Influence of Architectural Solutions on Building Heat Protection with Example of Historical Rural Houses in Northern Cassubia

The investigations concerning the existing historical rural building development were carried out in randomly selected villages in northern coastal Cassubia. This region is characterized by certain defined common features (Fig. 1a). The basic criterion of the selection of the area for investigations was the specific climate conditions affecting the shaping of architectural elements of the traditional rural houses in unique ways.

Figure 1.

The southern and middle part of Cassubia has been described in literature, cf. [11, 12]. In the investigations on the Cassubian material culture, the publication by J. Knyba [13] is the first monograph which comprehensively presents the characteristic features and development processes of the folk architecture of this region from the end of the 17^th until the beginning of the 20^th century. There is only few studies, however, containing information about the rural architecture of coastal Cassubia and they present too little material to show both the features and the development process of the tradition of this region. According to the authors, the most important source of knowledge about this topic are the standing objects of the rural traditional architecture, preserved until today, and the information, obtained from the oldest inhabitants of the villages, concerning those objects of the folk architecture of this region which do not exist anymore. There are over ten preserved traditional objects from the 19^th century in northern coastal Cassubia. Among them, noteworthy are historical rural houses in the open-air ethnographic museum (“skansen”) in Nadole, on the Żarnowiec Lake, as well as in Kluki, on the Łeba Lake.

During the investigations concerning the architecture of the existing houses in the context of the buildings’ thermal protection, the authors have been inspired by the traditional rural architecture represented by several objects – presented in the paper – from the 19^th century: modest, austere, having great architectural and artistic simplicity.

The main feature of the selected regions of coastal Cassubia is their climate – having a transitional character between the marine climate typical for Western Europe and the continental one typical for Eastern Europe [14]. According to the accepted classification, the area investigated by the authors belongs to the eastern-coastal region (RIII), covering the eastern part of the Slovincian Coast (Polish “Pobrzeże Słowińskie”, German “Slowinzische Küste”) and a part of the Cassubian Coast. The specificity of the climate conditions of this area consists i.a. of a relatively high number of cool days with precipitation. On average, there are almost 53 cool days, almost 30 cool and clouded days, and 32 cool days with precipitation. Moreover, this area is characterized by the highest annual wind speed in Poland (5-6 m/s⁻¹ on the height of 30 m.o.g.l.), what means that it is rated among the most profitable regions for the development of wind power engineering in Poland. Southwest and north-west winds are predominating. It is connected with the general atmospheric circulation of the zone of moderate latitudes winds blow in all directions in this zone but with the distinct advantage of the western direction. They are rather heavy, particularly in autumn and winter. The specific conditions of coastal Cassubia enable the use of this unconventional energy source in this region through construction of wind power plants which decidedly affect the landscape shaping (Fig. 1b).

The houses stood out because of their dense mass, usually on a rectangular plan, which fundamentally affects more advantageous thermal conditions.

In folk architecture, a high roof was the main factor affecting the thermal protection of a building as well as its mass and the architectural expression of the house connected to this mass – and, above all, it was the roof’s area, shape, and appropriately selected proportions in comparison to the house walls. The form of the roof was shaped, first of all, according to climate conditions, mainly wind influences and precipitation affecting the construction of the cover, the shape of its spatial form, the slope angle of the roof, the way of covering, and the area of eaves. The roof slope angle, favoring the fast flow of water and the slipping down of snow for a given covering material, as well as the protruding of the eaves’ edge out of the wall, were almost directly proportional to the precipitation sum in a given region. The largest eaves were found in the northern Poland as well as in Beskids and Podhale [15].

The protruding eaves were this element of the roof which was characteristic for rural houses played the role of arcades and, most importantly, protected the walls against moisture from precipitation. They also often played a role of an entrance protection. Simultaneously they shaped a microclimate around the house and, on sunny days, they threw a deep horizontal shadow which protected the rooms against overheating in summer.

