Thermal Behaviour of Traditional Architecture in the City of ...alexandria.tue.nl/openaccess/635611/p0613final.pdfPlea2004 - The 21th Conference on Passive and Low Energy Architecture

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Thermal Behaviour of Traditional Architecture in theCity of Florina in North-Western Greece

Aineias Oikonomou1 and Flora Bougiatioti1

1National Technical University of Athens, School of ArchitectureDepartment of Architectural Technology

42, Patission St., 106 82 Athens, Greece.email: [email protected], [email protected]

ABSTRACT: The main goal of this paper is to explore the thermal behaviour of traditional buildings ofthe 19th century in the city of Florina, in North-western Greece, and to investigate the degree ofthermal comfort of the users. For this purpose, it is necessary to analyse the climate of Florina, theconstruction methods and the building materials, as well as the patterns of use of the differentspaces. In most cases, the ground floor contains the winter rooms, while the upper storey is used asthe summer living space. This fact is intensely reflected in the construction of the house. The groundfloor is built as a heavy structure with thick stone (or adobe) walls and small openings. At the sametime, light timber-framed walls filled with adobe, construct the upper storey, giving the freedom forlarge windows and cross ventilation in the summer rooms and in the common spaces. The thermalbehaviour of a typical traditional building of Florina is analysed with the calculation of thethermophysical properties of the different building elements, and with the use of thermal analysissoftware.

Conference Topic: 8 Traditional solutions in sustainable perspectiveKeywords: traditional architecture, NW Greece, construction methods, thermal performance

INTRODUCTION

The vernacular architecture of every area is basedon the accumulated experience and practice of manycenturies and can constitute a continuous source ofknowledge. The use of local materials and theharmonisation with the local environment and climateare some of the factors, which contribute to thedistinct architectural identity of every area.

2. CLIMATE OF THE CITY OF FLORINA

2.1 TopographyThe city of Florina lies in a mountain valley, which

is crossed by a river from West to East. The longitudeof the city is 21°23'59'', the latitude is 40°46'58'', andthe altitude is 662 m.

2.2 Climatic DataThe mesoclimate of the area is affected by the

presence of large mountainous volumes. Theprefecture of Florina has a cold continental climate,with long, cold, humid winters and short, warm, anddry summers.

The mean maximum temperature in January(coldest month of the year) reaches 4.6 degrees C,the average temperature is 0.5 degrees C, while themean minimum temperature is -3.5 degrees C. Themean maximum temperature in July (hottest month ofthe year) reaches 28.8 degrees C, the averagetemperature is 23.1 degrees C, while the meanminimum temperature is 14.4 degrees C. The

corresponding relative humidity values are 82.1 % forJanuary and 57,4 % for January (Table I).

Table I: Monthly climatic data values for Florina. [1]

Jan Feb Mar Apr May JunMean Min Temp (C) -3.5 -1.7 1.3 5.1 9.2 12.5Average Temp (C) 0.5 2.7 6.7 11.6 16.8 21Mean Max Temp (C) 4.6 7.3 11.8 16.7 22 26.2Rel. Humidity (%) 82.1 78.1 70.9 64 63.4 59.8Aver. Rainfall 57.6 52.3 57.9 57.9 58.9 37.3Days of Rain 12 12 12.3 11.3 11.2 7.4Wind Direction W N W W W WWind Speed 2.5 3.3 4.1 4.6 4.8 4.8

Jul Aug Sep Oct Nov DecMean Min Temp (C) 14.4 14.2 11.2 6.9 2.5 -1.6Average Temp (C) 23.1 22.5 18.4 12.6 7 2.2Mean Max Temp (C) 28.8 28.7 25.2 19 12.1 6.3Rel. Humidity (%) 57.4 58.3 63.9 72.1 78.7 81.8Aver. Rainfall 34 31 41.1 62.1 69.4 86.2Days of Rain 6.1 5.8 6.1 8.4 10.8 12.9Wind Direction N N W N N SWWind Speed 4.6 4.3 3.5 3.4 3.2 2.5

Florina has relatively high precipitation values,with a monthly average value of approximately 55mm. Also, the area is characterised by an extended


snowing period, which starts from November andends in April. The direction of the prevailing winds iseither west or north, depending on the seasons.

