Structurally insulated panels are one of the most environmentally responsible building systems available. The envelope of a SIP building provides continuous insulation, is extremely hermetic, allows better control of indoor air quality, reduces construction waste and helps save natural resources. The advantages of SIPs are the reduction of thermal bridges and easier control of heat, air and humidity. The solid insulation built into the panels means that the air seal should be easier.
I had never seen or tested fan doors before building with SIP, and I measured an air leak rate of 1.7 air changes per hour at 50 pascals (ACH50) when I tested the house when I finished testing the house. My panel company (Eco-Panels, North Carolina) requires that not only the outside of the house be sealed, but also the interior. My next option would be a nail-based product (I have a friend who calls it IP) after installing and sealing the structural sheet. The panels consist of an insulating foam core sandwiched between two structural coatings, which are usually oriented fiber panels (OSB).).
Structurally insulated panels are oriented fiberboard (OSB) sandwiches on each side and rigid expanded polystyrene (EPS) foam in the center. However, after building and living only in homes in the Southwest, my personal experience is that the U-value they provide helps compensate for lower R-values for insulation. In general, square-shaped SIP houses and buildings are easier and less expensive to build than structures with unique curves and angles. During the 1970s, more and more builders began using SIP for its high insulating value, airtightness and strength compared to frame construction made of wood.
The interior of the roof is a van pine cladding bolted to the underside of the SIP roof panels. The cumulative effect is a big problem in my market (climate zone) and the main reason why I avoid projects involving SIP panels. I wonder if there is any anecdotal evidence of what happens to these panels with SIP sealant after a few years of EPS shrinkage. What I prefer is continuous outdoor insulation with a product that is more open to steam, such as Rockwool, or one of the newer wood fiber products (I haven't had a chance to try rigid wood fiber insulation yet, I hope soon).
While SIPs have a high insulation index, they have a low thermal mass compared to insulated concrete products, such as ICF Fox Blocks. You mentioned the addition of external insulation on the outside to eliminate the formation of thermal bridges between the striations. To reduce costs and waste, architects must design panel-sized SIP walls without protrusions, bulges, or angles that do not reach 90 degrees.