An attic inside the high roof of the rural house was a good insulator of the ground floor and generally was not used for dwelling; only sometimes it served as storage for foodstuffs or crops. A gable roof or half-hip roof predominated in northern Poland, a hip roof or gable roof with smaller cubature of space under the roof ridge – in southern Poland and in some central regions. Hip roofs have survived for the longest time in Lesser Poland, Podlasie, and in some regions of Mazovia, gable roofs were characteristic mainly in Podhale and the Beskids [16, 17].

Another characteristic elements in rural architecture, having essential influence on the thermal protection of the house, were canopies and porches. They played an important role of sheltering the house entrance against precipitation and wind, and, in summer, also against the sun.

The hut of northern (coastal) Cassubia is represented by several variants, differing from each other. However, it is always a house with wide frontage, usually without a canopy [13]. Only in tightly built-up settlements, the gable side has a canopy in the form of a recess which shelters an entrance. It is sometimes found in hamlet-type settlements where the buildings unite both a dwelling and farming part under one roof. Other common features of the dwelling houses in northern Cassubia are: high half-hip roof (rarely gable roof) with rafter-type construction, usually with a squint window under a ridge, framed in wind braces and finished with a decorative finial on the top (called “śparogi” – only plural), loosely covered with reed (rarely straw), and, in extremely poor regions, with heather.

The examples of Northern Cassubian huts are the preserved buildings from the 19^th century in Ostrów, Swarzewo, Dębki, Nadole, Kluki, Smolno, and Karwieńskie Błota – the reconstruction (Fig. 2).

Figure 2.

The Cassubian hut in Karwieńskie Błota is an example of a building of hamlet-type settlements where the connection of dwelling and farming parts under the common roof was a characteristic feature. It contributed to a significant improvement of the energy balance of the object thanks to a reduction of the area of external walls. A similar solution of the connection of dwelling and farming parts characteristic of the huts in Swarzewo, where one object with a gable roof rarely found in this region was preserved. Such covering can be found also in traditional fishermen’s huts, and the historic house in Dębki can be an example of this.

The preserved dwelling houses in Kluki, Nadole, Ostrów, and Smolno are typical for the architectural landscape of northern Cassubia of the 19^th century. In Smolno, a tightly built-up settlement, apart from the huts without canopies characteristic for this region, the houses were erected also with a canopy in the form of a recess protecting the entrance zone against the negative influence of atmospheric conditions. Special attention should be drawn to a dwelling house localized in a historical homestead in Nadole, representing a type of traditional rural complex preserved in the vicinity of Żarnowiec Lake. The hut is singled out by the architectural elements typical for this region and affecting the building’s thermal protection: the tight mass on a rectangular plan, advantageous for thermal protection, as well as the high rafter roof of half-hip type, covered with reed, with the squint window under the ridge. The covering has an appropriate roof slope angle, equal ca. 48, and eaves protruding out of the external walls at 80 cm. This solution constitutes the protection of the external walls – including the gable walls, additionally sheltered with the gable – as well as the entrance zone against negative atmospheric conditions. The attic of the dwelling house – as the place of grain storage – was a good insulator of the ground floor. Quite small usable height of the rooms in this building, equal ca. 2.2 m, contributed to the thermal protection of the building.

The heat protection in folk architecture manifested in the room layout in buildings as well. The rooms had quite low height – equal ca. 2.2 m [18]. Depending on the regions in Poland, different layouts of dwelling houses developed – affected not only by functional reasons or local traditions but also by climate conditions. It is noteworthy that the one-bay layouts were found mainly in the southern, south-eastern, and partly central regions of Poland. The transitional systems, one-and-half-bay layouts, consisted of rooms of different heights, were characteristic of houses mainly in the mountain and sub-mountain regions, whereas the two-bay layouts were more popular in the northern and north-eastern regions, where mean daily temperatures are lower and winters last longer [19]. This is justified by the fact that the two-bay layout is more advantageous on account of the limitation of heat loss from the building. Simultaneously in the prevailing part of northern Poland predominated houses on a tight plan with square-shaped outline. In the southern regions, however, houses were characterized by an elongated plan. The number of bays, such as the house’s width and length, had crucial influence on the type of roof and its proportion related to the house’s walls. The room layout was adapted to various climate conditions and work organization in summer and winter, which manifested in the changing functions of the dwelling chambers, mainly the kitchen and entrance hall [20]. The latter, however, at first played a role of shelter against climate factors. Especially noteworthy is the division of the building onto warm and cool zones.

