Biltmore continues to move at their good and steady pace.  The roof went on a few weeks ago, followed quickly by interior framing.  But first, the ceiling air barrier was installed.  Every airtight house (and Passive Houses are the ultimate airtight houses!) need to have a continuous air barrier.  Our ICF walls are pretty straightforward air barriers, but each penetration (doors, windows, ERV ducts, etc.) and change of plane (wall to ceiling and slab) need careful attention to detail.  I’ll cover windows in an upcoming post, but in this post would like to show how we dealt with the wall to ceiling transition.

Taking shape: the roof is on!

We laid a sheet of plastic over the top of the wall and under the wood top plate on which the roof trusses sit.  This sheet is taped to the exterior face of the ICF form and to the plywood diaphragm that we attached to the bottom of the trusses.  All the seams in the plywood diaphragm will be taped with Siga tape, and plumbing and electrical penetrations will be sealed with Roflex gaskets we got from 475 High Performance Building Supply.  It’s great having these suppliers in the US!

This plastic gets taped to interior ceiling and exterior face of ICF

Instead of holding up interior framing until the entire ceiling air barrier was taped, the builders simply taped seams that were to be crossed by interior walls.

Air sealing at ceiling/wall and window/wall
Look closely and you’ll see the stitches of tape where walls pass under air barrier seams

And speaking of air barriers–this is how we dealt with the slab: our radon barrier is our air barrier, so we used Stego Wrap since it’s tough; utility penetrations are taped off to it, and it in turn is taped to the inside face of the ICF form.

StegoWrap radon/air barrier taped to interior face of ICF

 Stay tuned–windows will all be in this week, so the next post will soon follow!