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Mike Natal Posted: Sep 25, 2008 08:49 AM	Can closed cell be sprayed over open cell? Can closed cell be sprayed over open cell? The reason Im asking is my rafters in my attic were sprayed with open cell, but the contractor srayed some areas 1/2" thick in some areas and 2" in other areas and 5" in other areas. So he was going to respray the rafter to correct the problem, but only has closed cell to do it with. What would be the pros or cons of this?
Greg Pruitt Posted: Sep 25, 2008 11:08 AM	I see no reason you could not do it, although if you paid for 1/2 lb, he is obligated to complete the job properly. I have gone back on jobs before. It is part of the job. The difference between the hard and soft foam, other than sound is that the hard foam, will not allow water to pass through in case of a leak, and that can cause rot.
Greg Pruitt Posted: Sep 25, 2008 11:08 AM	I see no reason you could not do it, although if you paid for 1/2 lb, he is obligated to complete the job properly. I have gone back on jobs before. It is part of the job. The difference between the hard and soft foam, other than sound is that the hard foam, will not allow water to pass through in case of a leak, and that can cause rot.
Jim Coler Posted: Sep 25, 2008 05:03 PM	I agree that it should be done right by w****ver did the .5lb job. It should be 6" thick with a general tolerance of about 3/4". We typically say 5" minimum. So, go back to the first guy and see if he'll complete the job since it wasn't completed properly to date and if he won't do it, then get someone else to add it to a 5" minimum thickness. Just make sure that w****ver you get to do it pays close attention to detail and sprays more than what appears necessary because once a spray job is messed up by someone else, it's not always easy to see all of the blind spots created by the bad install. Open cell is going to be your best bang for the buck and will help over fill any bigger cracks and voids in the existing uneven surfaces. I know I bid on a job like this where it was only 1/2" thick to 7" thick and all over the place and the previous guy must have used whatever he could get his hands on because there was open cell and closed cell mixed together with no consistency. It's guys like these that make it difficult for us who do it right. This was the only instance where I noticed any condensation and it was even on the closed cell where it was only 1/2" thick.
Gerry Wagoner Posted: Sep 25, 2008 08:30 PM	What kind of foam do you spray Greg?
Robby Chapman Posted: Sep 25, 2008 08:40 PM	I'm tired of people saying that closed cell will rot your roof. I've been in the business for five years which is not a long time is some people, but I have never seen evidence of this. But if you realy think about it, how long will it take for that water to get through five or six inches of open cell. I think it would take a very long time depending on the size of the hole in the roof. Now during that time that it takes that water to reach the attic space, what do you think that water is doing to the plywood decking. I spray both foams, more closed than open cell. But that water is not going to just pour through the open cell like they say. It's going to sit there and soak up more water and that water will not evaporate. So to say closed cell will rot your roof, is wrong, if any foam will rot your roof out it would be open cell.
Posted: Sep 26, 2008 06:25 AM	cause rot...come on greg brilliant,,friggin brilliant!!! what about mold man....you could sell with that buzzword too!!! WHAT OPEN CELL FOAM DO YOU SPRAY???? yes the job should be fixed. yes you could use either foam... i wonder why the guy dont have the open cell he sold you initially,,,hillbilly foamer maybe??? i have sprayed numerous conditioned lids,,,open and closed cell,,,if the roof leaks and water violates the building envelope it will manifest it self somewhere on the lid,,,eventually,,,you dont stop water from the inside,,,water is a bitch...most often it will "find" the closed rafter truss and work its way down the truss to the heel or somewhere in between,,see spot,,,see spot drip... have a nice day :) dude
Jim Coler Posted: Sep 26, 2008 06:44 AM	FFI, Water will evaporate from open cell faster than from closed cell. Just so everyone knows, closed cell will also absorb water because it's only >90% closed cell. That's why you can't use it for floatation of hot tub covers alone. The water does come throgh thd open cell faster than the closed cell and will spot on the drywall somewhere. As Dude said, it will find it's way through either foam. Your last statement was is completely uncalled for and wrong! Open cell will not rot your roof more than closed cell and neither are likely to rot your roof. So, please keep your emotions at bay and refrain from false statements like this! this kind of emotional verbiage - not based on facts - is what hurts us all in the industry!
Robby Chapman Posted: Sep 30, 2008 06:36 PM	It's not me giving foam a bad name, it's the open cell guys that are doing that. I agree, we are in this together and we should stick togther. This is he first time I have ever said anything bad about open cell. I'm having a hard enough time selling foam we don't need all this juck about closed cell rotting the roof. Yes, water will evaporate if you sit the foam in the sun light, but your talking about something that never sees the sun light.
Jim Coler Posted: Oct 01, 2008 06:25 PM	It will evaporate even if not in sunlight. Let's go back to the physics of moisture movement. Moisture moves through air movement, and diffusion through solid materials from high moisture to low moisture. So, sunlight only produces heat which changes the moisture pressure/saturation level and causes a higher vapor drive condition. In some cases like masonry, it can drive the moistsure deeper, but most materials which insulate tend to dry out. When wood gets wet, it will dry out - so why wouldnt' open cell foam? It does too! It's closed cell foam that takes much longer to dry out if it gets wet inside and granted, it takes lot more to get the water inside it. The best prinicple I've heard of to follow is: Design to keep moisture out and let it out when it gets in! So, Open and Closed cell foams each haave their benefits and applications and balnket statements about one of the other being bad should be avoided.
Eric Smith Posted: Oct 08, 2008 12:02 AM	So what is the consensus on OC vs. CC for roof decks?
Jim Coler Posted: Oct 08, 2008 10:28 AM	OC or CC will work fine to the underside of the roofdeck. OC will be less expensive than the closed cell.

