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Block One

Block One


Radomir is a small town of around 16,000 people situated near Bulgaria’s western border with Serbia. The Radomir refurbishment was a PHARE-funded demonstration project promoting energy efficiency in multi-family housing. Commencing in 1996 the project was summoned to address inefficient residential high-rise built in the 1980s and 1990s, when energy prices were very low. The buildings were chosen as the measures applied could be widely replicated. This was due to factors such as building fabric, heating infrastructure, ownership and supporting institutional configuration.
Commencing in June 1995 and taking 41 months the project included insulation of the external walls, roof and basement ceiling, and overhaul of the heating system.

Block One. Before refurbishment

Building details

Type of building: Block One is one of six buildings refurbished as part of the Radomir project. It is a seven storey multi-family high-rise comprising 21 owner-occupied flats. The external envelope was constructed from prefabricated concrete panels, with wooden doors and double glazed, wooden framed windows. Some balconies were also glazed in metal frames. The windows in the corridors, main entrances and staircases had broken glass, cracks and gaps. As the buildings were under-heated, the temperature in these areas did not differ much from the outside temperature.

The space and hot water heating for all six buildings was connected to a local district heating system. This service was suspended due to financial problems and was not expected to recommence due to its poor overall condition. However, the pipe infrastructure within the buildings appeared to be in reasonable order and most radiators were still connected to this system. However, in practice over half of all residential rooms were not heated, and of those that were, most were only heated temporarily by electric radiators or heat accumulators.

Year of construction Block one was built in 1980.
Heating and cooling / measures installed _ All building joints were stopped, glazed balconies were improved and all windows and doors were either improved or replaced. A new boiler was commissioned and the central heating was restored. Pump and heating valves were installed to equalise heating across the building. TRVS, heat meters and timers were integrated and electric DHW heaters were installed into every flat.
Energy label/CO2 emissions An energy audit of Block One calculated the total energy consumption as 373 kWh/m2a and obtained a space heating energy consumption before refurbishmen t of 245 kWh/m2a


Aim The project aims to:
- Promote energy efficiency in multi-family housing.
Key points The improvements
- Roof: Additional cement and plaster (50mm) was added to the lower layer of the concrete roof, and plaster, bitumen and waterproofing was added to the upper layer.
- Walls: 30-60mm extruded polystyrene foam was glued the existing rendered 200mm concrete panel walls. This was followed by a thin layer of plaster, reinforced fibreglass grid, an external layer of plaster including lime and finally a coat of finishing plaster. Air stops were also applied to the building joints.
- Basement Ceiling: 39mm insulating board was mounted on the concrete slabs using plastic dowels.
- Wood windows: The existing double-glazed windows were composite thermo-windows with wooden frames. These frames were poorly fitted and cracked, and often the outer glass was not air-tight leading to further heat loss. The wooden frames were retained and repaired for a number of reasons; they are relatively light with low heat conductivity; the material is recyclable; the low thermal expansion means they adjust to masonry much better than plastic framing; and they do not require metal reinforcement, reducing heat accumulation.
- Balconies: Many of the balconies had been modified to form a small extra room with metal-framed single glazing. These windows were of poor quality and were replaced with new PVC windows.
- Main Entrance Doors: The wood joinery of the main entrances was replaced with PVC windows and doors.
- Heating system: A circulation pump and heating unit valves were set to allow an even distribution of heat to all rooms. The new system incorporated a weather-dependent flow was regulated to maintain desired mean room temperature throughout the heating season. TRVs, heat meters and timer controls were fitted to all radiators. Electric DHW heaters were fitted in each flat.
Reason for inclusion as Shining Example Energy efficient high-rise refurbishment can be successfully coupled to the progressive development goals of accession countries, as so clearly depicted in this case study. This was achieved by combining institutional and financial support from the European Commission and EU15 Member States with local government and private sector engagement, and resident consultation.

Block One. After refurbishment


Costs &


The refurbishment was carried out between 1996 and 1998. During this period there was significant economic upheaval including hyperinflation and devaluation of the Leva in 1999. Consequently it is very difficult to provide an accurate representation of costs or payback period. The following figures therefore are indicative at best.

See the table containing the measures for thermal insulation and their payback period

Benefits - Roof: U-values were improved to 0.8 W/m2K.
- Walls: U-values improved from 2.9 to 0.52 W/m2K.
- Wood windows: These were repaired to restore a theoretical U-Value of 2.6 W/m2K.

Calculated energy savings Block One: Annual fuel requirements per m² of gross building area (including non heated spaces):

- Before the refurbishment: 198 kWh/m²a

- After the refurbishment: 107 kWh/m²a

- Energy saved: 91 kWh/m²a or 46%

The calculated energy savings assume a normally heated building. Before the refurbishment the Radomir buildings were under-heated. Consequently the main outcome from the project was an increase in thermal comfort rather than substantive energy savings. However, given the anticipated increase in Bulgaria’s per capita income and concomitant shift to more ‘standard’ heating patterns, the project managers expect energy savings to accrue over the coming years.

An energy audit of Block One calculated the total energy consumption as 373 kWh/m2a:

- Space heating energy consumption before refurbishment: 245 kWh/m2a

- Heated Area energy consumption after refurbishment: 132 kWh/m2a

An energy audit of Block One calculated the total energy consumption as 373 kWh/m2a:

- Space heating energy consumption before refurbishment: 245 kWh/m2a

- Heated Area energy consumption after refurbishment: 132 kWh/m2a


Partnership details The Radomir refurbishment was a PHARE-funded demonstration project promoting energy efficiency in multi-family housing.

The Committee of Energy was the contracting authority and coordinator of this project while a consortium including the Exergia SA (Greece), ENERGOPROJEKT (Bulgaria) and ICEU (Germany) carried out the works.


Achievements Residents were consulted during the design stages of the project and then again after the works had been executed, by way of a mailed questionnaire. They were able to comment on changes in the thermal comfort of their homes, and heating and hot water expenses. The municipality of Radomir was also consulted and undertook further promotion of the project. Resident and local authority support formed part of the funding obligation under the PHARE programme.

To know more



Sofia Energy Centre
Contact Evelina Stoykova

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