Energy, Economic, and Environmental Performance of a Single-Family House in Chile Built to Passivhaus Standard

The energy consumption of buildings accounts for 22% of total global energy use and 13% of global greenhouse gas emissions. In this context, this study aims to evaluate the energy, economic, and environmental performance of housing in Chile built according to the Passivhaus (PH) standard. The standard was applied to housing in eight representative climate zones with a single-family residence as reference. The analysis incorporated passive strategies, which are considered as pillars of the PH. The energy performance was analyzed using the Passive House Planning Package software (PHPP), version 9.6a. The results showed that when every passive strategy is implemented, the heating energy demand decreases by 93%, while the refrigeration demand is nonexistent. These results were achieved through a 37% increase in the overall initial budget investment, which will be amortized over an 11-year period. In this way, the primary energy consumption is reduced by 32% and, correspondingly, CO2 emissions are reduced by 39%. In modern Chile, it is difficult (but not impossible) to incorporate PH. However, governmental programs and aids could represent an initial step. Therefore, this research will help to identify strategies for incorporating PH in Chile, with the aim of improving the energy performance of housing.


Introduction
The human influence on climate conditions is evident, resulting in anthropogenic greenhouse gas emissions reaching their highest recorded values in history.
Greenhouse gas emission projections vary greatly depending on both the level of socioeconomic development and the climate policies implemented in each country [1].
The construction sector is responsible for over one-third of the total global energy consumption and almost 40% of the total CO 2 emissions (both direct and indirect). Furthermore, the energy demand of buildings and building construction is on the rise due to countries having improved access to energy, both increased ownership and use of electronic devices, and the fast growth of the construction sector [2,3].
The energy used for heating, refrigeration, domestic hot water, and lighting represents the highest total energy percentage in the different stages of a building's lifespan, being collectively responsible for 22% of the total global energy consumption and approximately 13% of global GHG emissions [4]. This type of consumption typically ranks first as the largest source of CO 2 emissions, surpassing the energy necessary to extract and manufacture materials, and even the energy necessary for the construction of buildings [5].

Materials and Methods
The methodology applied in this research can be divided into five stages ( Figure 1): (i) the Passivhaus standard context, where the requirements of the standard are explained; (ii) the building context in Chile; (iii) the description of housing under study; (iv) the presentation of the representative climate zones considered; and (iv) the simulation of the house using PHPP software. tralian case, where the use of Passivhaus as a design tool allowed the design team to overcome limitations of the Australian building code [29]. Therefore, it is necessary to evaluate different strategies according to the climate in order to achieve PH. In tropical climates, the main strategy entails cooling and dehumidification [30]; in China, the use of an mechanical ventilation with heat recovery ( MVHR) system is essential [31], and for all types of climates in Germany, Romania, and Ukraine, energy demand increases as latitude increases, so this strategy aims to increase insulation levels based on location [32]. On the other hand, studies show that to achieve PH, it is necessary to place special emphasis on summer overheating and on shading strategies to achieve thermal comfort [33]. Given the outlined context, this study suggests incorporating the PH standard for housing in Chile through the addition of building construction improvements for housing situated across the country and reflecting various climates. Likewise, it evaluates whether or not PH is a good strategy at the national level in terms of energy savings, necessary investments, and environmental externalities. At the same time, the goal is to promote a concrete methodology to fight climate change. For this purpose, the 9.6a version of the energy balance tool Passive House Planning Package (PHPP) was used [34]. As a part of the certification process, it is mandatory that each PH housing development be modeled and verified with PHPP [35].

Materials and Methods
The methodology applied in this research can be divided into five stages ( Figure 1): (i) the Passivhaus standard context, where the requirements of the standard are explained; (ii) the building context in Chile; (iii) the description of housing under study; (iv) the presentation of the representative climate zones considered; and (iv) the simulation of the house using PHPP software.

