Green facade for energy savings in buildings: The influence of leaf area index and facade orientation on the shadow effect. (1st February 2017)

• Record Type: Journal Article
• Authors: Pérez, Gabriel; Coma, Julià; Sol, Salvador; Cabeza, Luisa F.
• Is Part Of: Applied energy. Volume 187(2017)
• Page Start: 424
• Page End: 437
• Publication Date: 2017-02-01
• Subjects: Vertical greenery systems (VGS) -- Green facades -- Energy savings -- Buildings -- Leaf area index (LAI) -- Shadow effect; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2016.11.055
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Leaf area index to measure the shadow potential of a green façade. Indirect method to measure LAI is suitable for green facades. GF provide comparable shadow factor for all orientations than artificial barriers. For a LAI of 3.5–4, 34% of energy savings was measured. Energy savings provided by GF are wall orientation dependent. Abstract: To "green" building envelopes is currently one of the most promising ways to provide energy savings in buildings and to contribute to the urban heat island effect mitigation. The shadow effect supplied by plants is the most significant parameter for this purpose. One way to characterize the potential shadow effect of greenery is to calculate the facade foliar density by means of the leaf area index (LAI). As LAI is commonly used in horizontal crops, their use in vertical greenery systems (VGS) has generated dispersion and uncertainty in previous studies both in terms of methodologies and results obtained. In addition, a lack of data relating to the influence of the facade orientation in the final contribution of vertical greenery to the energy savings has been observed in previous studies. This study aims at establishing a common and easy way to measure LAI and to lick it to the energy savings provided by VGS. Moreover, the energy savings achieved as well as the influence of facade orientation on the final thermal behaviour of two different VGS, a double-skin green facade and a green wall, was studied. From the results, it can be stated that the most simple and quick procedure to measure LAI in order to characterize the foliar density of VGS is the indirect method based on the amount of light transmitted through the green screen. From the experimental tests interesting energy savings were obtained (up to 34% for Boston Ivy pant specie with a LAI of 3.5–4, during summer period under Mediterranean continental climate). Moreover, the dependence on facade orientation was confirmed with representative contribution over the whole energy savings from East and West orientation.