This paper presents the results of the updated boundaries of thermal zones in the tree southern regions of Chile, based on the method of heating degrees-days according to hourly temperature measurements at meteorological stations in the last decade. The Ministry of Housing and Urban Planning of Chile has not updated these boundaries since 1999. Using the Climatic Severity index method, the relative energy consumption of dwellings was analyzed for cooling and heating in summer and winter periods, respectively. The analysis revealed that, within the limits of a single thermal zone, the energy costs for cooling in the summer period of the same house may differ by 50 %.
The correct definition of climatic zones for building construction allows building materials to be adequately selected for different geographic regions, thus minimizing energy costs for heating and cooling (Carpio et al., 2014, 2015). Chile is the longest country in the world from north to south and is characterized by the presence of multiple climatic zones (from tropical climates in the north to the Antarctic in the far south) (Kottek et al., 2006). With the additional effect of the altitude zonation of the Andes, Chile's climates exhibit not only meridional variability, but also latitudinal variability (Sarricolea et al., 2016). Therefore, from the point of view of building climatology, Chile is a very interesting country for studying and developing this field of applied meteorology.
Chile maintains an official document to regulate construction norms and
materials that should be used in different geographical parts of the country,
known as Thermal Regulation (TR) of the General Ordinance of Urban Planning
and Constructions of the Ministry of Housing and Urban Planning of Chile
(MINVU) (Ministry of Housing and Urban Planning of Chile, 2009). In TR
document, construction recommendations have been developed for seven thermal
zones, which in turn were determined in 1999 by the heating degree-days (HDD)
method with base temperature of 15
Three regions in the south of Chile were selected for our study. The La Araucania, Los Rios and Los Lagos regions are characterized by Mediterranean and temperate oceanic climate types, with relatively warm and rainy winters and relatively cool and dry summers. The construction of houses in these regions is mostly based on minimizing energy costs for heating buildings. In winter, these regions consume the most firewood for stove heating, which yields a high level of atmospheric pollution (Hernández and Arroyo, 2014; Ministry of the Environment of Chile, 2014).
Therefore, the main purpose of this work is to update the thermal zones based on meteorological station measurements over the past decade in the three southern regions of Chile; to analyze the feasibility of applying the Climate Severity Index method (de la Flor et al., 2006; Markus, 1982) for climatic zoning in construction for the studied regions; and to analyze the relative energy consumption of heating and cooling buildings in various thermal zones.
A widely used method of estimating the energy costs of buildings for heating
and cooling. The annual number of HDD is calculated as the sum of the daily
average positive differences between the comfort temperature inside the room
and the outside temperature:
Thermals zones of Chile according to TR MINVU.
The wide application of the method of degree-days in construction climatology also imposes limitations. This method is based only on the thermal regime of a certain geographic area, and this method is optimally applicable in regions where solar radiation and wind speed have a negligible contribution to the thermal balance of the building. On the other hand, the use of this method is not entirely suitable for commercial buildings (Makhmalbaf et al., 2013), therefore in this work we consider residential buildings.
This method was developed based on modeling the energy consumption of houses
in 50 cities of Spain under different climatic conditions (Government of
Spain, 2006; de la Flor et al., 2006). For this model, absolute values of
energy consumption for heating and cooling of premises in each city were
translated into relative indices (Summer Climatic Severity Index – SCSI and
Winter Climatic Severity Index – WCSI) and normalized for energy consumption
in the city of Madrid. The index of relative energy consumption for cooling
and heating buildings was associated with the climatic values of
meteorological indicators by the equation:
Climatic zones (Government of Spain, 2016).
In this paper, we used the temperature and total solar radiation data obtained from the meteorological stations in the studied area of the Ministry of Agriculture of Chile (Agromet), the Ministry of Environment (MMA) and the Directorate General of Civil Aviation (DGAC), a total of 44 stations. Their spatial-geographical locations are shown in Fig. 1.
Geographical location of the study area and meteorological stations.
At the first stage of the study, the HDD15
Old thermal zones
Boxplot of the average monthly maximum and minimum temperatures over the last 30 years by the NCEP/NCAR reanalysis data and the total solar radiation by the climatological data of study area in Chile and continental part of Spain.
Calculated values of HDD15
Average values of HDD, WCSI and CSCI for thermal zones of Chile of the study area.
In the central part of the Los Rios region, the houses previously constructed in zone 5 are now in zone 6, resulting in large energy costs to maintain a comfortable indoor temperature. In the case of changing zone 5 to zone 4 the energy of heating of dwellings can be reduced; further, the costs of insulation materials of future houses will be reduced.