Passivhaus Standard
Passivhaus buildings minimize heat flow through the building's envelope and, therefore, combine high thermal comfort, extremely low energy demand, and a relatively low lifespan cost. The operational costs are low since improved enclosure performance leads to a smaller, mechanical service system required to maintain comfort. In general, the maximum heating or refrigeration load is lower than 10 W/m 2 of the living area [24]. These types of constructions can be built almost anywhere in the world, from the Arctic to Scandinavia and the Mediterranean, where concepts allow for the provision of buildings with

Passivhaus Standard
Passivhaus buildings minimize heat flow through the building's envelope and, therefore, combine high thermal comfort, extremely low energy demand, and a relatively low lifespan cost. The operational costs are low since improved enclosure performance leads to a smaller, mechanical service system required to maintain comfort. In general, the maximum heating or refrigeration load is lower than 10 W/m 2 of the living area [24]. These types of constructions can be built almost anywhere in the world, from the Arctic to Scandinavia and the Mediterranean, where concepts allow for the provision of buildings with similar interior qualities and equivalent energy demands without impacting the architect's design freedom [20]. A building must comply with specific criteria to obtain PH certification (Table 1) [36], for example, having maximum values of 15 kWh/m 2 per year (equivalent to 10 W/m 2 of power) for heating/refrigeration demand. Likewise, the primary energy demand must be equal to or lower than 120 kWh/m 2 per year. The airtightness level must be equal to or lower than 0.6 air changes per hour for pressurization and de-pressurization at 50 Pa pressure, and thermal comfort should allow for only 10% of annual hours above 25 • C. Primary energy consumption refers to the amount of demand for the site's primary energy and the losses that occur during generation, transmission, and energy distribution [20].

Building Context in Chile
The housing sector in Chile is regulated by the General Construction and Urbanism Ordinance (OGUC) [11]. This ordinance sets the maximum value for thermal transmittance (U value) for envelope elements in new constructions. The OGUC's 2007 update restricts the U value for walls, roofs, suspended floors, and glazed areas. However, it leaves out several unsolved regulations regarding the building's energy development, such as the risk of overheating and infiltrations, among others. These regulatory shortcomings are more evident when national regulations are compared to international regulations; for example, the Spanish Technical Building Code (CTE) [14]. The CTE has similar features to the Chilean regulation as they share several climate types. When comparing these two norms, it is possible to identify differences ( Table 2) that directly affect energy demand [8,37]-for example, more explicit specifications regarding carpentry or climate zones for simulations. Since Chile has more diverse climate variability than Spain, it should have a broader climate zone classification. On the other hand, Chilean regulations do not restrict infiltration levels, with the national average being 12.9 h −1 [7], differing vastly from the regulated 0.3 air changes per hour in European countries like Germany, Austria, Belgium, Slovenia, Lithuania, and Norway, among others [38].
Given this context, 86% of Chile's housing built before 2000 does not have any kind of insulation. Between 2001 and 2006, 12% of built housing only had roof insulation. Lastly, only 2% of houses built between 2007 and 2015 comply with the current thermal regulations [39].
Regarding building materials, concrete is predominantly used in the north of Chile, masonry in the center, and wood in the south [40]. There are similar architectural typologies throughout the country.
Based on this scenario, and attempting to mitigate climate change, Chile has committed itself to reducing its GHG emissions by at least 30% by 2030 based on its emissions in 2007 [41]. The construction sector's guidelines state that construction should be accomplished efficiently, minimize energy requirements by at least 30%, and minimize environmental externalities in reaching the appropriate comfort levels. The successful implementation of PH would mean achieving these goals.

