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Luke Kujacznski Posted: Jul 16, 2007 02:09 PM	Hybrid Mason, I have been installing a lot of hybrid systems. Where I spray between 1 and 2 inches of foam and then filling the wall cavity will wall spray celluose. Am I creating a moisture nightmare or do you feel this is a pretty safe and sound system? I know that each system is golden on there own but the combination I have not seen any data on. I know that there was an article endorsing this system in the sprayfoam mag a few months ago but I would like your opinion on the science of it. Thanks for your time.
mason Posted: Jul 16, 2007 02:16 PM	Its a very good question. Hybrid systems can work well in most climates and construction design. The application of closed cell sprayfoam stops air infiltration and allows the cellulose insulation to perform better. The application has been used with great success in South Texas for over 30 years and in other areas of the country over the last 10 years. But as you suggest, in colder climates and in higher humidity environments a thicker application of closed cell SPF is required to prevent condensation. Hygrogthermal calculations should be performed to determine the suitable thickness of SPF to prevent condensation. However a rule of thumb that seems to work, for interior humidity ranging up to 55% 1/2 to 1 inch minimum in hot or mixed climates. 1-1/2 - 2 1/2 inches minimum in colder climates. Mark Bomberg of U of Syracuse and formerly with the National Research Council of Canada recommends at least 40 mm (1.6 inches) of closed cell foam to prevent condensation while Neal Ganser of Corbond recommends 2 to 2 1/2 inches of closed cell in the coldest climates in the continental US. Hope this helps.
Luke Kujacznski Posted: Jul 16, 2007 02:38 PM	Would lower Michigan be considered mixed or cold climate? We install 1 inch average. Which with 245 foam is hard to achieve so most of the time it is closer to 1.5 inches. A lot of the jobs we put one inch in a 2x6 cavity so the ratio of foam to celluose is greater, would those be more of a problem?
mason Posted: Jul 18, 2007 08:46 AM	You would need to look at the climate charts to determine that. Upper Michigan definitely is in the cold climate range. Ask your supplier if they can perform a WUFI analysis or comparable hygrothermal modeling analysis on your project and area.

Author

Comments

Luke Kujacznski

Posted: Jul 16, 2007 02:09 PM

Hybrid

Mason,

I have been installing a lot of hybrid systems. Where I spray between 1 and 2 inches of foam and then filling the wall cavity will wall spray celluose. Am I creating a moisture nightmare or do you feel this is a pretty safe and sound system? I know that each system is golden on there own but the combination I have not seen any data on. I know that there was an article endorsing this system in the sprayfoam mag a few months ago but I would like your opinion on the science of it. Thanks for your time.

mason

Posted: Jul 16, 2007 02:16 PM

Its a very good question. Hybrid systems can work well in most climates and construction design. The application of closed cell sprayfoam stops air infiltration and allows the cellulose insulation to perform better. The application has been used with great success in South Texas for over 30 years and in other areas of the country over the last 10 years.

But as you suggest, in colder climates and in higher humidity environments a thicker application of closed cell SPF is required to prevent condensation.

Hygrogthermal calculations should be performed to determine the suitable thickness of SPF to prevent condensation.

However a rule of thumb that seems to work, for interior humidity ranging up to 55%
1/2 to 1 inch minimum in hot or mixed climates.
1-1/2 - 2 1/2 inches minimum in colder climates.

Mark Bomberg of U of Syracuse and formerly with the National Research Council of Canada recommends at least 40 mm (1.6 inches) of closed cell foam to prevent condensation while Neal Ganser of Corbond recommends 2 to 2 1/2 inches of closed cell in the coldest climates in the continental US.

Hope this helps.

Luke Kujacznski

Posted: Jul 16, 2007 02:38 PM

Would lower Michigan be considered mixed or cold climate? We install 1 inch average. Which with 245 foam is hard to achieve so most of the time it is closer to 1.5 inches. A lot of the jobs we put one inch in a 2x6 cavity so the ratio of foam to celluose is greater, would those be more of a problem?

mason

Posted: Jul 18, 2007 08:46 AM

You would need to look at the climate charts to determine that. Upper Michigan definitely is in the cold climate range. Ask your supplier if they can perform a WUFI analysis or comparable hygrothermal modeling analysis on your project and area.

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