-10

-5

0

5

10

15

20

25

30

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Deg

rees

C

50

55

60

65

70

75

80

85

90

%MEAN MIN TEMP AVERAGE TEMP MEAN MAX TEMP REL HUMIDITY

Figure 1: Monthly air temperature and relativehumidity values. [1]

2.3 Climatic Analysis - ClassificationThe climate classification for Florina was defined

using the software Meteonorm v4.0 [2] to generatehourly climatic data, which were then imported to thesoftware Weather Tool v1.10 [3]. The psychrometricchart generated with the Weather Tool, for the wholeyear for Florina, demonstrates that climatic conditionsare way beyond thermal comfort throughout thewinter period (November to March) (see Fig. 2 and3).During the months October and April, the climate israther cool, while from May to September the climateis moderate to warm-dry (August).

Figure 2: Monthly diurnal average temperaturevalues plotted against thermal neutrality zone forFlorina. [3]

Figure 3: Psychrometric chart for Florina. [3]

3. ANALYSIS OF BUILDING CONSTRUCTIONOF TRADITIONAL BUILDINGS

3.1 Construction ElementsThe construction of the house is made in the

following way (Fig. 4): the upper part of the foundationwalls is formed with the placement of wooden beams8 x 8 cm on the inner and on the outer side.Afterwards, beams with dimensions 8 x 13 cm areplaced every 50 cm upon the foundation walls andalways breadthwise. These beams support the floorof the ground floor.

The structural elements of the ground floor areusually walls made of local stone or adobe bricks.These walls are 60 to 65 cm thick, and have anaverage height of 240 cm. Every 80 cm (distanceequal to one third of the total height of the groundfloor wall) horizontal wooden beams are inserted. Theopenings are constructed in a slightly different way:the lower part of the window begins at 60 cm from thefloor and the total height of the window is equal to 120cm, thus giving a different division of the total wallheight. In many cases, vertical beams are alsointegrated in the structure, thus forming a frame-likewooden substructure. All the horizontal and verticalparts of the substructure are interconnected. Beamswith dimensions 8 x 13 cm are placed every 50 cmupon the ground floor walls and always breadthwise.These beams support the floor of the upper level.

Figure 4: Typical wall configurations.

The structural elements of the upper floor areusually light-weight walls called tsatmas. These wallsare 20 to 25 cm thick, and are formed by a woodenframe structure, which is filled up with adobe bricks,or, in some cases, small stones and mud. Thewooden frame structure comprises of horizontal,vertical and diagonal beams, with dimensions 8 x 8cm or 10 x 10 cm. The vertical beams are not placedin equal distances, but depend on the existence ofopenings in the wall. The horizontal beams are placedbetween the vertical ones, in a way similar to theground floor structure (every 60 to 80 cm, dependingon the existence of openings). Furthermore, diagonalbeams are placed in the frames, thus giving thestructure rigidity. Finally, the remaining voids are filledup with adobe bricks. The external and internalrenderings of the ground and upper floor walls consist


of two layers. The inner one is a mixture of clay mudand straw, while the outer is lime-plaster.

The construction of the roof is made in thefollowing way (Fig. 5): beams with dimensions 8 x 13cm (grenties) are placed every 50 cm upon the upperfloor walls. Above the partition walls, wooden trussesare constructed with vertical (orthostates or babades)and diagonal (ameivontes or tsimpidia) beams of 10 x10 cm. These trusses support horizontal elements 13x 8 (tegides) placed every 120 cm. Afterwards,diagonal elements 8 x 8 cm (epitegides orpanotsimpida) are placed every 50 cm. Theseelements support the final layer of the roof, whichcomprises of wooden boards with a width of 10 to 15cm, and clay tiles anchored with mud.

Figure 5: Typical roof axonometric section.

3.2 Building MaterialsThe materials, which were used for every part of

the structure, came from the surrounding area. Thestone blocks, which were used, were made oflimestone and/or slate, and came mainly from nearbyquarries. In some cases, especially for the houseslocated on the south side of the city (mountainside),the stone blocks were made of the stone, which wasexcavated from the site. The adobe bricks were madeon the site, from the earth, which was dug out for theconstruction of the foundations and the basement.Finally, the structural wooden elements were made oflocal hardwood, i.e. beech and oak, which came fromthe nearby woods, while the rest of the wooden partswere made of local softwood, i.e. poplar and fir.

3.3 Thermal behaviour of construction elementsThere are three main wall configurations found in

traditional buildings of Florina: a thick stone wall, athick adobe wall, and a lightweight wall (tsatmas). Thethermal behaviour of these elements can bedescribed by their thermophysical properties (seeTable II). The U-value data was derived from [4],whereas the time lag values were calculatedaccording to the Thermal Time Constant (TTC)formula cited by Givoni in [5].