Description of Housing under Study
The study is based on housing that is in compliance with the identification of building parameters, as described in official reports (typology, materials, area, and infiltrations) [7,[42][43][44], which represents the majority of the housing stock in Chile (Table 3). Given this context, the research focuses on single-family masonry housing, with concrete pillars and beams of 81.72 m 2 , two bedrooms, two bathrooms, one living room, one dining room, one kitchen, and a laundry area (Figure 2A), designed for three people. This type of housing has foundation walls that are 500 mm high by 400 mm wide, with 400 mm high by 200 mm wide footings. The external wall is made of 140 mm thick brick masonry. The roof contains galvanized steel trusses covered by asphalt roof tiles. The interior roof structure contains 60 mm mineral wool panels and, underneath, plasterboard, leaving an unventilated space. The floor consists of a 70 mm concrete floor slab with a 10 mm wood parquet. The windows are single-glazed and have an aluminum frame with no thermal bridge break. According to the identified features, the areas of the non-glazed and glazed envelope are obtained (Figure 2b) as well as the air volume used to ventilate these areas (Table 4). These values correspond to the areas inputted in the PHPP software. These areas are essential as they are in contact with the outside environment. The entrance door is included in the glazed area.  These characteristics were selected from conventional construction systems certified by current national thermal regulations [45][46][47] because each new innovative construction system that is to be used in Chile must go through a certification process. Therefore, these Sustainability 2021, 13, 1199 6 of 15 characteristics were chosen in order to comply with the energy performance of Passivhaus, increase the thickness of insulation, or use constructive solutions present in the regulations. Moreover, it should be noted that the PHPP software only takes into account traditional construction solutions.
According to the identified features, the areas of the non-glazed and glazed envelope are obtained (Figure 2b) as well as the air volume used to ventilate these areas (Table 4). These values correspond to the areas inputted in the PHPP software. These areas are essential as they are in contact with the outside environment. The entrance door is included in the glazed area. Furthermore, through these materials, it is possible to obtain values for the conductivity and thermal transmittance of the building elements (Table 5). Thickness and conductivity values were obtained for the different building solutions identified throughout the country [45]. Regarding facilities, the housing under study does not contain heating systems. For domestic hot water, a 15 kW nominal power gas boiler was considered.
In Chile's southern cities, the most used fuel in the residential sector is biomass, at 38% of the total. On the other hand, cities in the center and north use more electricity in residences at 38% of the total [48]. Biomass and electricity inflation percentages in Chile are 3.9% and 2.4%, respectively [49,50].

Climate Zones
Chile has various landforms, including the Andes range, the Coast range, and the Pacific Ocean. Thanks to this particular configuration, there is broad climate variability, ranging from extremely hot and arid areas in the north to the glaciated areas and ice fields of the south.
This study identifies representative climate zones in the territory using the nine climate zones defined in the National Institute of Standardization of Chile (NCh) 1079-2008 [51]. This code includes the highest number of climate parameters in the country, more than the Thermal Regulation (RT) policy [52]. While the RT divides thermal zones based on only one meteorological variable (heating degree days), it does not consider the location's thermal oscillations between day and night. NCh 1079-2008 is based on meteorological variables that define a type of climate. These variables are average temperature, daily temperature oscillation, sun exposure, relative humidity, cloud cover, rain, prevailing winds, ice, snow, salinity, and altitude.
It is necessary to define the cities for simulation of each climate zone and the parameters by which these cities will be selected. In this context, PH reduces energy consumption and improves indoor air quality, making it an excellent alternative for cities with poor air quality indexes. Based on this premise, this study chose the most polluted cities in each thermal zone [53], leaving the Andean zone out due to its climate harshness not complying with habitability requirements. In this way, the eight cities for research are defined (Table  6): Calama, Copiapó, La Serena, Viña del Mar, Santiago, Temuco, Valdivia, and Coyhaique. In Chile's southern cities, the most used fuel in the residential sector is biomass, at 38% of the total. On the other hand, cities in the center and north use more electricity in residences at 38% of the total [48]. Biomass and electricity inflation percentages in Chile are 3.9% and 2.4%, respectively [49,50].

Climate Zones
Chile has various landforms, including the Andes range, the Coast range, and the Pacific Ocean. Thanks to this particular configuration, there is broad climate variability, ranging from extremely hot and arid areas in the north to the glaciated areas and ice fields of the south.
This study identifies representative climate zones in the territory using the nine climate zones defined in the National Institute of Standardization of Chile (NCh) 1079-2008 [51]. This code includes the highest number of climate parameters in the country, more than the Thermal Regulation (RT) policy [52]. While the RT divides thermal zones based on only one meteorological variable (heating degree days), it does not consider the location's thermal oscillations between day and night. NCh 1079-2008 is based on meteorological variables that define a type of climate. These variables are average temperature, daily temperature oscillation, sun exposure, relative humidity, cloud cover, rain, prevailing winds, ice, snow, salinity, and altitude.
It is necessary to define the cities for simulation of each climate zone and the parameters by which these cities will be selected. In this context, PH reduces energy consumption and improves indoor air quality, making it an excellent alternative for cities with poor air quality indexes. Based on this premise, this study chose the most polluted cities in each thermal zone [53], leaving the Andean zone out due to its climate harshness not complying with habitability requirements. In this way, the eight cities for research are defined (Table 6): Calama, Copiapó, La Serena, Viña del Mar, Santiago, Temuco, Valdivia, and Coyhaique.

