When analyzing large panel buildings, it is very rare to take into consideration the requirements connected with the overheating effect. This issue is closely related to the thermal comfort of the building, especially during the summer months. Based on the simulations conducted in the Design Builder program, the authors determined the influence of building orientation, individual flat location and thermal insulation on the thermal comfort of the different flats of a large multi-family panel building

Nowak-Dzieszko, Katarzyna

Rojewska-Warchał, Małgorzata

Portal Czasopism Naukowych (E-Journals)

* M.Sc. Eng. Katarzyna Nowak-Dzieszko, M.Sc. Eng. Małgorzata Rojewska-Warchał, Institute 
of Building Materials and Structures, Faculty of  Civil Engineering, Cracow University 
of   Technology.
KATARZYNA NOWAK-DZIESZKO*, MAŁGORZATA ROJEWSKA-WARCHAŁ*
SIMULATION ANALYSIS OF MICROCLIMATE 
CONDITIONS IN A MULTI – FAMILY LARGE  
PANEL BUILDING
ANALIZA SYMULACYJNA WARUNKÓW MIKROKLIMATU 
W WIELORODZINNYM  
BUDYNKU WIELOPŁYTOWYM
A b s t r a c t
When analyzing large panel buildings, it is very rare to take into consideration the requirements 
connected with the overheating effect. This issue is closely related to the thermal comfort 
of the building, especially during the summer months. Based on the simulations conducted 
in the Design Builder program, the authors determined the influence of building orientation, 
individual flat location and thermal insulation on the thermal comfort of the different flats 
of  a large multi-family panel building.
Keywords: large panel building, thermal comfort of the panel buildings, PMV (Predicted Mean 
Vote), PPD (Predicted Percentage of Dissatisfied)
S t r e s z c z e n i e
W analizie budynków wielkopłytowych bardzo rzadko uwzględnia się problem przegrzania 
pomieszczeń. Problem ten jest ściśle związany z komfortem cieplnym budynku, szczególnie 
w miesiącach letnich. W oparciu o symulacje przeprowadzone w programie Design Builder 
autorzy określili wpływ orientacji, lokalizacji poszczególnych lokali oraz termomodernizacji 
na komfort cieplny w mieszkaniach wielkopłytowego budynku wielorodzinnego.
Słowa kluczowe: budynek wielkopłytowy, komfort cieplny w budynkach wielkopłytowych, 
PMV, PPD
TECHNICAL TRANSACTIONS
CIVIL ENGINEERING
3-B/2014
CZASOPISMO TECHNICZNE
BUDOWNICTWO
380
1. Description of problem
Based on statistical information, about 4 million flats in Poland are made of prefabricated 
elements in different systems. Moreover, almost a quarter of Poles live in large system panel 
buildings. That is why the issues related to this subject are very important and common. 
The most important aspect is the improvement of the building energy certificate of those 
buildings. It is connected with the thermal modernization of the building envelope.
Unfortunately, when considering and designing the thermal modernization, no one 
takes into consideration the thermal comfort and overheating issues which seems to be 
very important from the occupants’ point of view. The average usable area of dwelling 
in a prefabricated building is about 55 m2 and the average number of occupants is 4, which 
gives less than 15 m2 for one person [8]. It makes those issues even more essential.
2. Thermal comfort
Thermal comfort is related to the thermal balance of the body which is affected by 
different parameters: personal and environmental such as human activity; clothing insulation; 
environmental parameters (air temperature, average radiation temperature, air flow speed 
and relative humidity). These factors make up what is known as the ‘human thermal 
environment’. Evaluation of thermal comfort is based on the PMV (Predicted Mean Vote) 
and PPD (Predicted Percentage of Dissatisfied) indexes.
International standard PN-EN ISO 7730 (Ergonomics of the thermal environment. 
Analytical determination and interpretation of thermal comfort using calculation of the PMV 
and PPD indices and local thermal comfort criteria) uses Fanger’s method to estimate thermal 
comfort. The Predicted Mean Vote (PMV) model stands among the most recognized thermal 
comfort models. It was developed using principles of heat balance and experimental data 
collected in a controlled climate chamber under steady state conditions. Fanger’s method 