Author

Comments

Mike Natal

Posted: Sep 25, 2008 08:49 AM

Can closed cell be sprayed over open cell?

Can closed cell be sprayed over open cell?

The reason Im asking is my rafters in my attic were sprayed with open cell, but the contractor srayed some areas 1/2" thick in some areas and 2" in other areas and 5" in other areas. So he was going to respray the rafter to correct the problem, but only has closed cell to do it with.

What would be the pros or cons of this?

Greg Pruitt

Posted: Sep 25, 2008 11:08 AM

I see no reason you could not do it, although if you paid for 1/2 lb, he is obligated to complete the job properly. I have gone back on jobs before. It is part of the job. The difference between the hard and soft foam, other than sound is that the hard foam, will not allow water to pass through in case of a leak, and that can cause rot.

Greg Pruitt

Posted: Sep 25, 2008 11:08 AM

Jim Coler

Posted: Sep 25, 2008 05:03 PM

I agree that it should be done right by w******ver did the .5lb job. It should be 6" thick with a general tolerance of about 3/4". We typically say 5" minimum. So, go back to the first guy and see if he'll complete the job since it wasn't completed properly to date and if he won't do it, then get someone else to add it to a 5" minimum thickness. Just make sure that w******ver you get to do it pays close attention to detail and sprays more than what appears necessary because once a spray job is messed up by someone else, it's not always easy to see all of the blind spots created by the bad install.

Open cell is going to be your best bang for the buck and will help over fill any bigger cracks and voids in the existing uneven surfaces. I know I bid on a job like this where it was only 1/2" thick to 7" thick and all over the place and the previous guy must have used whatever he could get his hands on because there was open cell and closed cell mixed together with no consistency. It's guys like these that make it difficult for us who do it right. This was the only instance where I noticed any condensation and it was even on the closed cell where it was only 1/2" thick.

Gerry Wagoner

Posted: Sep 25, 2008 08:30 PM

What kind of foam do you spray Greg?

Robby Chapman

Posted: Sep 25, 2008 08:40 PM

I'm tired of people saying that closed cell will rot your roof. I've been in the business for five years which is not a long time is some people, but I have never seen evidence of this. But if you realy think about it, how long will it take for that water to get through five or six inches of open cell. I think it would take a very long time depending on the size of the hole in the roof. Now during that time that it takes that water to reach the attic space, what do you think that water is doing to the plywood decking. I spray both foams, more closed than open cell. But that water is not going to just pour through the open cell like they say. It's going to sit there and soak up more water and that water will not evaporate. So to say closed cell will rot your roof, is wrong, if any foam will rot your roof out it would be open cell.

Posted: Sep 26, 2008 06:25 AM

cause rot...come on greg
brilliant,,friggin brilliant!!!
what about mold man....you could sell with that buzzword too!!!
WHAT OPEN CELL FOAM DO YOU SPRAY????

yes the job should be fixed.
yes you could use either foam...
i wonder why the guy dont have the open cell he sold you initially,,,hillbilly foamer maybe???

i have sprayed numerous conditioned lids,,,open and closed cell,,,if the roof leaks and water violates the building envelope it will manifest it self somewhere on the lid,,,eventually,,,you dont stop water from the inside,,,water is a bitch...most often it will "find" the closed rafter truss and work its way down the truss to the heel or somewhere in between,,see spot,,,see spot drip...

have a nice day :)

dude

Jim Coler

Posted: Sep 26, 2008 06:44 AM

FFI,
Water will evaporate from open cell faster than from closed cell. Just so everyone knows, closed cell will also absorb water because it's only >90% closed cell. That's why you can't use it for floatation of hot tub covers alone. The water does come throgh thd open cell faster than the closed cell and will spot on the drywall somewhere. As Dude said, it will find it's way through either foam.

Your last statement was is completely uncalled for and wrong! Open cell will not rot your roof more than closed cell and neither are likely to rot your roof. So, please keep your emotions at bay and refrain from false statements like this! this kind of emotional verbiage - not based on facts - is what hurts us all in the industry!

Robby Chapman

Posted: Sep 30, 2008 06:36 PM

It's not me giving foam a bad name, it's the open cell guys that are doing that. I agree, we are in this together and we should stick togther. This is he first time I have ever said anything bad about open cell. I'm having a hard enough time selling foam we don't need all this juck about closed cell rotting the roof. Yes, water will evaporate if you sit the foam in the sun light, but your talking about something that never sees the sun light.

Jim Coler

Posted: Oct 01, 2008 06:25 PM

It will evaporate even if not in sunlight. Let's go back to the physics of moisture movement. Moisture moves through air movement, and diffusion through solid materials from high moisture to low moisture. So, sunlight only produces heat which changes the moisture pressure/saturation level and causes a higher vapor drive condition. In some cases like masonry, it can drive the moistsure deeper, but most materials which insulate tend to dry out. When wood gets wet, it will dry out - so why wouldnt' open cell foam? It does too! It's closed cell foam that takes much longer to dry out if it gets wet inside and granted, it takes lot more to get the water inside it.

The best prinicple I've heard of to follow is: Design to keep moisture out and let it out when it gets in! So, Open and Closed cell foams each haave their benefits and applications and balnket statements about one of the other being bad should be avoided.

Eric Smith

Posted: Oct 08, 2008 12:02 AM

So what is the consensus on OC vs. CC for roof decks?

Jim Coler

Posted: Oct 08, 2008 10:28 AM

OC or CC will work fine to the underside of the roofdeck. OC will be less expensive than the closed cell.

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