LED Light Sources and Their Complex Set-Up for Visually and Biologically Effective Illumination for Ornamental Indoor Plants

Abstract

Ornamental plants are often used in indoor environments as part of biophilic design to improve the health and wellbeing of occupants, and to support sustainable, green architecture. Unfortunately, many plants do not thrive and need to be continuously replaced, which is economically unsustainable. The wavelengths and spectrum ratio of commonly used light sources such as light emitting diode (LED), and the lack of an appropriate light dark cycle (photoperiod), appear to be crucial influencing factors. Therefore, this study focuses on determining the optimal action spectrum of LEDs for visually and biologically effective illumination for plants, and humans as end users. This practice-based research study applies critical analysis of literature, photographic evaluation of the appearance of plants under various LED lighting in the form of a visual assessment questionnaire-based survey, and provides various measurements that record the properties of light including correlated color temperature (CCT), color rendering index (CRI), spectral power distribution (SPD), peak light wavelength (λP), photosynthetic photon flux density (PPFD) and daily light integrals (DLI). Research confirms the LED lighting used for horticultural food production cannot be applied to ornamental indoor plants due to fundamental differences in purpose. Such illumination provides fast growth for market consumption and usually makes plants appear unnatural, whereas ornamental plants in an indoor environment should grow at an appropriate speed which reduces maintenance costs and they should have a natural appearance. These new findings, supported by evidence and data, can help investors, clients, architects, landscape and lighting designers, as well as luminaire manufacturers, make improved, biophilic-sustainable lighting design choices.

Nature-Based Solution for Reducing CO2 Levels in Museum Environments: A Phytoremediation Study for the Leonardo da Vinci’s “Last Supper”

“…Besides acclimation, the potential stomatal sink strength for CO 2 is often limited by the suboptimal growth conditions typically found in indoor environments [36,39,48]. Among these, low light quality and intensities, as well as the lack of an appropriate light-dark cycle (photoperiod), have been recognized as the main sources of limitation for the physiological activity of indoor plants [63]. In our case, light saturation of photosynthesis in L. nobilis occurred at PAR 1000 µmol m −2 s −1 , similarly to what highlighted for other woody species in interiorscapes [31].…”

Lighting for Green Walls

“…In spaces without daylight, well-lit green walls can contribute towards the biophilia hypothesis by making these spaces feel less gloomy. As green walls are generically categorised under ornamental plants, the electric lighting requirements have a dual function: render a natural visual appearance to green walls as well as enable plant-growth at an appropriate biological speed [23][24][25]. While existing literature about the use of electric light on plants has primarily focussed on plant growth for functionalistic food production, plant growth within green walls is best discouraged to reduce constant maintenance such as pruning or trimming to maintain the ornamental form of the walls [20,23].…”

Seven Different Lighting Conditions in Photogrammetric Studies of a 3D Urban Mock-Up

“…The mock-up measurements did not feature the use of black matt fabric to avoid any reflectance around the mock-up, as in the example from [72]. The mock-up was not perfectly isolated against reflections occurring between its surrounding elements.…”