Do Looks Matter? A Case Study on Extensive Green Roofs Using Discrete Choice Experiments

Jan Vanstockem,Martin Hermy,Liesbet Vranken,Brent Bleys,Ben Somers

doi:10.3390/su10020309

Abstract

Extensive green roofs are a promising type of urban green that can play an important role in climate proofing and ultimately in the sustainability of our cities. Despite their increasingly widespread application and the growing scientific interest in extensive green roofs, their aesthetics have received limited scientific attention. Furthermore, several functional issues occur, as weedy species can colonize the roof, and extreme roof conditions can lead to gaps in the vegetation. Apart from altering the function of a green roof, we also expect these issues to influence the perception of extensive green roofs, possibly affecting their acceptance and application. We therefore assessed the preferences of a self-selected convenience sample of 155 Flemish respondents for visual aspects using a discrete choice experiment. This approach, combined with current knowledge on the psychological aspects of green roof visuals, allowed us to quantify extensive green roof preferences. Our results indicate that vegetation gaps and weedy species, together with a diverse vegetation have a considerable impact on green roof perception. Gaps were the single most important attribute, indicated by a relative importance of ca. 53%, with cost coming in at a close second at ca. 46%. Overall, this study explores the applicability of a stated preference technique to assess an often overlooked aspect of extensive green roofs. It thereby provides a foundation for further research aimed at generating practical recommendations for green roof construction and maintenance.

Highlights

Extensive green roofs are a promising type of urban green that can play a substantial role in the sustainability policy of cities [1]
As discrete choice experiments (DCEs) build upon the random utility maximization (RUM) framework [43], this function consists of deterministic (Vij) and stochastic components, which make up the utility (Uij) for a respondent j for alternative i
As the main goal of this study was to investigate the importance of visual aspects for extensive green roof perception, most attributes were directly linked to these characteristics

Summary

Introduction

Extensive green roofs are a promising type of urban green that can play a substantial role in the sustainability policy of cities [1] They typically consist of multiple layers, are deliberately vegetated, usually do not interfere with other urban land uses, and are easy to construct on both existing and new buildings with roof inclinations ranging from 1 to ca. For instance, play an important role in storm-water management [6], while noise pollution [7], the urban heat island effect [8,9], and the cooling needs of buildings [10,11] are reduced (see [12]).

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