1. Thermal Retrofitting Of Dormitory Under Historic Protection - Case Study
Jerzy KWIATKOWSKI, Jerzy SOWA, Andrzej WISZNIEWSKI
Warsaw University of Technology, Faculty of Building Services, Hydro and Environmental Engineering,

2. nZEB standard in Poland
In Poland a nZEB standard has been define by primary energy indicator (EP)
For public buildings, like educational building maximal value of EP has been state as sum of three indicators:
for heating and domestic hot water – 45 kWh/m2a;
for cooling – 25*(Af,c/Af) kWh/m2a (where Af,c is a cooled area and Af is a total regulated temperature area);
for lighting – 25 kWh/m2a for time of light operation <2500 h/year and 50 kWh/m2 a for time of light operation ≥2500 h/year.
In total maximum EP may vary from 70 to 120 kWh/m2a.
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3. nZEB definition in KODnZEB project
Energy consumption for:
heating,
cooling,
hot water preparation,
lighting,
auxiliary energy for HVAC system,
Dynamic hourly calculation
Cost optimal EP indicator for educational building – 40 and 55 kWh/m2a
Maximum EP <20 kWh/m2a
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4. Building description
Part of a dormitory complex of Warsaw University of Technology build before and in 1950
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5. Energy performance of the building – existing state
EP indicator [kWh/m2a]
Heating and ventilation
140.8
Domestic hot water
69.1
Lighting
85.3
Auxiliary energy
3.3
PV installation
Sum
298.5
Any modernizations must be agreed with heritage protection officer.
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6. Retrofitting measures - envelope
Insulation of external walls –aerogel panels (λ=0,015 W/mK and the thickness of 4 cm); decrease of the heat transfer coefficient of walls from U=1,09 W/m2K down to U=0,279 W/m2K
Insulation of the ceiling between the top floor of the building and the unheated attic - mineral wool (λ=0,035 W/mK and a thickness of 16 cm); decrease of the heat transfer coefficient of the ceiling from U=2,02 W/m2K down to U=0,197W/m2K
Replacement of windows - an improvement of the heat transfer coefficient of windows from U=1,87 W/m2K to U=0,70 W/m2K; decrease the air tightness coefficient from n50=3,0 1/h down to n50=1,5 1/h
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7. Retrofittong measures - ventilation
Mechanical exhaust ventilation with air to water heat recovery from living spaces:
single rooms - 20 m3/h and 50 m3/h when the shower recess is used (+15 min after);
for units when one shower recess is dedicated for 1 double and 2 single rooms - 0 active contactors m3/h, 1 active contactor - 50 m3/h, 2 or 3 active contactors - 80 m3/h
Balanced mechanical ventilation with air to air heat recovery in other zones (corridors and staircase, shared kitchens, shared bathrooms, service rooms);
Natural ventilation of unused rooms in the basement of the building.
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8. Retrofitting measures – other systems
Space heating system - replacement of the radiators and installation of regulating valves
Domestic hot water system - air to water heat pump using exhaust ventilation air flow from living units
The lighting system - replacement of the existing lighting fixtures and light sources, installation of a lighting control system, reduction of lighting installed power from 11,22 W/m2 down to 3,34 W/m2
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9. Retrofitting measures - RES
PV panels cannot be seen from the street level;
PV system data:
APV=374,8 m2;
PPV=79,35 kWp;
EPV= kWh/a
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10. Analysis of proposed measures
Simple pay-back time [years]
Decrease of primary energy indicator [kWh/m2year]
Cost of reduction of primary energy indicator reduction [€/(kWh/m2year)]
External wall
58.8
26.6
12 844
Roof
7.1
11.5
1 561
Windows
26.9
14.9
5 889
Ventilation system
5.7
69.4
1 286
Heating system
23.9
7.6
5 279
Lighting
73.9
48.0
4 405
Hot water system
0.6
33.3
131
Heat pump (hot water only)
9.1
42.6*
750
PV system
55.9
58.6
4 967
All measures
22.8
280.2
3 980
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11. Conclusions and remarks
It was shown that by common work of architects, constructor and HVAC engineers EP ratio was decreased from 298,5 kWh/m2a to 18,3 kWh/m2a
Such a result needs holistic approach (envelope, HVAC systems, lighting, BACS, RES)
The internal thermal comfort has been incerased (decrease in hours with overheating)
The economic efficiency of proposed measures is related to the specific of a building
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12. Jerzy KWIATKOWSKI
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