Table II: Thermophysical properties of typical wallconstruction of Florina. [4] [5]

Thickness U-value Time lag(cm) (W/m2K) (h)

Stone 60 2.35 61Adobe 60 1.02 109Tsatmas 20 2.24 14

It can be seen that the first two wall configurationsare characterised by an increased thermal lag,whereas the third wall configuration has a relativelylow time lag. The high thermal inertia wall types weremainly used in the ground floor, which was occupiedduring the cold period, whereas the lightweight walltype was used in the upper floor, which was occupiedduring the warm period.

4. THERMAL ANALYSIS USING SOFTWARE

4.1 Thermal ModellingThe thermal analysis calculations were performed

with the software Ecotect v5.2 [4]. First, the model ofa representative building type was constructed.Second, the model was modified in order to representthree variations based on existing examples, withdifferences in the orientation, the openings and thewall configurations. These variations included ahouse with northern orientation, one with easternorientation, and one with southern orientation, whichare referred from now on as N House, E House and SHouse, respectively (Fig. 6-8).

Figure 6: N House. Ground and upper floor plans.

Figure 7: E House. Ground and upper floor plans.

Figure 8: S House. Ground and upper floor plans.

The thermal modelling was based on a series ofassumptions. The ground and the upper floor wereused inter-seasonally, while the different rooms ofeach level were used either throughout the day, or forspecific hours during the morning. These diurnal andinter-seasonal differences in the use of the housewere represented with different schedules. The wintercomfort band was set at 16 to 26 degrees C, whereasthe summer comfort band was set at 18 to 28degrees C. The winter spaces (ground floor) were


assumed with no ventilation apart from the airinfiltration, while the summer spaces (upper floor) hadnatural ventilation. The infiltration rate for all thezones of the building was set at 1 air change perhour.

4.2 Hourly Temperature ProfilesFor the coldest day (January 26th), the main

winter living spaces of the N House demonstrate avery slight diurnal variation and range between -2 and0 degrees C, with outside temperatures below -12degrees C. On the most overcast day (January22nd), the exterior temperature is about -2 degrees C,while the interior temperatures of the two zonesthroughout the day are around 0 and 2 degrees C.

For the hottest day (August 25th), the exteriortemperature ranges from 22 degrees C (early in themorning) to 34 degrees C (around noon). Thesummer living spaces of the N House are warmer inthe morning and in the night (25 degrees C), butsignificantly fresher around noon (29 degrees C). Onthe brightest sunny day (July 20th), the outside airtemperature ranges from 14 degrees C to 34 degreesC, whereas the interior air temperatures of the mainliving spaces range from 22 to 27 degrees C.

In the case of the E House, the interior airtemperature of the main south-eastern room on thecoldest day (January 26th) ranges from -1 to 3degrees C, while the outside temperature is below -12degrees C. This diurnal range is not observed in thecase of the most overcast day (January 22nd), wherethe inside temperature stabilises around 3 degrees C.(Fig. 9)

Figure 9: Hourly temperature profile of the mainwinter living spaces of the E House (26/01). [4]

Figure 10: Hourly temperature profile of the mainsummer living spaces of the E House (25/08). [4]

The upper-storey main living room of the E Househas a diurnal air temperature range from 24 degreesC (early in the morning and late at night) to 29

degrees C (around noon), with corresponding outsidetemperature between 22 and 34 degrees C. On thebrightest sunny day (July 20th), the outside airtemperature ranges from 14 degrees C to 34 degreesC, while interior temperatures are between 22 and 27degrees C. (Fig. 10)

For the coldest day (January 26th), the mainsouth-western living space of the S House has adiurnal variation, which ranges between -2 and 0degrees C, with outside temperatures below -12degrees C. On the most overcast day (January22nd), the exterior temperature is about -2 degrees C,while the interior temperatures of the space areslightly over 0 degrees C, and invariable throughoutthe day.

On August 25th, the exterior temperature rangesfrom 22 degrees C (early in the morning) to 34degrees C (around noon). The summer living spacesof the S House are warmer in the morning and in thenight (25 degrees C), but significantly fresher aroundnoon (29 degrees C). On the brightest sunny day(July 20th), the outside air temperature ranges from14 degrees C to 34 degrees C, whereas the interiorair temperatures of the main living spaces range from22 to 27 degrees C.

