Evaluation of facade systems in different climate zones regarding energy, comfort, emission, and cost

Abstract

Currently, advanced technologies have been developed to reduce energy consumption and carbon emissions. The fact that the building envelope causes energy losses of up to 73% leads to the search for the right solutions in the design of building systems. Providing human comfort in interiors with current design strategies would decrease the need for using active systems and bring along energy gains. As a result, less fuel will be consumed, and fewer emissions will be generated, contributing to a healthier environment on a global scale. In the scope of this study it is aimed to evaluate different facade applications on a reference building for three provinces located in different climate zones, which are Karabük, Konya, and Mersin in Turkey. In addition, façade scenarios in the direction of east-west and north-south axes were evaluated to determine the energy waste or gains caused by orientation. The scenarios were analyzed considering heating-cooling energy demand, thermal comfort, carbon emissions, and payback periods. REVIT and Design Builder were used for 3D modeling and simulations. Results indicated that an opaque ventilated wall is the most advantageous scenario for the Mediterranean climate zone in all parameters. This façade system performs better than the others in reducing carbon emissions and saving costs for all the regions. Although the solar chimney makes a significant contribution to the reduction of especially heating loads for all regions, this system is not applicable when the payback period is considered. In terms of thermal comfort, southward orientation minimizes the humidity and temperature fluctuations indoors throughout the year.

Keywords:

• Building envelope
• carbon emission
• climate
• heating-cooling loads
• orientation
• payback period
• thermal comfort

1. Introduction

The buildings are built to minimize the negative effects of the external environment (Oberfrancová, Legény, & Špaček, 2019), to maintain a healthy environment (Aydin & Mihlayanlar, 2017), and to keep human comfort at a constant level (Pulselli, Simoncini, & Marchettini, 2009). However, while providing comfortable conditions, it is essential to be aware of the energy consumption with regard to primary resources, especially during the operation period of the building (Asdrubali et al., 2018).

It is well-known that 30–40% of energy consumption in Western countries (Pulselli et al., 2009) and 30% of global greenhouse gases (Nadoushani, Akbarnezhad, Jornet, & Xiao, 2017) originate from the building sector annually. In addition, 50% of this consumption is due to air conditioning, heating, and cooling systems (Al-Badi & AlMubarak, 2019). With the effect of the energy crisis that has been experienced since the 1970s, developments towards energy saving have accelerated (Özmen & Beşiroğlu, 2020).

The energy performance and thermal comfort conditions of a building are closely related to the building form, structural design, building materials, environment, local climate, and the use of the building (Lapisa, 2019; Mesmoudi, Soudani, Zitouni, Bournet, & Serir, 2010), as well as the right decisions on orientation, shading elements, and glazing types (Pacheco, Ordóñez, & Martínez, 2012; Qurraie, 2022). In a study, it has been observed that with a proper direction and a compact form, up to 81% reduction can be achieved in heating and cooling loads. However, this value varies according to geographical conditions (Lapisa, 2019).

When a building is oriented to the south, there is an increased chance for sun utilization and daylighting (Heravi & Qaemi, 2014). Although most researchers recommend that buildings should be oriented in the south direction, there is a widespread consensus that the best option is to orient 20–30° south (Pacheco et al., 2012). The context should be considered in the design phase because the building envelope performs continuous heat exchange with the external environment depending on the climatic conditions (Pulselli et al., 2009). External environmental conditions differ from one region to another (Oberfrancová et al., 2019). The variables of external factors should be stabilized with minimum energy consumption with high-performing facades, and interior comfort conditions should be accomplished. Also, context and climate should play a leading role in the development of appropriate design strategies (Aksamija, 2016). To produce sustainable architectural examples, adverse environmental effects should also be considered (Shahda, 2018).

The building envelope is where the heat transfer occurs between the interior and exterior sides of the building. Therefore, it plays a vital role in energy efficiency. In a study by Pulselli et al. (Pulselli et al., 2009), three different building envelope samples were evaluated in three different climate zones. Increasing the wall thickness in extreme climatic conditions led to more effective energy performance. Solmaz (Solmaz, 2021) argues that 73% of the heat losses in the building are caused by the building envelope. From this point of view, the design of the building envelope with passive systems not only diminishes the addiction to the mechanical systems but also regulates indoor weather conditions (Barbosa & Ip, 2014).

Insulation is another factor that influences the energy performance of the building shell. Altun et al. (Altun, Akgul, & Akcamete, 2020) studied the impact of building envelope insulation on energy, cost, and carbon. They found that thanks to insulation applications, 70, 73, and 75% savings can be accomplished in annual heating energy demand, total cost, and total carbon emissions, respectively.

