As the U.S. Green Building Council gets ready to roll out LEED v4 at the Greenbuild conference Nov. 20-22, now is a good time to pause and reflect on how just how far green and sustainable design have come since LEED first launched in 2000.

Once considered a fringe movement within A&D circles, green building and green products have helped to keep the industry afloat during the post-recession economic stagnation. The most recent Dodge Construction Green Outlook forecasts that the market for green and sustainable projects will triple between 2012 and 2014. And that is not just in the U.S. Green building is expanding to all parts of the globe.

But green's success has not come without its critics. Some claim that many green buildings are not occupant-friendly. Others believe that LEED covers only some of the issues that a truly sustainable and eco-friendly environment should address.

Energy and water conservation, waste management, recycling and reuse, sustainable sourcing and minimizing the carbon footprint are critical to maintaining the health of the eco-sphere. But how else might we "green" our environments to make them healthier, more efficient and more closely linked to the natural world?

"What we need is LEED-certified interiors that talk about biophilia," suggests Grace Ehlers in a recent Metropolis blog. "We yearn to connect with the outdoors, whether we verbalize this need or not. And yet we rarely get the opportunity to make this essential connection to nature."

Biophilia is the concept that humans have a deep subconscious or instinctual connection to the natural environment. We yearn for daylight, natural landscapes and other living things. We also need "dens" or retreats where we can withdraw from danger or too many distractions to rest and reflect.

Judith Heerwagen, Ph.D., a psychologist whose research has focused on the relationship between buildings and psychological well-being and who has written widely on biophilia, believes biophilia evolved as an adaptive mechanism to protect people from hazards and to help them access such resources as food, water and shelter. Although we now spend most of our time indoors, that connection to nature is vital to our sense of security, health and well-being.

Ehlers discusses the benefits of biophilic design for workers, but it is also a central topic of research and experimentation in healthcare, education and senior living. Numerous studies have demonstrated the positive effects of incorporating nature, both visually and literally, into interior spaces.

Studies have shown that patients who have access to natural views heal faster than those who do not. Workers who are exposed to natural daylight are more productive and have lower incidences of absenteeism. Simply adding plants to an office space, medical office or classroom can improve occupants' overall sense of well-being.

As the practice of green building matures, more and more designers are recognizing that "green" must include healthy as well as eco-friendly environments. Areas such as improving indoor air quality and incorporating daylight have long been part of sustainable solutions.

Let us also recognize the real need we have to feel connected to nature, which is part of our own physical and psychological ecology. It’s time to go beyond daylighting and bring biophilia into the fold of sustainability.