Roof Size Research Articles

Green roof and ground-level invertebrate communities are similar and are driven by building height and landscape context

Abstract Green roofs are increasingly promoted for urban biodiversity conservation, but the value of these novel habitats is uncertain. We aimed to test two hypotheses: (i) green roofs can support comparable invertebrate family and order richness, composition and abundances to ground-level habitats and (ii) green roofs planted with native species from local habitats will support a richer invertebrate community at family and order level than other green roofs. We sampled the invertebrate community on green roofs dominated by native grassland or introduced succulent species in Melbourne, Australia, and compared these to the invertebrate community in ground-level sites close by, and sites with similar vegetation types. The only significant differences between the invertebrate communities sampled on green roofs and ground-level habitats were total abundance and fly family richness, which were higher in ground-level habitats. Second hypothesis was not supported as invertebrate communities on green roofs supporting a local vegetation community and those planted with introduced Sedum and other succulents were not detectably different at family level. The per cent cover of green space surrounding each site was consistently important in predicting the richness and abundance of the invertebrate families we focussed on, while roof height, site age and size were influential for some taxa. Our results suggest that invertebrate communities of green roofs in Melbourne are driven largely by their surrounding environment and consequently the effectiveness of green roofs as invertebrate habitat is highly dependent on location and their horizontal and vertical connection to other habitats.

Rainwater harvesting in Jordan: potential water saving, optimal tank sizing and economic analysis

ABSTRACT This paper presents an integrated approach regarding rainwater harvesting that includes investigating potential water savings, optimal tank sizing and cost-benefit analysis at different rainfall zones in Jordan. It is found that a maximum of 30.5 × 106 m3/year of rainwater can be collected from the roofs of residential buildings which is approximately 8% of the total supply for the year 2015. In addition, water harvesting yields and optimal tank size are calculated for any roof area in different rainfall zones in Jordan. Benefit-cost analyses results revealed that pear shape tanks will be economically feasible in all rainfall zones when a 1 $US/m3 is assigned as a cost of water saving. Concrete tanks will not be economically feasible at this cost. Payback period analysis indicates that the costs associated with the installation of rainwater harvesting systems could be equalized within 5–45 years depending on the rainfall condition, roof size, price of water savings and tank type.

Effects of climate change on water savings and water security from rainwater harvesting systems

Climate change presents major uncertainties in future safe water access especially in rural communities that are already faced with water insecurity. For Uganda, rainwater harvesting has become a major adaptation strategy to ensure the attainment of safe water access for all. However, climate change effects on rainwater harvesting potential remains largely unexplored. Therefore, this paper assesses climate change effects on water savings and water security from rainwater harvesting systems for Kabarole district, Uganda. The top performing Global circulation models (GCMs), used in this study included; MIROC5, BCC-CSM-1-M, CNRM-CM5, ACCESS1-0, HADGEM2-ES and HADGEM2-CC using projections for 2025–2055 (2040s) and 2060–2090 (2070s) periods. Seasonal analysis used the 4 seasons for Uganda, namely; the 2 dry seasons of December, January, February (DJF) and June, July, August (JJA) and the 2 rainy seasons of September, October, November (SON) and March, April, May (MAM). Although there are conflicting model predictions, generally, the models agree that water savings and security will reduce in DJF and MAM and increase in JJA and SON seasons. MAM rain season will be most affected with water savings and security projected to reduce by more than 50% in the 2070s period. Therefore, households should harness the increased water savings in JJA and SON to cater for the predicted reduction in water savings in MAM and DJF seasons especially for the 2070s period. A larger tank of 5 m3 along with at least 50 m2 roof size combined with a low cost household water treatment is thus recommended.

