Bring comfort to walkers to bring walkers to paths

Church Street in Burlington, Vt., offers several kinds of canopy that moderate the micro-climate.

Church Street in Burlington, Vt., offers several kinds of canopy that moderate the micro-climate.

Research suggests that after solid footing and a sense of safety, a pleasant micro-climate contributes more than any other amenity to path use. John Zacharias and his fellow researchers summarized one of their studies of urban open spaces, “Use within spaces varies chiefly as a function of micro-climate.”  Since most places at times become uncomfortably hot or cold, wet or windy, paths intended to invite strollers need to avoid cold pockets, block glare, ward off rain, moderate the wind, and offer both sun and shade.

Indeed, tempering climate around walkways worldwide will be increasingly needed as weather intensifies and as people increasingly migrate to cities. Urban settings are especially challenging because, as Zacharias noted in the same study, “Micro-climatic conditions in business district open spaces tend to be more extreme than prevailing weather conditions.”

Thermal comfort forms the basis for a pleasant micro-climate. Up to about 22° C/ 72° F most people seek out predominantly sunny places to walk. Above that temperature people increasingly seek out shade. As Zacharias reported, “It was found that temperature has a preponderant effect on [the presence of people outdoors], combining positively with sunlight and negatively with wind through a threshold temperature of 22° C, whereon public presence in sunlight begins to decline, along with overall presence in public space.”

While macro-climate is beyond our immediate control, micro-climate is readily adjustable. Walkways can be placed and their surroundings shaped to moderate climatic extremes. For example, in northern temperate climates walkways to the south of hills and woods thwart northerly winter gales, while east-west walkways capture westerly summer breezes. In hot, dry climates, narrow streets running east and west between light-colored buildings block direct sun but capture incident light.

Because the micro-climate among buildings is one of the most important determinants of outdoor comfort, urban planner Jan Gehl in Livable Cities stated, “Careful climate planning should be a requirement for all new building.” Clusters of relatively low buildings mixed with trees drive wind up and over themselves, protecting people between them, as contrasted with tall individual buildings that capture and concentrate winds and send them plummeting to the ground. Design makes a difference because, in temperate climates, modest reductions in wind create major increases in perceived outdoor comfort.

Proper placement of paths below hill tops and above streams maximizes walkers' comfort.

Proper placement of paths below hill tops and above streams maximizes walkers’ comfort.

Research of Peter Bosselmann and others at the University of California at Berkeley in 1984 revealed the discomfort due to high winds and deep shade at street level brought on by tall buildings in San Francisco. Publication of the study’s results put a stop to skyscraper building in San Francisco since 1985.

Despite varied climates, a few limited design generalities can be offered. Paths should be sheltered, like linear refuges, so they often hug the edges of open spaces. Any above-the-head roof along the path—tree canopy, overhanging shrub, awning, arcade, projecting cornice or marquee—is welcome. So are niches, nooks, and other refuges along the route. Trees or tall shrubs also can be used in masses to buffer high winds or in converging lines to funnel summer breezes.

Mid-slopes generally provide better protection than hilltops or valley bottoms. High up, paths are usually placed on the military crests—the shoulders below ridgelines or hilltops. There they tend to be out of the worst winds, while offering prospects and refuges. Low down, paths on shelves or knolls above the bottomland minimize floods, fog, and frost while receiving more sun. Native Americans, superb path makers, hewed to these patterns, following river terraces above flood level and, where available, low, well drained ridges overlooked by higher mountains.


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