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Insulation INTRO:

Numerous types of infill insulation materials can be used in conjunction with many of the wall and roof systems covered in this book. These materials cannot be used structurally (though a few have some structural significance within a wall). They are placed, formed, sprayed or stuffed into cavities in a structural wall.

Whats not included in this Section

There are wall and wall insulation materials that are feasible to use but do not meet our sustainability standards for inclusion in this book. Drawing such lines is always controversial, and there will be green building advocates and practitioners who see this as folly. However, we will present our opinion on these materials and readers who disagree will find ample information in other sources to work with if they choose to pursue these options.
The SIP system uses two thin skins of structural sheathing bound to an insulated core to create a wall (or roof) with excellent structural and insulative properties. In theory, these are ideal building materials as they provide structure and insulation with a single installation, and have reduced thermal bridging and unwanted gaps or voids in the thermal control layer. They are relatively quick to install too.
Unfortunately, most SIPs are made from oriented strand board (OSB) as the structural sheathing and some type of foam as the insulated core. Both materials rely heavily on the petrochemical industry for their component parts. The glues used to bind OSB are typically formaldehyde-based and off-gas for a long time after installation. The reliability of these glues is questionable, especially when exposed to water, and lifespan issues are critical considering these skins provide most of the structural strength of the wall.
Measuring the impacts of the foam insulations used in SIPs will reveal high embodied energy figures and carbon outputs, but these alone are not really reason enough to exclude this category of products. As the foam industry is quick to point out, there is a degree of energy savings from using these products (though the same savings are available with similar amounts of other insulators) that can render the embodied energy less grievous over time. But straight energy analysis, or even life cycle analysis, do not measure the deeper issue as they are typically carried out. Neither of these approaches takes into account the full impact of the petrochemical industry that produce these products. The full “chain of custody” for foam products needs to address the environmentally disastrous processes of this industry (for a fuller discussion of this subject, see the Foam ICF section of Chapter 1: Foundations).
Foam insulations also create vapor-impermeable walls, which are more prone to moisture issues unless continuous mechanical ventilation is provided for the building.
OSB/foam SIPs also represent a problematic disposal issue at the end of their useful life, as neither material is easily recyclable or reusable and the two are bonded together in a way that makes separation difficult and unlikely. The final resting place of a SIP (and all offcuts created during construction) is the landfill.
Not all SIPs are made from OSB and foam, and other options that use the same excellent principle in combination with more environmentally friendly materials have been developed (see Straw Bale SIPs sidebar) and are likely to be developed (see Mycelium foam above).
Foam ICFs are described in the foundation section of this book, but are sometimes used to build continuous foundation and wall systems.
Foam ICFs combine all the suspect characteristics of petrochemical insulation (see Foam ICF section of Chapter 1: Foundations) with high concrete and rebar usage, both of which have high embodied energy and carbon output issues.
This combination of materials will also prove very difficult to disassemble and separate at the end of its life, meaning it’s most likely headed for landfill and not recycling. The whole system is just too dubious in its environmental impacts to recommend in any way, especially when the alternatives that exist are every bit as feasible and practical.

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