According to a study of the building envelope of a residential building, energy savings of approximately 22 to 39% were achieved through insulation, glazing, window to wall ratio (WWR), shading, and thermal mass in the context of five climate zones of Saudi Arabia. Gülaçmaz et al. (Gülaçmaz, Başdemİr, & Gülaçmaz, 2022) studied passive and active systems for energy retrofitting in existing buildings. They found out that when the U value of the building components is minimized, the dependence on external climatic conditions diminishes.

In addition to the thermal mass feature of some building materials, ventilated cavity wall and solar chimney alternatives from facade applications can be evaluated under the heading of energy conservation measures.

Thermal mass: The feature of a material that can store heat. In well-insulated buildings, thermal mass can significantly reduce heating and cooling loads by minimizing temperature fluctuations indoors (Nadoushani et al., 2017).

Opaque ventilated cavity wall: Opaque thermal façades absorb and reflect heat but do not allow heat to penetrate directly into the building. Thermal mass and solar chimneys are also evaluated within the scope of opaque solar facades (Quesada, Rousse, Dutil, Badache, & Hallé, 2012). Opaque walls with ventilated voids consist of two opaque facades and a ventilated channel between them. This system has a particular interest in Southern Europe due to its capacity to reduce thermal loads (Ibañez-Puy, Vidaurre-Arbizu, Sacristán-Fernández, & Martín-Gómez, 2017). This system provides a reduction in energy demand and enhances the comfort of the building users. According to a study, 20–55% of energy saving can be achieved by using opaque ventilated façades (Gagliano & Aneli, 2020). Maciel and Carvalho (Maciel & Carvalho, 2019) investigated the energy performance of opaque ventilated façades in Brazil for nine climates. They concluded that these façades systems propose a decrease in passive cooling demand compared to façades with cladding and savings on electricity up to 43% for the cities in hot climates.

Double skin facade systems: Double skin facade systems consist of a channel between two different layers, which are generally glazing systems. This cavity is used to collect or remove heat from the structure and is widely applied in Europe, especially for cold climate regions (Zhou & Chen, 2010). There are many discussions on the effective performance of the air gap channels of this system. Radhi et al. (Radhi, Sharples, & Fikiry, 2013) stated that the air gap in the range of 70–120 cm would help to establish a balance between heat gain and conduction, while Rahmani et al. (Rahmani, Kandar, & Rahmani, 2012) stated that widths up to 1 meter would increase heat gain, but further expansions may reduce the efficiency of the facade system.

On the other hand, Ji et al. (Ji et al., 2007) stated that the shading elements can improve the natural air flow by 35% and help reduce the heating load of the interior channel by 75%. Due to the research done at Karabük (Qurraie & Kıraç, 2022), double-skinned green facades with a 30% foliage coverage were shown to have better energy efficiency. And according to a study conducted in Dubai, double skin façades can decrease annual cooling energy use by 22% compared to conventional curtain wall systems (Aldawoud, Salameh, & Ki Kim, 2021).

The pros and cons of double-skinned façade systems are given holistically below (Table 1).

Table 1. Advantages and disadvantages of double-skinned facades (Adapted from (Solmaz, 2021)).

Feature	Achievements	Deficiencies
Double layer	Thermal comfort	Overheating in case of inadequate ventilation
Natural and passive ventilation	Clean indoor air quality when ventilation is provided effectively	Risk of the rapid spread of fire
Sound insulation	Acoustic comfort	Acoustic problems in case of insulation failure
Solar shading	Protection of solar shading elements	Reduction in daylight utilization in case of design failure

Currently, investigations on energy conservation through building envelope systems have become very popular. Especially double-skin façades gain great attention on a global scale. In Turkey, there is a lack of application of double skin façade systems, the contrary of Europe and North America, which plays an important role in energy savings, especially for colder climates (İnan & Başaran, 2013) compared to other countries.

Solar chimney: A system that works with the chimney effect and helps to improve natural ventilation (Charvat, Jicah, & Stetina, 2004). Taking advantage of the temperature difference allows the hot air to rise along the chimney and be removed from the facade and the fresh air to be taken in through the gaps in the lower parts of the chimney. It can be applied by integrating into double-walled systems (Shi et al., 2018). Double-skin façades and solar chimneys use similar principles in terms of the utilization of an air channel between two layers (Nguyen, Nguyen, Pham, Manh, & Huynh, 2021). Solar chimneys can be used for heating and cooling purposes (Tavşan, Tavşan, & Karahaliloğlu, 2021). It ameliorates thermal comfort depending on the climate.

