BIOPHILIC RESPONSES TO WOOD

According to Terrapin Bright Green’s 2022 publication, The Nature of Wood – An Exploration of the Science on Biophilic Responses to Wood, “Designing elements of nature into the built environment can have health benefits including stress reduction, improved cognitive performance, enhanced moods, and increased preference for spaces. These benefits are often referred to as ‘biophilic responses’ and we have a particularly strong biophilic response to wood, more than almost any other material.” These biophilic responses include the haptic response, olfactory experience, and visual experience. Wood can also have a thermal response on the body and sound absorption qualities that can make a space more pleasant to inhabit, but there have been fewer studies about these biophilic responses to wood.

Haptic Response

The haptic response, or our sense of touch, is elicited by the tactile feel of wood. In a blindfolded experiment that aimed to clarify the physiological effects of touching wood with the palm, in comparison with touching other materials on brain activity and autonomic nervous activity, participants placed their palms on a panel of stainless steel, tile, marble, or white oak. Touching the oak panel led to increases in activity of the parasympathetic (rest and calming) portion of the nervous system that did not occur with the other materials. The study says, “These results may be due to wood having lower thermal conductance than metal or stone, and therefore feels closer to the perceived ambient temperature of a space.”

Olfactory Experience

Smell has a way of quickly and powerfully eliciting memories and a physiological response to these olfactory experiences. The natural smell of cedar and other woods can elicit a biophilic response that is calming and triggers neuropathways similar to antianxiety drugs. It can also level blood pressure and heart rate. For example, a study of the respiratory response and heart rate among participants who slept in a bed made of fragrant stone pine showed significant physiological improvements compared to those in a bed made of chipboard covered in melamine. The researchers attributed this outcome to the conifer resins, including limonene.¹⁵ It should be noted that the natural scent of wood will dissipate over time, so the olfactory experience should not be heavily relied upon in biophilic design.

Visual Experience

Most of the research on our biophilic responses to wood centers around the visual experience. Nature-made and human-made objects and environments are processed differently in the brain, with humans typically preferring the former. The brain visually identifies and processes images by association, subconsciously separating things as living or non-living. Terrapin Bright Green says, “While wooden objects are crafted by humans—a process that is often considered manufactured or unnatural—the wood itself is still considered to be ‘natural,’ which may hint at why research suggests we like having wood around us in buildings. Wood has been used in the construction of shelters and artifacts for thousands of years in cultures around the world. It historically has been a plentiful resource that is readily shaped by simple tools.”¹⁶

The visual presence of wood in a room leads to perceptions of warmth and comfort, which lowers blood pressure levels and heart rates and activates the parasympathetic nervous system, which restores the body to a calm and composed state. People visually identify natural objects by their surface characteristics, which, for wood, include color, grooves, knots, and grain. Regarding color, people tend to prefer untreated wood in the red-to-yellow spectrum, which evokes warm feelings and calm. Think of western red cedar. The Nature of Wood states, “When the brain looks at wood, it is (almost) instantaneously identifying the curves of the wood grain and surface appearance to determine the type of material. Whether the object is a chair, guitar, spatula, beam, or sheet of plywood, it is identified as wood by the patterns on the surface.”

Collinear, contour, curvilinear, parallel, and radial patterns are ubiquitous in nature, so when people see these recognizable patterns in the built environment it makes visual processing easier. Likewise, fractals are layered self-repeating mathematical patterns that occur frequently in nature (e.g., snowflakes, fern leaves, waves, and dappled light from a tree canopy) and create a biophilic response when viewed. They are so common in nature that when we see fractal patterns, even in man-made objects, it is easy for the brain to process the image and measurably lowers our stress level. This is called fractal fluency.¹⁷

People have a visual preference for patterns with mid-range complexity, which can elicit restoration and relaxation. But highly complex patterns cause stress. Similarly, lines running in the same direction are easier to process, while lines running in multiple directions take more effort. “The brain will follow curvatures and contours, and even connect short segments of lines to discern a longer curving pattern. These pattern conditions occur frequently in nature and our brains, it could be argued, are predisposed to easily decipher them.”¹⁸ In the built environment, wood grain that features collinear lines and nested fractal patterns (layered oval shapes in the wood grain) is easy to process and therefore desirable, making it a strong driver of biophilic design. Because we see these patterns so often in nature, they elicit a response when we see them in wood.

Why Use Western Red Cedar in Biophilic Design?

Western red cedar is an optimal wood species choice for biophilic design. The wood’s rich tonal range and beautifully pronounced grain immediately connect people to nature. It’s also a top-performing building material that will enhance the well-being of occupants for decades to come. Western red cedar comes in a wide range of sizes, grades, and profiles, which gives design teams flexibility in creating their desired look.

DESIGN CONSIDERATIONS FOR USING WOOD IN THE BUILT ENVIRONMENT

Wood provides warmth and richness that contrasts well with more modern materials such as concrete, steel, and glass. When using wood in the built environment, it’s key to prioritize the wood grain and contour lines by making them readily visible rather than hiding the grain with paint or a stain that is so dark that it hides the grain. The number of grooves and knots is also an important consideration. The look of knotty cedar may be desired, as it adds texture and contrast, enhancing the symbiotic dynamic between a home’s interior and exterior. Occasional knots do not distract from the contour lines, but too many knots can “negate the stress reduction characteristics of the collinear and contoured patterns in wood.”¹⁹

It’s also important to consider the amount of wood used in a space. Too much wood can have a negative effect on physiology and psychology, while too little won’t elicit a response.

The number of building products on the market today that attempt to simulate the color, grain, and texture of wood is astounding, but synthetic wood products don’t hold a candle to real wood. Wood creates an immediate and seamless connection to natural surroundings that no synthetic wood can replicate. This is because wood was alive and has a cellular structure that is present even after harvesting. Light bounces off those cells, giving wood a reflective quality that is unique to the material. “This can make both the grain pattern and surface color appear to change. Fake wood does not have a cellular structure and thus far cannot replicate this visual experience.”²⁰ Nature still knows best—despite all efforts at imitation, no man-made product can match the beauty, performance, and longevity of western red cedar.