Ten questions concerning future buildings beyond zero energy and carbon neutrality

Highlights

• Future buildings will be tied to the local ecosystems and supplies and constantly monitor their environmental impact.

• Future buildings will rely on centralized and decentralized utility networks and can operate in low-resource situations.

• Future buildings will adapt to function or condition changes and being connected by a multimodal transportation network.

• Future building will learn occupant behavior and provide personalized environment with minimum resource consumption.

• Future buildings will consist of modular, interoperable components and embrace dynamic envelope to provide complex functions.

Abstract

Architects and planners have been at the forefront of envisioning a future built environment for millennia. However, fragmental views that emphasize one facet of the built environment, such as energy, environment, or groundbreaking technologies, often do not achieve expected outcomes. Buildings are responsible for approximately one-third of worldwide carbon emissions and account for about 40% of primary energy consumption in the U.S. In addition to achieving the very ambitious goal of reducing building-associated greenhouse gas emissions by 75% by 2050, buildings must improve their functionality and performance to meet current and future human, societal, and environmental needs in a changing world. In this article, we introduce a new framework to guide potential evolution of the building stock in the next century, based on greenhouse gas emissions as the common thread to investigate the potential implications of new design paradigms, innovative operational strategies, and disruptive technologies. This framework emphasizes integration of multidisciplinary knowledge, scalability for mainstream buildings, and proactive approaches considering constraints and unknowns. The framework integrates the interrelated aspects of the built environment through a series of quantitative metrics that aim to improve environmental outcomes while optimizing building performance to achieve healthy, adaptive, and productive buildings.

Introduction

Buildings are responsible for approximately one-third of global primary energy consumption and one-third of total direct and indirect energy-related greenhouse gas (GHG) emissions [1]. The ambitious goal of reducing building GHG emissions by 75% by 2050 [2] remains challenging because fragmented solutions that emphasize only a single driving factor, such as innovative energy systems [3], control of climate tipping points [4], or water resource engineering [5], may fall short of the desired outcomes that minimize environmental impacts while achieving healthy, adaptive, resilient, and productive buildings.

Buildings are a challenge and an opportunity for environmental sustainability. On one hand, population and economic growth and urbanization [6], with the increasing demand for energy, land, water, and other resources, are causing major economic and environmental transformations. Buildings are a reflection of this growth and are where humans spend over 90% of their time [7], directly contributing to many energy and environmental issues. Buildings use significant volumes of water for direct consumption and power generation and affect long-term water availability by contributing to storm water runoff and climate change [8]. The GHG emissions, landfill waste, and pollution (SO₂, airborne particulates) produced from building construction and operation are directly related to health threats [9]. On the other hand, urban living promotes energy efficiency from dense buildings and reduced land use [10], with the addition that a well-designed, positive indoor environment can significantly increase occupant satisfaction, health, and productivity [11].

Aggregate building development at the district and city scales and beyond has profound effects on environmental and human health and well-being. One critical outcome of urban building development since World War II has been sprawl—characterized by unplanned and uneven patterns of growth, driven by processes such as the advent of personal vehicles, market demands, and public infrastructure investments, and leading to inefficient resource use [12].

What should be the long-term vision for our total built environment? Past visions for buildings that draft solutions based on a clean slate (such as Bruno Taut's Utopian City in 1919 [13], Le Corbusier's Radiant City in 1924 [14], Frank Lloyd Wright's Broadacre City in 1932 [15], and Paolo Soleri's Arcosanti in 1970 [16]) proved difficult to realize. Current benchmark frameworks for sustainable buildings are focused on driving near-term market transformation or describing specific sets of goals for exemplary performance [17], [18], [19]. An integrated vision that is concerned with the long-term evolution of the U.S. building stock is needed that moves the full breadth of buildings from exemplary to “typical” performers. Furthermore, this vision acknowledges that the individual buildings of the future will connect to community systems and resources such as transportation, utility infrastructure, and land use. Emerging 21st Century challenges, such as vulnerability to a changing climate and the need for a more resilient built environment, are historical opportunities to develop a forward-looking vision of future buildings.

According to the International Energy Agency [1], more than half of the current global building stock will still be standing in 2050; in OECD (Organisation for Economic Co-operation and Development) countries (where buildings are more frequently refurbished than replaced), perhaps three-quarters of existing buildings will still be in use. Assuming an 80-year average life of buildings in the U.S. [20], Fig. 1 shows one scenario of the U.S. building stock turnover in the next 100 years. (Note that the median expected lifetime for nonresidential buildings in the U.S. ranges from 50 to 65 years, depending on the use type.) Building evolution is a relatively slow but continuous process. A third to a half of the building stock is always over 40 years old and needs major renovations. Retrofitting the existing stock of buildings is an ongoing effort, which applies not only to existing buildings, but also to those in the future — i.e., buildings that are being built and will be built in the next decades.

With sustainable development calling for even longer building service life, the challenge is to keep up with the fast-changing technologies and consumer preferences in the future. This requires innovative ways to rethink how buildings can be designed and constructed. Acknowledging the gradual but dynamic building stock turnover process that will occur over the next century, we envision common building characteristics that will apply to retrofits of existing buildings as well as to new construction. A vision described for buildings 100 years from today may take 100 years to realize.

We conducted a year-long research effort through panel discussions and structured workshops that involved collaboration among hundreds of thought leaders in various fields related to building development. The topics included resilience, biomimicry and biophilia, smart cities and urban informatics, building-grid integration, building codes and regulations, public health, occupant behavior, enabling technologies and building controls, information technologies and Internet of Things, building envelope technologies and additive manufacturing, real estate market dynamics, and security [21]. A special issue of the ASME Journal of Solar Energy Engineering includes a number of articles that address some of these aspects in more detail [22].

Acknowledging the unpredictability of the future, we consider the common context under all future scenarios to include changing demography, demand for affordable housing and livable environments, and continuing pursuit of health and wellbeing. Aging population, due to rising life expectancy and declining birth rates [23], [24], poses more challenges to building development, which needs to accommodate the physical and social needs of the growing senior population. Buildings in urban areas will remain the focus of discussion as population growth and urbanization continue throughout the century [23], [25], [26]. The pursuit of built environments that support health and wellbeing is considered as the major driver of building and city developments. During our panel discussions, we asked participants what the most important attributes of future buildings would be. Increasing health, productivity, and wellbeing was rated as the most important building characteristic among the nearly 600 respondents, regardless of their background.

Based on the above projections, we explored a new framework to guide the evolutionary design process of the U.S. building stock. The framework includes desired characteristics of future buildings that are derived from multidisciplinary perspectives (i.e., environmental science, climatology, transportation, urban planning, public health, building and urban science). We use energy and GHG emissions as the common thread to examine interrelated aspects of the built environment and investigate the potential implications of supporting design paradigms, strategies, and technologies that could change the built environment. After developing descriptive building characteristics, we developed corresponding quantitative metrics, as well as average nationwide 100-year targets. Through the following 10 questions, we discuss 14 metrics for measuring future building performance. Many of these metrics use GHG emissions as a common measurement to cross-compare various aspects of buildings. These proposed metrics and associated 100-year targets directly tie building functions, occupants, and economics to buildings' environmental impact.