To increase the performance of the solar chimney, it is recommended that the ratio of the height of the chimney to the gap width is 10. In addition, air inlet and outlet vents with equal dimensions, a 5 cm thick insulation wall, two or three layers of glass, and the use of an absorber with high absorbency and oscillation are among the recommended parameters (Shi et al., 2018).

Hong et al. (Hong et al., 2019) studied a detached two-story house to analyze a solar chimney. It was claimed that a solar chimney with 1 m depth, 8 m height, and 1.6 m wide could save 9% of the energy consumed by the HVAC systems annually. This reduction was achieved by the application of a solar chimney placed on the west façade to make maximum use of the wind, thus, natural ventilation.

Energy retrofitting of traditional buildings: Some Previous studies have looked into building renovation and retrofitting as the most environmentally friendly way to keep the built environment functional. Mahdavi (Mahdavi, 2010), in his study, concentrated on evaluating the building’s interior and exterior conditions, then modeling potential retrofitting solutions. Litti et al., Ma et al., and Şahin et al. (Litti, Audenaert, & Lavagna, 2018; Ma, Cooper, Daly, & Ledo, 2012; Şahin, Arsan, Tuncoku, Broström, & Akkurt, 2015) conducted research on climate analysis, including energy considerations of potential changes to the envelope and windows. Saafi and Daouas (Saafi & Daouas, 2019) looked examined the energy savings and financial viability of incorporating PCMs into Tunisian building envelopes. The double-skin facades are appropriate for the idea of restoring the original structure because they envelop it in a second fully glazed layer (Ascione, Bianco, de Rossi, Iovane, & Mauro, 2022). In order to enhance the thermal and energy performance of a genuine office building in Southern Italy, their article has suggested an energy efficiency intervention using cutting-edge technologies.

According to the Literature Review and the recent research on the use of double-skinned facades energy retrofitting of historical buildings, in the field of improving the energy of historical buildings in Turkey, three methods are implemented on its outside walls, and their results are examined. These three methods are ventilated cavity walls, double-skin façades, and solar chimneys.

2. Aim and scope

Energy retrofitting of existing buildings is a worth-studying area in the building sector. However, there are few studies on this subject in Turkey. Not only energy savings but also sustainability principles such as economic, social, and environmental should be considered for a holistic approach. Therefore, within the scope of this study it is aimed to examine energy performance, thermal comfort, carbon emissions, and payback periods depending on the heating and cooling loads through four different facade scenarios to be integrated into an existing reference building in the context of Karabük, Konya, and Mersin. The selected structure is in use as an academy of arts and science.

Passive design strategies such as thermal mass and orientation, as well as building envelope systems such as ventilated cavity walls, double-skin façades, and solar chimneys, form the basis of the study.

3. Materials and method

The building, which is the primary material of the study, has a compact form with a rectangular plan of 17 × 25 meters. . The window to wall ratio (WWR) of the building is 21%. The building has Fan Coil Unit with 4 pipes and air-cooled chiller for heating, cooling, and air conditioning (HVAC) system. Mechanical ventilation and domestic hot water (DHW) are supplied during the working hours. The building is occupied between 09:00–17:00 on weekdays. The energy consumption is calculated based on the heating loads from October to March and the cooling loads from April to September.

The models were generated in REVIT (Revit, 2003), (2021 version, academic Licence), and Design-Builder (Tindale, 2005), (6.1.0.006 version, Single User Licence) was used for the energy simulations, determining the total annual CO₂ production in terms of environmental affects and discomfort hours in terms of thermal comfort.

Masonry rubble wall constitutes the reference case. Stone is a material with a thermal mass property that can store heat. For the other two scenarios, a secondary facade to the building envelope is proposed. The first one is the ventilated opaque cavity wall system supported by bricks in addition to an insulation layer, and the second is the solar chimney system created with glass. The materials of the proposed facades are shown in Figure 1. The U-value of the first scenario is 1.5 W/m²K while the second and third were calculated as 0.33 W/m²K. Solar chimney wall was only applied to the northern façade because of the concern of insulating the longer cold façade. The characteristics of the solar chimney can be described as follows: The height/width ratio was taken as 10, single glazing was applied as the second layer, and a multi-story, double-skin, interior louvered façade was preferred to enclose the northern façade. On the top and bottom of the chimney, grille vents were placed with 17,6 m² area and set as active between 09:00–17:00 on weekdays except the heating season (December–February).

