Evaluation of a Residential Green Roof System for Stormwater Runoff Retention

While much green roof research has been directed towards commercial and industrial buildings,
less is known about the sloped roofs of residential buildings. The purpose of this study was to
evaluate a pitched residential green roof system and determine its ability to retain stormwater
runoff. In order to do this, 18 shingled roof models were constructed on three slope angles – 1°,
20° (5/12 pitch), and 40° (10/12 pitch) of which 9 were randomly fitted with a modular green
roof system across three replications. The 42.1% mean stormwater runoff retention for the green
roof systems of was significantly greater than the 18.3% for shingled roof decks. A residential
product (Steep Paks®) performed within the conventional range of previous stormwater retention
studies. The residential green roofs effectively reduced stormwater runoff during periods of light
precipitation compared to periods of heavy precipitation. No difference was found in percent
stormwater runoff retention between the three residential green roof slope angles.

Bench-Study of Green-Wall Plants for Indoor Air Pollution Reduction

Potted-plants have the potential for improving indoor air quality (IAQ), however there has been little research on the performance of green-walls as indoor biofilters. The aim of this investigation was to compare rates of air pollutant reduction with two commonly used indoor species, and to assess the effects of added substrate airflows on the capacity of green-wall modules to remove two prevalent indoor airborne contaminants - particulate matter (PM), and volatile organic compounds (VOCs), using benzene as model. The species tested were Chlorophytum comosum (Spider Plant) and Epipremnum aureum (Pothos). The results showed that each species could significantly reduce increasing doses of PM, with or without augmented substrate airflow, however benzene removal rates decreased with increasing aeration. The findings provide a first assessment of the ability of green-wall plants to reduce indoor air pollution, and responses to two types of pollutant, particulate and gaseous.

Photovoltaic Array Influences the Growth of Green Roof Plants

A multi-faceted research project was conducted on a modular green roof in semi-arid, high elevation Denver, Colorado U.S.A. A photovoltaic (PV) array ran along the southeastern edge of the research area and visibly influenced the plant growth, cover and biomass. Plants grown near the PV prospered compared to plants in the exposed area. Average summer temperatures in the modules under the PV array were cooler with less temperature variation compared to the modules located in the exposed areas of the green roof. Shading structures integrated on green roofs may produce effects that resemble natural ecotones tending towards greater plant coverage and biomass, and therefore greater green roof resilience.

Catalyzing Design-Science Feedback Loop in Green Roof Optimization for Hot Climates

Synthetic ecosystems such as rain gardens, green roofs, engineered wetlands and urban meadows are becoming increasingly popular for their intrinsic environmental and ecological benefits as well as for their aesthetic value. But, as in many emerging technologies, communication between the academic institutions generating basic and applied science and the design disciplines is not as efficient as it could be, and strengthening this link will improve the performance of these systems. The case study serves to illustrate the process of linking research, design and implementation. Scientific research, performed by the authors and found in the literature, is used to inform design, and design challenges are used to suggest avenues of research. The research itself is briefly outlined where appropriate, but the focus of this paper is the process of linking science and design in a feedback loop.

Deploying Shipping Containers for Innovative Living Architecture Design Education

Academic training and investigation for innovative living architecture demands educational
settings be conceptual, experiential, and cost effective. To assist, we advance the idea that
shipping containers offer an acceptable setting for faculty and students investigating kinetic
forms of living architecture and opportunities for reflective thinking. Described here are three
separate, uncoordinated academic engagements exploring moving, sliding and mobile green
roofs and walls on shipping containers that occured in the design studio, field laboratory, and
public setting. When collectively viewed, the outcomes of the projects indicate a positive use of
shipping containers as conceptual and participatory spaces for living architecture education and

Deploying Living Walls as Kinetic Facades

This paper explores ideas for integrating moveable exterior living walls with the facades of
high-rise buildings to enhance urban ecosystems while contributing opportunities for personal
interaction with the natural world. Rethinking the typical static nature of living walls, kinetic
green walls convey a dynamic aesthetic that provides multiple potential benefits including
habitat, passive cooling and opportunity for personal expressions in dense urban
environments. This article proposes prototypes of kinetic green walls and suggests their
expanded application to the ultra-urban built environment. It offers a preliminary typology,
presents a moveable green wall system prototype installed in an urban university setting in
Seattle, and demonstrates how the kinetic qualities afford flexible operational, educational,
and aesthetic functions. Reflecting upon the challenges and solutions for the built project, this
article identifies essential considerations for designing and constructing moveable living
walls, illustrated through photographs, construction details and diagrams of new kinetic
living wall applications.