combines the following environmental features: air temperature, air velocity, mean radiant 
temperature and relative humidity and two personal variables (clothing insulation and activity 
level) into the index that can be used to predict the average thermal sensation of a large 
group of people. Also, psychological parameters such as individual expectations may affect 
thermal comfort. The thermal sensation 7 level scale with values between –3 and 3 describes 
the thermal sensation between ‘hot’ and ‘cold’.
Occupants can control their thermal environment by means of clothing, operable windows, 
fans, heaters, internal and external sun shades.
3. Description of analyzed building
The aim of the building simulations was to analyze the influence of thermal insulation and 
flat location on the thermal comfort of particular parts of the panel building. The simulations 
were conducted for part of W70, a 5 storey large panel dwelling building, the usage area 
of  analyzed building part was 150 m2. The basement is below entire building and the building 
has a flat roof. Visualizations of different building elevations are presented in Fig. 1.
381
The building has natural ventilation and a central heating system with convection heaters. 
A communication area is located in the central part of each building level. In the analyzed 
part of the building, there are three flats at every level. Exterior walls made of prefabricated 
panels in the W70 system, insulated with 15 cm of styrofoam with plasters at both sides: 
U = 0.20 [W/m2K] (before thermal modernization U = 0.75 [W/m2K], double glazing 
windows: U = 1.5 [W/m2K]).
The calculations were carried out in Design Builder v.3. The program has been specifically 
developed around Energy Plus, allowing the simulation of the building envelope and building 
interiors. The simulations conducted for the Polish climatic conditions (building located 
in Cracow) allowed the evaluation of the microclimate conditions of the entire building 
as well as of particular dwellings.
4. Simulation settings
The main aim of simulations was to determine the temperature and PMV index 
of  particular flats at different elevations during the summer months. Figure 2 presents typical 
arrangements of dwellings on a storey of the building.
Fig. 1. South-east and south elevations of analyzed building
Fig. 2. Typical zones’ visualization on every building level: a) Two rows of balconies 
at south elevation, b) Building rotated 90 degrees clockwise – two rows 
of  balconies at west elevation
382
Every single flat was modelled as separate thermal comfort zone due to the small usage 
area of different flats. It was assumed that the doors between rooms are usually opened. Three 
different flats were analyzed:
1. Flat M1 – usage area 56 m2, balcony at south elevation.
2. Flat M2 – usage area 31 m2, balcony at south elevation.
3. Flat M3 – usage area 36 m2, balcony at east elevation.
Area of balcony windows is 5.2 m2.
Three simulation steps were analyzed – the building model before thermal modernization 
(two different building rotations, as shown in Fig. 2) and the building model after thermal 
modernization. Data for three different flats located at four different levels were compared. 
The period of time between 15th of May and 15th of September was taken into consideration 
because at this time in Poland, there is a risk of overheating.
The assumptions for the simulations:
1. Heating system on from September to March (22°C), 7 days a week, 24 hours a day.
2. Occupancy density: flats – about 1 person per 15 m2,
3. Operating schedule: flats – 100% occupancy density between 4 pm and 7 am, 5 days 
a week; at the weekends and between 6 pm and 9 am; 50% reduced occupancy between 
9 am and 6 pm.
4. Metabolic activity: factor 1.2 met, winter clothing – clo = 1.0, summer clothing clo = 0.5.
5. Ventilation requirements per polish national standards PN-83/B-03430 [2], in every flat 
70 m3/hour for kitchen and 50 m3/hour for bathroom.
5. Test results
All simulation results presented below, have shown that during few days between 15th 
of  May and 15th of September the average interior air temperatures of different dwellings 
exceed 30°C and the PMV factor is higher than 2.  Those microclimate building conditions 