Figure 1. Wall sections for three facade types: (1) uninsulated thermal mass, (2) ventilated cavity wall, (3) solar chimney- the chimney was applied only to the northern wall.

Since it was determined that the long façade of the building was oriented in the direction of the east-west axis, another scenario was developed in this context to distinguish the effect of the orientation on the heating and cooling loads. In this scenario, the building was rotated 90°, and the building envelope was not changed (Figure 2). The original ground and first-floor plans can be seen in Figure 3.

Figure 2. Orientation scenarios and solar chimney: (1) East-west direction, (2) North-south direction, (3) Solar chimney.

Figure 3. Ground and first-floor plan of the existing building (Adapted from (Beyazoglu, 2021)).

The provinces were selected according to the Köppen-Trewartha climate classification, considering different climate zones. According to this classification, Karabük has a temperate maritime climate, Konya has a continental temperate climate, and Mersin has a subtropical dry summer climate (Figure 4). While the share of the annual cooling load is much higher in Mersin, in Karabük and Konya, the annual heating load is greater than the cooling.

Figure 4. Köppen-Trewartha climate classification (Sensoy, Demircan, Ulupinar, & Balta, 2008).

The annual weather data of the selected cities can be seen from Table 2.

Table 2. Annual weather data of the provinces (WeatherandClimate, 2022).

Province	KARABÜK		MERSİN		KONYA
Month	Dry-Bulb Temperature	Relative Humidity (%)	Dry-Bulb Temperature	Relative Humidity (%)	Dry-Bulb Temperature	Relative Humidity (%)
January	2.1	91.2	11	85.5	8.5	87.1
February	4.4	90.1	12.4	79.38	2	82.1
March	7.1	82.9	15.4	74.12	7	75.9
April	12.9	68.7	18.4	68.88	11	64.9
May	16.3	75.2	22.7	72.12	15.9	68.0
June	21.9	63.8	25.6	47.94	21.2	50.2
July	21.9	60.2	28.6	36.69	25.4	38.4
August	23.5	61.9	29.4	37.69	24.6	41.2
September	18.6	52.9	27.2	41.31	20.1	37.9
October	14.1	63.5	23.5	63.81	13.9	62.9
November	7.8	76.8	18.4	74.06	7.9	80.4
December	3.7	84.9	13.6	81.56	1.3	83.4
Annual average values	12.9	72.7	20,5	63.6	13,2	64.4

The building is occupied between 09:00–17:00 on weekdays. The energy consumption is calculated based on the heating loads generated from October to March and the cooling loads from April to September. The thermal comfort range was considered as 18–24 °C in the assessment. Total annual carbon emissions are calculated for the environmental impact category. During the evaluation of comfort conditions, monthly fluctuations in temperature and relative humidity in interiors were evaluated. In terms of cost, the total price of the facade materials per square meter was found, and the payback period was determined.

Thus, it is aimed to determine the behavior of the designed façade scenarios and orientation to determine the optimum choice for each region in the scope of environmental impact, human comfort, and economy. All the analyses were conducted by using the Design Builder program including the cost analysis. The façades scenarios are hereinafter referred to as FS01, FS02, FS03, and FS04 (Table 3). Currently, the desired building is used by the university and has a heating system in the cold seasons. The comparison of two last years’ energy consumption bills (electricity and natural gas) of the building and its correspondence with the chart obtained from the energy simulation performed. By comparing with actual measurement, the differences are not significant according to ASHRAE guideline 14, so the validation of obtained information is proved.

Table 3. Analyzed façade system scenarios.

Façades	Case	Layers	Properties	Orientation
FS01	Reference	One façade (opaque)	Uninsulated thermal mass	East-west
FS02	Alternative			North-south
FS03	Alternative	Two façades (opaque + opaque)	Ventilated cavity wall	North-south
FS04	Alternative	Two façades (opaque + glazing)	Thermal mass + solar chimney	North-south (chimney is in the North)

The methodology of the study can be seen from Figure 5. According to base case, other three façade scenarios are evaluated regarding three different climate zones. Thereafter, the results are analyzed and discussed in terms of energy, comfort, emissions, and cost.

Figure 5. The research method of the study.

4. Results and discussion

In this section, the four façade alternatives were compared in terms of the selected parameters, which are energy performance, human comfort, carbon emissions, and cost.

4.1. Energy performance

Heating and cooling loads were evaluated for different climate zones. When the heating loads are considered, it is seen that the highest performance for all three provinces is achieved through the solar chimney scenario (FS04) applied in the North. The reason for this is to provide insulation with the addition of a secondary facade to the coldest northern facade and to provide passive heating in the indoor environment by heating the air accumulated in the space between the opaque and transparent surfaces with the help of the sun rays. When FS04 is evaluated, it is seen that the highest energy saving compared to reference case (FS01) was obtained in Mersin with 72%, followed by Konya with 60% and Karabük with 47% (Table 4).

