Foto: Lenka Mitrenga, Czech Environmental Partnership Foundation
Open Gardens in Brno
The Open Gardens Education Centre owned and run by Czech Environmental Partnership Foundation – today it is used for education and to motivate investors and professionals as well as the public. But in 2006 there were neglected buildings on the plot surrounded by abandoned gardens.
In addition to the educational garden and the city farm, it also includes two office buildings meeting the passive standard. Rainwater in the area is retained thanks to three green roofs, gray water is purified in a reedbed treatment plant and electricity is produce in a solar power plant.
All of these solutions and many other tweaks affect the operation of the entire complex. Its consumption is monitored every day by 73 measuring devices and valuable data prove that the technology used saves both nature and money.
The Adaptation Journey
The positive impact
Combining various technologies help us fight the rising temperatures in the city, so called urban heat island which is created by concentration of transport, people, built-up areas and lack of green spaces and water.
At the same time, the aim of Open Gardens is carbon-neutral operation, using renewable sources of energy and lowering the consumption of energy, water and other sources.
How does it work?
Open Gardens Educational Centre consists of a renovated administrative building B, a newly built seminar centre C, a street facing residential building A and an educational garden and an urban farm located on rented premises owned by the Congregation of the Sisters of Mercy of St. Borromeo.
In 2006, Czech Environmental Partnership Foundation invested a part of its endownment into the Open Gardens with the vision of changing of transforming it into a model example of the city's ecological development. And it worked. The foundation prepared a project of a new center with facilities for non-profits and education in a modern passive building C, which is connected to Špilberk hill with a green roof. When the construction started in 2011, the Foundation decided to simultaneously renovate the 200-year-old administrative building B to reach the passive standard. Skanska worked on both buildings simultaneously and put them into operation at the end of 2012 and beginning of 2013.
Thrifty operation is the aim in the entire area of the Open Garden. A small photovoltaic power plant with an output of 19,725 kilowatt-peaks located on the roof of building B produces electricity and can cover six months of consumption of one of the office buildings. Electricity from a photovoltaic power plant in the village of Hostětín, partly owned by the foundation, adds to the carbon-neutral balance of running Open Gardens.
8 deep ground-source heat boreholes with a length of 905 meters and a system of 4 heat pumps with a heating factor of 5.2 and an output of 68 kilowatts are used to get energy for heating and cooling for both the buildings with a total floor area of 2,000 square meters.
Although the system consumes up to 20 megawatt hours per year, it can multiply the received energy up to 6 times. In the passive building C, the active concrete core - the concrete pipes in the ceiling through which the cool or hot liquid goes through, also helps with cooling and heating. There is also a rotary heat exchanger built in the engine room of the complex, which heats the fresh air flowing into the building in winter and cools it in summer.
The entire building C is controlled by an intelligent control system which automatically coordinates all active elements such as blinds, lighting or recuperation syste. All of this contributes to the lowest possible energy consumption.
In addition to the solar power plant, there are also solar panels on the roof of building B which together with heat pumps heat the water. Water for flushing in building C and for watering the garden comes from the drainage system and from the rain water tank . Using rainwater in the buildings saves about 60 percent of drinking water consumption per year. All water taps are equipped with water savers mixing water with air bubbles when running. Gray water from the washbasins goes to the horizontal root wastewater treatment plant made of gravel and planted with moisture-loving perennials.
The retention capacity of the intensive vegetation roof on building C (30 centimeters of substrate) and two extensive light green roofs on garden sheds with SedumTop stonecrop carpets on a mineral wool or recycled Retex base is currently being measured on site. The obtained data verify the great potential of vegetation roofs for retaining torrential rain and cooling the urban microclimate. Monitoring the soil temperature on the green roof of building C confirms the positive effect of the vegetation layer on the temperature stabilization of the building and its surroundings.
A number of technologies are used in the Open Gardens and their effectiveness is also monitored in detail, including the return on investment.
