Description of the action

The Slovenian case study on national scale of EPISCOPE concerns the housing stock of the residential buildings in Slovenia, which has set ambitious goals for energy efficiency related to national plans. National goals for 2030 are:

• Reduction of final energy consumption in buildings by 30 % compared to 2005;
• At least two thirds of energy consumption in buildings from generated from renewable sources;
• Reduction of GHG emissions in buildings by at least 70 % compared to 2005;
• To reduce particulate matter emissions from energy use in buildings by 50 % during the period 2015-2030.

The challenge of the existing housing stock for the long term in Slovenia is to tackle the thermal efficiency of the housing stock, much of which is older and/or ‘harder to treat’. The IEE EPISCOPE project is intended to highlight where the initial potential for refurbishment exists and in which types of households. A key aim of the project is to evaluate more realistic refurbishment scenarios.

The targets for emissions are intended across all sectors as a whole, rather than for housing in particular. In practice each sector may have more or less to contribute in terms of savings towards the total budgets into the future, however for modelling purposes in this project it is assumed that housing will aim to meet the targets as given.

The Slovenian pilot project on local scale of EPISCOPE concers the housing stock of the Municipality Kočevje, which has set ambitious goals in its local energy concept [LEK 2008], [Covenant of Mayors 2014]. Its short-term goals for 2020 are a reduction of gas emissions by at least 30 % compared to the emissions in 2005 and an increase of the share of renewables up to 50 %. The main advantage of the city for exploitation of renewables is its local biomass district network. The municipal plan is continuous expansion of the network in order to increase the share of renewables with exploitations of local wood.

Scenario Approach

The scenario approach uses a calculation model (developed in MO Excel and M Visual basic) with “three layers” for both national and local building stock. The first layer is a long-term model of the building stock. It quantifies the expected future annual in-use stock of dwellings (#) and reference floor area (m2) on the basis of the assumed past and future demand, i.e. the assumed development in persons, per-sons per dwelling and reference floor area per dwelling, potential for (partial/full/deep) renovation, based on the assumption for renovation and new build rates.

This layer of the model also follows the ageing development of each type/age segment of the stock, with predicted lifetime of building component and it’s technologies for heating and DHW, after which the building becomes the potential for renovation. Based on the renovation rates for each age band, buildings in each year, the model identifies the buildings for renovation, respective to their age of construction, potential (based on a time from the last renovation) and type. The second layer of the model is an energy and emission layer. Here are pro-vided as model input data energy intensity values (deriving from typology) for different energy carriers, for each type/age segment of the stock and for each scenario. The last layer takes into account local or national plans, which can be implemented into a model on several different ways, e.g. more intensive renovation rates in specific year due to increased subsidies fund, increased share of grid connections due to network expansion in a city district.

To be able to carry out a comprehensive analysis, all EPCs from the database were studied. In Slovenia, the EPC database collects data on the building stock, refurbishment measures, and the development of energy efficiency of buildings.

Description of the Basic Case and the Most Relevant Scenarios

The starting point, which determines the current state of the building stock and its energy balance is the basis from which arise all scenarios. The first step is to gather the data and to determine the potential for energy renovation. The current state of the building depends on its potential for renovation, where four possible levels of the current state are considered:

• Unrefurbished: Based on the existing data, the building was not subjected to any renovation in the past, therefore it has potential for renovation on all components of the thermal envelope (walls, roof, and windows). Unrefurbished buildings can be subjected to partial, full and LE renovation.
• Part_Renovation: Based on the existing data, the building was subjected to renovation of one building construction (walls, roof or windows) in the past, therefore the building has potential on two components of the thermal envelope (walls, roof or windows). Buildings with partial renovation can be subjected to partial or full renovation.
• Full_Renovation: Based on the existing data, the building was subjected to renovation of two building constructions (walls, roof or windows) in the past, therefore the building has potential on one component of the thermal envelope (walls, roof, and windows). Buildings with full renovation can be subjected to partial renovation only.
• LE_Renovation: the building was subjected to major renovation works in the past, all building constructions had been renovated and is thus considered as a building with low energy (LE) demand for space heating. Buildings with LE renovation are not considered as a potential for renovation.

One of these states was determined for each representative of building typology of the build-ing stock. Renovation rates in the model do not apply for rates of one building component only, e.g. 3 % of walls renovation, but apply to the extent of possible renovation (partial, full, low energy). Partial renovation in the model covers renovation works on building’s envelope only, while full and LE renovation can include the replacement of a heat, DHW supply sys-tem, as well as installation of a mechanical ventilation system. All buildings cannot be renovated in one year only so the model is taking into account several limitations when renovating the building stock.

Results

Key results are shown are presented in the picture bellow. All the observed scenarios show great promise in the fulfilling the regional contribution to national goals for the reduction of final energy use and GHG emissions. According to policy targets and EPISCOPE benchmark levels, shown are met in both the observed years – 2020 and 2030.