Low Carbon South East Europe

Project outputs

Green Castle
January 20, 2015
Name of GP initiative

Green Castle

Number of GP initiative  

Croatia/Zagreb County

Author/Email miroslava@luznica.hr / iprzulj@regea.org

Sisters of Charity of St. Vincent de Paul/North West Croatia Regional Energy Agency (REGEA)

Year of implementation: 2012
Time horizon of initiative/map/etc.: Long term

General description:

The Baroque Luznica castle is a listed historical monument. Within the Green Castle project, a geothermal heat pump was installed in the castle with the help of local contractors, to provide heating in the winter and cooling in the summer. Lower energy costs have enabled the sustainable operation and redevelopment of the castle.

During the winter months, the project has helped to generate monthly savings of about HRK 40,000 compared to gas heating.

Steps in creating the initiative/roadmap/strategy:

The first phase of the project was the building of a facility within the castle complex based on low-energy standards. Due to the rules for the protection of historical monuments, Luznica castle only implemented those measures that were agreed with the Conservation Department of Zagreb County. These included the reconstruction of the facade and the modernisation of doors and windows. In the castle annex, various energy-efficient features were introduced, including sealing around doors and windows (overall heat transfer coefficient, or U value, of 1.1 W/m2K), heat insulation with a thickness of 10 cm, and underfloor heating (Figure 1).

Figure 1. The new castle annex at the finalisation of the first phase

The second phase of the project was the installation of renewable energy sources, involving the mounting of 50 m2 of solar cells for producing hot water for the kitchen and bathrooms (Figure 2).

Figure 2. New castle annex at the finalisation of the second phase

The third phase was the replacement of the outdated heating system in the castle with a new system of geothermal heat pumps for heating, cooling and hot water.

Targets and target determination:


  • Preservation of natural and cultural heritage
  • Reduction of greenhouse gas emissions
  • More efficient use of energy


  • Lower costs for energy fuels
  • Revenue from the rental and use of cultural facilities
  • Employment of local industry


  • Preservation of local cultural traditions
  • Employment in construction work and the redevelopment of cultural facilities

Success factors/barriers:

As Luznica castle is a listed historical monument, permission had to be obtained from the Conservation Department of Zagreb County for all the planned reconstruction work. The rules for the protection of historical monuments are sometimes in conflict with the rules for energy efficiency improvements, thus additional efforts were needed. Many other legislative restrictions were also encountered during the project, such as the law prohibiting the drilling of wells in the castle park for heat pumps.

Implementation costs:

EUR 100,000 (third phase only)

Economic effects:

Annual energy savings as a result of the renovation of the castle and the building of the new castle annex based on a low-energy model are about 40,618 kWh. In addition to the energy efficiency measures, the use of geothermal heat pumps saves about 365,696 kWh per year, and energy savings from the use of solar cells for hot water supply are about 17,000 kWh. This means total annual energy savings of 423,314 kWh.

The reduction in carbon emissions as a result of these savings is about 73,38 tonnes, with 47 percent lower emissions of CO2. The CO2 savings have been calculated separately with respect to the technology employed. The usage of geothermal heat pumps increases electricity consumption and reduces gas consumption. Hot water supply using solar cells reduces electricity consumption by replacing electric boilers. Heat insulation reduces the consumption of gas. Energy savings were read directly from the energy facility infrastructure, and standard conversion factors were used to convert the kWh savings into CO2 savings.

This document was developed in the framework of the LOCSEE project.
European Union SEE Regional Policy Network collaboration area (members only) Regional Policy Network