Replies

1. GBA Editor
   Martin Holladay | Apr 24, 2017 03:00pm | #1

   Ralph,
   Every insulated assembly needs an air barrier. If you are installing a drywall ceiling with cellulose above, the drywall is usually the air barrier. For this approach to work, you need to make sure to seal air leaks in all penetrations (plumbing vents, wiring penetrations, and attic hatches). You need to avoid the installation of any recessed can lights. And you need to select airtight electrical boxes if your ceiling includes any electrical boxes.

   Building codes do not require (and building scientists do not recommend) a vapor barrier for this type of ceiling; all you need in Zone 5 is a vapor retarder (a less stringent layer than a vapor barrier). Most builders use vapor-retarder paint (a primer) for this purpose -- that's usually a cheaper approach than Certainteed MemBrain. However, if you want to use MemBrain, it will certainly work.

   For more information on this issue, see Do I Need a Vapor Retarder?

   -- Martin Holladay

2. 
   Stripes7 | Apr 24, 2017 03:14pm | #2

   In terms of electrical boxes, including ceiling and walls, is the moldable putty a smarter option than fire-rated spray foam or caulking?

3. GBA Editor
   Martin Holladay | Apr 24, 2017 03:23pm | #3

   Ralph,
   I'm a fan of airtight electrical boxes. Below is a list of manufacturers or distributors. Note that this list might be out of date -- check availablility.

   Other methods, including the use of caulk or putty, can work, as long as the airtightness is verified with a blower door. Be careful with spray foam -- filling an electrical box with spray foam is a code violation.

   FastCap
   5016 Pacific Highway
   Ferndale, WA 98248
   888-443-3748
   http://www.fastcap.com

   Allied Moulded Products, Inc.
   222 North Union St.
   Bryan, OH 43506
   419-636-4217
   Fax: 800-237-7269
   http://www.alliedmoulded.com
   Airtight electrical boxes (Vapor Seal boxes)
   They call them "energy-efficient" electrical boxes or "vapor seal" electrical boxes.

   Airfoil
   8685 Black Maple Drive
   Eden Prairie, MN 55344
   612-280-8331
   http://www.airfoilinc.com
   [email protected]

   American Aldes Ventilation Corp.
   4537 Northgate Court
   Sarasota, FL 34234-2124
   800-255-7749
   941-351-3441
   Fax: 941-351-3442
   http://www.americanaldes.com
   Distributor / retailer of Ryeco Enviroseal airtight electrical boxes

   Backboxx
   from Shelter Supply

   Energy Federation Inc.
   14 Tech Circle
   Natick, MA 01760
   800-876-0660
   508-870-2277
   Fax: 508-870-9933
   http://www.efi.org
   Retailer of energy-saving equipment, including airtight electrical boxes
   LESSCO airtight electrical boxes
   Enviroseal airtight electrical boxes

   LESSCO Low Energy Systems Supply Company, LLC
   W1330 Happy Hollow Road
   Campbellsport, WI 53010
   920-533-8690
   http://www.lessco-airtight.com
   Manufacturer of Lessco airtight electrical boxes

   Pine Ridge Builders
   613 2nd Street NE
   Jamestown, ND 58401
   701-320-1111
   http://www.energyblock.com
   [email protected]
   Foam box for air sealing electrical boxes -- Energy Block

   RYECO Products
   1 Church Street #10
   Keswick, ON L4P 3E9
   Canada
   905-476-5336
   800-470-7772
   Fax: 905-476-0475
   Ryeco is the manufacturer of Enviroseal airtight electrical boxes (The boxes are actually manufactured by their sister company, LDI Industries)
   The boxes are sold in the U.S. by EFI
   Also sold by:
   American Aldes Ventilation Co.
   Hanson Energy, Newcastle, ME

   Thomas & Betts Corp.
   8155 T&B Blvd.
   Memphis, TN 38125-8888
   901-252-5000
   800-685-9452
   800-816-7809 ??
   Fax: 901-252-1305
   http://www.tnb.com
   Manufacturer of the NuTek electrical boxes
   Plastic boxes with a stiff flange and a compressable gasket.
   NuTek plastic airtight electrical boxes are available from:
   Shelter Supply
   http://www.sheltersupply.com