Editor’s note: This article is part of a series about sustainable cities. Read the other articles: "Sustaining our cities," "Curbing urban sprawl," "Room to grow," "Easing off the gas," "A city that you love" and "Nature by design."

The first thing that many people picture when they hear the word “city” is a glittering, glass-and-metal skyline. While cities are many things, they always include a collection of buildings. Download Full Image

Houses, office parks, skyscrapers, restaurants – the urban environment is a study in construction lined up and framed against the sky. It makes sense, then, that a key step toward creating a more sustainable city might be to create more sustainable buildings.

The U.S. Environmental Protection Agency (EPA) defines sustainable building as “the practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building's life-cycle from siting to design, construction, operation, maintenance, renovation and deconstruction.”

A number of researchers at Arizona State University have turned their attention to making buildings more sustainable – both environmentally and for human health. They are figuring out how to improve the design of buildings in order to save energy, use materials with less negative impact and get one step closer to that elusive “sustainable” label.

Start with efficiency

Kristen Parrish, assistant professor in the School of Sustainable Engineering and the Built Environment, thinks energy efficiency is one of the best ways to make buildings more sustainable. It is the cheapest and easiest tool in the sustainability shed and it humanizes the problem of energy consumption by putting a more positive spin on it – “efficiency” and “savings” are more palatable to people than “sacrifices.”

T. Agami Reddy, a professor in ASU’s Design School and the School of Sustainable Engineering and the Built Environment, says that energy efficient buildings are also referred to as “green buildings.”

“When people say sustainable buildings, they are really thinking of green buildings,” says Reddy. These are buildings that he says are “very energy efficient, operationally low-energy and which have a low impact on their environment.”

Achieving this goal typically involves a combination of human behavior and building design. Behaviors that promote efficient energy use include shutting off lights when no one is around and raising the thermostat in summer. Increasingly, these and similar energy-saving behaviors can be facilitated by energy management programs that use smart sensors and controls, and can give real-time feedback to building occupants and managers about energy consumption. High-efficiency lights and appliances can help as well.

Buildings can also have energy efficiency built into their design. Passive solar design takes advantage of a building’s materials and the site’s climate to minimize energy use. For example, windows can be positioned to take advantage of the sun’s light and heat. And building materials that have a high thermal mass, such as concrete, brick or stone, absorb heat and act as insulation.

Parrish realized early in her career that we are actually quite skilled at designing buildings with excellent energy efficiency. We’re not as good at actually building them.

To find out why, Parrish studies the relationship between building designers, builders and building managers. Building designs on paper are frequently able to achieve levels of energy use that are 40 percent below the building-code-mandated levels. Yet actual buildings do not often achieve these projected levels of energy efficiency.

“I'm trying to understand how we can better specify, how we can better communicate, so that [the designer’s] intention is carried all the way through the operational phases of the building,” Parrish says.

Figuring out what’s causing this discrepancy, and how it might be fixed, will improve the modeling tools that designers use to make energy projections for a building and improve building construction and operation. It will also advance the goal of improving building sustainability through energy efficiency.

Materials matter

Mick Dalrymple, a practice lead in ASU’s Walton Sustainability Solutions Initiatives, says human health is another aspect of sustainable buildings. Given how much time modern urbanites spend indoors, one would assume that buildings are created to be healthy environments, but this isn’t always the case.

For example, the EPA says that indoor air pollution is often two to five times higher than outdoor air pollution. There are many different types of indoor pollutants, ranging from mold to formaldehyde (a carcinogen found in paper, plywood and some resins and household products) to carbon monoxide. Indoor pollutants can be generated from seemingly innocuous sources, such as damp carpets, insulation, pressed wood materials, cleaning products and heating and cooling systems.

Much like energy efficiency, pollution can be controlled both through building design and its use after being constructed. Design components could include using non-toxic building materials and providing suitable ventilation, while occupants can take actions like changing air filters, cleaning up mold and controlling pests.

But a building can even have negative impacts on human health even before it is built. Building materials that create pollution during manufacturing or disposal can negatively affect both the people and the environment around those facilities.

A building life-cycle assessment (LCA) is a tool researchers can use to understand the complex web of impacts a building can have. An LCA examines the environmental and social impacts of the energy and material inputs and outputs throughout an object’s creation, use and disposal. This helps to assess the true environmental and social costs of a building, and can help determine how materially sustainable it actually is.

“Part of green building is trying to remove toxins from building products in every phase of the product life-cycle,” says Dalrymple. “Our building products – all of our products – should be designed for disassembly and/or composting or recycling, and not going into the landfill.”

This includes every material used in a building down to its foundation. As a geotechnical engineer, Ed Kavazanjian works to improve the ground so that it is easier to build structures on top of it or tunnel through it. Traditionally, the methods used are “brute force,” he says, and include mixing cement with the soil, driving piles into the ground and other structural reinforcements. But the Portland cement often used in these tasks is one of the least sustainable building materials. It requires huge amounts of energy to create and, when cured, releases carbon dioxide.

