DATA-DRIVEN DESIGN OPENS DOORS

The need for affordable carbon-positive housing is profound. Studies show one-third of urban dwellers, 1.6 billion people, will struggle to secure decent housing by 2025⁽¹⁾. Suburban home-seekers, especially in developing countries, are igniting the demand⁽²⁾. Research reveals that 55% of global citizens reside in urban locations, increasing to 68% by 2050. This migration and world population growth will add 2.5 billion more people to urban centers by 2050, with 90% of the increase in Asia and Africa⁽³⁾. The UN Department of Economic and Social Affairs notes future global populations will concentrate in several countries — India, China, and Nigeria — representing 35% of urban growth. This projection means 65% of future housing will occur elsewhere, mostly in developing countries⁽⁴⁾. The crisis expands exponentially, considering residential construction and operations contribute 20% of world carbon emissions⁽⁵⁾.

Among the myths about future cities, many think high-rise buildings must dominate housing construction, but most of those constructed thus far fail to meet net-energy and net-carbon goals. Observers also think land is unavailable for low-rise housing when in reality, cities have under-used, idle, and public-owned locations waiting for discovery⁽⁶⁾. These potential sites represent parking lots, vacant manufacturing sites, and even the rooftops of other buildings. Nonetheless, one of the greatest sources of new housing is the existing housing stock itself — preserving and upgrading single-family residences to accommodate larger family groups. Larger households range from traditional family multigenerational relationships — children, parents, grandparents, aunts, uncles, and the like — to more contemporary societal “family” groups who share space according to common occupations, beliefs, and social structures within a structured co-living environment. Some observers believe constructing accessory dwelling units, tiny homes, and second or upper-story micro-apartments can significantly increase affordable housing availability by encouraging single-dwelling expansion options ⁽⁷⁾. Expanding existing homes occurs most frequently almost anywhere globally and has powerful consequences.

Consider the modest Monte dos Judeus Building Rehabilitation by OODA Architects in Porto, Portugal. The project achieves building renewal, carbon sequestration, and new affordable housing comprised in one gesture. Imagine the impact on world housing availability if every existing residential building globally expanded its occupancy somehow. Where does digital design come into play; you may wonder? Let’s begin with the existing OODA project, which models easily using the cove.tool platform after making some assumptions about the structure.

The Monte dos Judeus Building has thick stone walls and wood timber framing determined from research. By estimating heights, the structure’s floor area, and related R-and U-values, we can reverse-model the building and establish its existing energy use intensity EUI and embodied carbon. Next, we add the new square footage, modified R-and U-values, systems, equipment, and other upgrades to the model. The program immediately provides cost optimization studies to determine the best project delivery outcomes. The analysis yields an encouraging baseline of 20.54 EUI, substantially below the target 2030 EUI baseline of 30.34. Furthermore, if we add solar panels to the mansard roofs, the EUI significantly drops to 1.80 — well below the 2030 target of 6.07. The result quadruples the occupancy at an impressive achievement of 0.90 tonnes of CO2e/yr, equivalent to two-tenths of one gasoline-powered passenger vehicle driven for a year⁽⁸⁾. The same methodology is applicable to almost every house in the world.

Due to the extent of embodied carbon invested in existing buildings, the approach helps achieve carbon-positive objectives individually and works equally well in large-scale applications where developers create new habitats on top of existing buildings, transportation centers, and similar types of public infrastructure, establishing a second significant source for new housing development. The concept especially works for adding housing stock to low-rise and mid-rise commercial structures like residential complexes, regional malls, and parking structures — wherever appropriate conditions and related safety concerns allow. New housing locations can mushroom existing urban habitats by developing these new real estate opportunities. However, shared air rights and airspace create new legal and related design considerations requiring careful resolution. These include structural, seismic safety, fire/life/safety, access for people with disabilities, energy use intensity, solar and wind access, real property ownership, access rights, continuous occupancy and operations, and the related liabilities that accompany similar considerations.