Until 2006, the buildings at Údolní 33 served as the headquarters of a financial group and part of the buildings were used as appartments. There were also unkept appartment buildings. The neighbouring former gardens on the northern slope of Špilberk were deserted and gradually inhabited by homeless people; the lands were overgrown with trees and full of rubbish.
Operation and maintenance
In the case of an intensive green roof, this involves the cost of mowing and watering the intensively used part during the summer heat. It is assumed that after about 40 years, the wooden facade of building C will have to be modified. The titanium-zinc facade of building B has a durability of at least 90 years.
The designer presented the idea of artificial irrigation for an intensively used part of the garden already at the beginning of the construction. However, the foundation rejected this initiative with the regard to the northern slope and the seasons rich in rain water at the time. Intensive traffic (attendance of around 30,000 people per year) and extremely dry recent years have led the foundation to fit automated irrigation of the sunniest and most used lawn areas, including part of the green roof of seminar building C.
Experience from operation has also led to a number of modifications to the ventilation and heating regime in various parts of the buildings.
It also turned out that the savings on the measurement and control system in the reconstructed building B have an adverse effect on the energy consumption in this building (especially the consumption of cold in the summer).
One of the practical findings is that for such demanding operation (flushing, irrigation) rainwater from roofs and paved surfaces is not enough and it is necessary to replenish the tank from a drilled well.
Why was the measure chosen?
When planning the construction of administrative building C, the foundation considered a wooden building. However, it did not meet the requirements for thermal stability of the building in the summer, so a reinforced concrete structure was chosen, which has a high storage capacity and does not overheat in the summer. The plaster is clay.
Obstacles and challenges
The project preparation of building C proceeded systematically and very openly. The project was opposed by a circle of experts around the Passive House Center. Discussions on various details of the building solutions were sometimes quite heated.
From the urban point of view, the biggest problem was the narrow shape of the plot in the slope which did not allow to place the programme of the centre in the built-up part of the courtyard. The winning design of the Projektil architects studio dealt with this by breaking the building line, submerging the building into the ground of the slope and compensating this by building a green roof which you can use today to walk from Špilberk hill straight into the seminar center building. The Commission recommended this solution and the city of Brno was convinced that the complex will serve the public and the relocation of the construction line will not become an opportunity for private investors.
During the construction itself, the biggest challenge was the access to the building plot which was then solved by creating an entrance through the neighboring plots managed by a school and the State land office. It was the narrow entrance to the courtyard that was the main reason why the foundation decided at the last minute to renovate the building B from its own resources at the same time as the new building, and to add one extra floor. Everything happened quickly, there was not enough time for a detailed implementation project, structural issues were being solved and the whole reconstruction cost about 20 percent more than the original estimate.
Simultaneous completion of both buildings in a very limited space with a binding completion date for the subsidized project was very complicated as well.
The attitude of the herritage protection department to the location of solar power plant on the roof of the technical reconstruction B in the courtyard was an unexpected problem. On the grounds that the building is located in the protection zone of the National Cultural Monument Špilberk Castle, the Office initially permitted only panels on one part of the roof (end of 2013) and only in 2015 after complex negotiations and the involvement of the National Monuments Institutethe whole roof could be used for the powerplant with a total output of 19,725 kilowatt-peaks.
How much did it cost?
The reconstruction of the original building B, the creation of the educational garden and the construction of the passive building C cost a total of CZK 103.9 million without VAT (EUR 3.86 million). The reconstruction with a total cost of about CZK 35 million (EUR 1.3 million) was paid for by the foundation from its own resources, just like the co-financing of a European grant from the Operational Program Environment in the amount of 25 percent. Part of the land was exchanged by the foundation with the city of Brno.
The return on individual technologies used in the Open Garden area is between 7-10 years. Their expected service life is at least 20 years (photovoltaics). The lifespan of a passive house is considered to be between 40-80 years.
Administrative buildings Zieleń miejska Water purification and recycling Use of rainwater Heating Zelená střecha Biodiverzita Vlny horka a tepelný ostrov Povodně a přívalové srážky Nedostatek vody a sucho Zelená energie Úspory energie