Life Cycle Cost Analysis of Extensive Green Roofs in Switzerland and the Netherlands

Extensive green roofs in Switzerland and the Netherlands are economically sustainable when considering the added energy savings, municipal incentives and storm water fee reductions. By combing surveys, interviews, and reviews of municipal regulations for fifteen projects the Life Cycle Cost (LCC) was calculated by discounting green roof cash flows over a 50 year time period to determine a Net Present Value (NPV). This research finds that an extensive green roof NPV in Switzerland costs 27% - 37% less than a conventional flat roof. Similarly in the Netherlands, the NPV of green roofs is determined to be 16% - 26% less than a conventional flat roof. Presented here is summary of the results and the explanation of local influences of municipal incentives.

Kelp Extract (Ascophyllumnodosum) Can Improve Health and Drought Tolerance of Green Roof Plants

The soil additive Ascophyllumnodosum (Norwegian kelp) can increase drought tolerance of plants, and promote seed germination, yet there has been no published research testing this amendment on green roofs. Liquid A. nodosum extract in two volumes and a slow release fertilizer were tested in a pot culture experiment for annuals, perennial cultivars, and three native species. Kelp extract did not improve the germination percentage of any of these species. In drought conditions both on a green roof and in the greenhouse, kelp treatments increased plant biomass relative to controls for some species only; plant health and longevity weregenerally improved when kelp was applied as an amendment. Soil water content was higher in kelp treated pots compared to fertilizer treated pots, and higher than controls in kelp treated pots for some species. Application of this local renewable resource to green roof plants could help to improve plant and substrate health while improving drought tolerance of plants on green roofs.

Controlling Ivy Attachment to Wall Surfaces by Applying Paints, Metal Meshes and Sheets

Growing ivy around buildings has benefits. However, ivy potentially damages buildings which limit its use. Options for preventing ivy attachment were investigated to provide ivy management alternatives. Indoor and outdoor experiments were conducted, where metals (Cu, Zn) and anti-graffiti paints were applied to model wall panels. Metal treatments, in both indoor and outdoor experiments, fully prevented ivy attachment. For Hedera helix, silane-based antigraffiti paint prevented attachment in the laboratory and required under half the peak detachment force necessary to detach the control in the outdoor experiment. In conclusion, metals and silane-based paint are management possibilities for ivy attachment around buildings.

Green Roof Plant Trials for the Central Great Plains

Forty-three taxa representing native and adaptable plants were trialed for 4 years on an irrigated
(as needed) 15 cm (6 inch) deep extensive green roof in Lincoln, NE. Twenty-three of the taxa
showed good performance with minimal maintenance. At the end of the trial in fall 2014, 32 of
the taxa still had at least one specimen surviving. Drought impacts in the trial’s second year
eliminated several taxa. Presented here are results and the positive findings of four new extensive
green roof taxa, Festuca cinerea, Carex glauca, Eragrostis trichodes, and Distichilis spicata

Observation of Biodiversity on Minimally Managed Green Roofs in a Tropical City

While much of the land in Singapore has been urbanized, green roofs have the potential to be part of an urban ecosystem where limited human interference can promote natural processes. This study observes the establishment of flora and fauna communities on two newly installed green roofs using a mix of seeding, transplantation and spontaneous colonization installation methods and operating under minimal management over a period of 16 months. Recorded here are plant compositions and spatial distributions of flora growth of 64 species over this period. The minimally managed green roofs in this study possess increased plant species richness, highlighting a way to enhance urban diversity in a tropical city.

Insect Communities On Green Roofs that are Close in Proximity but Vary in Age and Plant Coverage

The effects of roof age and plant coverage on insect communities were investigated between three green roofs located on the campus of Southern Illinois University Edwardsville. Insect collections were made using pitfall traps on green roofs that were established between 0.5 month and five years prior to insect collection. The green roof with the greatest insect collection rate was the oldest but intermediate in size and percent plant coverage. The oldest green roof had similar collection rates as a nearby ground-level rain garden; however measures of species diversity and evenness were greater in the rain garden.

Substrate Loss is Minimal in Vegetated and Un-vegetated Extensive Roof Modules Over a 14-Month Period

The presence of vegetation is thought to reduce loss of soil substrate after roof installation; however, few attempts have been made to quantify this effect. Twelve green roof modules placed at a 2% slope were used to quantify the effect of wind, precipitation intensity, vegetation and vegetation type on modular green roof substrate depth. The presence of vegetation reduced substrate loss immediately after installation of equipment, yet had little effect on substrate depth once the substrate had settled. Neither wind speed nor precipitation rate had a direct effect on substrate depth, although after some large rainfall events substrate depth increased due to media expansion caused by the retained water. Overall we observed negligible substrate depth decrease, regardless of vegetation presence, wind speed or precipitation intensity.