Table 4. Distribution of monthly and annual heating loads as well as annual saving rates compared to FS01 (reference case) for three zones (kWh).

Heating (Gas, kWh)	Karabük				Mersin				Konya
Months	FS01*	FS02	FS03	FS04	FS01*	FS02	FS03	FS04	FS01*	FS02	FS03	FS04
January	13,496	10,791	10,593	7,891	2,807	2,871	1,782	987	16,426	16,612	11,956	7,734
February	8,272	6,686	6,592	4,324	686	805	502	113	9,513	9,451	7,315	3,842
March	5,305	4,459	4,162	2,494	86	123	64	2	4,985	5,164	3,958	1,119
April	0	0	0	0	0	0	0	0	0	0	0	0
May	0	0	0	0	0	0	0	0	0	0	0	0
June	0	0	0	0	0	0	0	0	0	0	0	0
July	0	0	0	0	0	0	0	0	0	0	0	0
August	0	0	0	0	0	0	0	0	0	0	0	0
September	0	0	0	0	0	0	0	0	0	0	0	0
October	142	111	48	48	0	0	0	0	753	641	621	95
November	4,340	3,451	3,135	1,804	4	5	2	0	3,251	3,145	2,662	803
December	9,122	7,335	6,735	5,010	947	994	587	183	11,172	11,096	8,251	4,828
Annual total heating load (kWh)	40,677	32,833	31,265	21,571	4,530	4,798	2,937	1,285	46,100	46,109	34,763	18,421
%	0	−19	−23	−47	0	5,9	−35	−72	0	0	−25	−60

The facade scenarios that cause the lowest energy consumption in terms of heating performance are FS04, FS03, FS02, and FS01, respectively. In addition, it can be noticed that the orientation of the building (FS02) has a negligible impact on the heating performance (Figure 6).

Figure 6. Heating performance of all façade scenarios.

In terms of cooling loads, the ventilated cavity wall (FS03) presents the best results in all provinces. The highest gain was obtained in Mersin with 24%, followed by Karabük with 20% and Konya with 17%. It is seen that the air accumulating and warming up inside the solar chimney increases the cooling load in all three zones compared to other alternatives. Based on the reference (FS01), there is a loss of 27%, 1%, and 36% in FS04 for Karabük, Mersin and Konya, respectively. In addition, it is seen that rotating the building to a north-south direction provides positive results in terms of reducing the cooling load. This may be because the longer façade is positioned perpendicular to the prevailing wind, which mostly blows north-south throughout the year (Table 5).

Table 5. Distribution of monthly and annual heating loads as well as annual saving rates compared to FS01 (reference case) for three zones (kWh).

Cooling (Electricity, kWh)	Karabük				Mersin				Konya
Months	FS01*	FS02	FS03	FS04	FS01*	FS02	FS03	FS04	FS01*	FS02	FS03	FS04
January	0	0	0	0	0	0	0	0	0	0	0	0
February	0	0	0	0	0	0	0	0	0	0	0	0
March	0	0	0	0	0	0	0	0	0	0	0	0
April	244	211	127	598	1,665	1,554	1,421	2,559	54	40	64	429
May	1,166	1,030	793	1,940	4,565	4,300	3,692	5,590	804	707	678	1,794
June	3,340	2,916	2,509	4,283	7,228	6,648	5,625	7,772	2,385	2,200	1,986	3,723
July	4,490	4,111	3,639	5,269	9,846	8,745	7,060	9,222	4,541	4,312	3,640	5,379
August	3,996	3,701	3,503	4,508	11,290	10,025	8,396	10,014	4,003	3,794	3,453	4,598
September	1,633	1,511	1,368	2,264	7,681	7,172	5,799	7,531	2,259	2,173	1,851	3,145
October	0	0	0	0	0	0	0	0	0	0	0	0
November	0	0	0	0	0	0	0	0	0	0	0	0
December	0	0	0	0	0	0	0	0	0	0	0	0
Annual total cooling load (kWh)	14,869	13,480	11,939	18,862	42,275	38,444	31,993	42,688	14,046	13,226	11,672	19,068
%	0	−9	−20	27	0	−9	−24	1	0	−6	−17	36

Glazing systems that allow the sun rays to penetrate the interior through radiation and thus negatively affect thermal comfort may not be a suitable solution, especially for hot climate regions, as seen in the example of Mersin (Figure 7).

