Rainwater Harvesting Systems In Buildings Research Articles

The Feasibility of Rainwater Harvesting Systems in Buildings with Green Roofs: A Case Study Based on the Köppen Climate Classification

The construction of green roofs (GR) combined with rainwater harvesting systems (RWHSs) in buildings can increase the advantages of each of these technologies, being a very promising solution to combat climate change and increase the sustainability of cities. However, the viability of this joint solution significantly depends on local climatic conditions. The planet’s climate classification, known as the Köppen climate classification, is one of the most widely used climate classification systems. The Köppen climate classification divides climates into five main climate groups, with each group being referenced based on seasonal precipitation and temperature patterns. In the specific case of mainland Portugal, according to the Köppen classification, the climate is divided into two regions. In this article, case studies are developed for two Portuguese climatic regions, seeking to demonstrate the possibility of using the Köppen classification as a decision criterion for the eventual inclusion of rainwater harvesting systems in buildings with green roofs. For this study, the results of a previous study were applied, through which we obtained an expression to determine the runoff coefficients of green roofs common in Portugal, concluding that the Köppen climate classification can be used as a prior decision criterion regarding its incorporation or exclusion in rainwater harvesting system buildings combined with green roofs, depending on the location.

Modular life cycle assessment approach: Environmental impact of rainwater harvesting systems in urban water systems

The environmental assessment of urban water systems through life cycle analysis can be facilitated by using a modular approach. This study aimed to use such an approach to assess the impact of implementing rainwater harvesting systems in buildings in the urban environment during their lifespan, from manufacture to disposal. For this purpose, urban systems were divided into components (water treatment plant, potable water distribution, consumer water use, wastewater collection and wastewater treatment plant). The impacts were quantified using the ReCiPe 2016 H impact assessment method, which considers eighteen impact categories. A case study was carried out in the Belém river basin in central Curitiba, southern Brazil, to validate the method. The results showed a reduction of environmental impacts of up to 23.0 % on water treatment plants, up to 19.0 % on potable water distribution and up to 11.3 % on wastewater treatment plants with the implementation of rainwater harvesting systems. The consumer component was the most significant contributor in eight and seven impact categories in the scenarios with and without rainwater harvesting, respectively. Despite the increased infrastructure materials, the results showed potential for environmental impact reduction with rainwater harvesting, mainly in urban water systems' operation process (energy and chemicals consumption). By analysing the total impacts, implementing rainwater harvesting reduced the impacts in eleven out of eighteen impact categories analysed (up to 11.0 % reduction). The principal reductions occurred in ozone depletion, ionising radiation and water use. Finally, the modular life cycle assessment approach proved to be a comprehensive analysis, which can aid in the analysis and decision-making for different scenarios.

Combining green roofs and rainwater harvesting systems in university buildings under different climate conditions

Rainwater Harvesting Systems (RWHS) are an alternative solution with the potential to increase water supply security and reduce the pressure on water resources and urban stormwater drainage systems. Likewise, Green Roofs are a nature-based solution with several ecosystem services able to improve well-being in densely urbanized areas. Despite these benefits, the combination of both solutions is still a knowledge gap to be explored. To address this issue, the paper explores the potential of integrating traditional rainwater harvesting systems (RWHS) with extensive green roofs (EGR), while simultaneously evaluating the performance of traditional RWHS in buildings with high and variable water consumption patterns across different climatic conditions. The analyses were carried out assuming two university buildings hypothetically located in three distinct climates (Aw - Tropical Savanna, Cfa - Humid Subtropical, and Csa - Hot-summer Mediterranean). The results show that the relationship between available water and demand is the key factor that defines if the system is most suitable for saving water, reducing stormwater runoff rates, or dual-purpose (when there is a balance between non-potable water supply and capture of stormwater). Combined systems were most effective when there is a balanced rainfall distribution over the year, as in humid subtropical regions. Under these conditions, a combined system designed for dual purposes could potentially have a green roof coverage of up to 70% of the total catchment area. Conversely, climates that have well-defined rainy and dry seasons such as Aw and Csa, may limit the effectiveness of a combined system (RWHS+EGR), being not able to supply water demands during certain periods of the year. However, if the primary objective is effective stormwater management, a combined system should be strongly considered. Because green roofs provide other ecosystem benefits that can contribute to enhancing urban resilience in the face of climate change.

A rainwater harvesting system in buildings with green roofs and a rooftop greenhouse in Pyongyang

A rainwater harvesting system in buildings with green roofs and a rooftop greenhouse in Pyongyang

Comprehensive Environmental Assessment of Rainwater Harvesting Systems: A Literature Review

The feasibility of installing rainwater harvesting systems in buildings is usually defined based primarily on economic analysis. In this perspective, we reviewed the literature related to water consumption in buildings, rainwater use, and environmental assessment tools to evaluate the impact of rainwater harvesting on the environment. Identifying water end uses in buildings showed a high potential for potable water savings through alternative sources (e.g., rainwater use for non-potable purposes). Most studies reviewed found potential for potable water savings from 20 to 65%. Moreover, the literature reported that rainwater harvesting systems might reduce the runoff volume from 13 to 91%. However, other possible benefits and impacts of the systems on water flow and the environment must be assessed in addition to the potential for rainwater harvesting. Life cycle assessment, life cycle cost assessment, and water balance modelling have been used in urban water management. Most life cycle studies reported that rainwater harvesting systems have better environmental performance than centralised systems. The water balance method may effectively determine the impacts these systems cause on the water cycle. Using life cycle assessment and the water balance method together is essential to evaluating rainwater harvesting systems integrated into the urban environment.

