7 Smart Enclosure Principles
The Smart Enclosure principles are fundamental decision-making guidelines for the building design process. The principles help ensure that the building successfully addresses occupant comfort, health, and safety; that it be sustainable and encourage biodiversity; and that it can produce negative carbon emissions. These are not passive suggestions, but calls to action. Action to make a better future.
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).
In an energy efficient building, even after 15 to 20 years of operation, 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 barrier. 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.
To make a high-performance enclosure today, we don’t need to reinvent the way we build. We need to focus on the fundamental principles to update typical details, standard specifications, and traditional means and methods. In our continuous paths of improvement, it's just a course correction to integrate these new habits. What’s required are smarter, more intentional choices that improve the environment.