Figure 7. Cooling performance of all façade scenarios.

The reason is why FS04 is the most appropriate alternative for heating its trombe wall effect. In winter, the air in the gap between the glass and wall heats up by absorbing the sunrays. Afterwards, this heated air is released to the indoor environment through thermal mass.

Within the framework of each province, heating and cooling loads should be evaluated together to find the most energy-efficient facade alternative yearly. According to the table below (Table 6), considering the annual total energy consumption, compared to the reference case (FS01), it can be noted that the most appropriate choice for Karabük and Konya is FS04, and for Mersin, FS03.

Table 6. Annual electricity consumption of the façade scenarios (kWh).

	KARABÜK				MERSİN				KONYA
	FS01	FS02	FS03	FS04	FS01	FS02	FS03	FS04	FS01	FS02	FS03	FS04
Annual total heating load (kWh)	40,677	32,833	31,265	21,571	4,530	4,798	2,937	1,285	46,100	46,109	34,763	18,421
Annual total cooling load (kWh)	14,869	13,480	11,939	18,862	42,275	38,444	31,993	42,688	14,046	13,226	11,672	19,068
Annual energy consumption (kWh)	55,546	46,313	43,204	40,433	46,805	43,242	34,930	43,973	60,146	59,335	46,435	37,489
Savings in total energy (%)	0	−16.6	−22.2	−27.2	0	−7.6	−25.4	−6.1	0.0	−1.3	−22.8	−37.7

In Figure 8, the difference in heating-cooling loads between provinces can be easily seen. When FS04 is used, the difference between heating-cooling performances is minimal in Karabük and Konya. On the other hand, when FS04 is evaluated in Mersin, it is remarkable that the difference between heating and cooling performances reaches the highest level. FS03 can be considered the ideal façade scenario among the façades analyzed for that region in terms of energy consumption (Figure 8).

Figure 8. Annual energy consumption due to façade scenarios and regions.

4.2. Thermal comfort

In this section, among other thermal comfort parameters, only the relative humidity (%) and operative temperature (°C) values of indoor thermal comfort are discussed. In all three provinces and façade scenarios, relative humidity hovers between 30% and 60% throughout the year. This is the ideal humidity range sought indoors.

The comfort range for operative temperature was accepted between 18–24 °C. In Design Builder program, regarding temperature and humidity, the comfort hours throughout the year were analyzed and then the number of comfort hours were calculated. Regarding temperature and humidity, the number of comfort hours throughout the year was calculated. According to this, FS03 performs the best performance in Karabük, while the majority of comfort hours differ for relative humidity and operative temperature in Mersin and Konya (Table 7).

Table 7. Comfort hours calculation of the façade scenarios.

KARABÜK
Relative Humidity (%)	FS01	FS02	FS03	FS04	Operative temperature (°C)	FS01	FS02	FS03	FS04
<30%	373.0	158.0	437.0	206.0	<18 °C	3,219	3,139	2,904	2,328
30%> =comfort hours< =60%	7,371	6,237	7,540	7,490	18 °C> =comfort hours< =24 °C	3,601	3,756	4,255	3,635
>60%	1,016	2,365	783	1,064	>24 °C	1,940	1,865	1,601	2,797
% of comfort hours	84.0	71.2	86.1	85.5	% of comfort hours	41.0	42.9	48.6	41.5
Average	48.4	53.9	47.4	48.9	Average	19.4	19.6	19.8	21.0
gain or loss in comfort hours based on FS01 (%)	0.0	−15.4	2.3	1.6		0.0	4.3	18.2	0.9
MERSİN
Relative Humidity (%)	FS01	FS02	FS03	FS04	Operative temperature (°C)	FS01	FS02	FS03	FS04
<30%	547	572	588	467	<18 °C	926	887	589	294
30%> =comfort hours< =60%	7,454	7,368	7,315	7,637	18 °C> =comfort hours< =24 °C	2,944	3,056	3,868	2,514
>60%	759	820	857	656	>24 °C	4,890	4,817	4,303	5,952
% of comfort hours	85.0	84.1	83.5	87.2	% of comfort hours	34.0	34.9	44.2	28.7
Average	47.3	46.9	47.5	45.1	Average	24.0	24.2	23.9	25.5
gain or loss in comfort hours based on FS01 (%)	0.0	−1.2	−1.9	2.5		0.0	3.8	31.4	−14.6
KONYA
Relative Humidity (%)	FS01	FS02	FS03	FS04	Operative temperature (°C)	FS01	FS02	FS03	FS04
<30%	1,841	1,819	1,955	1,141	<18 °C	3,604	3,628	3,197	2,304
30%> =comfort hours< =60%	6,677	6,681	6,700	7,216	18 °C> =comfort hours< =24 °C	2,936	3,000	3,508	3,313
>60%	242	260	105	403	>24 °C	2,220	2,132	2,055	3,143
% of comfort hours	76.0	76.3	76.5	82.4	% of comfort hours	34.0	34.2	40.0	37.8
Average	38.7	38.8	37.6	41.0	Average	19.0	19.0	19.6	21.2
gain or loss in comfort hours based on FS01 (%)	0.0	0.1	0.3	8.1		0.0	2.2	19.5	12.8

