Green Façade/Roofs Design Tool: Cloud-based Simulation Tool for Evaluating Lighting Condition for Plants in Dense Urban Areas

Ganji, Abolfazl; Kasravi, Morteza

Green Façade/Roofs Design Tool

Cloud-based Simulation Tool for Evaluating Lighting Condition for Plants in Dense Urban Areas

Paper by Abolfazl Ganji Kheybari · Morteza Kasravi

Presented on October 12, 2022 at Facade Tectonics 2022 World Congress

Overview

Abstract

Climate change and related thermal issues, draw attention to the impact of green facades and roofs on energy savings and thermal comfort. Besides, by putting facades and rooftops to use, local food production, enhancing the biodiversity, and improving urban life standards can be achieved. On the other hand, selection of the plants is crucial and the minimum requirements for growth of plants need to be evaluated considering the microclimate conditions. Providing a tool for predicting the environmental parameter for the green surfaces is the main aim of the authors.

Light is the fundamental parameter in plant growth which is normally expressed by photosynthetically active radiation (PAR) (400–700 nm) and daily light integral (DLI). PAR changes seasonally and varies depending on the latitude and time of day. This requires a climate based daylight simulation to consider different sky conditions, surface orientation, and material of the surrounding buildings. However, most available daylighting tools and metrics are developed for humans and need to be tailored deeply to be used for plants. In addition, lighting requirements for every desired plant species should be available for the decision making process.

This paper introduces a cloud-based tool which includes both parts: a climate-based daylight simulation tool and a database of plants requirements. This tool informs designers in the early stage of design about the right place for a desired plant type, or the right cultivar for a desired place. Besides, it estimates the cost of additional electrical energy required for supplemental lighting?

This paper also introduces new annual lighting metrics for plants such as daily light integral autonomy (DLIa) and spatial daily light integral autonomy (sDLIa). DLIa describes the percentage of the year when natural light is in the optimal range of DLI for a desired plant. Finally, three different case studies in New York, Frankfurt, and Tehran will be studied to explain the whole process of decision making for green facades and roofs in a dense urban context.

Authors

Abolfazl Ganji Kheybari

Researcher and Building Physics Expert

fazel.ganji@gmail.com

Morteza Kasravi

Computer Scientist

kasravi@gmail.com

Keywords

urban habitat and the building facade, daylighting-glare-shading, energy efficiency, high performance, performance-based design

Introduction

Climate change and related thermal issues, draw attention to the impact of green facades and roofs. In particular, urban surfaces are involved in three key elements, energy, water, and food. Several strategies have been introduced to tackle the issues and mitigate the effects of climatic change.

Among all green solutions in the urban environment “green building elements” are the main focus of architects who apply solutions on the building envelope both Horizontal greening systems (HGS) and Vertical greenery systems (VGS) and balcony gardens [1].

Urban horticulture (aka urban farming) term includes several approaches “to produce more food on less land”. Many of the urban farming techniques rely on fully closed and conditioned environments which are energy-intensive and increase carbon emissions [2]. Building-integrated agriculture (BIA) is one of the solutions which can contribute to urban horticulture as rooftop or vertical farming, edible walls, or balcony gardens [1].

In addition to local food production, making facades and rooftops green enhances the biodiversity, and improves urban life standards in densely populated city districts. Recent studies suggested a holistic perspective that accounts for impacts on both food production and energy consumption by using rooftops, back yards, and balconies for growing vegetables [2].

The urban green infrastructure has a reduction potential on both indoor and outdoor heat hazard. The cooling effect of vertical greenery on building surfaces due to shading, transpiration, and insulation helps to mitigate the urban heat island effect and thermal discomfort outdoors and indoors. VGS reduces exterior and interior wall temperatures by up to 17 K and 2.9 K, respectively [3]. The green surfaces also reduce energy consumption for cooling range from 2 to 16 kWh/m² depending on the construction and the climate conditions [3].

In another study conducted for tropical climates, the impact of three types of green façade were measured on thermal comfort. Effective temperature from green façade with different leaves coverage area were recorded 1.9 to 9.9 K less than bare wall. The results also revealed that the building with green façade had less risk of high temperatures and never exceeded 26°C [4].

Moreover, rooftops can also supply clean electricity, and can be used to collect rainwater. By considering proper systems, the gained electricity and water can be used to provide the growing conditions for vegetation and making it a self-sufficient solution for working year round.

Having said all the benefits, designing green surfaces normally does not go beyond the conceptual sketches and beautiful renderings on the design proposals. Previous studies on the potential benefits of adopting biophilic design (BD) highlighted the lack of a tool to support designers through a clear design framework toward environmentally sustainable design (ESD) [5].

At the first place, minimum requirements for the growth of the selected plants need to be evaluated under the microclimate conditions. Each green surface should be assessed for the amount of radiation, temperature, and their impact on the selected type of vegetation on very early stage of the design. Questions such as "whether the selected plant is able to survive maximum temperature in summer, minimum temperature and short days in winter?" or "what would be the consequences of a green design solution in terms of energy and water to keep this green walls living?" are important and must be answered. If a tool provides such information, biophilic designer can go through different alternatives and find the more suitable and sustainable solutions. Providing such a tool for predicting the environmental parameter for the green surfaces (including PAR radiation) is the main aim of the authors.

Methodology

For this study we selected a hypothetical dense urban district and used this 3D model for evaluating the potential of both horizontal greening systems (HGS) and vertical greenery systems (VGS)