The location of the chimney in the hut was tightly connected to the building’s interior layout. However, in the significant majority of cases, only one chimney is observed, which means that the kitchen and heating elements are concentrated in the central part of the building. This solution enabled the heating of rooms localized near the home’s bonfire. The most noteworthy is special care that both builders and dwellers took of the chimney system which provided the economical management of energy. One of the advantages of the traditional ovens was that they accumulated heat and removed excess moisture from the rooms, mainly from over the kitchen stove, thanks to an uptake hole. In the buildings of southern and central Poland, for example in Mazovian huts, the chimney chambers were mostly a bit narrower than those in southern Poland [17].

The hut in Nadole, like other dwelling houses presented in the paper, represents the two-bay layout, characteristic for Cassubia, dividing the interior into a cool and warm zone (Fig. 3a). The south-western, warm zone was occupied by grandparents, young hosts with children, and a housemaid. The main entrance to the building led from the direction of a flower garden, through a hall paved with fieldstones, to the main big chamber where family life concentrated (Figs. 3c, d). The hall protected the building’s interior against wind and inflow of freezing air. Beyond the main chamber, in the cool zone of the building, a larder was localized, full of objects connected to the processing and storing of food. The opposite, smaller part of the hut was occupied by grandparents (Fig. 3e). A corner annex with a small window in the building’s cool zone served as a bedroom and, mainly, as a cubbyhole for more precious clothes and belongings (Fig. 3f). It is noteworthy that the building’s cool zone is made up of farming rooms according to the zone rule; the rooms with lower heat requirements are situated on the northern side of building.

Figure 3.

The specific role in the building was played – as mentioned – by the fire system. A “black kitchen” – a chimney shaft, wide at its base was entered from the hall. The shaft functionally connected the inlet to heating stoves, fed with lumber and peat, with the smoke and soot offtakes from niche fireplaces in the rooms (Fig. 3b). Apart from the “black kitchen”, found in northern Cassubia and popular among the German population, also a “white kitchen” was found in middle and southern Cassubia, an “evolutionary” variation of the “black kitchen” as well as niche kitchen hearths.

Folk architecture used building materials which were accessible in a given region, with help of simple devices. Thus it was organic, and its form, developed through generations, can inspire modern architects. Low temperature and its daily variations affected the selection of traditional materials for the construction of external baffles, allowing the natural diffusion of air and the regulation of humidity. Traditionally, the basic building material in Poland was wood, and its application had direct connection to the afforestation level in the separate regions of the country. Wood is characterized by many advantages but the most important of them is that it has good properties concerning heat protection and buildings made of it ensure the optimum health conditions to their dwellers. A log system predominated in the constructive solutions of solid wooden walls; the joints between separate beams were sealed with moss, couch grass or heather, then covered with decorative straw plaits or usually filled with clay and straw and limewashed. Wall thickness depended on climate regions. A certain conformity is observed between the regions with low winter temperature and the regions where the walls of rural houses had bigger areas of section compared to other regions [21]. Construction of solid wooden walls of the log system predominated in the central and southern parts of Poland. Lesser Poland and Podlasie are the regions where it has survived for the longest time in the pure form. Timber framing, characterized by the ability of heat accumulation and wood saving, prevailed in the northern and western regions of Poland, mainly in Żuławy and Greater Poland [16, 17]. When one talks about traditional folk architecture, they usually think about buildings made of wood and forget those made of clay, brick, or stone. The significance of these materials, however, increased tremendously during the reconstruction of the country after the introduction of property rights reforms, especially in northern and western Poland.

The roof cover in traditional folk architecture was mainly straw and reed. The predominating cover in the middle and southern regions, i.e. those where farming was intensive, was straw thatch; light and having good thermal and insulating properties consisting in keeping up the optimal temperature in all rooms, both in winter and summer. Straw cover, more resistant to humidity and drought as well as better resistant to water, was used mainly in the northern regions of Poland, in Pomerania and the Lake District [16].