Water efficiency and economic assessment of domestic rainwater harvesting systems in buildings with one- to three-floor elevations

Abstract The focus of the paper is the evaluation of the performance of domestic rainwater harvesting (DRWH) systems in multi-family buildings with one- to three-floor elevations by means of a cost–benefit analysis. The rainwater is here used for both indoor and outdoor non-potable water consumption. The study was carried out with reference to different residential building typologies (flat and condominium) in a specific local climate condition (Ancona). The buildings are characterized by different rooftop areas (100–400 m2), building floor elevations (one to three floors) and inhabitant numbers (3–54 persons). Moreover, in order to highlight the role of the tank capacity on the performance of DRWH, its capacity was changed in the range 50–200%. The combinations of all these parameters led to 276 test cases. The technical performance is evaluated by means of the water saving and retention efficiencies. The economical assessment is provided by comparing the costs and the savings due to the replacement of the water supplied with the rainwater. It is found that the payback periods changed in the range 10–35 years for the site-specific variables such as local rainfall and water service tariff. Cost–benefit analysis can help the design of DRWH systems, with particular attention to the sizing of the tank.

Reuse of resources in the use phase of buildings. Solutions for water

Circular economy can be considered not only in relation to building construction materials, but also in relation to resources that are used in the use phase of buildings, such as water, energy or even nutrients. On the other hand, some constructive solutions are becoming increasingly important in the current scenario of climate change, taking into account the need to increase the resilience of the urban environment and the mitigation of emissions. This is the case, for example, of green roofs and living façades, which are an alternative to traditional grey infrastructure, offering many benefits to both citizens and cities. Beyond the ability to improve environmental conditions and quality of life, they can augment the energy efficiency of buildings, reduce flood risks in urban areas and be combined with rainwater harvesting systems. So, taking into account these trends for constructive solutions in the future, this paper analyses the possibilities of a circular use of water in buildings, aiming to create in the future “zero water” buildings. Particular attention is given to the compatibility between new green roofing solutions and rainwater harvesting systems in buildings, but the reuse of grey water and the possibility of nutrient recovery in buildings, such as urine (phosphorus) - which can be used in the building itself on green roofs - living facades or urban agriculture, are also referred to.

Contributions to the design of rainwater harvesting systems in buildings with green roofs in a Mediterranean climate.

Green roofs (GRs) are becoming a trend in urban areas, favouring thermal performance of buildings, promoting removal of atmospheric pollutants, and acting as possible water collection spots. Rainwater harvesting systems in buildings can also contribute to the management of stormwater runoff reducing flood peaks. These technologies should be enhanced in Mediterranean countries where water scarcity is increasing and the occurrence of extreme events is becoming very significant, as a result of climate change. An extensive pilot GR with three aromatic plant species, Satureja montana, Thymus caespititius and Thymus pseudolanuginosus, designed to study several parameters affecting rainwater runoff, has been in operation for 12 months. Physico-chemical analyses of roof water runoff (turbidity, pH, conductivity, NH4(+), NO3(-), PO4(3-), chemical oxygen demand) have shown that water was of sufficient quality for non-potable uses in buildings, such as toilet flushing. An innovative approach allowed for the development of an expression to predict a 'monthly runoff coefficient' of the GR system. This parameter is essential when planning and designing GRs combined with rainwater harvesting systems in a Mediterranean climate. This study is a contribution to improving the basis for the design of rainwater harvesting systems in buildings with extensive GRs under a Mediterranean climate.

Energy intensity of rainwater harvesting systems: A review

Rainwater Harvesting Systems (RHS) are increasingly used in buildings to mitigate water shortage and rising prices of centralised water supply. Notwithstanding the benefits of RHS, they may also promote adverse impacts mainly related to the high consumption of energy. In this context, energy intensity (i.e. unit of energy per unit of water) is a crucial parameter for assessing the environmental feasibility of different RHS. However, only recently has attention been drawn to the connection between water and energy consumption, which has been prompted by the increasing importance of water security, energy efficiency and economic feasibility. This connection, known as the water-energy nexus, has been increasingly acknowledged as a key principal for water planning. The objective of this study is twofold: (i) to review the energy intensity data reported for RHS; and (ii) to outline strategies to enhance the energy performance of RHS in buildings. For the reviewed literature, the median energy intensity of theoretical studies (0.20 kWh/m³) was considerably lower than that described in empirical studies (1.40 kWh/m³). This implies that theoretical assessments of energy intensity may not sufficiently consider the energy used for pump start-ups and standby mode, as well as the true motor and pump energy efficiency. However, to some extent, this difference may also represent the amount of energy that can be reduced by optimising RHS design and operation. When comparing RHS to conventional town water supply systems, the reviewed empirical studies showed that RHS tend to be three times more energy intensive, although optimised RHS can have more comparable values. Ultimately, it is predominately the local characteristics, such as rainwater demand, building type (single-storey or multi-storey), RHS sub-systems design, potable water plumbing system design, and town water energy intensity, among other factors that will determine whether or not the environmental and economic performances of RHS are acceptable.