High-Performance Building Enclosures in the Anthropocene
By Erika Mayer, 475 High Performance Building Supply
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In the past century, builders used giant resources of energy and new chemical-based materials to conquer the vagaries of nature through power and mechanical engineering. An unintended consequence of these methods is that, today, our buildings contribute approximately 40% of total global greenhouse gas emissions. In the Anthropocene, human carbon emissions are driving global warming. Because of this, we can no longer default to past industry norms.
In the early 21st Century, we find ourselves in a race against time. By 2050, we need to reduce carbon emissions by 80-90% globally to mitigate the worst effects of climate change. The decisions we make today will determine our success in 2050. Our goalposts have shifted, and our buildings need to become a part of the solution, not perpetuate the problem.
What Defines a High-Performance Enclosure Today?
Fortunately, the tools we can use to mitigate climate change will also promote the health, comfort and safety of occupants, provide new opportunities for aesthetic and environmental delight, and equip us to achieve a new advanced high performance.
High performance today is not about making buildings less bad, but about making life better. High performance is not about complex technological systems that compensates for poor design, but about the the building fabric itself, the architecture. To accomplish this, we don’t need to reinvent architecture, just acknowledge relevant foundational principles which are immediately actionable.
These principles and actions include:
Principle 1: Lower Embodied Carbon
The harvesting and manufacturing of building materials alone is responsible for approximately 10-20% of all human-made greenhouse gas emissions. Depending on a building’s efficiency, the embodied carbon of construction materials can account for between 20 and 100% of the building’s total lifetime emissions. And even when a building is moderately energy efficient, embodied carbon can easily exceed the total operations emissions for 25 years – severely limiting the potential near term positive impact.
Action:
• Use fewer construction materials and ensure that the materials used have low embodied energy to significantly reduce short-term emissions.
• Utilize less processed and more natural materials. Using more timber based construction, that is harvested with sustainable forestry will reduce the use of steel and concrete structures and foam insulations.
• Use existing structures whenever possible. Because the structure of a building can account for as much as 50% of total embodied emissions, retrofits are a huge opportunity to create a high-performance building with a very small upfront carbon cost.
Principle 2: More Carbon Sequestration
A building should become a storage container of carbon. By utilizing materials, like wood, that absorb atmospheric carbon over their growing life, we can lock-away that carbon in the building structure itself and provide greater long-term emissions security for generations to come.
Action:
• Use more wood and harvested carbon-based materials such as hemp, straw, CLT, wood fiber insulation, and cellulose. This depends on good forestry practices that support greater biodiversity and ecosystem health to be a sustainable solution.
Principle: More Natural Materials
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.
Action:
• Source more natural materials such as wood fibre, wool and cellulose insulations, timber structures and lime plaster finishes.
Principle 3: Lower toxicity
Human-made, bioaccumulative, and persistent toxic chemicals are now found the world over – even in the most remote locations. By reducing toxic chemicals in building materials we can help protect the health of the biosphere as well as the health of construction workers and building occupants. We don’t want to chemically sensitize people and the indoor environments need to be safe for people already chemically sensitive. The enclosure should not just not make us sick, but help make us healthier.
Action:
• Use the precautionary principle to avoid poisoning our environment, buildings and occupants.
• Avoid materials that can produce toxic VOCs like uncured spray foam and other off-gassing materials.
• Choose, more natural, no VOC materials, like wood or wool, which can also remove contaminants from the indoor air.
Principle 4: More Natural Materials
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.
Action:
• Source more natural materials such as wood fiber, wool and cellulose insulations, timber structures and lime plaster finishes.
Principle 5: Smart vapour, air and thermal control
Vapour, air and thermal control are inherent to the basic function of an enclosure: providing shelter. A high level of thermal control, with thermal bridge free detailing will ensure thermal comfort. Durable, smart vapour and air control help optimize the building’s energy efficiency, provide comfortable and healthy interior environments, and ensure the long-term durability of the construction. These control layers, systematically addressed, should reach for Passive House levels of energy efficiency and predictability.
Action:
• Smart vapour control ensures that highly insulated assemblies, which tend to stay wetter, longer – have maximum drying potential over the course of seasons. In cold climates, this typically means providing a vapour-open layer outboard of the insulation, and a vapour-variable layer inboard of the insulation, preventing wetting of assembly in winter and allowing drying inward in the summer. Wood, wool and cellulose insulations help buffer moisture levels.
• Airtightness maximizes the effectiveness of the insulation and optimize occupant comfort. The insulation should be surrounded in airtightness. This is done with a continuous inboard air barrier, which doubles as a smart vapour retarder, and a continuous, vapour open air barrier outboard of the insulation. We can achieve “wind tightness”, sufficient to protect the insulation from the outside, with tongue-and-groove wood fiberboard insulation.
• Thermal control is fundamental to comfort and energy efficiency. It must be continuous, connecting at joints, junctures and penetrations. Where the insulation is discontinuous, thermal bridges result, causing discomfort, inefficiency, condensation, and ultimately moisture damages.
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