The Smart Enclosure System offers a 21st century guide to advanced high-performance building assemblies. The System is a tool kit that can help you maximize the positive impact of your building projects: providing optimized comfort, safety, energy efficiency and negative carbon emissions.
The Smart Enclosure System lays out a new framework of decision making consisting of seven overarching principles and three tiers of assembly performance. This framework is customized for eight different assembly types. We’ve put these tools in place to help architects, engineers, consultants, contractors, building owners, and other building professionals make smarter, more intentional choices in their material selection and design process. Those choices can improve the lives of building occupants and the health of our biosphere.
How to Use the Smart Enclosure System
- Digest the logic of the System.
- Review the assemblies.
- Download the details.
- Copy, edit and make them your own.
Why We Need Smart Enclosures
In the 20th century, builders used giant energy resources and chemical-based materials to conquer the vagaries of nature. Our buildings now contribute approximately 45% of total global greenhouse gas emissions in the US (Architecture 2030, 2013). While scientists tell us a stable climate is assured at atmospheric CO2 concentrations of 350 parts per million (Hansen et al., 2008), today concentrations are rising past 410 parts per million.
Consequently, in the early 21st century, our building efforts must address climate change in two ways. By 2050 we need to reduce global carbon emissions in the developed world by 80% to mitigate the worst effects of climate change (Meinshausen, 2007). And, we have to go beyond just reducing emissions and start removing carbon from the atmosphere to return to the stable atmospheric CO2 concentration of 350 ppm.
The Smart Enclosure System isn’t a one size fits all prescription, but a range of strategies that can be adapted for each project and site. It can be applied to any wall assembly, including double-stud, I-Joist Outrigger, 2x framing and cross-laminated timber (CLT) or historic masonry and wood framed retrofits. Even enclosures that depend on metal and concrete can be Smart Enclosures. While the construction context may vary, in each case, the solutions are guided by these seven principles:
7 Smart Enclosure Principles
1. Lower Embodied Carbon
Use fewer construction materials and ensure that the materials used have low embodied energy to significantly reduce short-term emissions.
The harvesting and manufacturing of building materials, and renovation and demolition of buildings is responsible for approximately 10-20% of all human-made greenhouse gas emissions (Yamamoto, 2009). The embodied carbon of construction materials, depending on a building’s efficiency, can account for between 20-100% of the building’s total lifetime emissions (Giesekam et al., 2016).
Even in an energy efficient building, after 15 to 20 years of operations the majority of emissions will still be caused by the original embodied carbon in the materials (Strain, 2017). Like compounding interest, embodied carbon avoided at the start of the building’s life will have a greater beneficial effect than emissions saved later.
There are several ways to lower the embodied carbon of an assembly:
- Reuse and renovate existing structures
- Minimize waste
- Use less new materials
- Source new materials that are produced with less energy intensive processes and have higher recycled content
- Use plant-based materials that have a negative embodied carbon value
Doing so can provide significant short-term carbon-emissions relief and result in a building that operates from the start with a negative carbon balance. Because the embodied carbon in the structure of a building can account for as much as half of the building's total carbon emissions, retrofits maximize a high performance building’s immediate carbon savings (Kaethner, Burridge, 2012).
2. Greater Carbon Sequestration
Lock as much carbon storage into the structure as possible and provide long-term emissions security. Do this by using more harvested, plant-based materials that naturally sequester carbon like wood, hemp, straw, and cellulose. Through photosynthesis, plants remove CO2 from the atmosphere and store it. CO2 is considered sequestered if it is kept from re-entering the atmosphere as a gas for a significant period of time.
To be a sustainable solution, the benefits of sequestration depend on good forestry practices that support greater biodiversity and ecosystem health. By using our forests as a building material resource, we can increase the rate of forest CO2 absorption in a regenerative process, and create a virtuous cycle of negative carbon emissions (Ryan et al. 2010).
3. Lower Toxicity
Protect workers, occupants and the biosphere by choosing products that have lower toxicity in manufacturing, construction, and disposal. Use fewer plastics and less plastic foam. Human-made, bioaccumulative, and persistent toxic chemicals are now found the world over. After the packaging sector, the building sector is the biggest user of plastics. Ensure lower risk of toxins by using the Precautionary Principle, which exhorts us to resist products for which its ultimate effects are disputed, when selecting materials.
4. More Natural Materials
Source more natural materials such as wood fiber, wool and cellulose insulations, timber structures and lime plaster finishes. Natural materials typically require minimal processing and therefore have significantly lower embodied carbon. They are a healthier choice for indoor air quality, as they often help buffer humidity levels and, when properly selected, have no VOCs. Our building enclosures should not just not make us sick. They should help make us healthier.
