| Author |
Message |
Ronald L. Geren, RA, CSI, CCS, CCCA, MAI
Senior Member
Username: specman
Post Number: 368
Registered: 03-2003
| | Posted on Monday, December 11, 2006 - 02:45 pm: |    |
A contractor on a project (extreme southwest Arizona with ambient temperatures of 120 deg F.) has requested that we substitute the self-adhered, butyl air barrier specified, which has a maximum service temperature of 180 deg F., with a product that has a maximum service temperature of 240 deg F.
To my knowledge, I don't know of a product that can meet that requirement and still be an air barrier. If there is such a product, please let me know.
The air barrier is used behind an aluminum wall panel system, which will have temperatures that exceed the ambient temperature by a good margin, but I doubt they'll exceed the 180 deg F. maximum of the products we've specified.
Does anybody have a source of research information that has analyzed airspace temperatures behind various cladding systems? |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 238
Registered: 05-2005
| | Posted on Tuesday, December 12, 2006 - 02:20 pm: | |
Ronald,
Is the aluminum cladding installed with an vented air space behind so that ambient outdoor temperature will be relatively the same or is the aluminum cladding up close and personal to the air barrier membrane like at metal coping over high-temeprature S.A.M. underlayment? Is there any thermal insulation external of the air barrier membrane protecting it from higher temperatures. Placing insulation exterior of these self-adhered butyl air barriers is standard practice. If the insulation is not external of the air barrier (in the stud cavities), the air barrier product should be vapor permeable such as Henry Air Bloc 31 or 33, or one from Grace.
I would think that the sheet membranes from Grace and Henry would provide good inserve life behind aluminum cladding if a vented air space is included in the cladding (read rainscreen concept) and protected with insulation.
If the aluminum finish is light colored, perhaps the bulk of the heat will be radiated away from the cladding and not into the cavity. A dark color will perform the reverse. Dark colors are good for drying to the interior in the Pacific NW.
There are spary applied products from Prosoco and Sto that may meet the temperature requirement.
I have never worked or lived where the ambient temp is 120 deg F but placing the insulation outboard of the air barrier should be considered, if not already.
Contact your Grace and Henry reps for the research information. I will tap my building science resourses in Seattle.
Wayne |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 240
Registered: 05-2005
| | Posted on Tuesday, December 12, 2006 - 02:53 pm: | |
Ronald,
Grace's Vycor Ultra, which is butyl rubber, has an operating temperature limit of 240 degrees Fahrenheit and would serve quite nicely as an air barrier in the desert Southwest.
In your original posting, perhaps you are referring to rubberized asphalt membranes, such as Perm-A-Barrier Wall Membrane, when referencing an operating temperature limit of 180 degrees Fahrenheit.
Butyl membranes always have higher resistance to heat than rubberized asphalt membranes do.
Wayne |
Ronald L. Geren, RA, CSI, CCS, CCCA, MAI
Senior Member
Username: specman
Post Number: 369
Registered: 03-2003
| | Posted on Tuesday, December 12, 2006 - 03:53 pm: | |
Wayne:
You're right about the rubberized asphalt...that's what's in the spec, but I was looking at Vycor Ultra when I was writing my post and put butyl instead. The issue I have with the Vycor Ultra is that it's considered a non-permeable air barrier with a permeance of 2.9 ng/mēs Pa (0.05 perms).
However, I've been rethinking the need for a non-permeable air barrier for a couple of reasons: 1) there're no moisture-generating spaces inside the building (i.e. pools, showers, etc.), and 2) there're no non-permeable finishes installed on the interior faces of the exterior walls.
Thoughts?
BTW: I found Tamko's TW Moisture Wrap, which is a rubberized asphalt S.A.M., with a maximum service temperature of 245 deg F. However, it is also non-permeable. Anybody have experience with it? |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 241
Registered: 05-2005
| | Posted on Tuesday, December 12, 2006 - 06:02 pm: | |
Ronald,
Blueskin PE 200 HT from Henry.
According to my Henry rep, "does not flow at 230 deg. F and also works as good as Blueskin SA as an air and vapor barrier. It is far less expensive than butyl."
Get good air flow behind the panel which will keep temps from getting too hot. Are you able to use open joints or is this to late? AirBloc 33 is UV tolerant.
Tnemec also has an air barrier product but I have forgotten the name. NBBJ uses it locally. Will be back to you.
Wayne |
Ronald L. Geren, RA, CSI, CCS, CCCA, MAI
Senior Member
Username: specman
Post Number: 370
Registered: 03-2003
| | Posted on Tuesday, December 12, 2006 - 06:30 pm: | |
Wayne:
I found a couple of products that are listed as "high temperature," but they never say how high, including the Henry product--go figure.
Although the joints aren't open, they are also not sealed, so air should flow freely, but still be drainable (when it does rain, which is hardly ever). This is a custom-fabricated panel system using mill finish aluminum...no dark coatings. Therefore, the temparture behind the panels should be lower than panels with non-reflective finishes.
Tnemec makes an air barrier? Or did you mean Tremco? |
John Bunzick, CCS, CCCA
Senior Member
Username: bunzick
Post Number: 622
Registered: 03-2002
| | Posted on Thursday, December 14, 2006 - 08:30 am: | |
Another path to explore, for other projects if not this one, is heat-reflective coatings that some metal panel manufacturers can provide. These coatings perform like standard PVDF, except they contain ceramics that reflect heat, keeping the temperature lower. I have no idea what the cost premium is for this coating system. |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 242
Registered: 05-2005
| | Posted on Thursday, December 14, 2006 - 11:22 am: | |
Ronald,
The Tnemec product is Enviro-Crete 156 & 157. It meets the air barrier requirements of Massachusetts' Energy Code.
Product wil not meet your temperature requirements.
Enviro-Crete: (Dry) Continuous 175 Deg F; Intermittent 185 Deg F.
It's disadvantage is it does not come with a complete range of accessories for detail work, but relies on 3rd party products.
This product does not have an inservice track record in a wide variety of projects in my region. I know of only one design authority that uses Enviro-Crete for the air barrier on DensGlass Gold, apparently without issue but their projects are to recent to determine success or failure.
Wayne |
|
4specs.com Home Page