In part one about our East Coast design team manager Kyle Barber’s new home, we shared the beginning of Barber and his wife’s journey designing and building a legacy passive home that will ensure a safe life, free of harmful VOC’s and full of clean air and comfort for them, their kids, and generations to follow.
Recently, Barber and his team’s attention turned to “drying in” the home so that the slab and interior work could be completed. “The enclosure went up, then as soon as the roof went on, windows went in and we were dried in allowing us to do all of the layers for the slab.”
After closing the house in with a metal roof and high-performance enclosure (our weather resistant and vapor controlling open cavity wall system with 2X framing, 100mm layer of wood fiber continuous insulation, and pre-installed strapping), high performance windows shipped from Europe (supplied by Zola) were installed to complete the enclosure. Once windows were in, the concrete-free slab was able to follow.
With the concreteless slab, you have to worry about water and rain on the plywood subfloor a lot more since its sitting right on top of the vapor barrier and can only dry to the top side. For this reason, Barber says, “We had to wait until we were dried in to perform this work.”
Barber continues, “The biggest thing that happened since last time was, we installed the foam under the slab. We have two layers of four-inch EPS insulation, so eight inches total. This will be the only foam in the entire project. Gives us about an R35 below our feet.
I had a bunch of paver base material called Stone Dust delivered. We brought it in with wheelbarrows as we needed it (there was already a layer put in before the walls went up). Then we leveled the whole thing carefully, screeding it with a screed board as we went. Once we’d done that, then we'd set a piece of foam, kind of step on it, and see how it felt. Then we’d put a four-foot level each way on the foam and adjust as needed piece by piece through the whole house. Once you get the first layer set, all the other pieces go right on top. The second layer runs opposite and off set, so the joints don’t line up. This helps some with heat loss through the joints but also helps to stiffen up the floor.”
The use of foam for the slab was a tradeoff that Barber was willing to make to replace the use of a concrete slab to lower the carbon footprint of the project. Barber explains “The foam was needed with or without the concrete. We wanted a wood floor on top anyway. The concrete slab became a superfluous layer. Now we will have a plywood slab made up of two layers of three-quarter inch tongue and groove plywood, screwed and glued to each other.
We put that foam down as level as we could, then on top of that was the vapor barrier. We got that all taped in and detailed to connect to the membrane on the walls to complete our air barrier across the bottom below the plywood. We installed some of the membranes on the walls prior. We had to do some prep work for interior framing so that wherever an interior wall was hitting the exterior wall we insulated that cavity, that stud area, and got the membrane attached. Any area that wouldn’t be accessible later we made sure we had insulation, membrane and tape. In an ideal world all of that work would be done prior to interior framing, but the reality of construction schedules is that you have to be a bit flexible and figure it out to keep things moving. One example was a foot band of membrane on the bottom of the wall so I could tape that to the vapor barrier underneath the plywood. That will later get taped to the rest of the wall once its insulated.”
Barber expounds, “After we did those membrane preps, we did the ceiling membranes so that the crew could put the interior framing up to the ceiling, without worrying about the membranes. They're doing the interior framing this week, then we can get in there with rough ins for electrical, plumbing, mechanical. So, when they run their interior framing, we've already got the stuff behind that filled in. The hope is late January, early February will be drywall.”
For now, the windows have been installed, the front porch roof is on, the timber framing from our very own skilled timber framers is done, and all the metal roofing has been completed. The slab foam and vapor barrier have gone down, and the plywood and interior framing has been started on top of it.
Barber says, “I've got some windows to tape up still, and there's no front door installed yet. But, other than that, it's pretty tight. Once I get that door on and those windows taped up, we should be able to start to heat it up inside at least above freezing and get the roof insulated and sealed up on the underside”
As soon as the New Year hits and the dry wall is hung, the Barber’s house will be that much closer to becoming a home: a thoughtfully constructed and airtight building envelope that ensures operational efficiency, intelligent performance, and a relatively low carbon footprint. More importantly, the foundation will be set to fill the home with family, friends, and an eco-friendly future.
More to come ...
