Domestic Water Use in the United States: A Life-Cycle Approach

Water and energy are two primary natural resources used by building occupants. A life-cycle assessment (LCA) is performed for water-consuming plumbing fixtures and water-consuming appliances during their operational life for four different building types. Within the cycle studied, water is extracted from the natural environment, subjected to water treatment, pumped to buildings for use, collected for wastewater treatment, and discharged back to the natural environment. Specifically, the impacts of water use, electricity and natural gas generation, energy consumption (for water and wastewater treatment, and for water heating), and the manufacture of water and wastewater treatment chemicals are evaluated both quantitatively and qualitatively on a generalized national level in the United States of America.
It is concluded that water use and consumption within buildings have a much larger impact on resource consumption than the water and wastewater treatment stages of the life cycle. To study this more specifically, the resource consumption of four different building types-an apartment building, a college dormitory, a motel, and an office building-is considered. Of these four building types, the apartment has the highest energy consumption (for water and wastewater treatment, and for water heating) per volume of water used, whereas the office building has the lowest. Similarly, the calculated LCA score for the apartment building is typically greater than those of the other three building types.     

Toward the Ecological Footprint of the use and maintenance phase of buildings: Utility consumption and cleaning tasks

Due to poor design of buildings in terms of maintenance, there are a number of buildings today that remain extremely expensive to maintain, both economically and environmentally. In order to mitigate these overheads, the development of a cost database is needed with which the resources required to clean and maintain buildings can be estimated. This paper presents a methodology to estimate these costs and the environmental impact, in terms of Ecological Footprint (EF), associated to the utility consumption and to the cleaning tasks necessary during the service life of buildings. Given the numerous peculiarities identified for this type of activity compared to the construction of buildings, it is necessary to define a new methodology of calculation, with its own assumptions and formulae. This methodology is then applied to the case of a college hall of residence that houses up to 139 residents. The results show that the annual EF of cleaning tasks accounts for 11.42% of the EF of utility consumption. Together they total 67.334 global hectares per year (gha/yr), 88% of which corresponds to the carbon footprint. Within the EF of cleaning, about 71% is due to food consumed by labor, while 26% is due to the manufacture of cleaning products and tools, which are equally divided among the six categories of productive land. The development of this methodology is essential for the detailed quantification of the environmental impact of utility consumption and cleaning tasks that occur during the service life of buildings. The use of discount rates on results is included in terms of the EF of a baseline year, as an equivalent to the discount rate in economic terms.     

北京不同类型居住区树种组成结构及其三维空间配置

以北京城区3种不同类型居住区为对象,对其树种组成、相对重要程度以及在胸径、树高和树冠等级上的三维空间配置结构进行了分析.结果表明:不同类型居住区既有相同的核心树种又有各自的特色主导树种,其中,毛白杨(Populus tomentosa)、国槐(Sophora japonica)和侧柏(Platycladus orientalis)是各类居住区重要值均较高的共同核心树种,而泡桐(Paulewnia fortunei)、雪松(Cedrus deodara)、加杨(Populus canadensis)和银杏(Ginkgo biloba)等高大挺拔树种是单位附属居住区中的重要树种,臭椿(Ailanthus altissima)、白蜡(Fraxinus chinensis)和枣树(Ziziphus jujube)等传统乡土树种是胡同居住区中的重要树种,刺槐(Robinia pseudoacacia)、油松(Pinus tabulaeformis)、垂柳(Salix babylonica)和龙爪槐(Sophora japonica cv.Pendula)等优良园林景观树种则是混合居住区中的重要树种;从居住区树木三维空间配置结构来看,不同类型居住区树木在水平胸径等级、垂直树高等级和树冠等级结构上的总体分布均表现出向上发展的潜力,整个居住区树木仍处于一个快速生长阶段;从3种类型居住区的比较来看,单位附属居住区的树木密度、树冠覆盖度以及平均胸径、平均树高水平都明显高于其他两类居住区,其空间绿量相对充实,而胡同居住区由于受土地所限已难以大幅提升绿量水平,但混合居住区内仍有较大的空间绿量增加潜力.     