Native Forbs Produce High Quality Seeds on Chicago Green Roofs

Although a paucity of bees on Chicago green roofs suggests some plants may experience reduced pollination and thus poor seed production, a previous investigation revealed high seed set in green roof plants. However, high quantity of seeds does not always imply high quality. In this study, we compared seed germination between green roof and ground-level locations. We hypothesized that forb seeds from green roofs would have lower germination due to differences in maternal provisioning and environmental stressors. We found that green roof seeds did not have lower germination; this supports the continued use of native forbs on green roofs.

Vegetation Characteristics of Green Facades, Green Cloaks and Naturally Colonized Walls of Wooden Barns Located in the Mid-Atlantic Region of North America

We quantified the amount and diversity of vegetation on ten green facades and compared it to nine naturally colonized wooden barns located in the humid temperate climate of eastern North America. The leaf area index (3.3 m 2 -vegetation/m2 -wall) and canopy thickness (61 cm) of the green facades was nearly identical to that of the barns (3.1 and 69 cm), indicating that green facades mimic nature’s architecture. Predicting the biomass of façades from models developed for the barns’ canopies, indicated they should range from 1000 to 1400 g/m2 (5600 to 8000 g/m2 , fresh weight) but could be as much as 2900 g/m2 (21,000 g/m2 fw). The façades included a total of 14 vine species while the barns included 8. There was an average and maximum of 3.2 and 6 species on the facades and 2.3 and 4 on the barns. The biodiversity of the cultivated system closely mirrors the colonized system, suggesting that an optimum biodiversity may exist for vertical, vine based living architectures.

Observations on the Survival of 112 Plant Taxa on a Green Roof in a Semi-Arid Climate

The Denver Botanic Gardens (DBG) green roof, built in November 2007, is the first green roof on a city owned building in Denver, Colorado. To date, 112 plant taxa have been trialed, observed, and described on this low water green roof in the high and dry climate of the Colorado Front Range. Plant taxa survival was documented based on the original number of plants installed, and the surviving plants were rated on a scale of 1-4. Additionally, in 2011-2013, plant heights and widths were recorded. The data indicate that taxa can be grouped into categories of perish, survive, and thrive.

Aesthetics for Green Roofs and Green Walls

Do green roofs and green walls have aesthetic benefits? Most green roof proponents would say so. But what are they and how do they relate to green roof design in terms of species selection, planting arrangement, viewable context, access, maintenance and other factors? Aesthetics according to the Green Roof Design 101 Manual 2nd Ed (GRHC 2006) provides “pleasure- and psycho-physiologically-oriented benefits” but, this narrow understanding suggests that the aesthetic potential of green roofs is limited to what one might experience looking upon any garden. We suggest other ways that need exploring to make aesthetics more relevant and understandable to the practice of wall and roof greening.

We suggest other ways that need exploring to make aesthetics more relevant and understandable to the practice of wall and roof greening.

Living Architecture and Biological Dispersal

Many vegetative roof systems deliver biodiversity and conservation goals, but it may be less appreciated that roofs function as a nursery, exporting biological materials. Interestingly, we have observed one green roof performing two forms of plant dispersal, thus demonstrating the potential for vegetative roofs to offer nursery services to their surroundings. We describe the project, explain the dispersal strategies, provide a brief discussion, and define the terminology of terrestrial-roof link, agent dispersal, and self dispersal, in an effort to aid in understanding the nursery function of green roofs. Continuing and future research on the dispersal mechanisms of the roof are also briefly discussed.

Development and Features of the Green Roof Energy Calculator (GREC)

A data base-driven web tool has been developed from detailed energy modeling simulations to enable green roof practitioners to explore the energy, water, and urban climate implications of design decisions. Provided with basic characteristics of a green roof project, the Green Roof Energy Calculator performs a multi-layered interpolation within a database of 8000 simulations to estimate whole building energy use, storm water runoff, and sensible and latent heat exchange with the urban atmosphere. Output from each user query produces information for the specified green roof system, but also includes information for alternatives of both white and dark membrane roofs.

Seeding Green Roofs with Native Grasses

During six years of native grass establishment and growth on four green roofs, we sought to understand appropriate seeding seasons and spacing, the amount of time to reach the industry 80% coverage threshold (FLL 2008), the seed yield projections for volunteer plant infill. We also produced and tested methods for successfully and inexpensively seeding and determined “as needed” irrigation protocols. The suite of techniques examined improves and enhances the use, establishment, and management of native grasses on green roofs and reduces green roof costs.