to "lay out" on..if the foam is "glued to the substrate" as it should be in a hot lid application this air space is not there and the moisture will either migrate thru the structures elements to dry to the outside (probably not in this scenerio of 3-4" but pertinant for this discussion if a OC foam was used)if there is no elements above with a perm of less than 1(anyone thinkin about the metal roofs goin out on the cold side of the structure..uh perm less than 1,,if a filterglas lid the osb will rain..lol),,,or it will remain in the structure to be managed by the mechcanical ventilation as it should in a properly designed/applied conditioned lid applicition and hvac installation.... you describe 3 different conditions here sir.. each having its own nuances,, vapor transmission air barrier and gross water infiltration... they are not the same,,and can not be questioned as the same entity or problem. you do not tell us your climate zone..3-4inches in a "crappy irreguar" installation is not enough in a cold climate zone... which is why you hire a pro...not a newbee lookin for a check and tendering the low ball bid..you can not have steak on a hamberger budget..i have foamguys of somewhere sellin 6" of oc in lids here in the cornfield...the roof will sweat in the crap ass weather we had for the last month here...the builder got a cheap bid,,,beat mine by 40%...mine dont sweat,,,physics is friggin physics..you cant apply half the rvalue and expect a performance boost,,equilibrium maybe.. but reduction in energy costs,,no friggin way... if you have vent chutes under the foam you have now defined the building envelope at the undersurface of the ventchute not at the outer face of the roof deck,,thats outter face,,outside..like you have with a well applied conditioned "hot lid",... i deal with this crap daily,,,good intentions in most cases,,but uninformed decisions none the less... if gross water is gettin thru,,the roof is leakin,,,put the foam on the outside of the roof deck by a credible applicator like mac-aroni...will stop it there,,,hydrostatic pressure is a ******..ever seen a solid foundation leak when the water table is swollen on the outside,,,i thought you had after 35 years... hope this helps...rofl,,, serious...ask and ye shall recieve...
mason Posted: Jan 17, 2010 01:01 PM	Closed cell foam will resist water penetration. Samples can tell you a lot. density, compressive strength, open cell content, off ratio, exothermic heat reaction, cell formation, moisture contamination, and more. My advice send photos and samples, but some things may require an onsite inspection. For example maybe they didn't spray the foam in the right places, perhaps a pipe is leaking or creating condensation in a space, it might not be ventilated properly (allowing moist air in the wrong places).
Michael Fusco Posted: Jan 21, 2010 08:22 PM	If, and this is a big if, there is a void behind the foam, there can be an accumulation of moisture. If that void is a vent, then there is yet another surprise. Sometimes there can be a void from improper installation, like spraying over moisture.

Author

Comments

steve kester

Posted: Jan 14, 2010 09:11 PM

"Skin" on ccf

I am new to your forum but have been in the "building" industry for 35 years. My question relates to the surface skin that develops on ccf.

Does the formation of the skin relate in any way to the development of the vapor/air barrier qualities of the foam? Does a job that has a surface that is VERY irregular necessarily suffer from a lack of vapor/air barrier qualities?

I have looked at a job that was done within the last few years with ccf sprayed against a vented roof deck and have found a considerable amount of moisture on the back of the osb. The cavities have approx. 3 1/2" to 4" of a mix of two different product applications of ccf. There are a few spots where water has worked through the foam and stained the surface. If water can get through then water vapor and air can get through. any ideas of what may be going on with the foam to cause this condition?

mason

Posted: Jan 15, 2010 07:58 AM

While the foam skin is a higher density than the rest of the foam and will provide some additional moisture vapor retardency, it is not the prime reason for its MVT properties.

I would suspect other factors rather than the lack of a skin on the foam. such as
1. off ratio foam
2. poor cell structure (too many open cells)
3. low density foam
4. extremely high interior humidity (greater than 65%)
5. water leak
6. improper venting design

Dennis Davidson

Posted: Jan 15, 2010 10:23 AM

Does the foam feel spongy or crunchy? Could be cc installed off-ratio. From your description though it sounds more like it an oc and not a cc foam.

steve kester

Posted: Jan 15, 2010 07:54 PM

Thanks for the responses, the foam was definitely cc, although from two manufacturers. Original install was not to spec,(thickness issue). Installer then sprayed a second time with different foam then had to come back again and used same foam as original shoot.

