[mklein49]

Hi All,

I'm getting ready to finish the basement in our home. Not sure what all of the pertinent information regarding our home is, but here's a start: The home is located in St. Louis, MO. The home was constructed in 2008. The basement was built on a 9 foot poured concrete walls.

I had all but decided to use the building science approach on the walls. Then my father spoke to a represatitive at a local insulation company. He recommened a product called DryRight Insulation, by CertainTeed. http://www.certainteed.com/products/insulation/fiber-glass-insulation/317360.

Essentially the product appears to have a membrane that allows the concrete wall to dry. Seems like the claimed performance would make it ideal for the basement. I'm looking for feedback on whether or not this product would be suitable for my basement or if I should just stick 2" XPS + unfaced batts? And also for what reasons one would avoid or use this product?

Thanks,
Matt

 

[jklingel]

Hi All,

... or if I should just stick 2" XPS + unfaced batts? And also for what reasons one would avoid or use this product?

Thanks,
Matt

I am not familiar w/ the product, but Membrain is apparently a read good product. Myself, I will never again touch fiberglass, Membrain or not. Since using the product may be an expensive experiment, I'd stick w/ 2" EPS, taped, and rock wool batts in the (assumed) wall you'll build inside the foam.

 

[mklein49]

I am not familiar w/ the product, but Membrain is apparently a read good product. Myself, I will never again touch fiberglass, Membrain or not. Since using the product may be an expensive experiment, I'd stick w/ 2" EPS, taped, and rock wool batts in the (assumed) wall you'll build inside the foam.

Correct...I plan to build a 2x4 perimeter wall with the unfaced batts installed in the wall cavity.

Thanks for the response!

 

[Gary in WA]

That "Membrain" product is on the f.g. batt face. To stop condensation on the concrete walls- needs an insulating sheathing to retard the vapor entering/leaving the basement. That product is similar to asphalt-faced f.g., a variable vapor retarder; http://www.buildingscience.com/documents/reports/rr-0004-air-barriers-vs-vapor-barriers

Membrain: http://www.bestofbuildingscience.com/pdf/Brainy membrane HEM_23-4_p37-40.pdf

It has almost exactly the same variable permanence range as real plywood. I would use it above grade: "SVR" pp. 5; https://docs.google.com/viewer?a=v&...Y4XLUA&sig=AHIEtbTI8qHJ8nvDm0mvsNmmYf-psHZnLA

You may have read this from page 29/73: "Assuming the XPS is well sealed to the concrete foundation, the condensation plane is now the interior XPS surface and will be warmer than the concrete, which should result in less potential condensation, and less vapor diffusion from the concrete." It also acts as a thermal break from the studs to the basement temperature. How many of the systems here have a vapor retarder next to the drywall without moisture problems; http://www.buildingscience.com/docu...merica-high-r-foundations-case-study-analysis

Say you used that product and forgot the poly sill-sealer under the p.t. bottom plate--- basement air to the concrete wall to condense and wet the f.g. insulation, we know that's not good for the R-value; http://archive.nrc-cnrc.gc.ca/eng/ibp/irc/bsi/90-controlling-heat.html

Gary

 

[mklein49]

Wow. Thanks for the info! I'm staring to read the now.

One other note for my particular insulation to consider is that I'll have some unfinished space accessible by door. This unfinished area is connected to the air gap for one of the perimeter walls. Do I have to worry about the warm air reaching the concrete walls through this unfinished area?

 

[Gary in WA]

Unconditioned spaces should be separate from conditioned ones.

Gary