The Open Gardens education centre, owned and managed by the Czech Environmental Partnership Foundation. Today it serves as a platform for learning and inspiration for professionals and the general public. Yet back in 2006, on this site, among abandoned gardens, there stood only neglected buildings.
The complex includes not only an educational garden and an urban farm, but also two office buildings built to the passive standard. Ecological solutions are integrated into every aspect of its operation:
- Water resource management: Rainwater is collected and retained by three green roofs, and grey water1 is purified in a special reed-bed installation.
- Energy production: Electricity is generated by an on-site solar power plant.
All these innovative solutions optimise the complex’s operation. Its energy consumption and efficiency are constantly monitored using 73 measuring devices. The data obtained confirm that the technologies introduced help not only to conserve natural resources but also to save considerable money.
The path of adaptation
The combination of modern technologies helps the education centre effectively combat the urban heat island. This phenomenon arises from a high concentration of traffic, built-up areas, large numbers of people and, most importantly, an insufficient amount of green plantings and water bodies.
In addition, “Open Gardens” has an ambitious goal — to achieve carbon neutrality. This strategy is based on using exclusively renewable energy sources and significantly reducing the consumption of energy, water and other natural resources.
How does it work?
The “Open Gardens” education centre consists of the renovated administrative building B, the newly built education centre C, residential building A facing the street, as well as an educational garden and an urban farm located on leased land belonging to the Congregation of the Sisters of Mercy of St Charles Borromeo.
In 2006, the Czech Environmental Partnership Foundation invested part of its funds in the “Open Gardens” project with the aim of turning it into an exemplary example of the ecological development of a city. And it worked. The foundation prepared a design for a new centre with premises for non-profit organisations and education in the modern passive building C, which is connected to Špilberk hill by a green roof. When construction began in 2011, the foundation decided to simultaneously reconstruct the 200-year-old administrative building B so that it met the passive standard. The company Skanska worked on both buildings at once and put them into operation at the end of 2012 and the beginning of 2013.
Energy
The economical use of resources is a goal throughout the “Open Gardens” site. A small photovoltaic power plant with a capacity of 19,725 kilowatt-peaks2, located on the roof of building B, produces electricity and can cover half a year’s consumption of one of the office buildings. Electricity from the photovoltaic power plant in the village of Hostětín, partly owned by the foundation, contributes to the carbon neutrality of the “Open Gardens” operation.
The heating and cooling systems of both buildings, with a total area of 2,000 square metres, use 8 deep boreholes 905 metres long to extract thermal energy. The system operates with 4 heat pumps with a coefficient of performance (COP) of 5.2 and a total thermal capacity of 68 kW.
The system consumes up to 20 megawatt-hours of electricity per year and produces up to 120 MW (or 104 megawatt-hours of thermal energy, based on a COP of 5.2). It can provide 5.2 times more thermal energy than the electricity consumed. The passive building also uses an active concrete core: pipes embedded in the concrete slab through which a heat carrier circulates. This makes it possible to use the mass of the concrete as a thermal accumulator that helps with cooling and heating. In the complex’s boiler room, a rotary heat exchanger is installed that recuperates heat — in winter it warms the fresh air entering the building, and in summer it cools it.
The whole of building C is controlled by an intelligent management system that automatically coordinates all active elements, such as blinds, lighting or the recuperation system. All of this helps to minimise energy consumption.
Use of rainwater
In addition to the solar power plant, solar panels are also installed on the roof of building B, which, together with heat pumps, heat water. For the toilets in building C and for watering the garden, water comes from the drainage system and a rainwater reservoir. Using rainwater in the buildings makes it possible to save about 60 percent of drinking-water consumption per year. All taps are equipped with water-saving devices that mix the water with air bubbles during operation. Grey water from the washbasins goes to a horizontal treatment installation made of gravel and planted with moisture-loving perennials. At present, measurements of the water-retention capacity of the intensive green roof of building C (30 centimetres of substrate) and of two extensive light-green roofs of the garden houses with “SedumTop” covering based on mineral wool or recycled “Retex” are being carried out on site. The data obtained confirm the great potential of vegetated roofs for retaining stormwater and cooling the urban microclimate. Monitoring of the soil temperature on the green roof of building C confirms the positive influence of the plant cover on stabilising the temperature of the building and the adjacent area.
Data measurement
The effectiveness of the technologies used in “Open Gardens” is carefully monitored and studied, including the return on investment.