The fluctuations throughout the entire year can be seen in Figure 9. Façade systems with the least change in relative humidity indoors are FS02 and FS03 in most cases. It can be concluded that orientation is as important as insulation. Increasing the number of façade layers with a correctly oriented structure during the design phase would give optimum results in terms of thermal comfort.

Figure 9. Fluctuations in the relative humidity (%) and temperature values (̊C) throughout the year.

According to temperature values, FS04 increases the interior temperature in winter seasons due to its heating capability thanks to trombe wall effect. However, there is an overheating in each case for the summer seasons, especially in Karabük. The monthly relative humidity and temperature values for all regions can be seen in Figure 9.

4.3. Carbon emissions

When the facade scenarios are examined by using Design Builder in terms of carbon emissions that occurred while the building was in use, it has been revealed that the ideal facade preference is the ventilated cavity wall (FS03) for all regions. The decrease in the amount of carbon emission in FS03 compared to the reference case is 31%, 23%, and 33% for Karabük, Mersin, and Konya, respectively. This may be due to the extra layer of insulation applied to the façade that acts as a barrier between the inside and outside (Table 8 and Figure 10).

Figure 10. Annual total carbon emissions (kg).

Table 8. Change of annual carbon emissions according to facade types (kg).

Carbon emissions (kg)	Karabük				Mersin				Konya
Façade Scenarios	FS01	FS02	FS03	FS04	FS01	FS02	FS03	FS04	FS01	FS02	FS03	FS04
Total	30,893	25,374	21,323	30,281	40,810	38,457	31,298	40,799	31,797	31,277	21,345	29,700
January	3,710	2,935	2,767	2,727	1,728	1,717	1,025	1,399	4,346	4,383	2,941	2,665
February	2,653	2,108	1,878	1,968	1,248	1,253	750	1,156	2,963	2,952	1,955	1,856
March	2,042	1,633	1,435	1,563	1,067	1,070	873	1,079	2,034	2,067	1,254	1,289
April	1,522	1,210	732	1,777	2,408	2,315	1,504	2,966	1,405	1,398	676	1,675
May	2,233	1,820	1,172	2,741	4,280	4,125	2,901	4,952	2,003	1,948	1,068	2,652
June	3,391	2,849	2,126	4,017	5,757	5,409	4,008	6,132	2,826	2,713	1,794	3,678
July	3,897	3,402	2,744	4,404	7,142	6,475	4,793	6,799	3,940	3,788	2,706	4,470
August	2,525	2,243	2,221	2,838	6,934	6,179	5,186	6,175	2,531	2,403	2,190	2,893
September	2,365	1,998	1,522	2,790	6,047	5,723	4,155	5,982	2,754	2,693	1,788	3,324
October	1,273	989	1,009	1,294	1,246	1,246	3,068	1,284	1,404	1,375	1,222	1,301
November	2,396	1,900	1,628	1,984	1,583	1,583	1,968	1,630	2,237	2,215	1,452	1,781
December	2,886	2,287	2,089	2,178	1,370	1,362	1,067	1,245	3,354	3,342	2,299	2,116
Total	30,893	25,374	21,323	30,281	40,810	38,457	31,298	40,799	31,797	31,277	21,345	29,700
%	0	−18	−31	−2	0	−6	−23	0	0	−2	−33	−7

According to total emissions, FS03 has a noticeable difference compared to other scenarios (Figure 11). Since the results vary according to the parameter taken into consideration, it can be stated that the decisions taken depending on the heating and cooling loads should also be evaluated in terms of environmental impact.

Figure 11. Carbon emissions due to the façade scenarios (kg).

