Welcome to our 5 part series on the Smart Enclosure System. This is part 3: The Three Tiers of the Smart Enclosure system.
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So now we take the principles, and in looking to apply the principles to our enclosure assemblies, use a framework of three tiers.
The Three Tiers of the Smart Enclosure System are guide-posts to help architects, engineers and consultants better understand the general effectiveness of their efforts at making a more sustainable building. The Three Tiers are not precise demarcations of success but indicate a general direction of improvement, compared to each other, and to typical industry practice, which we describe as the Standard High-Performance Default approach.
We don’t doubt there is room for debate about particulars, but the direction we need to go is clear.
To illustrate the Three Tiers we use common 2x stick framing as the initial points of reference and then apply the basic principles across assembly types, adapting them as appropriate. For all the assembly types we address, see part 4 of this series.
Industry standard: (DEFAULT)
Again, we start with industry Standard High-Performance Default approach: It is one with spray foam and board foam. It has a relatively high level of embodied carbon, and has no significant carbon sequestration. It is high in toxicity and has less resilience in terms of maintaining high levels of moisture safety and airtightness. 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.
Tier 1: (MODIFIED DEFAULT)
Tier 1 looks to modify common construction practice at a seemingly superficial level - yet fundamentally transform what it’s capable of. It utilizes 2x framing with plywood sheathing, wood fiber board and wood dense-pack insulations. In-board, an airtight smart vapor retarder INTELLO PLUS membrane is installed with a service cavity. Outboard airtight and vapor open monolithic weather resistant barrier, SOLITEX MENTO , or windtight wood fiberboard by GUTEX is provided with a back-vented rainscreen protecting them.
These simple shifts from plastic insulations to wood, with systematic airtightness and vapor control, drastically change the performance in all categories. Creating a healthier, more durable, carbon negative enclosure that directly addresses the needs of our climate at the outset - and for the life of the building.
Tier 2: (SIMPLIFIED AND IMPROVED)
So, for Tier 2, what we would consider an improvement on Tier 1, is then going sheathingless. The sheathing really isn't needed. Sheathing is a historic artifact based on habit and tradition. With diagonal bracing the wood GUTEX insulation board can act as a WRB and outboard windtight layer. For temporary weather protection you can wrap the framing in a Pro Clima Solitex Mento airtight WRB before applying the insulation board. The inboard air and vapor control and outboard back vented rainscreen are similar to Tier 1.
Tier 2 removes not only the sheathing material, but also the labor associated with installing it - and makes the assembly even more robust, and resilient.
Tier 3: (OPTIMIZED)
Tier 3 further reduces layers and complexity, while providing greater future flexibility, and in so doing makes it more robust. This approach is a direct descendant of the PERSIST enclosure, developed by the National Research Council Canada.
Like Tier 2, Tier 3 has no sheathing, and now the wood fiber based insulation is moved entirely outboard of the framing, with a back-vented rainscreen exterior finish. Before installing the Gutex wood fiberboard insulation be sure to install the air tight, smart vapor retarder and WRB, INTELLO X.
This can be the simplest, lowest carbon, most robust, and healthiest assembly.
This general approach of the three tiers of first modifying common practice, then simplifying and finally optimizing can then be applied to a range of common building assembly types - for both retrofits and new builds.
And that’s where we’re going next. See you in part four, The Assemblies.