Kavazanjian, a professor in the School of Sustainable Engineering and the Built Environment, is addressing the high environmental impacts of Portland cement through what he calls “geo-alchemy” – changing sand into stone. This process happens naturally over thousands of years, but it has also been observed to happen fairly quickly – and disastrously – in places such as water treatment plants, where filters sometimes get clogged with cemented soil.

“We're trying to learn how to take that process and make it happen someplace where it's beneficial to us, like under a building, so we can strengthen the soil under a building, make it more resistant to earthquake loading, or make the cost of building the foundation for the building cheaper,” says Kavazanjian.

He and his students are using microbial processes in their material transformations, an emerging area of study known as bio-inspired or bio-mediated geotechnics. In other words, they are learning how to “build things better, more sustainably and more economically,” by observing how nature operates.

Desert challenge

Sometimes nature provides extra challenges to sustainable building, such as the harsh climate around Phoenix, Arizona. Many best practices for sustainable building in Phoenix can actually be drawn from times before people had air conditioners.

"Historically, a lot of buildings in Arizona built before we had cooling responded very well to the climate. We had outdoor sleeping porches, we put up wet sheets that created an evaporative cooling effect, people slept outdoors very comfortably,” says Harvey Bryan, a professor and architect in The Design School and the School of Sustainability.

Some other pre-AC techniques for cooling include building courtyards, which create air circulation, and having small water fountains and some vegetation, both of which helped cool the air. Thick adobe walls acted as mass as well as insulation, and shade trees could also help keep temperatures down in and around a building. Even tiles were used to keep buildings cool.

“Saltillo tiles were used very effectively in Mexico as a cooling element because you wet it down in the morning and it created an evaporative cooling plain on your courtyard for the rest of the day,” says Bryan.

Most of our modern sustainable building techniques, however, were created in a non-desert climate, and “don’t translate well to the desert,” according to Parrish.

For instance, the efficiency of mechanical systems and materials can be thrown off when summer heat is at its peak. Part of Parrish’s work in translating design efficiency to actual building efficiency could help identify critical temperatures at which materials and technology need to be altered to remain efficient in the Phoenix heat.

Certifiably sustainable?

One popular way to approach sustainable building is through a certification system, such as LEED and the Living Building Challenge. These assess a building’s design, performance or both, and then give it a sustainability rating.

In 2005, Arizona Gov. Janet Napolitano passed an executive order requiring that all state-funded buildings be LEED Silver certified or higher. In 2009, ASU approved additional sustainable design guidelines in order to help the university meet its own sustainability goals. ASU owns the largest number of LEED-certified buildings in Arizona, and built state's first-ever LEED Platinum building, the Biodesign Building B on the Tempe campus.

LEED has gone a long way in promoting more sustainable building but for a time, the certification was based on building design, not performance. As Parrish’s research has shown, design isn’t always well translated into the actual building.

“[People ask], 'Why am I only performing at a LEED Silver level despite having designed at a LEED Platinum level?' That's one of the things that my research tries to answer,” says Parrish.

LEED is changing its process to require evidence of how a building performs over time. This will make certification an even more accurate statement of how sustainable a building is.

The Living Building Challenge is also performance-based, although it isn’t known or used as much as LEED. Dalrymple is a proponent of the system and is currently co-teaching a class on it. The class will be working with the city of Phoenix to create a business park, based off of the Living Building Challenge concepts, which will turn trash into resources.

Overall, says Parrish, certification systems are good tools to have and have helped increase general knowledge about sustainable building. However, they are made to be broadly applicable. In order to work on a specific site, a building needs to be adapted to that site. For this reason, Parrish says, pursuing certification shouldn’t be the only step taken to make a building sustainable.

What’s in a name?

So where does this leave us in understanding a building’s sustainability? Does sustainable mean that the building is LEED certified? Or does it mean a building is designed to be energy efficient, or was constructed with recycled materials? Should we even be thinking of sustainability in terms of individual buildings?

Reddy thinks the word “sustainable” is overused and shouldn’t be applied to buildings at all.

“A building is too small of an entity to be sustainable,” he says.

Sustainability encompasses environmental impact, economic prosperity and social equity. A single building could never address all three of these themes, according to Reddy. However, the way buildings are designed in general might be able to. So rather than saying any one building is sustainable or not, it might be more accurate to say that sustainable building is about making the way buildings are designed in general more sustainable.

While Parrish thinks this view has merit, she doesn’t necessarily think it’s conducive to creating a more sustainable built environment. She thinks it’s better to “think of it as sustainability, one building at a time.”

“That sends the message that it's important to make every building as sustainable as possible, but we're not going to achieve sustainability through only one building,” she says.

Kavazanjian thinks the term is relative. A totally sustainable building, or totally sustainable anything, is a bit of a pipe dream. Becoming more sustainable is a more realistic goal.

“What we strive to do is come up with approaches, processes, techniques, that are more sustainable than what's being used right now,” Kavazanjian says. “What is truly sustainable? I don't know. If and when we'll get there? I don't know. But we need to do the best we can. I think that's what it's all about, just trying to make things better.”

The School of Sustainable Engineering and the Built Environment is a unit of the Ira A. Fulton Schools of Engineering. The Design School is a unit of the Herberger Institute for Design and the Arts.

Written by Erin Barton, Office of Knowledge Enterprise Development