A small scale physical timber prototype was designed, constructed and tested to shade a target-shade area of 0.6m × 0.6m in Princeton (NJ, USA, latitude 40.36N). The louvered shell covers a plan area of 2.4m x 3.4m with a maximum vertical clearance of 0.8m at the boundary arches, and maximum interior clearance of 1.7m. A three-day sample of the recorded UV Indices, measured by seven sensors is shown for the period September 5th to September 7th 2013 below.  Sensors 1 through 5 are within and bounding the target-shade area, with sensor 6 beneath the structure but outside this area, and sensor 7 fully exposed to radiation atop the structure. On September 5th, the site was exposed to a cloudy sky, significantly reducing the UV radiation below theoretical clear-sky values at certain times, when the sun was partially or fully obstructed by cloud cover. The UV Index, even on the fully-exposed sensor (7), occasionally dropped below the EPA moderate risk level of 2.5. On September 6th and 7th, generally sunny days, the UV Index measured atop the louvered shell by sensor 7 approaches a value of 8, representing very high risk as per EPA recommendation. The UV Indices on the boundary and within the target-shade area consistently remain within safe levels (ranging from 0 to 1.4, all less than 2.5). The sensor beneath the structure but outside the target-shade area (6) is shown to approach critical limits in the early morning hours, but also never quite reach moderate-risk levels for the dates shown.

The results presented above represent a small but varied sample of the data collected. Data through June 5th, while expectedly varied particularly in the magnitude of the fully-exposed UV Index, lead to the same observations. While the recorded UV indices atop the shell and on the ground outside the target-shade area might be in excess of the health hazard limit of 2.5, the Indices recorded within and on the boundary of the target-shade area do not reach those limits. These observations are supported by the data below, which shows daily maximum values for the entire monitoring period, and hence validates the design methodology for these louvered shells.

© Matthew Horner 2014