Data Input
In the second stage of the research (where housing is taken from its current state to PH standards), the thermal envelope features must be improved (Table 7) by incorporating continuous insulation on every element, adding double-glazed windows in Calama, Copiapó, and La Serena, and triple-glazed windows in Viña del Mar, Santiago, Temuco, Valdivia, and Coyhaique. Furthermore, a controlled ventilation machine with a heat recovery rate of 81% is considered, as well as an airtightness plate, ensuring an n50 value of 0.6 h −1 . For Coyhaique, a PH-certified door is implemented due to climate harshness. Lastly, thermal bridges are reduced to 0.01 W/mK at conflictive points in every city.

Results
The evaluation of the results is based on the incorporation of five "building improvements": thermal insulation, free construction of thermal bridges, airtightness, controlled ventilation machines with heat recovery, and high-performance carpentry.

Energy Analysis
Once building improvement data were inputted to the PHPP, an energy comparison between the housing under study in each city and the PH housing was carried out. Figure 3 shows the heating demand results. The country average is 300.2 kWh/m 2 per year. The country's average heating saving is 93% after incorporating PH into housing. In terms of refrigeration, it is not necessary to implement active elements to cool indoor air. Since the indoor temperature does not exceed 10% of temperatures over 25 • C, there is no overheating and no refrigeration demand as the controlled ventilation machine with heating recovery is responsible for this. This study considered the machine as a passive element as it requires a small amount of energy to operate.

Results
The evaluation of the results is based on the incorporation of five "building improvements": thermal insulation, free construction of thermal bridges, airtightness, controlled ventilation machines with heat recovery, and high-performance carpentry.

Energy Analysis
Once building improvement data were inputted to the PHPP, an energy comparison between the housing under study in each city and the PH housing was carried out. Figure  3 shows the heating demand results. The country average is 300.2 kWh/m 2 per year. The country's average heating saving is 93% after incorporating PH into housing. In terms of refrigeration, it is not necessary to implement active elements to cool indoor air. Since the indoor temperature does not exceed 10% of temperatures over 25 °C, there is no overheating and no refrigeration demand as the controlled ventilation machine with heating recovery is responsible for this. This study considered the machine as a passive element as it requires a small amount of energy to operate.  Energy loss was analyzed alongside the heating demand ( Figure 4) to identify its source and to use this information when implementing a strategy to reduce energy demand. Energy loss was analyzed alongside the heating demand ( Figure 4) to identify its source and to use this information when implementing a strategy to reduce energy demand.
Most energy loss occurs through exterior walls, then through ventilation, windows, roofs, floor slabs, thermal bridges and, finally, through non-usable heat gains.

Financial Analysis
The financial analysis helped to evaluate the investment increase when introducing PH and, therefore, to assess the feasibility of building PH housing. Table 8 shows the cost Most energy loss occurs through exterior walls, then through ventilation, windows, roofs, floor slabs, thermal bridges and, finally, through non-usable heat gains.