5. Smart Vapor, Air, and Thermal Control
Include air, vapor, and thermal control layers to provide Passive House levels of energy efficiency, comfort and durability. Today, we have access to materials that provide a robustness previously unavailable to the industry.
Airtightness maximizes the effectiveness of the insulation and optimizes occupant comfort. The insulation should be surrounded by airtight layers with a continuous inboard and outboard air barrer. The inboard air barrier should be a smart vapor retarder. In heating dominated climates, the outboard air barrier should be vapor-open.
Smart vapor control ensures that highly insulated assemblies, which tend to stay wetter longer, have maximum drying potential over the course of the seasons. Consequently, the insulation is drier, and drier insulation is better at insulating. Wood, wool, and cellulose insulations help buffer moisture levels.
Thermal control is fundamental to comfort and energy efficiency. It must be continuous. Where the insulation is discontinuous, thermal bridges result, causing discomfort, inefficiency, condensation, and ultimately, moisture damage.
6. 100+ Year Durability
Maximize the building’s climate mitigation effectiveness by making it functional for generations. Having to replace or rebuild portions of the enclosure adds significant embodied emissions over the building’s lifetime. To ensure durability, we need to use reliable materials that are put together correctly, are repairable, and are protected from damage for the life of the building.
This can be accomplished by using materials that are lab tested for 100+ year durability, most importantly the adhesive connections that come under long-term stress. Materials like spray foam that will degrade do not belong in a high-performance enclosure. Protect the air, vapor and thermal control layers with a service cavity inboard, and a back-vented rainscreen outboard to prevent damage in the course of regular use and during future renovations.
7. Fully Integrated Performance
Holistically integrate the enclosure system into the building design. Siloing systems will result in an inefficient building, with each individual system only accomplishing one goal and producing a building that is less than the sum of its parts. The goals should be ambitious, supporting operations that have Passive House levels of efficiency, zero energy, and carbon negative outcomes.
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
This 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.
Mass Timber, Metal or Concrete
Cross Laminated Timber (CLT) Smart Enclosure
CLT is an exciting, modern mass timber option. CLT is made with layers of boards stacked perpendicular. There are many performance benefits, including fire resistance, acoustic performance, material stability, and construction efficiency.
The CLT Smart Enclosure compliments the wood CLT structure with wood fiber insulation, maximizing carbon sequestrations and negative carbon potential.
Today, building codes allow for CLT construction up to six stories tall in many jurisdictions. We can fill our cities and towns with timber buildings, transforming urban areas into massive carbon sinks instead of leaving them as massive carbon emitters.
However, we caution that given the amount of material it uses, CLT provides an optimal solution only for multifamily and commercial buildings from two to twelve stories in height (and taller). Use in single family homes is suboptimal and should be avoided, with the possible exception as a test application for an architect and builder.
We hope these buildings become widely adopted quickly as they have the potential to make an enormous contribution to the climate solution.
Straw Bale & Hemp
Straw bale and hemp building materials can sequester large amounts of carbon. Straw and hemp are rapidly renewable resources. In combination with timber framing, these structures can reach two stories or more. Typically utilized in single-family homes, the possible applications are numerous.
Can Metal and Concrete Enclosures be Smart?
Metal and concrete are problematic because they have high embodied energy. So high that, like the default construction, the critical phase of climate mitigation efforts between now and 2050 will be past before any carbon benefits are realized. But the reality is, metal and concrete are not going away, so we need to work to make these assemblies smarter. We do that in several ways: by limiting other materials with large embodied energy like foam plastic insulation; by making the enclosure more durable and operationally efficient for 100+ years; and by maximizing the use of wood and other natural materials in the overall design strategy.
Metal Frame Smart Enclosure
Masonry/Concrete Smart Enclosure
If we can bolster these other Smart Enclosure Principles, the upfront embodied energy of construction can be lessened in metal and concrete buildings.
The Smart Enclosure Assemblies & Details
The Smart Enclosure Assemblies and the Three Tiers are organized by common construction types into DWG files and corresponding ebooks - divided by retrofit and new construction.
- Masonry Retrofit
- Wood Frame Retrofit
- 2x Wood Framing
- Double Stud
- I-Joist Outrigger
- Cross-Laminated Timber
- Metal Frame
We hope you digest the concepts, review the assembly types, and download the corresponding PDF ebooks and DWG CAD files, edit them, and make the details your own.
Let's Do It
Architects, engineers, consultants, and builders have tremendous power to mitigate climate change; to not only do less bad, but to fix systems, and actively create a better future. There is no one solution. But any possible solution must address occupant comfort, health, and safety, be sustainable and encourage biodiversity, and produce negative carbon emissions. The Smart Enclosure System presents an array of solutions that meet these criteria. Find the solution that best supports your project’s goals to make the Smart Enclosure System work for you.