Therefore, it is important to update the climatological information regularly, because this influences costs of construction.
In the second phase of the study, to justify the adequacy of the use of Eqs. (3) and (4) for calculation WCSI and SCSI in the climatic conditions of Chile, we analyzed the climatic data of solar radiation in summer and winter in Chile (Ministry of Energy of Chile, 2017) and Spain (Sancho et al., 2012), as well as the climatic values of the average monthly maximum and minimum temperatures in summer and winter by the NCEP/NCAR reanalysis data (NOAA, 2018), respectively (Fig. 3). The summer period for Chile is defined between the months of December and March, and the winter period between the months of June and August. The summer period for Spain is defined between the months of June and September, and the winter period between the months of December and February. The graphs show a relatively significant degree of similarity between the thermal and radiation regimes in the study area and in Spain.
WCSI and SCSI values for all meteorological stations were calculated from temperature and actinometrical measurements. If no solar radiation data was available at a station, model data of total solar radiation was obtained from the Ministry of Energy of Chil “Explorador solar” website (Ministry of Energy of Chile, 2017).
We can see the minimum WCSI
Based on the data in Table 3, and using the Kriging interpolation method, the spatial distributions of WCSI and SCSI for the studied area were recovered. On the basis of climatic zoning (Table 2) climatic zones for construction in the studied area were restored (Fig. 4). It can be seen that most of the region studied is attributed to the climatic zone D1, minor areas to the zones C1 (around major cities and the north-western oceanic coast) and E1 (in the northeast).
Climatic zones (Government of Spain, 2016) of the study area.
All calculated SCSI values were less than 0.66 (Table 3); therefore, for the energy consumption of cooling houses in summer, the entire studied area is referred to the summer climatic zone number 1. Winter climatic zone D corresponds to the energy consumption level of buildings for winter heating in the city of Madrid.
The definition of the Spanish construction climatic zones will allow us to further simulate energy consumption by houses according to the norms and recommendations that the Spanish government developed. And to make a comparison with the use of houses, which will be obtained when simulating the construction norms of the Chilean government. Chilean building codes emphasize energy efficiency for heating in winter, while Spanish building codes target both winter and summer
At the last stage of the study, we considered the relationship between the
two methods of climatic zoning for construction. The boundaries of the
thermal zones (Fig. 2 on the right) and the spatial grid of 0.
Negative values of SCSI indicate that with a high probability in this part of
the study area there will be no cost for cooling the houses during the summer
period to a comfortable temperature of 20
We can see that for the study area the difference in energy consumption is equal to the identical building located in the northern part of the thermal Zone 7 will be 37 % more than if this building was located in zone 4.
In the work (Martín-Consuegra et al., 2016), the authors note that in
Madrid (WCSI
In another work (Bustamante, 2009), the author notes that in the city of
Temuco (WCSI
In work (Martín-Consuegra et al., 2016), the average energy costs for
cooling a single-family house built before 1979 in Madrid are estimated at
26.5 kWh m
The application of more stringent building codes and recommendations will help reduce energy costs in the first place for heating houses in the study area, but this should be further verified by modeling energy consumption and natural experiments.
With the use of meteorological stations data, the boundaries of thermal zones
in the three southern regions of Chile have been updated. Over the past
decade, importantly noted is the tendency of shifting the warmer zones to the
south, as compared to the old borders of 1999, is noted. For example, the area of thermal zone 4 increased by 2.5 times and shifted by about 2.5
The application of the Climatic Severity Index method allowed us to obtain an estimate of the relative energy consumption of houses in thermal zones. The presence of significant differences in the theoretical estimation of the energy consumption of buildings for cooling in summer within the limits of one thermal zone raises the question of the adequacy of the use only of hating degree-days method for thermal zoning in the construction of Chile.
Boundaries of thermal zones should be revised and evaluated with modeling of energy consumption of buildings in future studies in others parts of Chile.
Data are available through email request to the corresponding author.
The authors declare that they have no conflict of interest.
This article is part of the special issue “17th EMS Annual Meeting: European Conference for Applied Meteorology and Climatology 2017”. It is a result of the EMS Annual Meeting: European Conference for Applied Meteorology and Climatology 2017, Dublin, Ireland, 4–8 September 2017.
This work was funded by the following research project: CONICYT FONDECYT 11160524.Edited by: Lucien Wald Reviewed by: three anonymous referees