The original state
Before 2006, the buildings at Údolní 33 served as the headquarters of a financial group; part of the buildings was used as residential premises, and part stood empty. The area of the neighbouring former gardens on the northern slope of Špilberk was neglected, overgrown with trees, littered with rubbish and gradually populated by homeless people.
Operation and maintenance
During intensive operation of the green roof, it is necessary to plan for the costs of mowing and intensive watering during the summer heat. And therefore, it is expected that after about 40 years the wooden facade of building C will have to be modified. Building B, by contrast, has a titanium-zinc facade with a service life of at least 90 years.
At the very start of construction, the idea of artificial irrigation was proposed for the intensively used part of the garden. However, the foundation abandoned this initiative, taking into account the location on the northern slope and the abundant seasonal rains at that time.
Intensive attendance (about 30,000 people a year) and the extremely dry recent years forced the foundation to install automatic irrigation of the sunniest and most-used lawn areas, including part of the green roof of the education building C.
The operating experience also led to a number of changes in the ventilation and heating regime in different parts of the buildings.
It also turned out that the savings on the measurement and control system in the reconstructed building B negatively affect energy consumption in this building (especially the consumption of cooling in summer).
One of the practical conclusions is that for such demanding processes (flushing, irrigation) rainwater from the roofs and paved surfaces is not enough, and it is necessary to replenish the reservoir from a drilled borehole.
Why was this particular measure chosen?
When planning the construction of administrative building C, the possibility of a wooden structure was considered first. However, it did not meet the requirements for maintaining thermal stability in summer, so a reinforced-concrete structure was chosen, which has a high heat capacity and does not overheat in the hot season. Clay plaster was used for the finish.
Obstacles and challenges
The preparation of the design of building C proceeded systematically and very openly. The project met with resistance from a group of experts associated with the Passive House Centre. Discussions about various details of the construction solutions were sometimes quite heated.
From an urban-planning point of view, the main problem was the narrow, elongated shape of the plot on the slope, which did not allow the centre’s design to be placed within the built-up part of the courtyard. The winning design by the architectural studio Projektil solved this problem by breaking the existing building line, sinking the building into the ground of the slope and compensating for this by creating a green roof. Today this roof serves as a pedestrian route connecting Špilberk hill directly with the education centre building. The jury supported this solution, and the city of Brno was convinced that the complex would serve the public interest and that the shift of the building line would not become a pretext for private investment projects.
Construction challenges and their solutions
During construction, the most serious challenge was the limited access to the building site. This created significant logistical difficulties. The solution was obtaining permission to use neighbouring plots belonging to the school and the State Land Agency. This step made it possible to establish uninterrupted supply of materials and ensure the operation of machinery.
The narrow entrance to the courtyard was the reason for another important decision: the foundation at the last moment agreed to renovate building B at its own expense and add another floor to it. This was done in parallel with the main works on the new building.
Because of the lack of time, the design was not worked out in detail, and many structural issues had to be resolved during the work itself. Such haste led to a significant increase in costs: the total cost of the reconstruction exceeded the initial estimate by about 20%. This example demonstrates how unforeseen circumstances and quick decisions can affect the financial result of a project.
The simultaneous completion of construction of both buildings on a very limited area with a mandatory completion date for the subsidised project was also a very difficult task.
An unexpected problem was the attitude of the Department for the Protection of Cultural Heritage towards placing a solar power plant on the roof of building B during the technical reconstruction in the courtyard. Given that the building is located in the protection zone of the National Cultural Monument of Špilberk Castle, at first the department allowed panels to be installed on only one part of the roof (at the end of 2013), and only in 2015, after difficult negotiations and the involvement of the National Heritage Institute, was the whole roof allowed to be used for a power plant with a total capacity of 19,725 kilowatt-peaks.
How much did it cost?
The reconstruction of building B, the creation of the educational garden and the construction of the passive building C cost a total of 103.9 million Czech crowns excluding VAT (€3.86 million). The reconstruction, with a total cost of about 35 million Czech crowns (€1.3 million), was paid for by the foundation from its own funds, as was the co-financing of the European grant from the “Environment” Operational Programme in the amount of 25 percent. Part of the land was exchanged by the foundation with the city of Brno.
The payback of the individual technologies used in the “Open Gardens” area ranges from 7 to 10 years. Their expected service life is at least 20 years (photovoltaic systems). The service life of the passive building is 40 to 80 years.