exceed the optimal internal summer temperature of 25°C and recommended value 
–0.5 < PMV < +0.5.
5.1. Building before thermal modernization – base case
Simulations of the building before thermal modernization have shown that in all 
dwellings, on all levels the operative temperature for most of the time is significantly higher 
than 25°C. The daily maximum interior temperature is 33.80°C (flat M2) and the PMV value 
is above 2.9. The number of discomfort hours, with the temperature above 25°C, in the 
assumed period of time is 1555. Those negative flat conditions continue almost for the entire 
day and do not change significantly during the night. The flats can be cooled by occupants 
during the night through the opening of windows.
Figures 3a, 3b and 3c present the number of discomfort hours for all three flats at different 
levels. The most unfavorable microclimate conditions are noticeable in flat M2 where the 
number of discomfort hours with temperatures above 32°C is the highest. Regarding the 
influence of the building storey, the worst conditions can be observed on the fourth floor 
(Fig. 4).
383
Comparing flats M1 and M2, both with balcony windows at the south elevation, thermal 
comfort conditions are worse in flat M2 due to its smaller usage area (31 m2 compared 
to 56 m2).
Fig. 3a. Number of overheating hours for flat M1 (south-west) at four levels – base case
Fig. 3b. Number of overheating hours for flat M2 (south-east) at four levels – base case
Fig. 3c. Number of overheating hours for flat M3 (east) at four levels – base case
384
5.2. Building before thermal modernization rotated 90 degrees clockwise
The overheating problems are closely related to the orientation of glazing and 
the worst thermal conditions are usually observed in rooms with windows oriented 
to the west. It is connected with the angle of solar radiation. In the analyzed building, 
the windows located at south elevation are shaded by the balconies at higher levels 
which lessen the solar gains. In the next step of simulation, the building was rotated 
90 degrees clockwise to analyze the microclimate conditions in the rooms with balcony 
windows located at the west.
After rotation of the buildings the worst microclimate conditions are also observed 
in flat M2, the number of discomfort hours increased from 1555 to 1618. Again, comparing 
the M2 with flat M1 (balcony windows at the same elevations), less favorable results are 
noticeable in flat M2 due to its smaller usage area. Figure 5 presents the number of discomfort 
hours for flat M2 and Figure 6, a comparison of PMV indexes for all three flats located 
on the fourth floor. The daily maximum interior temperature is 34.70°C and the PMV value 
is above 3.1.
Fig. 4. Number of overheating hours for different flats at fourth floor – base case
Fig. 5. Number of overheating hours for flat M2 by floors – rotated building
385
5.3. Building after thermal modernization
Due to the recast to the European Energy Performance of Buildings Directive, buildings 
designed and modernized after 2021 should be zero-energy buildings. In connection with 
those provisions, since 1st of January 2014, the new requirements regarding building 
envelope thermal insulation were introduced Warunki Techniczne 2013 [4]. According to 
those regulations, thermal transmittance U of the heated building components cannot exceed 
0.25 W/m2K and after 1st of January 2021, 0.2 W/m2K.
In the next step, the simulations were conducted for the building after thermal 
modernization fulfilling the requirements of the standard [4] being in force since 2021. Only 
external walls were insulated with 15cm of styrofoam (λ = 0.04 W/mK).
Figure 7 presents the number of discomfort hours for flat M2 with the most unfavorable 
microclimate conditions. The worst conditions are again on the fourth floor (Table 1). 
The daily maximum interior temperature is 34.5°C and the number of discomfort 
hours in the assumed period of time is 2392. After thermal modernization, the number 
of  overheating hours in flat M2 on the fourth floor increased from 1555 to 2392.
Table 1 presents the number of overheating hours in all flats, at all analyzed levels before 
and after thermal modernization. A significant increase can be observed in all flats of even 
up to 60%.
