Tuesday, December 1, 2015

Floppy Bits

Floppy Bits
During my passive house training I learned a rather important "technical" term used pretty frequently during the construction process - Floppy Bit

A Floppy Bit is simply a section of material that is used to connect air barriers that are installed at different times.

I will be discussing the floppy bit installation connecting the basement wall to the 1st floor wall., but 1st I wanted to review how we came to define the interior surface of the foundation wall as our air barrier.

Before we installed the sub slab insulation and the basement slab we installed a radon barrier and sealed it to the foundation wall with glue and tape  See earlier blog post HERE

Now the next break in the air barrier is at the rim joist / mud sill. 

A Floppy Bit is installed in conjunction with the mud sill to connect the air barrier lines

We used Solitex Mento Plus as our floppy bit. This is a very durable vapor open weather resistant barrier. It will allow drying of the building assembly to the outside while preventing moisture from entering the assembly (much like a check valve for water vapor). 

Here is our assembly sequence:

1) Acoustical sealant bead on concrete

2) Sill Seal Gasket with another bead of acoustical sealant on top

3) Pressure treated mud sill

4) Solitex Mento Plus draped from inside to outside.

5) All corners and seams sealed with tape and Contega HF

6) Installed I-Joists on top of Mento 

7) Installed Rim Board

8) Installed Floor Plywood

9) Raised 1st Floor Exterior Walls

10) Wrapped the Mento up over the rim board 

11) We applied a bead of acoustical sealant between the zip board and the sub floor for good measure

12) Sealed and Taped the Mento to the Zip Wall System

This detail ensures a continuous air barrier between our foundation and exterior walls. 

Next post will be after the completion of exterior walls and possibly in conjunction with Truss installation.


  1. Thanks for sharing your building project with us. I like how you built your home for continuous insulation. I hear that can be a big energy saver. I'll have to consider making sure that I have that when I build my first home. http://brandxmetals.com/products/diamond-furr/3-inch-c-i-system/diamond-furr-3-ci-sys-os-corner-detail