Question

Is it okay to spray open-cell foam over a layer of closed-cell foam?

Asked by Steven L'Heureux
Richmond, VA

1" closed-cell polyurethane was sprayed on the underside of my roof deck for air barrier by first contractor. Fiberglass batts were to be used for insulation layer. New contractor wants to spray open-cell foam (Icynene) instead of batts.

Answer

Danny Kelly

Answered by Danny Kelly

Charlotte, NC

Kelly McArdle Construction

August 30, 2010

Sounds like you are shooting for an unvented, conditioned attic.

  • A closed-cell foam will qualify as an air barrier.
  • Once an air barrier is established at the roof deck, you can supplement the closed-cell foam with just about any product you like.

Is this new construction or an existing home? If it is an existing home, you may need to install some temporary ventilation of the attic and/or a humidifier until the attic acclimates to the conditioned portion of the home.

 

For more information:

Read Steve Saunder's excellent Q&A "I'm converting my attic into a non-vented conditioned space. Should I use open cell or closed cell foam to insulate?"

Tagged In: insulation, spray foam, attic insulation

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.