When you plan to build a greenhouse, the selection of glazing materials is a critical process as it significantly affects the light environment (intensity, quality, and uniformity) as well as the structure type and construction costs. Greenhouse glazing materials have high transmission in photosynthetically active radiation (PAR, 400-700 nm). However, the transmission in UV radiation range (300-400 nm) is largely different for different materials. This article briefly summarizes the effects of glazing on UV radiation available in the greenhouse.
USDA NASS (2020) reported that 75% of US greenhouse acreage was covered by plastic film (single or multiple-layer poly). Glass and rigid plastic-covered greenhouses are only 12 and 15%. However, among US food crop production greenhouses, the percentage of glass-covered greenhouses is 39%, a higher percentage compared to that for all crop types. As Both and Faust (2017) review, glass has various advantages including high and stable transmission in PAR range, and a long lifespan (30 years). However, for various reasons, users are choosing alternative glazing materials that meet their requirements.
Most commercially available glazing materials used for greenhouses are highly transmittable in PAR (photosynthetically active radiation) range (400-700 nm). Because PAR is similar to a human's visible radiation (~380 – ~780 nm), differences in spectral transmission outside of PAR range are difficult to visually notice without having more specific measured information. Sunlight contains radiation with wavelengths starting around 300 nm.
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