Financial Analysis
The financial analysis helped to evaluate the investment increase when introducing PH and, therefore, to assess the feasibility of building PH housing. Table 8 shows the cost of implementing construction improvements. For insulation, the price refers to the square meter and centimeter thickness. Source: [55] Implementing PH resulted in an average increase of 37% in construction costs for the country. Windows and wall insulations were identified as the highest costs ( Figure 5), at 10% and 8%, respectively. In second place, floor insulation and ventilation experienced an investment increase of 3% each, followed by airtightness at 2% and roof insulation at 1%.  The identified PH investment differential is significantly higher than the inter tional context, which indicates an increase between 8% and 15% [23,24]. However, i still amortized within a reasonable period in consideration of the building's lifespan the case of Chilean housing, the average amortization is 11 years (Table 9), making it m feasible to implement PH in the north of the country (6.8 years) than in the south (1 years).   The identified PH investment differential is significantly higher than the international context, which indicates an increase between 8% and 15% [23,24]. However, it is still amortized within a reasonable period in consideration of the building's lifespan. In the case of Chilean housing, the average amortization is 11 years (Table 9), making it more feasible to implement PH in the north of the country (6.8 years) than in the south (19.8 years). Nonetheless, savings on energy bills over the years make PH convenient throughout Chile. The PH amortization average in Chile ( Figure 6) indicates that savings made after 11 years of investment recovery correspond to more than 100% of the initial investment. Furthermore, this analysis does not consider the costs associated with house maintenance (which, in Chile, vary between 15% and 25%) and related to building quality deficiencies [56]. These considerations would increase the savings provided by PH housing.
inability 2021, 13, x FOR PEER REVIEW 11 of Figure 6. Average investment return period in Chile.

Environmental Analysis
The environmental analysis of this research is based on two indicators: primary e ergy and CO2 emission. Primary energy is the energy consumed by a house (heating us refrigeration, domestic hot water, and lighting) plus storage and distribution energy. E ergy consumption is defined as energy demand multiplied by a facility's efficiency facto In this context, the savings noted in this research (Figure 7) as resulting from incorporatin the PH standard into Chile's housing are 32% (country average). These savings are sign icantly noticeable in the south of the country, reaching 57%.

Environmental Analysis
The environmental analysis of this research is based on two indicators: primary energy and CO 2 emission. Primary energy is the energy consumed by a house (heating use, refrigeration, domestic hot water, and lighting) plus storage and distribution energy. Energy consumption is defined as energy demand multiplied by a facility's efficiency factor. In this context, the savings noted in this research (Figure 7) as resulting from incorporating the PH standard into Chile's housing are 32% (country average). These savings are significantly noticeable in the south of the country, reaching 57%. This primary energy consumption entails equivalent CO 2 emissions ( Figure 8) that fluctuate similarly, leading us to obtain country-level average equivalent CO 2 savings of 39% when implementing PH. Likewise, savings are more noticeable in the south of the country, reaching 65%.
The environmental analysis of this research is based on two indicators: prima ergy and CO2 emission. Primary energy is the energy consumed by a house (heatin refrigeration, domestic hot water, and lighting) plus storage and distribution energ ergy consumption is defined as energy demand multiplied by a facility's efficiency In this context, the savings noted in this research (Figure 7) as resulting from incorpo the PH standard into Chile's housing are 32% (country average). These savings are icantly noticeable in the south of the country, reaching 57%.

Discussion
When assessing the reference housing in terms of energy, none of the eight studied cities comply with PH requirements. Heating energy demand varies from 147.3 to 657.9 kWh/m 2 per year, far from the required standard of 15 kWh/m 2 per year. This difference occurs due to the current building regulations in Chile, which, as studies indicate, display significant disparities regarding key concepts that directly affect a building's energy performance. Infiltration is one of the essential unsolved concepts in Chilean regulation. In Chile, the average infiltration index is 12.9 air changes per hour [7], in contrast with the 3 air changes per hour required in most European countries and the 0.6 air changes per hour required by PH. The air changes per hour identified for the housing under study are 19 times greater than those contemplated by PH.
As with infiltrations, most of Chile's housing has deficient thermal envelope elements since the vast majority was built before the implementation of the regulations in 2000, and another significant percentage was built between 2007 and 2013, which resulted in elements of glazed and non-glazed areas being inferior to those required by PH.
This study identified a thermal transmittance U value for walls nine times higher than PH requirements, a window U value six times higher, and a roof U value five times higher than that identified in international studies [22,57]. Flooring in Chile is not the subject of thermal restrictions.
The significant differences noted in each of the thermal envelope elements and the infiltration levels are responsible for Chile's excessive housing energy demand.
On the financial side, international studies acknowledge that the additional contri-