The care of the building heat protection manifested also in the fact that the window and door openings – through which the significant quantity of heat escaped were limited to a minimum. Therefore, rooms not always were lit well. The windows usually had single panes which reduced their thermal and insulating properties. Simultaneously they were drafty, mainly due to improper fitting and not very thorough workmanship. However, decorative wooden shutters are noteworthythey were often used, usually closed for the night and in some regions, even for the whole winter. In this latter case, they were sealed with straw and opened only for spring. It must be emphasized that the shutters were a newer building element in the huts, although custom of the covering of windows is old. Long ago windows used to be insulated from the outside with straw mats attached with wooden pegs to the wall above the window opening. Window and door bands also protected against excessive heat loss; their role consisted mainly in sealing off the connection between the door or window frame and the wall [22]. Cassubian huts were usually built in timber framing, which was treated as a transitional form between wooden and brick construction which constituted a medley of foreign influences and native forms of architectural art. The walls, erected as a frame with free spaces filled with unfired clay, called “paca” (pronounced [pa-tsa]), imitated the timber framing filled with fired clay. The application of “paca” was connected to the lack of local brickyard centers, increasing the price of bricks. Timber framing ensured that heat was kept inside in winters and mildly cool air in hot summers. The massive filling of the wooden skeleton with clay was characterized by high heat accumulation and relatively advantageous thermal properties. Despite the appearance of trapping humidity inside, this construction in fact had a dry interior (Fig. 4a). Some timber-framed walls filled with brick were covered with pugging made of gravel and clay to improve thermal conditions inside as well as to protect the wooden elements of the construction (Fig. 4b).

Figure 4.

The most popular material for covering of roofs in this region, apart from straw, was reed (Fig. 4c). A roof covered with straw and reed survived for many years in Cassubian architecture despite bans and orders of the Prussian and then German and Polish authorities.

The windows in buildings were small, with single panes. The layout of windows in separate rooms is connected to the illumination of the hut’s inside. Apart from that, it is noteworthy that the window size was adapted to a zone depending on the temperature inside. The largest windows were situated in the building’s warm zone – in the living rooms, smaller – in the corner annex, the smallest – in the chamber and entrance hall belonging to the building’s cold zone. The four-pane frame in a small window was usually 0.65 ÷ 1 m wide and 0.6 ÷ 1 m high. The windows in the corner annexes usually had only two panes, arranged vertically. At the end of the 18^th and the beginning of the 19^th century, Cassubian huts had also some smaller openings which played a role of window vents in summer and were clogged with straw and moss in winter. Up until the beginning of the 19^th century windows played a role of light source in the wealthy farmers’ houses and until the end of the 19^th century in poor people’s houses, but they did not regulate the fresh air flow throughout the hut’s inside. As movable window casements had been introduced thanks to hinges, a need arose to mount windows in walls in a more durable way, using jambs, which also contributed to the reduction of heat losses from buildings. Shutters were an integral part of windows in Cassubian huts from the 19^th century on. Their task, apart from protection against thieves, was protection against excessive chilling of the hut’s inside. Shutters were placed on the windows having the larger area, whereas they were not applied to cover small, single-casement windows (Fig. 4d).

Climate conditions affected also the localization of rural buildings which were situated mainly in sunexposed windy areas. In Polish folk architecture, the mountainous regions excluded, across time people avoided to erect houses in valleys and terrain depressions. The traditional huts’ fronts were often southoriented which i.a. protected the chamber against overheating. Simultaneously, trees were planted on windward side.

The Cassubian huts in Karwieńskie Błota and Swarzewo are additionally examples of a building of hamlet-type settlements where the unification of dwelling and farming parts under the same roof was a characteristic feature. It contributed to significant improvement of the energy balance of the object thanks to a reduction of the area of external walls. The whole farmstead constituted a functionally justified structure, present for generations. It represented a centripetal system which has always been the most numerous and oldest group of functional and spatial types of settlements adapted to technologies based on physical work.