Possibly the grandparent of contemporary airspace use is FXCollaborative’s award-winning 35XV Residential Tower and Xavier High School expansion constructed in New York City. 35XV occupies a commercially-mixed, vibrant microcosm within the Chelsea, Union Square, Greenwich Village, and Flatiron District urban intersections. The complex resolves the project’s primary design objectives by using development rights available from the adjacent historic Xavier High School campus. First, the design provides crucial expansion space for Xavier High. Next, it creates new housing opportunities, exceptionally crafted to take advantage of a dense urban location. Last, the innovative massing optimizes New York City’s highly restrictive municipal bulk controls, while it relates strongly to the Xavier Campus, the neighboring streetscape, and spectacular surrounding views and vistas. The 170,000 square-foot structure creates a granite-clad cubic base wrapped in an expressive, textured façade to enclose Xavier High’s academic functions, while it employs dramatic cantilevers supporting a 19-story glass sculpture. The sloped glass tower contains 55 high-end residential units — constructed to USGBC LEED Silver standards⁽⁹⁾.

The 35XV design by FXCollaborative resolves complex three-dimensional issues involving air rights, zoning requirements, sky exposure, and volume restrictions on a densely populated downtown Manhattan site. A hybrid steel structural system provides space for classrooms, a STEM lab, rehearsal space, and a commons area for Xavier High, while a mixture of studios and two/three/four-bedroom units occupy the upper 18-floor levels. The seventh floor between the school and residents includes a gym, lounge, children’s playroom, and communal terrace for residents. The glass tower cantilevers 17 feet over the existing school building and 36 feet over the rear yard, creating 40 percent of the residential space. Completely independent MEP systems and vertical circulation infrastructure support the two main functions. With its dual identities, 35XV sets new standards in the growing trend of air rights development, meets the demand for housing in its dense, historic neighborhood, and provides needed support for public benefit, all within a contextually rich, dynamic composition⁽¹⁰⁾.

Little wonder 35XV won awards from the AIA New York Chapter, Council on Tall Buildings and Urban Habitat (CTBUH), The Chicago Athenaeum, Society of American Registered Architects, Urban Land Institute, and World Architecture News, among others⁽¹¹⁾.

Soon after 35XV, rooftops and airspace above metropolitan buildings, abandoned piers, waterways, and transportation hubs became welcome and desirable locations for new housing and mixed-use projects — evidenced by Penn Station, Hudson Yards, San Franciso’s Piers 30–32, and Stockholm Central Railway Station.

For example, Hudson Yards, a 26-acre space with 17 million square feet of buildings, is famously suspended over about 30 active train tracks. Imaginably, airspace resolution is extraordinary. Platform design and construction are essential to overcome the challenges. First, 3D modeling helped identify rail yard locations to drill caissons into the bedrock without disrupting the tracks. Then, over 300 caissons, each built with 90-ton encased concrete cores, serve as the foundation for load-bearing columns, with long-span bridge trusses spanning the “throat” of the railyard where 30 tracks converge into four to enter the station. Finally, contractors must perform the work to ensure the trains can continue their normal operation. The time and space constraints demand extreme efficiency where at some points, workers have only several hours to mobilize hundreds of tons of rigs into position, drill caissons, and remove everything before the trains pass through. The job requires incredible precision, with engineering tolerances often at an eighth inch⁽¹²⁾.

Consequently, data-driven design becomes a primary tool when considering complex and progressive development opportunities to determine optimum building configurations. As design professionals and developers explore new urban “airspace” sites, alternative massing schemes become invaluable to determining best-case scenarios. cove.tool produces optimum comparative alternatives for low-rise, mid-rise, or high-rise massing schemes to meet this challenge. The platform models massing characteristics and provides site analysis, EUI, and carbon production analysis for varying configurations easily and quickly.

For example, consider a potential 100-unit housing project proposed on the abandoned Pier 30–32 in San Francisco’s Embarcadero District. We can quickly model three different massing options using cove.tool’s drawing.tool. The drawing tool bypasses the need for more sophisticated 3-D modeling platforms and gets the user quickly involved with knowledge-bearing simulations. We do not need to worry about doors, windows, or detailed facades. The idea is to rapidly create massing schemes that achieve 100 apartment units based on identical assumptions for site location, wall and roof R-values, glazing/skylight/spandrel U-values, lighting, environmental systems, appliance use, and occupant numbers.

