After giving up on building a Passive House I decided there must be another way to achieve reasonable insulation values and airtightness while not breaking the budget.

I am considering and comparing a SIPS panel structure and advanced building methods.

The advanced building method I would utilize is based on tweaked statck-ups from Building Science for the foundation, wall, and roof. It is now standard practice to build using the ZIP system over a 2×6 wall which results in a very good shell with ample space for cellulose insulation. The ZIP system can be augmented with 2 layers of 1.5in polyiso foam taped at each joint.

Reclaimed foam is readily available and would not only bump the r-value of the wall but substantially reduce thermal bridging. R-values along the following could be easily achieved using the advanced building techniques:

Foundation Slab: R15+

Foundation: R25+

Walls: R30+

Roof: R50+

The sill and rim-joist area would be sealed with EPDM rubber gaskets and cavities filled with expanding foam. I believe this method could achieve code-superior insulation levels with an ACH50 rating of 2, which would reduce the heat load requirement enough to leverage two air source heat pumps.

More to come as we continue to model and tweak the envelope design.