Building My Net Zero Energy Home: Insulating the Basement Floor

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After the walls were poured and workers were out of the way, I laid the PVC pipe for waste water drainage.

We are installing a composting toilet, so these pipes will carry gray water from sinks and the shower to the septic tank, then on to our lagoon from which we hope to irrigate pastures during dry spells. (We have not leach field because of the extremely high clay content of the subsoil.)

Once the rough plumbing was in and I’d passed inspection, my workers and my son Skyler and I laid five inches of XPS (extruded polystyrene) insulation down over a layer of 6 mil polyethylene (below). We laid down 2 two-inch 4 x 8 sheets and one one-inch 4 x 8 sheet.

We alternated the sheets of the polystyrene so there were no open gaps. This process went quickly but did present some challenges. Working around conduit from the solar and wind systems and rough plumbing required extra effort.

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