New insights on span selection for Chinese solar greenhouses using CFD analyses

Chinese solar greenhouses (CSG), with thin plastic films on the south roof for transmitting the sun’s rays during the daytime and a heavy cover at night over the south roof with large thermal masses in the wall, north roof and soil to retain heat, can be used to produce vegetables and flowers year round without auxiliary heating during the winter. CSG spans can be increased to increase the production area; however, although the effect of increasing the span on the inside climate has been investigated experimentally, there is still no good guidance on selecting a suitable span configuration for growers. This investigation analyzed three groups of span configurations with spans of 10m, 12m and 14m. The first set of designs had all the other dimensions varied in proportion to the span width. The second set had the same dimensions for the north roof and north wall with the other dimensions varied to fit the longer spans. The third set had the same south roof with a longer north roof to fit the longer span. The analyses were based on a 12m span CSG simulation model validated in a former study with the thermal environments predicted using computational fluid dynamics (CFD) analyses. The results show that, for the CSG with all the dimensions varied in the same proportion, the inside air temperature is highest with the 14m span and lowest with the 10m span. For CSG with the same north roof and north wall dimensions, the air temperature is the highest with the 12m span and lowest with the 14 m span. For the configurations using the same south roof size, the 10m span with the taller north wall has similar air temperatures as the 12m span, with temperatures inside both spans being higher than the other 10m span with the shorter north wall height. Analyses of the solar heat gains, heat losses and temperature distributions for each group give good guidance for span selections for the growers.

An approach to quantifying rainwater harvesting potential using imagery, geographic information systems (GIS) and LiDAR data

Abstract Geographic Information Systems (GIS) software is used to analyze rainwater harvesting potential in Escambia County, Florida, USA. The approach presented can be replicated using LiDAR data, and the infrared spectrum of National Agriculture Imagery Program (NAIP) imagery. GIS surface maps are analyzed in combination with local utility consumption data to determine potential reductions in potable water consumption for households. The results indicate an extensive urban catchment of rooftop surfaces, and commensurate potential for rainwater harvesting and stormwater attenuation. Sixty two percent of the households analyzed consumed less water than could be potentially harvested. The remaining 38% consumed more water than could be potentially harvested. There are noted and significant differences between the two sample populations, including differences in water consumed and roof size. A comparison of lot size between the two sample populations did not yield any significant difference. The conclusions indicate that the widespread implementation of rainwater harvesting could substantially reduce potable water use in urban areas, and are of use to policy makers, planners, engineers and property owners everywhere.

ACCURATE AND FAST BUILDING DETECTION USING BINARY BAG-OF-FEATURES

Abstract. This paper presents a non-interactive building detection approach employing binary bag-of-features (BBOF), namely, extracting building roof contours in remote sensing images automatically, rapidly and accurately. The proposed method includes two major stages, i.e., building area detection and building contours extraction. In the first stage, it contains three modules. i.e., oversegmentation, intersection point classification, building area detection. Firstly, the orthophoto is over-segmented by the Simple Linear Iterative Clustering (SLIC) superpixel segmentation method, and the intersection points is obtained. Secondly, the oriented FAST and rotated BRIEF (ORB) descriptors are generated in LAB colour space from the patches that centred on the intersection points, and the BBOF classifier is adopted to classify the intersection points into two categories. Thirdly, the area that contains of the building roof are detected through reserving the regions around the intersection points in inner parts of building roof, and eliminating the regions around the intersection points in non-building roof. At last, we can roughly generate the building area. For the second stage, it is similar to the first one while the main difference is that its classifier has three categories. Finally, we provide an evaluation between two different classifiers, including ORB+BBOF and SURF+BOF. This evaluation is conducted on orthophotos with different roof colours, texture, shape, size and orientation. The proposed approach presents several advantages in terms of scalability, suitability and simplicity with respect to the existing methods.