4.3 Fabric Gains and LossesThe fabric gains and losses of the different zones

of the houses depend mainly on the constructionmaterials of their external walls.

In the cases of heavy-weight wall construction, i.e.thick stone walls, the fabric losses throughout the coldperiod are significantly reduced. This fact is mostlyobserved in the winter secondary rooms of all threehouses, and in the main winter spaces of the NHouse. The fabric losses during the winter alsodepend on the window area. As a result, spaces withfew and small openings, as is the case with theground floor of the N House, demonstrate few fabriclosses.

The fabric gains of the summer living spaces aresimilar for all three houses. The time lag of the wallsis such that the maximum fabric gains during thesummer occur in the evening. Considering the dailyexterior temperatures fluctuation (10 to 15 degreesC), this fact is very desirable in order to havecomfortable interior temperatures in the night.

The roof zone is characterised by extensive fabriclosses during the winter and intermediate seasonsand very high fabric gains in the noon and afternoonhours of the summer. (Fig. 11)

Figure 11: Roof zone fabric losses (light shades) andgains (dark shades). [4]


4.4 Direct and Indirect Solar GainsThe direct and indirect solar gains of the houses

are mainly based on their orientation, and on thesurface and orientation of their windows.

The N House has very few direct solar gains, dueto the lack of southern windows, during the winter.This is reversed in the summer living spaces, wherethere are increased direct solar gains throughout themorning, especially in the north-eastern main livingspace.

For the winter, the living spaces of the E Househave direct solar gains throughout the morningbecause of the eastern and southern openings (Fig.12). For the summer and the intermediate seasons,the living spaces of the E House have increaseddirect solar gains from early in the morning until noon.This is due to the large number of windows facingeast. The elevated sums of solar radiation contributepositively to the thermal comfort conditions during theintermediate seasons, but can lead to heat discomfortin the summer.

Figure 12: E House. Direct solar gains of winterspace (side areas of graph). [4]

The S House has direct solar gains only aroundnoon, during the winter, because of the southernwindows. The roof eaves efficiently shade thesouthern openings of the summer living spaces. Inthis way, the direct solar gains are minimised (Fig.13), during the summer, when they are not desirable.

Figure 13: S House. Direct solar gains in summerliving spaces (central area of graph). [4]

4.5 Inter-Zonal Gains and LossesThe inter-zonal gains and losses of the upper floor

for all three houses are governed by the thermalbehaviour of the roof. As a result, during the cold andintermediate periods, all the rooms, which areadjacent to the roof, demonstrate thermal lossestowards it. Of course, these rooms were rarelyoccupied during these periods. On the other hand, the

thermal contribution of the roof in the summer wassignificant, and contributed to the thermal loads of theadjacent -upper storey- zones. Nevertheless, it isknown that the efficient cross-ventilation and nightventilation of those spaces moderated this negativecontribution.

5. THERMAL COMFORT

5.1 Simulated Thermal ComfortThe overall simulated thermal comfort was similar

for all three houses. Thermal discomfort wascalculated for monthly percentage of time andassumed that the buildings were free running.

For the winter, the ground floor main living spacesof the S House have the less hours of cold discomfort(50% to 60% of the time) (Fig. 14). This is mainly dueto the direct solar gains from southern windows, andthe absence of other openings. On the contrary, theground floor areas of the N House and the E Houseare very cold. The cold discomfort in the E House isslightly worse, is due to the increased area ofwindows. On the other hand, the N House groundfloor is very compact, with few openings.

Figure 14: Percentage of cold discomfort for the mainwinter living spaces of the S House. [4]

For the summer, the main spaces of the upperstorey of the S House are warmer (hot discomfort for80% of the time) than the corresponding spaces ofthe other two houses (hot discomfort for an averageof 60% of the time). This is mainly due to the fact thatthe main living spaces of the N House face north, andhave reduced thermal loads, while the E House hasoptimised cross-ventilation, due to the increasednumber of openings (Fig. 15).

Figure 15: Percentage of heat discomfort for the mainsummer living spaces of the E House (central area ofgraph). [4]


Table III: Comparative matrix of calculations ofthermal comfort conditions (Ecotect analysis [4]).