The simulations, which use a high thermal mass building envelope in all cases, reveal surprising results. The high-rise solution achieves 17.66 EUI, the mid-rise shows 15.75, while the low-rise option has the lowest EUI of 12.19. When we add multi-crystalline silicon solar panels to the roof, the results become more dramatic, with EUIs ranging from 8.63, -0.76, and — 20.41. With the increase from 17 percent to 25 percent efficiency gained by advancing thin-film perovskite solar panel technology, comparative net positive energy production becomes even more magnified. While low-rise construction has more roof area for solar panels, the baseline EUI differences are still substantial. However, with other advancements in building-wall and façade solar panel technology, the solar surface area exposure will increase for mid and high-rise buildings. As an example, the Copenhagen International School Nordhavn by C.F. Møller Architects illustrates improved façade solar power production⁽¹²⁾.

Many design and construction professionals within the AEC community are engaging in the global affordable housing crisis by inventing the means to create new residential neighborhoods at affordable prices. Another fallacy suggests low-rise housing decreases economic productivity. Yet, evidence supports low-rise housing built where residents connect to employment and vital services by public transport boosts urban productivity and rising incomes, enables increased lifestyle quality, and helps drive economic growth. Moreover, low-rise solutions currently best meet the needs for immediacy and purposeful action until low-embodied high-rise construction methods advance. Nonetheless, low-rise or multi-story housing strategies become more critical considering the development opportunities afforded by leveraging data-driven design methods at previously restrictive sites made possible by innovating the available airspace above existing buildings, parking structures, transportation centers, and arteries and waterways.

(1). Woetzel, Jonathan, et al. “Tackling the World’s Affordable Housing Challenge.” McKinsey & Company, McKinsey & Company, 27 Apr. 2018, https://www.mckinsey.com/featured-insights/urbanization/tackling-the-worlds-affordable-housing-challenge.

(2). Badmus, Deji. “World Bank — Kenya Needs Two Million Houses to Stem Slum Eruption.” CGTN Africa, 12 Apr. 2017, https://africa.cgtn.com/2017/04/12/world-bank-kenya-needs-two-million-houses-to-stem-slum-eruption/.

(3.) Keffler, Natalie. “Solving the Global Housing Crisis.” World Finance, 7 Sept. 2021, https://www.worldfinance.com/infrastructure-investment/solving-the-global-housing-crisis.

(4.) United Nations. “68% Of the World Population Projected to Live in Urban Areas by 2050, Says UN.” UN DESA — Department of Economic and Social Affairs, United Nations, 16 May 2018, https://www.un.org/development/desa/en/news/population/2018-revision-of-world-urbanization-prospects.html.

(5). Margolies, Jane. “Energy-Efficient Isn’t Enough, so Homes Go ‘Net Zero.’” The New York Times, 16 Nov. 2021, https://www.nytimes.com/2021/11/16/business/net-zero-homes.html#:~:text=There%20is%20widespread%20agreement%20that,responsible%20for%20about%20half%20that.

(6). Woetzel, Jonathan. “A Blueprint for Addressing the Global Affordable Housing Challenge.” McKinsey Global Institute, McKinsey & Company, Oct. 2014, https://www.mckinsey.com/~/media/McKinsey/Featured%20Insights/Urbanization/Tackling%20the%20worlds%20affordable%20housing%20challenge/MGI_Affordable_housing_Executive%20summary_October%202014.ashx.

(7). Strong Towns. “5 Creative Strategies for Increasing Affordable Housing.” Strong Towns, 23 July 2019, https://www.strongtowns.org/journal/2017/4/26/5-creative-strategies-for-increasing-affordable-housing.

(8.) EPA. “Greenhouse Gas Equivalencies Calculator.” Energy and the Environment, Environmental Protection Agency, https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator#results.

(9.) AIA New York. “35XV.” AIA New York, American Institute of Architects, 9 Apr. 2019. https://www.aiany.org/architecture/featured-projects/view/35xv/.

(10.) González, María Francisca. “35xv/Fxcollaborative.” ArchDaily, 28 Feb. 2018. https://www.archdaily.com/889856/35xv-fxcollaborative.

(11.) “35XV.” FXCollaborative, 2019. http://www.fxcollaborative.com/projects/108/35xv-/.

(12.) Wolff, Larry. An Architect’s Journey — Mastering Future Trends in the Anthropocene. BookBaby, 2021. https://store.bookbaby.com/book/an-architects-journey.