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JohnPeters Posted: Jul 15, 2008 10:32 AM	Air Barriers per building code & SIPs Numerous states around the country are adopting "AIR BARRIER SPECIFICATIONS" to building code / energy conservation code for residential and commercial construction. I have seen this spec typically calling our for at least .004 scfm/ft2 tested per ASTM E-283. Most foams can accommodate this result. I have a few questions regarding this topic: 1.) Are you familiar with this air barrier spec and what are your thoughts on it? How will this effect the SPF industry? 2.) How does this differ from a vapor barrier? Doesn't a vapor barrier stop air movement? (in the north east we are already required to install a vapor barrier on the interior of a wall assembly) 3.) Correct me if I am wrong but this appears to be an exclusive opportunity for foam to take over the market. What else could be used to facilitate an air barrier besides foam? On a completely separate note I have a question on SIP vs. Stick and SPF. I have heard pros and cons for each with lower cost going in favor of SIP's. Would you mind elaborating on your personal opinion on these two different styles of construction? Personally, I do not see how blower door tests could compare between the two. I have heard nightmare stories on assembly utilizing SIPs. Thanks, John Peters
mason Posted: Jul 15, 2008 10:53 AM	John, There are large differences between vapor barriers and air barriers. A vapor barrier (or vapor retarder) reduces the transfer of moisture vapor through a given material such as exterior sheathing, brick, masonry, etc. The goal is reduce the moisture vapor transmission of specific materials. An air barrier is designed to reduce air movement through an assembly (such as a wall or ceiling)or a system (such as a room or a building). Good air barrier systems will reduce the transfer of air borne moisture but may not reduce the water vapor resistance of the building materials themselves. You are correct to assume that most moisture that goes into and out of a building is air borne and a good air barrier system will reduce that amount. But, moisture can still migrate through building materials and vapor retarders are used to reduce the ability of moisture vapor to travel through a given material. Closed cell SPF (at varying thickness) has been proven to work as an effective vapor retarder in most commercial and residential situations. (Note: in cases where vapor drive is always going in one direction such as swimming pools and freezers and additional vapor barrier type material should be incorporated to the warm side of the assembly to prevent the potential for condensation) Low density SPF typically can be used without an additional vapor barrier or retarder in most clmates in the US. But in colder climates, like Minnesota, Wyoming, Maine, etc. a vapor retarder element is required to minimize the potential for condensation. To answer your other question. SPF has unique physical properties that allow it to perform well as part of an air barrier system. But, there are other materials that are used to complete an air barrier system such as sealants & "peel and stick membranes". Combined with low perm rated building materials such as OSB, foam sheathing, etc, these can also provide a functional air barrier system. For additonal information check out SPFA's technical guideline AY 118, Moisture Vapor Transmission at sprayfoam.org and check out my articles Learning the Difference Between 1/2 lb and 2 lb SPF at masonknowles.com and blogs on air barriers.
JohnPeters Posted: Jul 20, 2008 09:44 PM	Thank you for the response. Judging from your answer, I am guessing you do not provide opinions. I can respect that. Keep on fighting the good fight and keep our nations foamers educated. jp
mason Posted: Jul 21, 2008 08:03 AM	I missed the second question about SIPS and Stick with SPF. SIPS construction can perform very well. It can provide a high insulative value and perform well as an air barrier. Drawbacks are typically at the joints and seams. The failures I have observed have been where there was movement and water deterioration at the seams. Sealants can be used to address this potential problem. SPF insulated stick built construction gives greater flexibility of design and less chance for moisture deterioration at the joints. Main drawback is having a good quality contractor installing the product and making sure it is installed in the right places with the proper mechanical ventilation.

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JohnPeters

Posted: Jul 15, 2008 10:32 AM

Air Barriers per building code & SIPs

Numerous states around the country are adopting "AIR BARRIER SPECIFICATIONS" to building code / energy conservation code for residential and commercial construction.

I have seen this spec typically calling our for at least .004 scfm/ft2 tested per ASTM E-283. Most foams can accommodate this result.

I have a few questions regarding this topic:

1.) Are you familiar with this air barrier spec and what are your thoughts on it? How will this effect the SPF industry?

2.) How does this differ from a vapor barrier? Doesn't a vapor barrier stop air movement? (in the north east we are already required to install a vapor barrier on the interior of a wall assembly)

3.) Correct me if I am wrong but this appears to be an exclusive opportunity for foam to take over the market. What else could be used to facilitate an air barrier besides foam?

On a completely separate note I have a question on SIP vs. Stick and SPF.

I have heard pros and cons for each with lower cost going in favor of SIP's. Would you mind elaborating on your personal opinion on these two different styles of construction?

Personally, I do not see how blower door tests could compare between the two. I have heard nightmare stories on assembly utilizing SIPs.

Thanks,
John Peters

mason

Posted: Jul 15, 2008 10:53 AM

John,

There are large differences between vapor barriers and air barriers. A vapor barrier (or vapor retarder) reduces the transfer of moisture vapor through a given material such as exterior sheathing, brick, masonry, etc. The goal is reduce the moisture vapor transmission of specific materials.

An air barrier is designed to reduce air movement through an assembly (such as a wall or ceiling)or a system (such as a room or a building).

Good air barrier systems will reduce the transfer of air borne moisture but may not reduce the water vapor resistance of the building materials themselves.

You are correct to assume that most moisture that goes into and out of a building is air borne and a good air barrier system will reduce that amount.

But, moisture can still migrate through building materials and vapor retarders are used to reduce the ability of moisture vapor to travel through a given material.

Closed cell SPF (at varying thickness) has been proven to work as an effective vapor retarder in most commercial and residential situations.

(Note: in cases where vapor drive is always going in one direction such as swimming pools and freezers and additional vapor barrier type material should be incorporated to the warm side of the assembly to prevent the potential for condensation)

Low density SPF typically can be used without an additional vapor barrier or retarder in most clmates in the US. But in colder climates, like Minnesota, Wyoming, Maine, etc. a vapor retarder element is required to minimize the potential for condensation.

To answer your other question. SPF has unique physical properties that allow it to perform well as part of an air barrier system. But, there are other materials that are used to complete an air barrier system such as sealants & "peel and stick membranes". Combined with low perm rated building materials such as OSB, foam sheathing, etc, these can also provide a functional air barrier system.

For additonal information check out SPFA's technical guideline AY 118, Moisture Vapor Transmission at sprayfoam.org and check out my articles Learning the Difference Between 1/2 lb and 2 lb SPF at masonknowles.com and blogs on air barriers.

JohnPeters

Posted: Jul 20, 2008 09:44 PM

Thank you for the response.

Judging from your answer, I am guessing you do not provide opinions.

I can respect that.

Keep on fighting the good fight and keep our nations foamers educated.

jp

mason

Posted: Jul 21, 2008 08:03 AM

I missed the second question about SIPS and Stick with SPF.

SIPS construction can perform very well. It can provide a high insulative value and perform well as an air barrier. Drawbacks are typically at the joints and seams. The failures I have observed have been where there was movement and water deterioration at the seams. Sealants can be used to address this potential problem.

SPF insulated stick built construction gives greater flexibility of design and less chance for moisture deterioration at the joints. Main drawback is having a good quality contractor installing the product and making sure it is installed in the right places with the proper mechanical ventilation.

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