The Growth of Urban Building Stock: Unintended Lock‐in and Embedded Environmental Effects

Building stocks constitute enduring components of urban infrastructure systems, but little research exists on their residence time or changing environmental impacts. Using Los Angeles County, California, as a case study, a framework is developed for assessing the changes of building stocks in cities (i.e., a generalizable framework for estimating the construction and deconstruction rates), the residence time of buildings and their materials, and the associated embedded environmental impacts. In Los Angeles, previous land‐use decisions prove not easily reversible, and past building stock investments may continue to constrain the energy performance of buildings. The average age of the building stock has increased steadily since 1920 and more rapidly after the post–World War II construction surge in the 1950s. Buildings will likely endure for 60 years or longer, making this infrastructure a quasi‐permanent investment. The long residence time, combined with the physical limitations on outward growth, suggest that the Los Angeles building stock is unlikely to have substantial spatial expansion in the future. The construction of buildings requires a continuous investment in material, monetary, and energetic resources, resulting in environmental impacts. The long residence time of structures implies a commitment to use and maintain the infrastructure, potentially creating barriers to an urban area's ability to improve energy efficiency. The immotility of buildings, coupled with future environmental goals, indicates that urban areas will be best positioned by instituting strategies that ensure reductions in life cycle (construction, use, and demolition) environmental impacts.     

Projection of Construction and Demolition Waste in Norway

Current waste generation from the construction and demolition industry (C&D industry) in Norway is about 1.25 million tonnes per year. This article presents a procedure for projection of future waste amounts by estimating the activity level in the C&D industry, determining specific waste generation factors related to this activity, and finally calculating projections on flows of waste materials leaving the stocks in use and moving into the waste management system. This is done through a simple model of stocks and flows of buildings and materials. Monte Carlo simulation is used in the calculations to account for uncertainties related to the input parameters in order to make the results more robust. The results show a significant increase in C&D waste for the years to come, especially for the large fractions of concrete/bricks and wood. These projections can be a valuable source of information to predict the future need for waste treatment capacity, the dominant waste fractions, and the challenges in future waste handling systems. The proposed method is used in a forthcoming companion article for eco-efficiency modeling within an evaluation of a C&D waste system.     

Interspecific interactions between wild felids vary across scales and levels of urbanization

Ongoing global landscape change resulting from urbanization is increasingly linked to changes in species distributions and community interactions. However, relatively little is known about how urbanization influences competitive interactions among mammalian carnivores, particularly related to wild felids. We evaluated interspecific interactions between medium‐ and large‐sized carnivores across a gradient of urbanization and multiple scales. Specifically, we investigated spatial and temporal interactions of bobcats and pumas by evaluating circadian activity patterns, broad‐scale seasonal interactions, and fine‐scale daily interactions in wildland–urban interface (WUI), exurban residential development, and wildland habitats. Across levels of urbanization, interspecific interactions were evaluated using two‐species and single‐species occupancy models with data from motion‐activated cameras. As predicted, urbanization increased the opportunity for interspecific interactions between wild felids. Although pumas did not exclude bobcats from areas at broad spatial or temporal scales, bobcats responded behaviorally to the presence of pumas at finer scales, but patterns varied across levels of urbanization. In wildland habitat, bobcats avoided using areas for short temporal periods after a puma visited an area. In contrast, bobcats did not appear to avoid areas that pumas recently visited in landscapes influenced by urbanization (exurban development and WUI habitat). In addition, overlap in circadian activity patterns between bobcats and pumas increased in exurban development compared to wildland habitat. Across study areas, bobcats used sites less frequently as the number of puma photographs increased at a site. Overall, bobcats appear to shape their behavior at fine spatial and temporal scales to reduce encounters with pumas, but residential development can potentially alter these strategies and increase interaction opportunities. We explore three hypotheses to explain our results of how urbanization affected interspecific interactions that consider activity patterns, landscape configuration, and animal scent marking. Altered competitive interactions between animals in urbanized landscapes could potentially increase aggressive encounters and the frequency of disease transmission.     

