Attitudes and aesthetic reactions toward green roofs in the Northeastern United States

Highlights

• Overall attitudes and aesthetic reactions to green roofs are positive.

• More negative aesthetic reactions are associated with a sense of messiness.

• Stoloniferous grass dominated green roofs are less well appreciated aesthetically than sedum or mixed perennial dominated green roofs.

• Attitudes and aesthetic reactions to green roofs are positively correlated with one another.

Abstract

Green roofs may provide environmental, aesthetic, and social benefits. Their environmental benefits have been the subject of considerable research in the past decade; the aesthetic and social aspects, however, have received less attention. Some authors have questioned the visual appeal of some green roof designs. Nonetheless, little research has examined aesthetic reactions toward green roofs or attitudes concerning them. We conducted visitor surveys at seven green roofs in the Northeastern US to assess visitors’ aesthetic reactions to different types of green roofs, determine general attitudes toward green roofs, and assess values concerning benefits and costs associated with them. Attitudes toward green roofs were positive with higher importance being placed on green roof benefits than costs. Aesthetic reactions were, in general, positive. Aesthetic reactions to roofs dominated by stoloniferous grasses were more negative than to either sedum-dominated or mixed perennial roofs. Principle component analysis showed that negative aesthetic reactions were associated primarily with a perception of messiness. Furthermore, respondents felt that the grass-dominated roofs blended less well with the building and surrounding landscape. Aesthetic reactions were positively correlated with attitudes and importance placed on the benefits of green roofs. Positive visitor reactions to sedum-dominated extensive roofs is a favorable result for the green roof industry as these are the most common type of green roof and this suggests that there is high promotion potential if more of these roofs are designed to be visible from street level.

Introduction

Understanding public reactions to green roofs and other relatively new building practices is important to the building design process. Along with a sober assessment of the benefits that green roofs provide, understanding public perspectives will aid in making the most appropriate design choices for a given project. While green roofs are only one of many sustainable building options, they may have a particularly profound visual impact. Understanding aesthetic reactions to green roofs, then, is essential to their use in building designs.

The green roof industry in the United States has grown steadily in recent years despite the general economic recession. During 2010 alone, there was a 28.5% increase in the construction of green roofs (Green Roofs for Healthy Cities, 2011). However, green roofs have yet to become a part of mainstream architecture and construction in the United States as they have in parts of Europe. While not the only limiting factor, green roofs need to be visible and understood in order to become widespread (Rogers, 2003). Green roofs have the potential to be highly visible but most are not. Intensive roofs, with deep media profiles and diverse plantings that often include shrubs and trees, have been integrated into some high profile buildings, such as the Rockefeller Center in NYC and Chicago's City Hall. Intensive roofs are, however, cost prohibitive to many organizations. Extensive roofs, with shallow media profiles and typically planted with succulents, are far more cost effective, but rarely accessible or visible from street level. Some authors further recognize semi-intensive roofs. These have media depths between that of intensive and extensive roofs or a mix of shallow and deeper areas. Semi-intensive roofs are less common though they may strike a balance between cost and planting options in some situations. Public aesthetic reactions to extensive and semi-intensive roofs are of particular interest as these roofs are more cost effective, widely replicable, and, if made visible, could have a high promotional value for the green roof industry.

Little research exists that is focused on public perceptions or aesthetic reactions specifically related to green roofs. Smith and Boyer (2007) point out the need for this type of research. Dunnett (2004) found that some survey respondents in the UK thought green roofs were visually too radical a departure for the residential landscape. In contrast, White and Gatersleben (2011) found that participants in an online, photograph-based survey preferred some types of vegetated residential buildings to non-vegetated ones. In the US, Kuper (2009) surveyed 100 students on the Temple University, Ambler campus in suburban Philadelphia and found they had little familiarity with green roofs and were mostly neutral about having a green roof in their neighborhood. A majority, however, did find green roofs attractive and believed that green roofs had environmental benefits.

For larger buildings, the research has focused on intensive roofs. In Singapore, Yuen and Wong (2005) addressed elements of public perceptions toward intensive green roofs on high-rise apartment buildings. They found that while awareness of the roof gardens was high (90%), and many people were willing to use them (84%), few actually did (17.7%). Of the same respondents, 40–65% had visited conventional, ground level parks. Access and visibility were cited as the main reasons for the higher visitation rates at parks compared to rooftop gardens. Most respondents (80%) said that they would like more roof gardens in their neighborhood. Their primary reasons for this included: leisure, beautification, access to greenery and nature, and better utilization of space. Loder (2011) conducted interviews with office workers in Chicago and Toronto and found that all participants preferred a green roof to tar or gravel roofs, but that participants were divided on whether they like the aesthetics of the mostly prairie-like green roofs. In addition, Loder (2011) found that visual access to green roofs had a positive influence on concentration but only physical access to the roof positively influenced the self-perception of health. Lee and Koshimitz (2006) found that the distance from a green roof influenced viewer perceptions.

Many gaps remain in our understanding of public attitudes and aesthetic reactions to green roofs. Public aesthetic reactions have been both positive and negative in different circumstances. When aesthetic reactions to various green roof designs or vegetation types were compared, this was accomplished through photographic surveys, with graphical representations of different types of vegetation superimposed on them, the validity of which has been both supported (Shafer & Richards, 1974) and questioned (Palmer, 2001). Attitudes toward green roofs have been neutral to positive with little indication of what might cause this discrepancy or how attitudes may differ among demographic groups. Both designers and clients would benefit from this information. This research addresses these gaps in our knowledge by assessing basic attitudes and aesthetic reactions to green roofs at gardens and universities in the Northeastern United States. Specifically our objectives were to: (1) determine visitors aesthetic reactions to publicly visible extensive and semi-intensive green roofs and whether these roofs are perceived as fitting in with the building and landscape; (2) determine whether some roof vegetation types are aesthetically preferred over others; (3) gauge visitors attitudes and values related to green roofs; (4) determine if a relationship exists between visitors aesthetic reactions and their attitudes or values; (5) determine whether attitudes, values, or aesthetic reactions to green roofs differ between demographic groups; (6) determine if public garden visitors differ from university visitors in their attitudes and/or aesthetic reactions to green roofs; and (7) determine whether people's attitudes or aesthetic reactions to green roofs change with increased knowledge or exposure to them.