oil based foams | Insulation/Energy/Building Envelope Q&A | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

Q&A Forums

Author	Comments
Josh Lowman Posted: Jun 01, 2007 07:11 PM	oil based foams I've heard something reasently. someone said oil based c.c. foams loses significant r-value as it ages. something about the foam calapses from the inside and loses its r-value. And for that reason is why they choose water blown c.c. foams and only spray those. Is thier any truth to this. I've heard it does tend to loose some but they claimed r21 would be reduced to r12 after a few years. Does water blown c.c. foams lose any r-value after time.
Luke Kujacznski Posted: Jun 01, 2007 07:23 PM	The R-value givin on the spec sheet is an aged r-value. Most "oil based" cc foam start out with an r-value over 8 and then it slowly loses r-value down to about 6.3-6.9 after that the loss in r-value is minimal. The r-value will not go to zero. The biggest loss iin r-value is in the first year which is why suppliers use the term aged r-value and that value is very stable
Josh Lowman Posted: Jun 01, 2007 07:55 PM	So what about waterblown c.c. foams do they have an age factor. I know about the aged R-value term, just heard someone telling their customers that was the reason they choose to spray water blown c.c. foams.
SprayFoamSupply.com Posted: Jun 02, 2007 08:32 AM	When you say oil based and compare it to water blown, I am going to assume that you mean 245 or gas blown, compared to water blown. When foam is sprayed, there is a complex mixture of gases given off, most of it is the blowning agent. These gases are trapped in the closed cells of the foam. As the foam cools and cures, the gas trapped in the cells wants to shrink and creates a vaccuum inside the closed cells. Over time, atmospheric air is drawn into the closed cells and mixes with the blowing agent. It is unknown how much of the blowing agent remains in the long term. This is why there is a decline in r-value. It is similar to an argon gas filled double window. Over time, it loses it's argon and it's extra U-value. With a water blown foam, carbon dioxide is the main gas trapped inside of the cells. There is no chemical blowing agent to lose. The R-value remains constant. Click the link to the left to read a good article about this. Is is Canadian, so all of the figures are metric. It was forwarded to me from Dick Russell, so I want to give him the credit. As far as the foam colapsing from the inside, I have heard that 245 is a solvent and over time it eats away at the walls of the foam until it can escape. Maybe that is what you are refering to? George
Richard Russell Posted: Jun 04, 2007 07:41 AM	To convert thermal resistivity values in the referenced article from (m-K)/watt to the "R" we know in the US as (sq.ft-Fahrenheit)/(BTU/hr - inch), divide by 6.9333. Thus the top curve, at 70 m-k/watt, becomes R 10.0/inch, and the bottom curve runs out to 43/6.9333 = R 6.2/inch.

Author

Comments

Josh Lowman

Posted: Jun 01, 2007 07:11 PM

oil based foams

I've heard something reasently. someone said oil based c.c. foams loses significant r-value as it ages. something about the foam calapses from the inside and loses its r-value. And for that reason is why they choose water blown c.c. foams and only spray those. Is thier any truth to this. I've heard it does tend to loose some but they claimed r21 would be reduced to r12 after a few years. Does water blown c.c. foams lose any r-value after time.

Luke Kujacznski

Posted: Jun 01, 2007 07:23 PM

The R-value givin on the spec sheet is an aged r-value. Most "oil based" cc foam start out with an r-value over 8 and then it slowly loses r-value down to about 6.3-6.9 after that the loss in r-value is minimal. The r-value will not go to zero. The biggest loss iin r-value is in the first year which is why suppliers use the term aged r-value and that value is very stable

Josh Lowman

Posted: Jun 01, 2007 07:55 PM

So what about waterblown c.c. foams do they have an age factor. I know about the aged R-value term, just heard someone telling their customers that was the reason they choose to spray water blown c.c. foams.

SprayFoamSupply.com

Posted: Jun 02, 2007 08:32 AM

When you say oil based and compare it to water blown, I am going to assume that you mean 245 or gas blown, compared to water blown. When foam is sprayed, there is a complex mixture of gases given off, most of it is the blowning agent. These gases are trapped in the closed cells of the foam. As the foam cools and cures, the gas trapped in the cells wants to shrink and creates a vaccuum inside the closed cells. Over time, atmospheric air is drawn into the closed cells and mixes with the blowing agent. It is unknown how much of the blowing agent remains in the long term. This is why there is a decline in r-value. It is similar to an argon gas filled double window. Over time, it loses it's argon and it's extra U-value. With a water blown foam, carbon dioxide is the main gas trapped inside of the cells. There is no chemical blowing agent to lose. The R-value remains constant. Click the link to the left to read a good article about this. Is is Canadian, so all of the figures are metric. It was forwarded to me from Dick Russell, so I want to give him the credit. As far as the foam colapsing from the inside, I have heard that 245 is a solvent and over time it eats away at the walls of the foam until it can escape. Maybe that is what you are refering to?

George

Richard Russell

Posted: Jun 04, 2007 07:41 AM

To convert thermal resistivity values in the referenced article from (m-K)/watt to the "R" we know in the US as (sq.ft-Fahrenheit)/(BTU/hr - inch), divide by 6.9333. Thus the top curve, at 70 m-k/watt, becomes R 10.0/inch, and the bottom curve runs out to 43/6.9333 = R 6.2/inch.

You need to login to reply to this topic. Please click here to login.