In line with passive house building principles, the airtight building envelope begins at the foundation and is continued throughout the entire construction process and the entire house. The under-slab vapor barrier, the yellow wrap, is placed on top of 2” of EPS insulation and then is covered by an additional 2” of insulation. Basically, the vapor barrier is sandwiched between 4” of EPS insulation. All of the seams are taped to insure an airtight barrier. Rebar is then installed in a checkerboard pattern to reinforce the concrete, prevent cracking, and provide structure for the PEX tubing to be attached to. Finally, the concrete is poured. The yellow vapor barrier will be taped up the side of the house, on top of the wall vapor barrier, on this project, the Zip System, to continue the building envelope. The next post will discuss our advanced framing building techniques.