I recently talked with Max Wolf, a built environment innovation scientist with Skidmore Owings & Merrill (SOM). He shared his thoughts on what design professionals, contractors, developers and others can and should do to support low-carbon design. He also shared what he is doing on his projects to move the needle.
Part one of our conversation dives into eco-centric design and his simple approach to façade-focused life cycle assessments (LCAs). Next month’s blog focuses on Wolf’s thoughts on resilience planning, the incorporation of the social cost of carbon in decision-making and the relative influence of architects on low-carbon design.
The Eco-Centric and Anthropo-Centric Design Spectrum
By way of introduction, Wolf is a registered professional engineer and architect in New York. He noted that his views are his own and do not necessarily reflect those of SOM.
Wolf’s goal as a built environment innovation scientist is to “expand design innovation in such a way that it makes peace with wilderness and altered ecosystems that we rely on for our existence.” He wants to transition design from “an increasingly anthropocentric trajectory back to an earlier, more integrated eco-centric perspective.”
Wolf describes anthropocentrism as a belief, most notably celebrated in Western cultures but quietly underpinning many others, that humans have the preeminent role on the planet and that all other species and their ecosystems may be sacrificed for our needs, desires, or entertainment. He suspects this attitude is “exacerbating the many tragedies of the commons in progress today, including climate change.” He suggests, “It is important to consider, as it presents a formidable barrier to stopping it.”
Conversely, Wolf says that ecocentrism is “a perspective largely supported by scientific evidence accumulated over many centuries–the fossil record, geology, phylogenetics and social evolution.”
When asked how this philosophy impacts the built design, Wolf says that it means considering the needs of the surrounding ecosystem. This can manifest in doing more than otherwise, resulting in more complex and/or expensive solutions. However, it also allows a richer understanding of how our world works and insight that can lead to breakthroughs in efficiency or new dimensions of beauty.
For example, designing bird-friendly buildings typically requires more expensive bird-friendly glazing or changing the design to reduce strike threats. Wolf notes, “Bird-friendly glass is currently more expensive than conventional glass, but once it becomes the default, it has an excellent chance of becoming much lower cost based on economies of scale.”
Economies of scale also appear to have played out in Brussels, Belgium, where, in 2015, it legislated that all new buildings conform to passive house standards. This triggered a temporary rise in construction costs since most contractors were inexperienced with the standards. Still, now that passive houses are the default, they have become competitive with the previous conventional construction that incurred higher utility bills and carbon emissions.
Is Envelope Design Changing?
When asked about the current impact of this philosophy on his envelope-related work at SOM, Wolf said that most designs were not radically different yet. Still, there has been some movement in the scope of conversation on projects.
“We have worked over the last few years on decarbonizing and detoxifying our specifications–for example, specifying low-carbon aluminum (now offered by Metra, Pandolfo, Hydro and others) and roof membranes with the lowest embodied carbon per year of service,” says Wolf. “We incorporate the critical effect of system service life, like rating a vehicle with miles per gallon. We also consider giving preference to membranes with recycling programs or lower embodied water.”
Wolf is helping to create a new normal by experimenting with at least two performance options for enclosures: A modestly beyond-code baseline envelope and an alternative delivering an area-weighted U-factor of close to half that of the first option.
As an example, a rainscreen system, with a window-to-wall ratio (WWR) of about 35%, which achieves a baseline design area-weighted U-factor of 0.26 BTU/hr.ft2.oF, the “alternative design” would come in at about 0.15 BTU/hr.ft2.oF. While not passive, the house level performance for the climate zone it is in would be in the range of 0.07 BTU/hr.ft2.oF, it makes a step change in operational energy reduction without incurring much additional embodied carbon.
Wolf asserts that the “main objective is to get contractors, consultants and ownership discussing options not just beyond code, but within striking distance of achieving large reductions in operational emissions using passive house principles.”
Wolf mentioned that cost-estimating is often a problem for the alternative options due to a “fear-factor” risk premium baked into the price. This may be due to using more sophisticated assemblies (thermal breaks) and new or different materials, of which only a few bidders may have the experience.
Preliminary Façade Lifecycle Assessments to Inform Design
To help designers understand drivers and trade-offs, Wolf occasionally does simplified LCAs for competing façade types. He calculates a façade’s embodied carbon (EN 15978, lifecycle stages A1-A4) typically by assuming:
- Service life: 60-year curtainwall and 30-year insulating glass (IG).