Discussion
When assessing the reference housing in terms of energy, none of the eight studied cities comply with PH requirements. Heating energy demand varies from 147.3 to 657.9 kWh/m 2 per year, far from the required standard of 15 kWh/m 2 per year. This difference occurs due to the current building regulations in Chile, which, as studies indicate, display significant disparities regarding key concepts that directly affect a building's energy performance. Infiltration is one of the essential unsolved concepts in Chilean regulation. In Chile, the average infiltration index is 12.9 air changes per hour [7], in contrast with the 3 air changes per hour required in most European countries and the 0.6 air changes per hour required by PH. The air changes per hour identified for the housing under study are 19 times greater than those contemplated by PH.
As with infiltrations, most of Chile's housing has deficient thermal envelope elements since the vast majority was built before the implementation of the regulations in 2000, and another significant percentage was built between 2007 and 2013, which resulted in elements of glazed and non-glazed areas being inferior to those required by PH.
This study identified a thermal transmittance U value for walls nine times higher than PH requirements, a window U value six times higher, and a roof U value five times higher than that identified in international studies [22,57]. Flooring in Chile is not the subject of thermal restrictions. The significant differences noted in each of the thermal envelope elements and the infiltration levels are responsible for Chile's excessive housing energy demand.
On the financial side, international studies acknowledge that the additional contribution of incorporating the PH standard fluctuates between an additional 8% to 15% [23,24]. On the other hand, in Chile, the incorporation of the PH standard would increase by an average of 37%. The reason for this difference is similar to the one found regarding energy. In European countries where price fluctuations are not significant, regulations control aspects that are not regulated in Chile and, therefore, the price per square meter is higher. Consequently, the additional contribution for compliance with PH is lower.
Regarding investment turnover, the country average is 11 years when considering energy savings and fuel inflation.
On the environmental side, incorporating the PH standard allows for a countrywide decrease of 93% in heating energy demand, which is in accordance with the experience internationally [22,24].

Conclusions
The Passivhaus standard refers to a building type designed to take advantage of the climate context in each specific zone. Theoretically, its incorporation is viable in any climate type, being more feasible in certain climates depending on a country's economic and regulatory contexts.
In Chile's case, the housing under study is well above the required PH values regardless of the climate zone. No overheating was identified in terms of refrigeration demand for the housing typology in the assessed climate conditions. Therefore, there is no need to incorporate active elements to cool the building in any season. This is due to the controlled ventilation machine with heat recovery (considered a passive element in this study) which conditions the air (both hot and cold). In Santiago's case, a bypass system is necessary for the summer to prevent the ventilation machine from overheating.
When implementing the PH standard, special caution is needed to not overinsulate areas with high solar radiation as this may cause overheating of the house, generating discomfort in the summer. This, in turn, would result in noncompliance with the standard's requirements.
On the other hand, the incorporated strategies and technologies go hand-in-hand with excellent execution. As this standard has minimal energy demands, the smallest error in execution will result in unnecessary energy loss, which may pass in a regular building, but could result in noncompliance with PH criteria in housing with these characteristics.
It was only possible to achieve the PH standard in each analyzed climate by incorporating passive elements, which are considered the pillars of this standard. This study focuses on the exclusive implementation of passive elements. However, it is necessary to consider each case to evaluate if it is more convenient (and, most of the time, it is) to incorporate active auxiliary systems that contribute to indoor comfort.
Furthermore, applying PH to the Chilean context promotes a reduction in GHG emissions, which aligns with Chile's goals for 2030.
It was shown that the PH standard is feasible for Chilean climates at a high cost (compared to other international contexts). However, it can be amortized within a reasonable period given that a building's lifespan is at least 50 years. The energy strategies result in energy cost reductions and offer residents spaces of higher quality with more stable and controlled levels of thermal comfort.
Finally, this study also demonstrates the feasibility of implementing Passivhaus in the different climatic zones of Chile with the current construction systems that are in place throughout the country. However, it is necessary to continue exploring thermomodernization solutions through parametric studies and by training workers who can execute them correctly in order to meet the design requirements.