4.4. Cost

To evaluate the cavity wall (FS03) and solar chimney (FS04) systems in terms of cost, payback periods were calculated depending on the initial costs and annual gains. The electricity tariff published by the Energy Market Regulatory Authority of the Turkish Republic (EPDK), which has been valid since 1/06/2022 (EPDK, 2022), and the natural gas tariff from the website of Istanbul Gas and Natural Gas Distribution Corporation (İGDAŞ) of the Istanbul Metropolitan Municipality (IGDAS, 2022) were considered for the conversion from kWh into TL. According to this, as of June 2022, the currency unit per kWh for unit electricity consumption has been taken as 2.45 TL, and the unit per kWh for natural gas has been taken as 0.38 TL.

The results showed an annual gain between 2.006–9.284 TL, even with the orientation alone (FS02). This gain could reach up to 25.796 TL thanks to the cavity wall (FS03). The solar chimney seems to apply only to Mersin (Table 9).

Table 9. Annual gains and losses.

	Karabük				Mersin				Konya
	FS01	FS02	FS03	FS04	FS01	FS02	FS03	FS04	FS01	FS02	FS03	FS04
Annual Energy Consumption (TL)	51,886	45,503	41,131	54,409	105,295	96,011	79,499	105,074	51,931	49,925	41,806	53,717
Gain (TL)	0	6,384	10,755	−2,853	0	9,284	25,796	221	0	2,006	10,124	−1,786

According to the calculations, to cover the cost of cavity walls, approximately 20 years for Konya, 19 years for Karabük, and 8 years for Mersin are needed. Since there are losses in annual energy consumption for FS04 compared to the reference case, this choice is not feasible for none of the territories (Table 10).

Table 10. Payback periods of facade costs according to heating and cooling gains.

	Initial cost (TL)	Annual Gain (TL)			Payback period (years)
		Karabük	Mersin	Konya	Karabük	Mersin	Konya
Thermal mass (FS01)	89.034	0	0	0	0,0	0,0	0,0
Cavity wall (FS03)	200.895	10.755	25.796	10.124	18,7	7,8	19,8
Solar chimney (FS04)	232.530	−2.523	221	−1.786	Not feasible

5. Conclusion

Structures consist of crusts that protect people from the adverse conditions of the external environment. There are many parameters to be considered in the selection of the building envelope, such as energy performance, human comfort, environmental effects, etc. The gain in one of these parameters may fall to negligible levels due to the loss in the other.

In this study, façade systems, such as thermal mass, ventilated cavity wall, and solar chimney as well as orientation, were evaluated and compared with each other to find out the ideal facade type for three regions and four parameters: energy performance, comfort, emissions, and cost. According to the results:

• It was seen that thermal mass without insulation is not efficient alone. Therefore, this scenario was accepted as a baseline in comparisons.

• Carbon emissions were reduced most in Karabük by %18 thanks to rotating the longer side facing north-south direction (FS02). However, the effect of this rotation on energy performance and comfort conditions was minimal, among other scenarios for all regions.

• FS03 offers a clear advantage in terms of emissions (FS03 = 23–33%, FS04 = 2–7%), payback period (FS03 = pay off between 8 to 20 years, FS04 = not feasible), thermal comfort (FS03 performs best in terms of operative temperature in all regions while FS04 is better in two regions in terms of relative humidity), and total annual heating and cooling energy demand (FS03 = 22–25%, FS04 = 6–38%).

The overall assessment can be seen in Table 11.

Table 11. Selection of the most suitable facade system.

Parameters	Karabük	Mersin	Konya
Heating-cooling energy demand	FS04	FS03	FS04
Thermal comfort	FS03	FS03-04	FS03-04
Carbon emissions	FS03	FS03	FS03
Cost	FS03	FS03	FS03

• Façade design should proceed with a holistic approach. While one alternative provides a reduction in carbon emission, another alternative may require less energy demand. Pros and cons should be regarded beforehand.

• As a result, it is essential to consider the building’s orientation, insulation, and climatic condition to reduce adverse effects on the environment, save budget and ensure human comfort. If an expensive system is to be used, the payback period of this system is another critical issue. Integrating a façade assembly cannot afford its own cost in use would be an inappropriate improvement. The effect of comfort conditions is another criterion to be considered, as it will affect the use of the active systems.

This study has tried to shed light on a tiny part of the choice of facade materials and system preferences, which should be evaluated holistically. For future works, new facade types suitable for different climatic zones can be examined. Not only the facade but also other components, such as the roof, glazing, etc., can be included in this comparison. Building envelopes are also responsible for the proper ventilation of interior spaces. In this respect, façade systems can be examined through their effects on natural ventilation, air flow rate, and indoor air quality.

Disclosure statement

No potential conflict of interest was reported by the authors.