Increasing the ultraviolet protection provided by shade structures (original) (raw)
Related papers
Scattered UV Beneath Public Shade Structures During Winter¶
Photochemistry and Photobiology, 2003
Broadband field measurements were conducted beneath three different sized public shade structures, small, medium and large, during the Southern Hemisphere winter. These measurements were compared to the diffuse UV to quantify the relationship of the UV under and around the shade structures to the diffuse UV. For the shade structures, a relationship between the diffuse UV and the UV in the shade has been provided for clear skies and solar zenith angles (SZA's) of 49 o to 76 o . This allows the prediction of the UV in the shade of these structures if the diffuse UV is known. The ultraviolet protection factors (UPF's) for the three shade structures ranged from 1.5 to 5.4 for decreasing SZA. For the greater SZA's of 70 o to 76 o , the erythemal UV in the shade was 65%, 59% and 51% of that in full sun for the small, medium and large structures respectively. For the smaller SZA's of 50 o to 53 o the erythemal UV in the shade was 35%, 41% and 18% for the small, medium and large shade structures respectively. From this research it can be concluded that the UV radiation levels in the shade in winter could cause erythema and other sun related disorders.
Protection Factor of small to medium sized built shade structures 2 3
2018
A method was proposed for calculating the ultraviolet protection factor (PF) of small to medium built shade structures. The method takes into account the amount of sky view visible from under the structure, the transmittance of the roof material, the relative amount of diffuse ultraviolet radiation (UV), the measurement position under the structure and the albedo of the relevant surfaces. The PF of four different shade structure designs was measured 90 cm above ground-level at the centre of the widest diameter of each structure. Measurements were only made on cloudfree days. Three structures had a thin metal roof and the fourth had shade-cloth. The proportion of sky view ranged from 4.6% to 15.4% for these structures. The influence of position was investigated for one structure, with the PF evaluated 50 cm in from each of the sides at 90 cm above ground-level. The reliability of the method was tested by comparing calculated and measured PF values for solar zenith angles ranging from 7 o to 49 o. The mean absolute difference between the calculated and the measured PF for these small to medium structures was 1.4 PF (14%). The proposed method is more likely to be widely used to measure the PF in situ compared to measuring UV in full sun and in the shade with a UV meter because many stakeholders do not have access to UV meters due to the cost or the degree of specialization required to use these meters effectively.
Photochemistry and Photobiology, 2004
To reduce ultraviolet radiation (UVR) exposure during childhood, shade structures are being erected in primary schools to provide areas where children can more safely undertake outdoor activities. This study to evaluate the effectiveness of existing and purpose built shade structures in providing solar UVR protection was carried out on 29 such structures in 10 schools in New Zealand. Measurements of the direct and scattered solar UVR doses within the central region of the shade structures were made during the school lunch break period using UVR-sensitive polysulfone film badges. These measurements indicate that many of the structures had UVR protection factors (PF) of 4-8, which was sufficient to provide protection during the school lunch hour. However, of the 29 structures examined, only six would meet the suggested requirements of UVR PF greater than 15 required to provide all-day protection.
MethodsX, 2019
A standardised procedure for making fair and comparable assessments of the ultraviolet protection of an established tree canopy that takes into account canopy movement and the changing position of the sun is presented for use by government, planning, and environmental health authorities. The technique utilises video image capture and replaces the need for measurement by ultraviolet radiometers for surveying shade quality characteristics of trees growing in public parks, playgrounds and urban settings. The technique improves upon tree shade assessments that may be based upon single measurements of the ultraviolet irradiance observed from a fixed point of view. The presented technique demonstrates how intelligent shade audits can be conducted without the need for specialist equipment, enabling the calculation of the Shade Protection Index (SPI) and Ultraviolet Protection Factor (UPF) for any discreet time interval and over a full calendar year. Tree shade UPF measurements are presented using video capture analysis of moving canopies A standard method for making accurate assessments of tree shade has been developed Tree shade comparisons are made without the need for specialist equipment
Ambient ultraviolet radiation levels in public shade settings
International Journal of Biometeorology, 1999
As people become better informed about the harmful effects of prolonged exposure to solar ultraviolet radiation (UVR, 280-400 nm) they will seek the protection of shade, particularly in tropical locations such as Townsville (19°south). Using broad-band radiation sensors for solar ultraviolet-B (280-315 nm), ultraviolet-A (315-400 nm) and daylight (400-800 nm) radiation, the exposure levels were measured in both the horizontal (shaded and unshaded) and vertical (shaded and unshaded) directions. The measurements were conducted at eight locations (shade settings) in Townsville during the period between December 1997 (summer) and May 1998 (beginning of winter). The quality of protection was assessed by the ratio of unshaded to shaded radiation exposure, the UVB/shade protection ratio (UVB-SPR). The UVB-SPR varies considerably between the different shade settings, with a beach umbrella showing the least protection and dense foliage the highest protection. The roof of a house verandah can provide only little protection if the verandah catches the afternoon sun. Increasing cloud cover decreases the UVB-SPR for all settings because of the increase in the diffuse fraction of the radiation. Only one setting provided a UVB-SPR of 15 or higher, as suggested for protective shading against solar UVB radiation. Shade from direct sunlight alone does not provide enough protection against high levels of solar UVR. Apart from the transmission qualities of the shading material, it is the construction of the whole shade setting that determines the exposure levels underneath. A shade structure with enough overhang is recommended so that high levels of scattered radiation do not reach the skin.