Should water be able to permeate properly installed foam? Does the spray technique and the number of lifts influence the quality of a job?

If I send a sample to the original manufacturer will they likely be able to pinpoint a deficiency?

Posted: Jan 15, 2010 08:12 PM

???"Does the formation of the skin relate in any way to the development of the vapor/air barrier qualities of the foam?"???? no,,but it does effect the air permience to a minimal degree(of no significance in CC foam out at the depths you describe)

???"Does a job that has a surface that is VERY irregular necessarily suffer from a lack of vapor/air barrier qualities?"??? most cc foams have a perm rating of <1 out at 1.5"...so no on the vapor barrier compromise,,,
and air barrier is achieved in the first 1/2" of application of closed cell or open cell foam...
they are 2 different properties(vapor/airbarrier),,and can not be used/compared in the same statement,,,

so how are you seeing moisture on the osb if the foam was spray to the roof deck????you say it was vented,,do you mean under the vent chutes,,,well go friggin figure,,you dont put vent chutes in a conditioned lid..ever,,,i hear folks doin it thinkin it is "safe" cause they just havent ever "heard of this foam shot right to the lid" and "a roofs got to breath to prevent ice damns" and " a roof need ventilation to prevent shingle damage",,"and it will void the warranty of the roof cladding" and all the other excuses/brilliant thoughts of the uniformed but frequently well intentioned...
you cant mix technologies,,,you do not ventilate a conditioned lid...if you do you are now creating a "airspace"...the airspace needed for condensation to lay down on if the dewpoint is met out closer to the cold side of the roof...
when hot meets cold condensation occurs,,,and the condensation needs an airspance to "lay out" on..if the foam is "glued to the substrate" as it should be in a hot lid application this air space is not there and the moisture will either migrate thru the structures elements to dry to the outside (probably not in this scenerio of 3-4" but pertinant for this discussion if a OC foam was used)if there is no elements above with a perm of less than 1(anyone thinkin about the metal roofs goin out on the cold side of the structure..uh perm less than 1,,if a filterglas lid the osb will rain..lol),,,or it will remain in the structure to be managed by the mechcanical ventilation as it should in a properly designed/applied conditioned lid applicition and hvac installation....

you describe 3 different conditions here sir..
each having its own nuances,,
vapor transmission
air barrier
and gross water infiltration...

they are not the same,,and can not be questioned as the same entity or problem.

you do not tell us your climate zone..3-4inches in a "crappy irreguar" installation is not enough in a cold climate zone... which is why you hire a pro...not a newbee lookin for a check and tendering the low ball bid..you can not have steak on a hamberger budget..i have foamguys of somewhere sellin 6" of oc in lids here in the cornfield...the roof will sweat in the crap ass weather we had for the last month here...the builder got a cheap bid,,,beat mine by 40%...mine dont sweat,,,physics is friggin physics..you cant apply half the rvalue and expect a performance boost,,equilibrium maybe..
but reduction in energy costs,,no friggin way...

if you have vent chutes under the foam you have now defined the building envelope at the undersurface of the ventchute not at the outer face of the roof deck,,thats outter face,,outside..like you have with a well applied conditioned "hot lid",...

i deal with this crap daily,,,good intentions in most cases,,but uninformed decisions none the less...

if gross water is gettin thru,,the roof is leakin,,,put the foam on the outside of the roof deck by a credible applicator like mac-aroni...will stop it there,,,hydrostatic pressure is a ******..ever seen a solid foundation leak when the water table is swollen on the outside,,,i thought you had after 35 years...

hope this helps...rofl,,,

serious...ask and ye shall recieve...

mason

Posted: Jan 17, 2010 01:01 PM

Closed cell foam will resist water penetration. Samples can tell you a lot. density, compressive strength, open cell content, off ratio, exothermic heat reaction, cell formation, moisture contamination, and more. My advice send photos and samples, but some things may require an onsite inspection. For example maybe they didn't spray the foam in the right places, perhaps a pipe is leaking or creating condensation in a space, it might not be ventilated properly (allowing moist air in the wrong places).

Michael Fusco

Posted: Jan 21, 2010 08:22 PM

If, and this is a big if, there is a void behind the foam, there can be an accumulation of moisture. If that void is a vent, then there is yet another surprise.
Sometimes there can be a void from improper installation, like spraying over moisture.

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