A GIS-based mapping methodology of urban green roof ecosystem services applied to a Central European city

Green roofs provide a number of different urban ecosystem services (UESS), e.g. regulation of microclimate, support of air quality improvement, or stormwater retention. To estimate the spatial variation of green roof UESS across an urban area, a GIS-based mapping and spatial analysis methodology was established and applied to the city of Braunschweig, Germany. Based on the analysis of available geodata, in a first step, a quantity of 14,138 rooftops in the study area (14% of all buildings) was found to be generally suitable for greening. This resulted in a green roof area of 3km2. Based on criteria such as roof slope and minimum roof size, nearly two-thirds of these buildings (8596 buildings, 8.6% of total number of buildings) were categorised ‘appropriate’ for greening and subject to green roof UESS analysis.The spatial distribution of green roof UESS was estimated based on the categories thermal urban climate, air quality, stormwater retention and biodiversity. Due to their potential benefits in the four UESS categories an overall assessment resulted in a number of 867 roofs (0.9% of total number of buildings) categorised as ‘high benefit’ from rooftop greening. Another 3550 buildings (3.5%) and 4179 buildings (4.2%) were defined as ‘moderate benefit’ and ‘low benefit’, respectively. The inner city area of Braunschweig appears as a hot-spot of green roof UESS, i.e. higher percentage of ‘high benefit’ green roofs in comparison to residential areas. The proposed method is a simple but straightforward approach to analyse urban green roof UESS and their spatial distribution across a city but it is sensitive to the quality of the available input geodata.

Horizontal and vertical island biogeography of arthropods on green roofs: a review

From an ecological perspective, urban green roofs can be viewed as green islands embedded in an urban matrix. Island biogeography theory suggests that species richness on an island is the outcome of dynamic equilibrium between immigration and extinction. Immigration is affected by the size of an island and distance of an island from a colonizing source. In the context of green roofs, building height and horizontal distance from green areas can potentially be a limiting factor for many species. Here, we considered two distance components of green roofs - vertical (building height) and horizontal (distance of building from open green areas). Based on island biogeography theory, we would expect species richness or community similarity to be negatively related to horizontal or vertical distances from colonizing sources. The green roof literature addressing such questions is currently sparse. In our review comprised of 10 studies, we were unable to identify consistent statistically significant richness-distance or community similarity-distance (vertical or horizontal) relationships. The absence of statistically significant relationships could be due in large part to low statistical power as a consequence of both the paucity of roofs and limited range of vertical distances in many of the existing studies. In addition, these roofs differ in numerous aspects (e.g. roof size, age, substrate type, plant composition and building height). The low number of replicates, combined with the lack of homogeneity among replicates combines to reduce statistical power and our ability to detect differences.

Substrate depth and roof age strongly affect plant abundances on sedum-moss and meadow green roofs in Helsinki, Finland

Green (i.e. vegetated) roofs are an increasingly popular measure to improve climate regulation in residential areas. However, there is limited knowledge on the effect of green roof characteristics (e.g. substrate depth and roof age, size and height), especially in northern climates, on plant species composition of the roofs, even though roof performance is mediated through the plants. We hypothesized that substrate depth and roof age, size and height shape the vegetation on green roofs. We inventoried vegetation on 51 green roofs in the metropolitan area of Helsinki in 2011 and found 230 plant species, of which seven are red-listed. We showed that substrate depth and roof age were predominant in structuring plant communities on green roofs. Thin substrates and young roofs maintained sedum and moss species, while thick substrates and older green roofs supported meadow plants. Roof size and height had variable effects on the vegetation. Our results provide knowledge on the dependence of plant species on roof parameters, which is useful in the planning for particular vegetation on roofs taking into account, e.g. load capacity and substrate depth, the wanted functional properties of the roof, and maintenance.

Rainwater Harvesting for Small-Holder Horticulture in Namibia: Design of Garden Variants and Assessment of Climate Change Impacts and Adaptation

The design of rainwater harvesting based gardens requires considering current climate but also climate change during the lifespan of the facility. The goal of this study is to present an approach for designing garden variants that can be safely supplied with harvested rainwater, taking into account climate change and adaptation measures. In addition, the study presents a methodology to quantify the effects of climate change on rainwater harvesting based gardening. Results of the study may not be accurate due to the assumptions made for climate projections and may need to be further refined. We used a tank flow model and an irrigation water model. Then we established three simple climate scenarios and analyzed the impact of climate change on harvested rain and horticulture production for a semi-arid region in northern Namibia. In the two climate scenarios with decreased precipitation and medium/high temperature increase; adaptation measures are required to avoid substantial decreases in horticulture production. The study found that the most promising adaptation measures to sustain yields and revenues are a more water efficient garden variant and an enlargement of the roof size. The proposed measures can partly or completely compensate the negative impacts of climate change.

