Giving Green Buildings a Smarter Skin

The Biomimicry Column

Giving Green Buildings a Smarter Skin

Building - http://www.flickr.com/photos/sashafatcat/ / CC BY 2.0

Of the three essential material necessities -- food, clothing and shelter -- buildings represent the biggest capital cost and embody the most energy. Depending on how you add up life cycle costs and inputs, they account for about 40 percent of our energy usage.

Many have long argued that we design and make buildings in a flawed way. It is only relatively recently, however, that alternatives have been proposed that employ paradigms, rather than just forms, from nature. Are these paradigms just extensions of the old “building as machine” utopian dream? I think they are fundamentally different and will outline below why I think so and describe one of the pioneering partnerships that may change the way we make buildings.

First off, how would nature design a building? The differences in techniques between nature and technology couldn’t be more pronounced. 

We work from static blueprints that detail all methods, materials and spatial arrangements at a fixed moment in time. Nature does not, preferring to impart information with recipes, rather than blueprints, starting with DNA. Recipes only tell you what ingredients are combined and how and when. The final form can vary widely, as my daughter can attest when I am in the kitchen.

We tend to work from the top down, setting goals and objectives, visions, five-year plans, national initiatives, company directives and building programs. Nature builds from the bottom up.

Modular construction? Nature perfected it long ago. Its building processes are based on stringing a tiny number of amino acids together to form thousands of types of protein molecules. These, in turn, are functionally differentiated by shape and comprise the organelles that make up cells, the building blocks of life. Incredibly, each of these cells (except reproductive cells) contains all the genetic information necessary for the entire organism, but only certain genes are expressed in that cell, making it part of a leaf, stem or root.  

We combine building materials; nature integrates them. This is a key difference that flows from the bottom up approach: Solutions in nature flow through the hierarchy of scales to facilitate function. Consider that root and all the levels of organization it employs to capture water and nutrients from the soil, from an efficient branching system to the guard cells at the tip of a growing root hair to the osmotic mechanisms within. 

In order to build we obtain materials and manipulate them to the shapes we want by bending, cutting, drilling and then fastening the parts together and throwing away the waste. Nature doesn’t bother with all that, instead forming to shape, as and when it is needed.

We build things to stay put, preferring stability and stiffness in most of our structures. Nature isn’t so concerned about such issues, and builds instead for toughness and durability. Steven Vogel, in his classic book Cats’ Paws and Catapults offers an excellent discussion of this. As he puts it, “Humans usually build to a criterion of adequate stiffness, while nature builds to a criterion of adequate strength.”

Our structures don’t change very much, because we are so concerned with them staying put. That's not so in nature. For an organism, “unchanged” means “dead.” Maintaining a dynamic disequilibrium is what keeps all the living world’s machinery humming. This is a key concept for making our built world more sustainable, in my opinion. “Surfing for free” on an existing chemical or physical gradient, as I have written before, will be an important strategy to mimic.

Since our structures don’t change very much, they don’t adapt. Nature is all about adaptability, and that, of course, means real-time feedback loops and all the sensors, actuators and information programs that go with it. We are just catching on. 

This also means, for nature, a fundamental focus on flexibility of parts. This is in contrast to our obsession with bracing, bolting, gusseting, screwing and nailing all these stiff members. The organic designs for this flexibility, for all sorts of survival strategies, are the most elegant forms in our world.

The elegance of natural forms is not lost on professors Luke Lee and Maria-Paz Guttierez of the University of California at Berkeley, but part of the beauty that they see lies in function. Lee, of the Bioengineering Department, and Guttierez, of the Architecture Department, have collaborated on several investigations that are edging us closer to a more nature-based functionality for buildings. 

They are concerned principally with a building’s skin and how that skin can exhibit some of the characteristics outlined above. Can it be smarter, more resilient, more efficient and more capable? Their idea represents a significant intellectual transfer of technical advances in the field of bioengineering to the field of architecture.

In one project, they propose to develop the basis for a new type of thin film building membrane. The purpose of the membrane is to control three things: humidity, light and temperature transmission into the building. Space heating, cooling and air conditioning account for roughly one-third of all end-use energy consumption in all U.S. buildings.

As in many natural processes, the membrane system uses the product of the environmental condition it seeks to control as an actuator. In the membrane, excess moisture, produced by the building’s atmosphere, triggers openings in the membrane that reduce that production to an acceptable comfort zone.

Other attempts have been made to design this type of system, but the authors claim that this is the first to combine bio-inspired principles in order to achieve such a level of automated control. The system relies on the physical properties of the materials being used, and therefore does away with the need for power and the bulk material of mechanical elements. What is revolutionary about their approach, according to Guttierez, is that “the material has become the system.”

There are several reasons why this work, although in its earliest stages, is significant.

Material and its structure at the nano and micro scale will be substituting for energy previously spent to solve the problem of climate control in buildings. In other words, matter is now active matter with the ability to adapt, regulate and control. This has implications beyond energy use, since such systems can conceivably be more durable and reliable than those dependent on electricity and mechanical armatures.

Scaling solutions to a new challenge also makes this type of work significant and pioneering. One possible benefit is the ability to calibrate building conditions more efficiently. Innovation takes many forms and this one is achieved by changing the scale at which one solves a problem like excess moisture. This type of innovation is likely to become more widespread as the transfer of scientific techniques to building applications continues. 

Also, if researchers can prove the practicality of their conceptual solutions, this should pull innovative manufacturing techniques. Guttierez sees a time in the future when many building processes will emanate from the laboratory as buildings become more and more calibrated to this molecular scale. This will only widen and accelerate the kind of interdisciplinary approach seen in this project.

Finally, the membrane system was presented as a solution to temporary housing in tropical areas, but impacts of this type of technology could be widespread within society. As Lee said, “…the social impacts are important here: for me providing a clean environment is number one, and saving energy is next.” The inveterate engineer, he is anxious to get working on the numbers to gauge that contribution.

 

[Editor's Note: This article was updated to simplify the explanation of the researchers' work; because it is a study in progress, the specifics of the work could change.]

Tom McKeag teaches bio-inspired design at the California College of the Arts and University of California, Berkeley. He is the founder and president of BioDreamMachine, a nonprofit educational institute that brings bio-inspired design and science education to K12 schools.

Building - http://www.flickr.com/photos/sashafatcat/ / CC BY 2.0