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University Research Centre, Technical University, Sofia, Bulgaria

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University Research Centre at the Technical University of Sofia, Bulgaria

 

The renovation of the University Research Centre at the Technical University of Sofia was performed with the objective of improving the university infrastructure and the building energy performance by no less than 45% when compared to the current norms.

 

Project summary

The University Research Centre case study at the Technical University of Sofia proves that a very low energy consumption can be achieved with moderate renovation measures applied to the building envelope (insulation of the walls to reach a U-value of 0.35 W/m²K and to the ceiling (unheated space) under the roof (10 cm mineral wool to reach 0.26 W/m²K) as well as new double-glazed windows together with a comprehensive improvement of the building service systems. The heating and cooling of the building is done by an ambient-based variable refrigerant flow heat pump in connection with the ventilation. Hot water is provided by local electrical heaters and the building features a low-energy lighting system. The total final energy use includes heating, hot water generation, cooling, ventilation, and lighting and amounts to 48 kWh/m².year. Sixty three percent (63%) of the final energy is provided by renewable energy sources.

 

Construction costs

The retrofit measures sum up to: 62,000 € for the renovated building envelope and 150,000 € for the Heating, Ventilation and Air Conditioning (HVAC) systems, lighting and the domestic hot water (DHW). 

These costs can be recalculated to 130 €/m².

 

Building size

1,630 m² built-up area (total gross floor area)

 

Building envelope

Walls: concrete and brick with thermal insulation

Roof: flat, unheated space, thermal insulation of 100 mm of mineral wool

Windows: PVC frames with double glazing

Building envelope U-values:

  • Wall: 0.35 W/m².K (717 m²)
  • Window: 1.7 W/m².K (432 m²)
  • Roof/ceiling to the attic: 0.26 W/m².K (425 m²)
  • Cellar ceiling/ground slab: 0.56 W/m².K (425 m²) 

 

Building service systems

  • Heating: ambient-based variable refrigerant flow (VRF) heat pump
  • Cooling: VRF based system
  • Ventilation: ambient air-based heat pump and heat recovery unit, including heating and cooling
  • Hot water: local electrical heaters
  • Low-energy lighting system 

 

Renewable energy systems

  • Heating: ambient-based VRF heat pump with seasonal COP = 4
  • Ventilation: ambient-based heat pump with seasonal COP = 4 (in cooling mode 4.5) and heat recovery unit, with seasonal efficiency of 75% (heating mode) 

 

Building Energy Performance

 

Final energy use:

Calculated

X

Calculation method:

National standard BDS EN ISO 13790 – national simulation tool

Measured

 

Monitored in year:

-

Heating

  5.40 kWh/m².year

(+RES 16.2 kWh/m².year =

21.60 kWh/m².year)

 

Hot water

  1.90 kWh/m².year

Cooling

  3.65 kWh/m².year

Ventilation

  2.23 kWh/m².year

(+RES 11.2 kWh/m².year =

13.43 kWh/m².year)

including heating and cooling

Lighting

  2.80 kWh/m².year

Electrical appliances

10.00 kWh/m².year

Total

15.98 kWh/m².year

(+RES 27.40 kWh/m².year + appliances 10.00 kWh/m².year)

Primary energy use:

Electricity

47.94 kWh/m².year

Primary energy factor: 3

Total

47.94 kWh/m².year

 

Renewable energy contribution ratio:

63.2% of the total final energy

(51.3% of the total final energy including appliances)

Improvement compared to national requirements:

77.6%

Compared to:

Annual final energy consumption (with district heating), according to the national require­ments defined by the Ordinance for heat retention and energy efficiency in buildings (updated in 2009)

 

Author(s) information

Name

Prof. Nikola Kaloyanov (Technical University, Sofia)

Name

Prof. Merima Zlateva (Technical University, Sofia)

Lessons learnt

The case study proves that a very low energy consumption can be achieved with moderate renovation measures to the building envelope together with a comprehensive improvement of the building service systems.

Award labels

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Source of funding

Funding description

Operative program "Regional development", National Research Fund

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