Por A. Sagrera, F. López, G. Wadel, L. Volpi
Abstract
This article describes the strategies of efficiency, substitution and reuse of water planned for the future building of the Museum of Science, Environment and Climate of Lerida. Compared to a building with similar characteristics, complying only with the minimum requirements of the standard regulation, it is expected to improve water saving efficiency up to 85%. The study has been carried out as part of a full environmental assessment (energy, materials, waste and water) commissioned by the designer, architecture studio Toni Girones Saderra. Several techniques based on a water balance concept were developed and implemented: water devices of maximum efficiency and reuse of rainwater/greywater, and the reduction of air conditioning demand, by cooling the building's courtyard air through water surface evaporation and water spraying.
Project credits:
Client: architecture studio Toni Gironès Saderra / Project origin: tender / Developer: Municipal Town planning enterprise of Lleida, Spain / Location: Turó de Gardeny, Lleida / Area: 4.750 m2 / Approximate Budget: 4.971.195 € / External collaboration: BOMA (structural engineering), PGI Group (building services) and Jordi Huguet - Aguapur (water specialist).
Introduction
Spanish territory has huge arid areas, such as the very site of the project, where scarcity of rainwater, of surface water courses and of underground courses will increase in coming decades because of climate change (20% according to the official estimates). While the country's water consumption for construction is not highly significant (16% of the total), when considering the water cycle on a drainage basin scale, if it is largely urbanized, it may reach a relevant percentage (up to 40% of the total). On this basis, the strategy of saving and replacing drinking water in buildings is very important: on one hand it helps to reduce the total drinking water consumption and its associated impacts (extraction, purification, infrastructure, pumping, distribution, collection, treatment, disposal etc…), on the other hand it contributes to improve the user's awareness of a new water culture.
Project description
The Museum of Science, Environment and Climate is located in the Gardeny area on the northern edge of the city of Lerida, which hosted several military installations in the past. The construction started in September 2010 as part of the urban restructuring of the area. It has prominent position, since it is integrated into a natural elevation of land with a view to and from the city. Its spaces are organized as a pedestrian route that begins at the top (the plain Gardeny Turó), descending to the bottom of the spiral-shaped site and surrounding a courtyard, connecting from there with the rest of the city through a green space, adapted to the new requirements for a museum. The program includes spaces for permanent and temporary exhibitions, auditorium, storage, administration and cafeteria. The aim is to realize the project with the fewest possible resources and to get the visitors involved in the environmental strategies.
Environmental goal
Maximum possible reduction of the whole water consumption and also maximum possible substitution of drinking water for rainwater and greywater.
Environmental strategies
After studying water consumption and its room for improvement in pre-project phase, it was decided to implement the strategies outlined below:
a) Reduction in water demand through rationalization of the hydraulic installation and the consumption points. Reduction of irrigation to zero except the first two years (until the plantation reaches maturity), by using plant species which do not need more water than the rain naturally provides.
b) Increment of efficiency through the use of sanitary installations with reduced flow, reduced operating pressure, incorporation of air into the water flow, reduced flush toilets, waterless urinals, etc.
c) Use of local resources, by capturing rainwater and recycling greywater for reuse as non-drinking water.
Sanitary and energetic uses of water
As in every museum, water is used for sanitary purposes (washing, sewage, etc.); wet cleaning (horizontal and vertical surfaces) and irrigation (plants). In this case, water is also used as an aid in energy saving, reducing air conditioning demand in the courtyard. This is achieved through cooling the air by water evaporation and by shading, with the intention not to exceed a maximum temperature of 28°C. For this purpose three elements have been designed to have a presence during the warm season of the year: a water mass with depth of between 5 and 8 cm at ground level (connected with a storage tank under the building), a green pergola of deciduous plants and a system of water nozzles spraying from the pergola downwards. Also the interiors of the building benefit from fresher air entering the building from the courtyard through cross ventilation.