Estimating the reliable residential water substitution from household rainwater tanks

In Australia, household rainwater tanks have come to be considered as one of the broad potential supply options for meeting household water demands. It has been viewed as an effective way of reducing the supply requirements by water businesses and can potentially defer future capital supply investments. With likely variability of future supplies and demands due to climate change impacts, rainwater tanks also have an important role in building future resilience to shifts in historical trends, and also can potentially play a role in mitigating stormwater damage. The substitution of mains supplied water by rainwater can vary significantly, with the major factors influencing yields being the roof size to capture the rain, water usage regime (having some level of internal water use) and tank size. Tank performance, with respect to reduced substitution as a result of functionality failure, is seldom included in yield calculations however. A review of a number of studies in Australia has illustrated that the vast majority of field studies have produced qualitative responses on the perceptions of the use of rainwater, the structural integrity of their rainwater capture infrastructure and the end-uses connected to the system. It was found that the data required to inform the impact of functionality on substitution is currently largely limited to qualitative responses on the perceptions of the use of rainwater tanks, the structural integrity of their rainwater capture infrastructure and the end-uses connected to the system. There is very little in the way of quantitative assessments. This paper offers an interim approach for overcoming this quantitative information gap on the role and extent of functionality failure.

A Benchmarking System for Domestic Water Use

The national demand for water in the UK is predicted to increase, exacerbated by a growing UK population, and home-grown demands for energy and food. When set against the context of overstretched existing supply sources vulnerable to droughts, particularly in increasingly dense city centres, the delicate balance of matching minimal demands with resource secure supplies becomes critical. When making changes to "internal" demands the role of technological efficiency and user behaviour cannot be ignored, yet existing benchmarking systems traditionally do not consider the latter. This paper investigates the practicalities of adopting a domestic benchmarking system (using a band rating) that allows individual users to assess their current water use performance against what is possible. The benchmarking system allows users to achieve higher benchmarks through any approach that reduces water consumption. The sensitivity of water use benchmarks are investigated by making changes to user behaviour and technology. The impact of adopting localised supplies (i.e., Rainwater harvesting—RWH and Grey water—GW) and including "external" gardening demands are investigated. This includes the impacts (in isolation and combination) of the following: occupancy rates (1 to 4); roof size (12.5 m2 to 100 m2); garden size (25 m2 to 100 m2) and geographical location (North West, Midlands and South East, UK) with yearly temporal effects (i.e., rainfall and temperature). Lessons learnt from analysis of the proposed benchmarking system are made throughout this paper, in particular its compatibility with the existing Code for Sustainable Homes (CSH) accreditation system. Conclusions are subsequently drawn for the robustness of the proposed system.

Green Roof Adoption in Atlanta, Georgia: The Effects of Building Characteristics and Subsidies on Net Private, Public, and Social Benefits

This research draws on and expands previous studies that have quantified the costs and benefits associated with conventional roofs versus green roofs. Using parameters from those studies to define alternative scenarios, we estimate from a private, public, and social perspective the costs and benefits of installing and maintaining an extensive green roof in Atlanta, GA. Results indicate net private benefits are a decreasing function of roof size and vary considerably across scenarios. In contrast, net public benefits are highly stable across scenarios, ranging from $32.49 to $32.90 m(-2). In addition, we evaluate two alternative subsidy regimes: (i) a general subsidy provided to every building that adopts a green roof and (ii) a targeted subsidy provided only to buildings for which net private benefits are negative but net public benefits are positive. In 6 of the 12 general subsidy scenarios the optimal public policy is not to offer a subsidy; in 5 scenarios the optimal subsidy rate is between $20 and $27 m(-2); and in 1 scenario the optimal rate is $5 m(-2). The optimal rate with a targeted subsidy is between $20 and $27 m(-2) in 11 scenarios and no subsidy is optimal in the twelfth. In most scenarios, a significant portion of net public benefits are generated by buildings for which net private benefits are positive. This suggests a policy focused on information dissemination and technical assistance may be more cost-effective than direct subsidy payments.