The majority of Cassubian villages were built-up in such a way that dwelling houses were sun-oriented, and that definitely affected the heat management in the building. Simultaneously, the localization of a flower garden did not overshadow the southern elevation of the house (Fig. 5a). The examples of Cassubian huts in the investigated region are Karwieńskie Błota, Mechowo, Strzelno (Fig. 5b); the roads there run in the east-west direction enabling to maximally expose the dwelling houses to the sun.

Figure 5.

The completed literature review and the authors’ own research illustrates the difference between the characteristic architectural elements of the historical rural houses from the 19th century in coastal Cassubia from the point of view of the thermal protection of buildings (Table 1).

The importance of planning low energy consumption and healthy rural houses while considering local climate conditions and basing construction on traditional methods, with simultaneous application of technological innovations being in favor of the building heat protection, acquires increasing significance. Each house should be built in relation to the environment and use the full potential of its surroundings.

It is noteworthy that part of the rules developed in folk architecture in the past connected to the thermal protection of buildings can become a part of the architectural trends concerning modern low-energy consumption buildings. These solutions, complying with the climate of a region, were developed by our ancestors mainly by means of empirical methods of solving of problems based on rational premises. Several solutions in this field can be treated as fundamental: a compact building mass, usually on a rectangular plan; a simple gable or hip roof with buffer spaces and wide eaves; the interior’s division into warm and cool zones; the exposure of the maximum part of a building to the sun; the protection of a building against the wind.

Simultaneously, still-increasing demands on energy savings force the application of external baffles with a low overall heat transfer coefficient which is binding nowadays in common building construction. The basic difference, apart from the technological progress, consists i.a. in materials and constructive solutions of external baffles. Methods of their erection in historical buildings depended on the availability of a building material in the given region but in the majority of cases (i.a. in the investigated region of coastal, northern Cassubia) they were independent of the exposure to the sun. The southern walls in the currently constructed low-energy consumption houses are designed in a different way than the northern ones. Ancient rural houses were thermally protected not only thanks to the appropriate location and simple architecture but also thanks to the small area of windows through which significant heat losses occur.

Nowadays, there is no such limitation. One can built low-energy consumption houses which simultaneously are fitted with glass in an optimal way and opened to the surroundings. Thanks to panes with advantageous ability of thermal insulation, reducing the heat loss from the inside as well as increasing the solar radiation permeability, it is possible to make an elevation with large glazed areas. It also enables creating rural architecture with new features and new aesthetic expression, moving with the times.

Not only is the beauty of ancient houses more often appreciated, but also the solutions, developed by our ancestors which now contribute to the thermal protection of buildings. This can be an inspiration prompting traditions in the future design of modern rural houses. These solutions have been known for ages, but only the technological development of our times allows us to implement them in a more perfect way. The architecture of the low-energy consumption buildings changes mainly thanks to the possibilities of new techniques in building construction, often even thanks to electronic equipment. The modern building should be the object containing the elements of rational solutions known from history combined with the elements of modern knowledge and technology. Hence, it is essential to combine the knowledge of our ancestors with modern technological achievements. Currently we strive to gain full control over environmental factors and convert them in a way which is most rational from the energy-saving point of view, so that, along with the building’s installations, they constitute an interior microclimate adapted to the users’ needs. The culmination of the quests for the highest possible effectiveness of the dwelling settlements, considering respect for energy, is the low-energy consumption architecture which is a synthesis of the best solutions developed across time [18].

The buildings erected at the beginning of the 20^th century in Karwieńskie Błota are especially noteworthy. They are characterized by regional timber framing construction, half-hip roofs, often covered by reed. Some of them use passive heating system thanks to glazing of the southern elevations and optimal positioning of the buildings towards the sun. It is only one of few enclaves in northern Cassubia where architectural aesthetics still continue, the aesthetics which retain advantages of the regional architecture with the use of traditional and modern solutions of the buildings’ thermal protection (Fig. 6).

Figure 6.