Hourly Tprofiles

Outside(°C)

NHouse

EHouse

SHouse

Coldestday

-12 -2-0 -1-3 -2-0

Mostovercastday

-2 0-2 3 0

Hottestday

22-34 25-29 24-29 25-29

Sunniestday

14-34 22-27 22-27 22-27

Thermalcomfort

N House(°C)

E House(°C)

S House(°C)

Colddiscomfort

40-70% 30-70% 45-60%

Hotdiscomfort

65-80% 65-80% 75-85%

5.2 Reported Actual Thermal ComfortThe actual thermal comfort of the people living in

the 19th century is significantly different from thecontemporary standards of thermal comfort. In orderto understand the perception of thermal comfort 150years from today, it is very important to point outagain the diurnal use of the different rooms and theinter-seasonal use of the ground and the upper floor.

During the cold period, people lived almostentirely on the ground floor, which is characterised byheavy mass and reduced area of openings in order tomaximise the time lag and minimise the thermallosses. The thermal comfort of the users dependedalso on factors, such as clothing and rudimentaryactive heating methods, such as fireplaces andbraziers.

The social and economic conditions in Florina, atthe time, enforced the use of heavy clothing inside thehouses. During the winter, the casual clothes likecoats, shirts, trousers, socks and hats, were made ofwool. At the same time, the intense everydayactivities in the intermediate seasons contributed tothermal comfort of the users.

As far as the active heating methods areconcerned, it should be noted that the fireplaces areplaced on the ground floor, and are usually integratedin the middle of the internal or the northern walls ofthe house. As a result, these walls have the samethickness (60-65 cm) both at the ground and at theupper floor, for construction and safety reasons.Usually, the internal walls, which accommodate thefireplaces, enclose a semi-open space (hayat). Inmany cases, the fireplaces do not face towards theliving spaces, but towards the hayat. This was mainlydue to the fact that in the older houses, many of thehousehold activities, like cooking and drying of fruitsand vegetables took place in the hayat, whereas theenclosed spaces were only used for light activitiesand sleeping. In some cases, fireplaces exist even inthe secondary rooms of the upper floor. This isreasonable, if we take into account that theintermediate seasons in Florina are relatively cold,with a possibility of snow, even in May.

During the summer period, the household wasmoved to the upper storey, were the design of therooms allowed the use of cross-ventilation in order topromote the natural cooling of the living spaces. Thesummer clothes were made of cotton, hemp andlinen, and all the intense activities were transferred tothe open air.

The cross-ventilation during the summer isachieved not only in the summer living spaces (odas)with the simultaneous opening of two or morewindows, but also in the whole house. In order to dothis, small openings are constructed in the upper partof the northern hayat wall. In this way, the staircaseand the hayat space contribute to the night cooling ofall the living spaces. Furthermore, the light-weightstructure of the upper storey walls, and the extensiveuse of wood in the construction (floor, ceiling andclosets) contribute to the quick rejection of heatduring the night.

CONCLUSION

This first approach to the thermal analysis of thetraditional buildings of Florina proves that the climateand the local environment drastically influencedvernacular design and construction methods.Therefore, it is an architecture, which can beregarded as highly sustainable and energy efficient.The construction and organisation of the living spacesaccording to their diurnal and inter-seasonal use, aretwo of the many features, which were pointed out inthis paper.

Finally, this paper revealed the need for a moredetailed thermal analysis of the thermalcharacteristics of traditional houses in Florina. It isimperative that the study should be extended toinclude more building types. Furthermore, it isstrongly believed that in order to obtain a morerepresentative and complete idea concerning thethermal behaviour of traditional architecture ofFlorina, in-situ measurements of dry-bulb temperatureand relative humidity should be conducted inrepresentative houses of the remaining building stock.

ACKNOWLEDGEMENT

The authors would like to thank architects M.Kouli, M. Papagiannakis, Y. Papaioannou and A.Stoios for providing some of the original drawings.

REFERENCES

[1] http://www.emy.gr/hnms/english/climatology/[2] Meteonorm software v4.0, Meteotest, J. Remund,et al., Bern - Switzerland (1999).[3] Weather Tool software v1.10, Square OneResearch PTY Ltd., Dr. A. Marsh,http://www.squ1.com[4] Ecotect Tool software v5.2, Square One ResearchPTY Ltd., Dr. A. Marsh, http://www.squ1.com[5] B. Givoni, Climate Considerations in Building andUrban Design, Van Nostrand Reinhold, New York(1998).

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Thermal Behaviour of Traditional Architecture in the City of ...alexandria.tue.nl/openaccess/635611/p0613final.pdfPlea2004 - The 21th Conference on Passive and Low Energy Architecture