- Embodied carbon of materials (stage A1-A3): Assigned embodied values (kgCO2e/kg) from Inventory of Carbon and Energy (ICE) or other databases for components (e.g. aluminum extrusions, glass, cladding), multiplied by the mass of each material.
- Fabrication and storage emissions (stage A3): Using the fabrication shop floor area and energy use intensity (EUI) to estimate the energy used in façade fabrication, multiplied by an emissions factor to estimate fabrication and storage emissions per unit of curtainwall produced. It is typically small relative to the emissions from the materials themselves.
- Transportation emissions (stage A4): Using ICE database and other data. Movement by sea has relatively low emissions compared to road transportation.
Two examples of embodied carbon estimates, including fabrication and transportation from Italy to New York City, are shown below: Unitized curtainwall with granite spandrel cladding (Figure 3) and unitized precast (Figure 4).
The embodied carbon totals are approximately 216 kgCO2e/m2 and 184 kgCO2e/m2 of façade, respectively. The total rises to approximately 266 kgCO2e/m2 and 209 kgCO2e/m2 of façade, respectively, with reglazing in 30 years, assuming no improvement in the embodied carbon of IG components. The aluminum framing dominates in both cases, hence the need for wider availability of low-carbon aluminum.
For the unitized precast, transport of the heavy unit is also dominant. Since precast façades in the U.S. are typically fabricated nearby to remain upfront cost competitive, Wolf underscores that this is a hypothetical comparison.
Simplified Operational Carbon Calculation Method
To estimate operational carbon emissions driven by the façade, Wolf uses a simplified spreadsheet-based approach to provide preliminary estimates. A high-level description is laid out below.
He asserts that “while there certainly may be more elegant, timesaving methods, such as a ‘shoebox’ energy model, if you do not have access to such software and have an interest in understanding the basic mechanics of heat transfer, a spreadsheet approach can be an instructive exercise.”
- Thermal transmittance: Calculate the area-weighted U-factor for each wall type.
- Identical climatic conditions: Assume the same latitude, solar orientation and shading.
- Estimate the total solar heat gain through the glazed portions of the façade: Estimate the solar heat gain for the 21st of each month using the solar heat gain factor method, which uses tables of hourly solar heat gain factors for various latitudes and orientations.
- Estimate total annual heat transfer: Sum the conductive and radiative components, as applicable for opaque and glazed areas, for each hour for the 21st day of each month. Then, the sum for each hour of the day yields the day’s heat transmission through the façade, and the number of days in the month is multiplied by the monthly value. The annual heat transfer is the sum of the monthly values.
- Translate energy to carbon: Use an appropriate emissions coefficient for the electricity grid.
Figure seven below shows Wolf’s estimates for annual operational carbon for three wall types:
- Aluminum unitized curtainwall, triple-glazed low-E IG, 36% WWR;
- Glass fiber reinforced concrete (GFRC) rain-screen curtainwall, triple-glazed low-E IG, 45% WWR; and
- Terracotta rain-screen curtainwall, triple-glazed low-E IG 73% WWR.
Lifetime Carbon Assessment: Conservative Estimates
Figure eight below shows the cumulative embodied and operational emissions for the three façade types noted above, projected over a 100-year service life, assuming all façade loads are supplied by electric power. It assumes no greening of the grid.
Wolf is cautious about assuming that grid decarbonization will occur according to pledges made, for example, by 2040 in New York state. He sees the trend of greening grids and electrification of buildings being highly mixed across the country because it is “politicized and historically erratic, with many politicians ambivalent or hostile to transitioning from fossil fuels even as they see negative effects of climate change emerging.” He adds, “Some offshore wind projects have been in permitting for many years due to disputes, delay tactics and supply chain issues.”
Wolf also notes, “The rate at which grids decarbonize is largely dependent on the loads they must support. If we continue to produce buildings and other projects with high energy consumption, it will take years more time and billions more in taxes for the green grids to be built because they must be proportionally larger and more widely distributed due to space constraints. This will, in turn, induce more climate damage. We need both ultra-efficient buildings and carbon-neutral energy.”
Heating-dominated climate zones, where electrification of buildings is moving peak load to winter early mornings rather than summer afternoons, are particularly impacted by building operational energy demand.
With many unknowns that must be projected decades into the future, he suggests a precautionary approach, which implies being realistic with grid projections and using either a zero or very low discount rate for determining the social cost of carbon for projects.
Next month, our discussion continues, exploring the impacts of resilience, the influence of architects on low-carbon design, façade service life and incorporating the cost of carbon in design decision-making.