Bratislava is the capital of Slovakia and, with a population of about 420,000, the country’s largest city. Bratislava is the political, cultural, and economic centre of Slovakia. Its area is 36 759 ha. The population density is 1,161 inhabitants per km2 (2007). Located in the south-western Slovakia, Bratislava is occupying both banks of the Danube River and the left bank of the Morava River. The city is the only national capital that borders two independent countries – Austria and Hungary and it has a long and proud history that dates back to pre-Roman times.
Administratively Bratislava is divided into five districts. For self-governance purposes, the city is divided into 17 boroughs. Bratislava belongs to the regions with very low unemployment’s rate. According to Eurostat the unemployment rate by NUTS 2 – Bratislava region, was in 2010: 6.2% and in the larger urban zone 2007-2009: 3.9%. Bratislava is a centre of industry, services and education. The GDP per capita is in Bratislava region 186% (2011) of the EU average and is the highest level of all regions in the new EU member states. There are 350,000 economically active persons, 22% with higher education and 66% in active productive age. The city is a target of daily mobility to work and schools (about 150 thousand people per day).
The district and the building stock
The appartment buildings, selected for the project EU-GUGLE demonstration are located in two districts: the wider city centre and the western part of Bratislava city. A wide range of different building types from different construction systems and construction materials were selected for the EU-GUGLE project demonstration and are representing the typical city´s building composition. Almost all of the selected buildings are characterized by high energy demands and present diverse typical technical difficulties. The buildings, in current stage, have very poor thermal protection of the envelope and require high amount of energy for space heating and domestic hot water preparation. Most of the buildings are connected to a district heating network.
The selection of pilot private apartment buildings is aimed to identify the wide spectrum of issues and problems that could prospectively occur in the renovation process of housing stock in the city. Between 60’s and early 90’s, due to city expansion and lack of housing units, many prefabricated concrete apartment blocks were built. The exemplary renovation of the municipal social housing is expected (the municipal Lodging-house for disadvantaged families and the House for elderly people)
• Total floor area to be renovated: ≈ 40,000m²
• Type of buildings: Both private apartment buildings and buildings own by community used for housing.
• Primary energy savings target: up to 60-75%.
Energy saving measures
The energy saving measures outlined below will result in 60 to 75 % reduction of energy use in buildings compared to present state. The proposed measures will be replicated in other apartment buildings, located in different city districts, which are constructed in the same or have very similar construction systems. The actions are focussed on following technical and non-technical measures:
• Improvement of the energy performance of buildings through renovation and retrofitting measures (thermal protection of peripheral constructions, roofs, replacement of existing windows with triple-glazed windows,) • Retrofitting of building technical system components and thermal insulation of distribution system pipes; reduction of energy use through technical measures • Implementation of renewable energy sources in district heating systems (eventually disconnection of buildings) • Replacing of fossil energy sources by several innovative technologies (application of heat recovery from the sewage, and air, heat pumps integrated in a lowenergy heat network, PV, cogeneration systems) • Renewal of elevators, increasing of energy and transport efficiency (duplex elevator group control system)
Non technical measures
• Introduction of metering and regulation control systems • Motivation of tenants (metering), communication measures and advisory activities to reduce energy consumption through user’s behaviour • Energy efficiency rental fee and other agreements with tenants
Because of the different construction and age of the buildings the proposed measures are variable, reflecting diverse economic possibilities of the tenants/flat owners and the localisation of the buildings. Due to the social structure of the owners, costs cannot be significantly increased in the next future. Housing stock is usually managed by public housing companies and most of the buildings are in private ownership (usually every apartment). The large number of owners or tenants and low level of awareness complicate any actions when renovating buildings. For the renewal of the building, a combination of credits from State found for housing development and from First home saving bank (PSS, a.s.) will be used. The Energy Performance Contracting (EPC) system will be applied for the social housing buildings owned by the City of Bratislava.
The estimated costs for direct structural measures and measures at energy supply are about 12.5 million Euros for next 4 years. The investments into building-integrated RES are included. Additionally, for replacement of lifts, renewal of lighting and metering systems can be estimated at about 0.2 million Euros. The direct subsidy from the EU-GUGLE project is 1 857 550 Euro. Analyses show that the installation of heat recovery system, appliances for heat and domestic hot water preparation combined with the heat pumps supplied from PV panels are leading to significant cost efficiency. The estimated pay-back time is 11.7 years. .
Energy savings compared to national regulation will reach up to 43 %. Lifespan and sustainability of the buildings will be increased as well as the living comfort of tenants. The buildings will serve as lighthouse projects motivating other owners to building renovation.
• Improve the life quality of the inhabitants
• Raise the inhabitants´ awareness of proper renovation of property, regardless if it is historical or contemporary buildings
• Increase knowledge in terms of environmental and ecological issues and fostering social interaction.