Reliability analysis of rainwater tanks using daily water balance model: Variations within a large city

A daily water balance model is used for the performance analysis and design optimisation of rainwater tanks at four different regions of Melbourne; North, Central, South-East and South-West. These four different regions of Melbourne are characterised by notable different topography and rainfall characteristics. From historical rainfall data, three representative years (dry, average and wet) are selected. Reliability is defined as percentage of days in a year when rainwater tank is able to supply the intended partial demand for a particular condition. For the three climatic conditions, a number of reliability charts are produced for domestic rainwater tanks in relation to tank volume, roof area and number of people in a house (i.e. water demand). It is found that for a relatively small roof size (100m2), 100% reliability cannot be achieved even with a very large tank (10,000L). Reliability becomes independent of tank size for tank sizes larger than 4000–7000L depending on the location. This is defined as threshold tank size, relationships with threshold tank sizes and annual rainfall amounts are then established for all the locations. A new factor named ‘Rainwater Accumulation Potential (RAP)’ has been introduced and maximum achievable reliabilities for different reasonable RAPs under different climatic conditions are presented for all the locations selected in this study. From these findings, for the design of rainwater tank size it is recommended to have a RAP value of 0.8–0.9 for greater Melbourne.

Reliability analysis of rainwater tanks: A comparison between South-East and Central Melbourne

A spreadsheet based daily water balance model is used for the performance analysis and design optimisation of rainwater tanks at two different regions of Melbourne, South-East and Central Melbourne. These two different regions of Melbourne are characterised by notable different topography and rainfall characteristics. From historical rainfall data, three representative years (dry, average and wet) are selected. Reliability is defined as percentage of days in a year when rainwater tank is able to supply the intended partial demand for a particular condition. For the three climatic conditions, a number of reliability charts are produced for domestic rainwater tanks in relations to tank volume, roof area, number of people in a house (i.e. water demand) and percentage of total water demand to be satisfied by the harvested rainwater. It is found that for a relatively small roof size (100m2), 100% reliability cannot be achieved even with a very large tank (10,000L). Reliability becomes independent of tank size for tank sizes larger than 5000–7000L depending on the location. This is defined as threshold tank size, relationships with threshold tank sizes and annual rainfall amounts are then established for both the locations. It is found that for a particular annual rainfall amount, threshold tank size for South-East Melbourne is higher than that of Central Melbourne. However, for a relatively large roof size (200m2), approximately 90% reliability can be achieved with a tank size of 10,000L and with further increase in tank size, a 100% reliability is achievable, except in a dry year. Furthermore, it is found that reliabilities for South-East Melbourne maintain consistent higher values as compared to Central Melbourne.

Reliability analysis of rainwater tanks in Melbourne using daily water balance model

With the aim of developing a comprehensive decision support tool for the performance analysis and design of rainwater tanks, a simple spreadsheet based daily water balance model was developed using daily rainfall data, contributing roof area, rainfall loss factor, available storage volume, tank overflow and rainwater demand. In order to assess reliability of domestic rainwater tanks in augmenting partial household water demand in Melbourne (Australia) area, the developed water balance model was used for three different climatic conditions (i.e. dry, average, and wet years). Historical daily rainfall data was collected from a rainfall station near Melbourne city central. From historical rainfall data three representative years (driest, average and wettest) were selected for the current analysis. Reliability is defined as percentage of days in a year when rainwater tank was able to supply the intended partial demand for a particular condition. For the three climatic conditions, several reliability charts are presented for domestic rainwater tanks in relations to tank volume, roof area, number of people in a house (i.e. water demand) and percentage of total water demand to be satisfied by harvested rainwater. In brief, for a two-people household scenario, ∼100% reliability can be achieved with a roof size of 150–300 m 2 having a tank size of 5000–10,000 L. However, for a four-people household scenario, it is not possible to achieve a 100% reliability, even with a roof size of 300 m 2 and a tank size of 10,000 L.