Determination of the Usage of Shade Structures via a Dosimetry Technique
Photochemistry and Photobiology, 2012
A measurement system is described that allows an objective review and evaluation of the amount of use by different population groups of provided shade structures. It employs the comparison of the erythemal UV exposure measured with dosimeters to either the vertex or forehead to that in full sun. The technique has been developed using three shade structures and found to provide a linear relationship with an R 2 of 0.99 between the exposure ratio and the time spent in the shade for the solar zenith angle range of 19-53 o and for both low-and highcloud levels. It provides an objective determination of the amount of shade use by population groups that have set periods of time outdoors.
Comparison of the spectral biologically effective solar ultraviolet in adjacent tree shade and sun
Physics in Medicine and Biology, 1999
The solar spectral UVR irradiances in tree shade and sunlight have been measured in a sub-tropical southern hemisphere summer. The spectral data allowed the UVB and UVA irradiances and the biologically effective irradiances to be calculated for different harmful biological processes to human skin and eyes. The average of the ratio of the UVA to UVB irradiances was lower by 26% in the shade compared with the same ratio in the sun. The spectral shade ratio calculated as the ratio of the spectral biologically effective irradiances in the shade to those in the adjacent sun decreased with increasing wavelength for all of the trees. The decrease in the shade ratio was approximately 42% at 400 nm compared with the shade ratio at 300 nm. Despite the UVR protection provided by tree shade, the erythemal UVR exposure received in 1 h in the tree shade exceeded the occupational limit for UVR exposure.
Effects of tree shade on solar ultraviolet exposures to humans
This paper investigates how much solar UV protection is provided by the shade of Australian trees and the anatomical distribution of personal UV exposures in the shade of these trees. Personal UV exposures in tree shade are of a high enough value to require additional UV reduction strategies. A well planned strategy using a combination of protective methods can minimize the level of exposure to harmful solar UV radiation in tree shade.
Environmental Modification Inside Photoselective Shadehouses
Hortscience, 2013
Shade nets are widely used to protect floricultural crops from excessive radiation, wind, hail, and birds. Although black nets are most frequently used, growers are experimenting with colored, gray, and white dispersive netting to impact vegetative vigor, dwarfing, branching, leaf variegation, and timing of flowering. We monitored environmental data inside replicated shadehouse structures (10 3 10 3 3 m high) with full covering of red, blue, pearl, and black nets (all 50% nominal shading factor) in central Florida over 12 months. Actual photosynthetically active radiation (PAR, mmol • m L2 • s L1) was reduced most by black nets (55% to 60% shading factor depending on the season) and least under red nets (41% to 51%) with blue and pearl nets intermediate. Spectral analysis revealed blue nets had distinctive peaks at the blue (450 to 495 nm) and far-red beyond 750 nm. Red nets had a minor peak ' '400 nm and major transmittance beyond 590 nm. Pearl nets transmitted more light above 400 nm compared with black nets but did not otherwise alter spectral composition in the visible range. No nets had red/far-red (R/FR) ratios (600 to 700/700 to 800 nm) significantly greater than ambient (close to 1), whereas blue nets had a consistently lowest R/FR ratio of ' '0.8. Both ultraviolet-B and ultraviolet-A (280 to 400 nm) were reduced most by pearl nets and least by red nets. We also noted elevated temperatures and wind resistance (but not relative humidity) under colored and pearl nets compared with black, probably as a result of the different net porosities. Our study documents the different environmental modifications inside structures covered with black, colored, and photoneutral translucent nets, which will help predict or interpret specific plant responses.
Assessment of the UVR Protection Provided by Different Tree Species
2007
In recent years, SunSmart campaigns have emphasized the importance of the use of shade as a strategy in the reduction of human exposure to solar UV radiation (UVR), particularly in early life with the provision of shade in schools. Trees can play an important role in shade provision, either as the main shade provider or to augment shade structures and increase UVR protection provided to the general population. A study to measure the protection provided by a range of trees common in Australian urban environments was undertaken during the summers of 2004 ⁄ 2005 and 2005 ⁄ 2006. Solar UVR beneath the trees was measured using UVR sensitive polysulphone badges positioned horizontally within the shaded area and were compared with those in full sunshine to give an indication of the protection provided. Measurements made on sunny days during the months of October to April indicated that the shade cover provided by the trees depended upon the tree species and changed with season as a result of changing foliage and sun angles. Measured protection factors ranged from 5 to 10 and were generally a maximum in the height of summer when the sun was highest in the sky and the foliage was densest.