1) Section through courtyard and water mass - 2) Spraying nozzles - 3) Spraying nozzles under the pergola
Water balance evaluation
The development of the project was at a pre-project stage at the time of being awarded and since then it has been accompanied by an assessment of demand and supply of water to quantify consumption, to determine its uses, to evaluate saving alternatives and to identify options to replace drinking water for rainwater and greywater. In order to evaluate technical and economic improvements, and to decide whether or not to incorporate the strategies in the final draft, two scenarios were determined and compared: the designed building and a reference building (the same building, but in compliance only with the minimum requirements of the current building regulations). For both cases fixed data were considered: expected occupation (160 persons / day), rainfall in the area (284 liters/m2), consumption of water surface of the courtyard (274 liters / day), the rainwater collecting surface (3368 m2) and sanitary building installation (sinks, WCs, urinals, showers, kitchen and machines spikes). In addition, variable data such as frequency in use of toilets, the water flow rate of the systems available on the market, the water consumption of garden plants and the consumption of water spraying system in the courtyard were considered.
Demand reduction and efficiency increasing actions
A drastic reduction in water consumption in the designed building, in comparison with the scenario of the reference building (accomplishing minimum), is obtained by the combination of rationalizing the needs of users, the choice of minimal consumption sanitary equipment available on the market and the use of plant species which don’t necessitate watering after the first two years. The tables presented below show how the choice of energy efficient systems, sanitary equipment, cleaning, irrigation and evaporative cooling, reduce the partial (column 3) and total consumption (column 4), although the frequency of use is held constant (column 2). The implementation of 3 liters flush toilets, of waterless urinals and sinks of two liters per use stand out. It is also noteworthy that water uses not directly related to the museum activity (cafeteria, courtyard irrigation and evaporative cooling) represent up to 50% of total consumption.
Actions of local resource utilization
Once the water consumption has been reduced to a minimum (about 2000 liters / day) next step is to replace the drinking water with rainwater and greywater in all possible uses. Thus, taking into account the demand and supply of water, it was determined that rainwater would meet the demand of toilets, sinks and evaporative cooling system of the garden (spray and water mass), as shown in the following figure and table consumption. Greywater quantity is low because it generates just from sinks and only one shower. It is used, therefore, only for the cleaning of the building.
Rain water covers 67% of consumption, so being the main system of water regeneration. Its design had to overcome several drawbacks: a low rainfall (284 liters / m2) with a consistent drop of precipitations in summer and, on the contrary, a concentration of demand in this season due to operation of the water mass and mist system. This led to design a large collection area (3368 m2) and a large underground storage tank made of reinforced concrete (100 m3). With these measures, as can be seen in the chart below, the water collected over the year is enough to cover all needs, despite the sharp drop in rainfall during summer.
Rainwater throughout the year: needs (black), collection (light blue) and water in the tank (dark blue)
Since part of the collection area contains gravel and vegetation, considering that the spray nozzles need particle free water and rainwater will also be used in sinks, the system of collection, storage, disinfection and distribution includes several filters that are unusual in a common residential installation. This way, a quality very close to drinking water is achieved, free from health risks when in contact with skin and respiratory system.
Rainwater: wiring diagram, from collection to distribution. Source: Jordi Huguet – Aguapur
Greywater covers 12% of consumption. It is obtained from sinks and showers, and treated by a device for domestic use (Pontos Hansgrohe Aquacycle) whose operating principle is made of three steps: a) arrival of water from sinks and showers, accumulation and sedimentation of solid particles (first tank), b) biological treatment using microorganisms (second tank), c) disinfection with UV radiation (third tank). The treated water is disinfected and pumped to the cleaning taps when they are opened.
Device sketch: HansGrohe Pontos Aquacycle
Savings reached
In comparison to an average building the designed museum allows total water savings of 40% due to reduced water demand and increased efficiency in facilities. Since 100% of the water that does not require drinking quality (toilet flush, cleaning, irrigation, water surface and vaporization of water) is covered with rainwater and greywater, the final reduction of consumption of drinking water reaches 85%.
Key words:
Water cycle in buildings, saving, efficiency, greywater, rainwater.
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Authors' bio:
A. Sagrera, F. López, G. Wadel and L. Volpi are architects and members of Societat Orgànica a sustainable-building consulting group, located in Barcelona, Spain. Their aim is the closure of material cycles, their perspective is the life cycle applied to the environmental vectors of energy, water, materials and waste. The team carries on project consulting (reduction of building impacts), communication (exhibitions, publications and design), teaching (courses on sustainability and architecture), R & D (innovation in materials and buildings) and greening (reformulation of work vision and methodology).
Dr. G. Wadel es el profesor del Programa de cursos online Edificación y sostenibilidad.
