The Smart Enclosure Tiers
To help architects and other professionals make choices and take action, the Smart Enclosure System is broken into Three Tiers of performance. These tiers will provide a better understanding of how to make a more sustainable building.
The Three Tiers are not precise demarcations of success. Rather they indicate the direction of improvement relative to the other tiers and to the typical industry approach we describe as the Industry Standard High-Performance Default.
To provide an overview of how the Three Tiers work, we use common 2x stick and metal framing as reference points to compare to the industry default.
Industry Standard High-Performance Enclosures: Default
The default approach is characterized by 2x framing with OSB sheathing, building wrap, and foam board and spray foam insulations. Today, the shortcomings of this default approach are apparent. Foam insulations have high embodied energy, provide no CO2 sequestration, and have compromised moisture resilience. The toxicity of foam in manufacturing, occupancy, and disposal is problematic, as is the durability and chemical composition of OSB.
Worse is high-performance metal frame construction today, which is typically wrapped in foam insulation. It has little moisture tolerance, no sequestered carbon, and very high embodied energy.
Any carbon savings realized through operational energy efficiency will be unable to offset the embodied carbon produced during construction before the critical window of 2050. In other words, the building will be adding to the problem of climate change for more than 30 years. While the ambitions of this default construction are sincere, they are executed using the wrong toolbox and are creating more problems than solutions.
Smart Enclosure System: Tier 1
Tier 1 modifies common construction practice at a superficial level, but fundamentally transforms its capabilities.
In Tier 1, we’ve replaced plastic insulations with wood or wool alternatives, increasing the assembly’s carbon sequestration and use of natural, non-toxic materials. We’ve added smart vapor, air and thermal control layers with Pro Clima membranes inboard and outboard of a continuous insulation layer. These airtightness and insulation measures greatly increase the assembly’s durability and have been executed through a holistic design process.
Metal framing, while less effective than wood framing, can move from being a climate liability to being part of the solution. Switching insulations from foam to wood with a complete smart vapor, air and thermal control approach are first steps in building a Smart Enclosure.
With this approach, the results start to meet the principles of lower embodied carbon, lower toxicity, and higher levels of efficiency, comfort and durability.
Smart Enclosure System: Tier 2
Tier 2 reduces the amount of materials and simplifies the design. It’s similar to Tier 1, but with the sheathing removed and replaced with cross bracing. The framing can be wrapped with waterproof, airtight, and vapor open SOLITEX MENTO membrane as a temporary WRB.
Tier 2 removes not only the sheathing, but also the labor associated with installing it, and makes the assembly even more robust, healthy, and resilient.
Smart Enclosure System: Tier 3
Tier 3 further reduces the layers and complexity, while providing greater future flexibility and robustness.
Tier 3 is a direct descendant of the PERSIST enclosure developed by the National Research Council Canada. Like Tier 2, it has no sheathing, but now the wood fiberboard insulation is moved entirely outboard of the framing, with a back-vented rainscreen exterior finish. Before installing the Gutex, Pro Clima INTELLO X is installed over the framing to provide a temporary WRB and long-term air and vapor control.
This is the simplest, lowest carbon (the wood frame version), most robust, and healthiest assembly.