Managing electromagnetic fields from residential electrode grounding systems: A predecision analysis

Several epidemiological studies have linked exposure to electromagnetic fields (EMFs) with health effects, including leukemia and brain cancer, but the research is still inconclusive. In particular, no clear causal mechanism has been identified by which EMFs may promote cancers. Nevertheless, the concerns raised by the positive epidemiological studies have led to increasing efforts to reduce EMFs from a number of sources. One source of EMFs are home grounding systems that are connected through water pipes in homes to water mains. This paper analyzes whether home owners who are concerned about electromagnetic fields exposure from home grounding systems should take any action to reduce fields. Assuming that the grounding system produces elevated magnetic fields (e.g., 2–3 mG or higher), this study investigates several readily available alternatives and evaluates them with respect to five criteria: risk reduction, cost, fire risk increase, worker risk, and electrical shock risk. Because of the lack of conclusive evidence about an EMF-cancer relationship, this study uses a parameterized approach that makes conditional estimates of health risk depending on future research outcomes and on the nature of the EMF/health effects relationship. This type of analysis, which is called predecision analysis because of its preliminary nature, is therefore highly dependent on a set of assumptions. Nevertheless, this predecision analysis had some fairly clear results. First, waiting for more research or taking a fairly inexpensive corrective action (insulating the water pipe to reduce ground current flow) seem to be the main contenders for the best decision for many different assumptions and parameters. Second, the choice between these two actions is very sensitive to variations in assumptions and parameters. Homeowners who accept the base-case assumptions and parameters of this study should prefer to wait. If any of the base-case parameters are changed to more pessimistic estimates or if psychological concerns (like worry and regret) are considered, then the best action is to insulate the pipe to reduce the current flow through the water pipes. © 1996 Wiley-Liss, Inc.     

A Transparent, Interactive Software Environment for Communicating Life-Cycle Assessment Results: An Application to Residential Windows

Life-cycle assessments (LCAs) can be used to support the selection of environmentally preferable building materials. But the dominance of the usage phase in the life cycle of building materials represents a special challenge for two reasons. First, many aspects of a building material's usage phase can be context specific. Second, the LCA outcome may rest on a building material's service life, a parameter for which there is typically insufficient information for proper determination. For example, in the selection of a window, important usagephase, context-specific factors that could be determinant include lo-cation/climate, heating-system characteristics (efficiency and fuel), and product durability. A prototype software tool, the Life Cycle Explorer, has been developed that enables decision makers to assess the relative importance of literally dozens of such influential parameters in determining the outcomes of LCA evaluations for building components. The software employed by the Life Cycle Explorer permits extensive layering while maintaining ease of browsing, with the intent of accessibility to both the layperson and the expert. An initial application of the tool addressed residential window selection; the design principles of the software are relevant to the communication phase of a wide variety of LCA and industrial-ecologyrelated modeling projects.     

Thermal comfort in naturally ventilated and air-conditioned buildings in humid subtropical climate zone in China

A thermal comfort field study has been carried out in five cities in the humid subtropical climate zone in China. The survey was performed in naturally ventilated and air-conditioned buildings during the summer season in 2006. There were 229 occupants from 111 buildings who participated in this study and 229 questionnaire responses were collected. Thermal acceptability assessment reveals that the indoor environment in naturally ventilated buildings could not meet the 80% acceptability criteria prescribed by ASHRAE Standard 55, and people tended to feel more comfortable in air-conditioned buildings with the air-conditioned occupants voting with higher acceptability (89%) than the naturally ventilated occupants (58%). The neutral temperatures in naturally ventilated and air-conditioned buildings were 28.3°C and 27.7°C, respectively. The range of accepted temperature in naturally ventilated buildings (25.0∼31.6°C) was wider than that in air-conditioned buildings (25.1∼30.3°C), which suggests that occupants in naturally ventilated buildings seemed to be more tolerant of higher temperatures. Preferred temperatures were 27.9°C and 27.3°C in naturally ventilated and air-conditioned buildings, respectively, both of which were 0.4°C cooler than neutral temperatures. This result suggests that people of hot climates may use words like “slightly cool” to describe their preferred thermal state. The relationship between draught sensation and indoor air velocity at different temperature ranges indicates that indoor air velocity had a significant influence over the occupants’ comfort sensation, and air velocities required by occupants increased with the increasing of operative temperatures. Thus, an effective way of natural ventilation which can create the preferred higher air movement is called for. Finally, the indoor set-point temperature of 26°C or even higher in air-conditioned buildings was confirmed as making people comfortable, which supports the regulation in China that in public and office buildings the set-point temperature of air-conditioning system should not be lower than 26°C.