Fig. 6. PMV comfort indexes for three flats located on the fourth floor – rotated building
Fig. 7. Number of overheating hours for flat M2 at different levels
386
It appears that the reduction of heat losses connected with the thermal modernization 
of the building envelope unfavorably affects the microclimate conditions in the leaving 
spaces.
Both before and after thermal modernization, the worst conditions for all flats, are 
noticeable on the fourth floor, however, the percentage increase in case of flat M1 and M2 
is noticed on the third floor. It can be explained by the fact that the roof was not insulated 
so the transmission gains through this part of the building stay at the same level.
T a b l e  1
Number of discomfort hours for all analyzed flats before and after thermal modernization
Number of discomfort 
hours – before thermal 
modernization
Number of discomfort 
hours – after thermal 
modernization
Percentage 
increase [%]
M1
1st level 736 946 29
2nd floor 827 1235,5 49
3rd floor 920,5 1477 60
4th floor 1245 1746,5 40
M2
1st level 1073 1391,5 30
2nd floor 1317,5 1916 45
3rd floor 1409 2225,5 58
4th floor 1555 2392 54
M3
1st level 999,5 1377 38
2nd floor 1137 1718 51
3rd floor 1293,5 1985 53
4th floor 1329 2153,5 62
6. Conclusions
The results of the conducted analysis show that the overheating problem appears in large 
panel buildings, both before and after thermal modernization. Windows in the prefabricated 
panel buildings in most cases are poorly shaded from solar radiation. Glazing is the source 
of the excessive heat gains and results in the overheating of the dwellings. The microclimate 
Fig. 8. PMV comfort indexes for flat M2 before and after thermal modernization
387
conditions in all flats are very uncomfortable and the parameters describing thermal comfort 
exceed the acceptable values.
Modernization of the building should be preceded by the extensive analysis of how the 
changes influence thermal comfort of the particular flats. The priority is heating cost reduction 
in the winter season. The conducted analyses show that improvement of the building envelope 
thermal insulation alone can unfavorably affect the internal conditions during the summer 
season. In the process of thermal modernization of panel buildings, use of internal or external 
shadings to reduce summer overheating should be taken under consideration. Those solutions 
are the subject of the authors’ further researches.
The work reported in this paper has been partially funded by the project L-1/116/DS/2013.
R e f e r e n c e s
[1] PN-EN ISO 7730 Ergonomics of the thermal environment. Analytical determination and 
interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal 
comfort criteria.
[2] PN-83/B-03430 Wentylacja w budynkach mieszkalnych zamieszkania zbiorowego i użyteczności 
publicznej – Wymagania.
[3] Rozporządzenie Ministra Infrastruktury z dnia 12 kwietnia 2002 w sprawie warunków 
technicznych, jakim powinny odpowiadać budynki i ich usytuowanie (Dz.U. nr 75, poz. 690 
z późn. zm. ogłoszonymi w Dz.U. z 2003 r. Nr 33, poz. 270, z 2004 r. Nr 109, poz. 1156, z 2008 r. 
Nr 201, poz. 1238, z 2009 r. Nr 56, poz. 461, z 2010 r. Nr 239, poz. 1597, z 2012 r. poz. 1289 oraz 
z 2013 r., poz. 926.
[4] Rozporządzenie Ministra Transportu, Budownictwa i Gospodarki Morskiej z dnia 5 lipca 2013 r. 
zmieniające rozporządzenie w sprawie warunków technicznych, jakim powinny odpowiadać 
budynki i ich usytuowanie (Dz.U. z 13 sierpnia 2013 r., poz. 926).
[5] Nowak K., Modernizacja budynków a komfort cieplny pomieszczeń, Energia i Budynek, listo- 
pad 2013, 29-33.
[6] Dębowski J., Cała prawda o budynkach wielkopłytowych, Przegląd budowlany 9/2012.
[7] Nowak K., Nowak-Dzieszko K., Rojewska-Warchał M., Thermal comfort of the rooms 
in the designing of commercial buildings, Research and Applications in Structural Engineering, 
Mechanics and Computation. SMEC Cape Town 2013, 651-652.
[8] Wierzbicki S.M., Problemy modernizacji budynków wielkopłytowych, Materiały Konferencji 
Naukowo-Technicznej ITB, Mrągowo 1999.



Simulation analysis of microclimate conditions in a multi – family large panel building

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Simulation analysis of microclimate conditions in a multi – family large panel building

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