An empirical correlation for the outside convective air-film coefficient for horizontal roofs

From measurements of surface heat transfer on the roofs of two commercial buildings in Northern California we have developed a correlation that expresses the outside convective air-film coefficient for flat, horizontal roofs as a function of surface-to-air temperature difference, wind speed, wind direction, roof size, and surface roughness. When used in detailed building energy analysis programs, this correlation is expected to give more accurate calculation of roof loads, which are sensitive to outside surface convection. In our analysis, about 90% of the variance of the data was explained by a model that combined standard flat-plate equations for natural and forced convection and that took surface roughness into account. We give expressions for the convective air-film coefficient: (1) at an arbitrary point on a convex-shaped roof, for a given wind direction; (2) averaged over a strip along the wind direction; and (3) averaged over a rectangular roof for a given wind direction.

Pitfall Trap Size and Capture of Three Taxa of Litter-Dwelling Arthropods: Implications for Biodiversity Studies

Cost-effective and ecologically sensitive monitoring techniques are required to assess effects of anthropogenic disturbances on biodiversity. Pitfall trapping is widely used in biodiversity monitoring programs to measure the diversity of organisms active within leaf-litter. We compared catch rates and species richness of ground beetles (Coleoptera: Carabidae), rove beetles (Coleoptera: Staphylinidae), and spiders (Araneae) across five different diameters of pitfall traps (4.5, 6.5, 11, 15, and 20 cm) and three sizes of rain covers (64, 79.2, and 225 cm2) to determine optimal trap size for studying litter-dwelling arthropod biodiversity. In general, larger pitfall traps collected more individuals, and more species, of all three taxa. Further tests on data standardized to trap circumference showed that catch rates are not directly proportional to trap size, and even the smallest traps collected a disproportionately high number of certain taxa. When catch rate data were standardized by trap circumference smaller traps collected more small-bodied carabid and staphylinid species and large traps collected more wolf spiders (Lycosidae) than smaller traps. Roof size had no effect on species richness or catch rate of beetles or spiders. For the purposes of ecological monitoring, using more small pitfall traps would be the most efficient sampling technique to characterize the dominant epigaeic arthropod fauna; small traps collect few nontarget vertebrates, and sorting the samples involves generally less processing time. From a conservation perspective, however, including several large pitfall traps in the sampling regime would help detect rare species.

Local peak pressure and conical vortex on building

Characteristics and cause of local peak suction are discussed through a relation with the conical vortex. The peak suction is induced by the large and strong conical vortex formed on the roof and the wall when the gust attacks a building instantly from a particular direction in any mean wind directions. The large-scale gust is responsible for the formation of the vortex and the occurrence of the peak suction, because the development of the strong vortex takes time at least when the fluid particle travels a distance 4–5 times the roof size. The modification of the edge is very effective to reduce the peak suction, as it controls effectively the separation of the shear layer. When the eaves of the flat roof are recessed by 1 10 of the height of the building, the peak suction can be reduced to 2 3 of that on the roof without the recession.

Conditions for fibronectin fibril formation in the early Xenopus embryo.

Fibronectin fibril formation on a multilayered cohesive cell sheet is studied in the Xenopus embryo. In the blastula, secreted fibronectin accumulates in the blastocoel, where it associates with mucous material. At the onset of gastrulation, a fibrillar fibronectin matrix develops on the blastocoel roof. Cells engage in this process stochastically within a 2-hr period. Fibril network formation requires more than 60 microg/ml of fibronectin, but the timing of fibrillogenesis is not regulated through the availability of fibronectin. With the exception of a few isolated mesoderm cells, only the cells of the blastocoel roof are able to form fibronectin fibrils. However, this requires that cells are provided with a free surface and, at the same time, with lateral adhesive cell contacts, i.e. fibril assembly occurs only on the surface of cohesive cells aggregates. This explains the observed restriction of fibronectin matrix formation to the inner surface of the blastocoel roof in the embryo. In addition, a minimum blastocoel roof size is required for fibril formation.