Introduction and brief notes on extant knowledge The mean age of school buildings in Italy is rather old and is estimated to be 52 years. The majority of them was constructed after world war II with a peak incidence (30% of the entire sample) that is concentrated in the time frame 1961-1976, during the years of the economic and demographic expansion in Italy. Two earlier peaks of construction are related to the “giolittian age” at the beginning of the 20th century and to the “fascist age” between the two world wars. A recent reports have estimated that 16% of school building have serious structural problems. Deficiencies related to environment and energy sustainability, are even more frequent and affects the majority of the sample. Heating and heat maintaining are, among these, one of the most relevant issue. This is responsible for elevated operating costs that could be significantly reduced by adopting simple technical measures. Domestic heating is a major source of severe atmospheric pollution. The principle local pollutants are PM10 and PM2,5 and NOx . Any project for energy saving of a school building should take into account the new strict limitations to air pollution established by law and also indicated by the European Community . Aim of the Study The main objective of the study was to perform a technical evaluation and an economic analysis on costs, mainly derived from heating, on a sample of four school buildings in Milan and to propose accordingly three restorations projects. Although any single restoration project for any single building has its own peculiarities, the idea was to create then three different models that could in the future be applicable to other constructions with similar characteristics. Secondary aims were to perform an analysis of the technical characteristics of the school buildings in Milan that have an influence on heating and an assessment of the pollutants concentrations in the Metropolitan Area of Milan in the last years including the recent COVID-19 shut down period. Methods Pollutants concentration assessment: Unpublished data requested and obtained from ARPA Lombardia, were personally analyzed. These were referred to the pollutants detection station of Brera, located in the city Centre. This choice was motivated by the need to reduce at minimum the influence of pollutants produced by traffic. As the matter of fact Brera is located in the Area C, a limited traffic zone. Technical characteristics of the school buildings in Milan Data for this analysis were obtained from the Technical Area for heating and cooling of the Municipality of Milan . Missing information were retrieved from Certificazione Energetica degli Edifici (CENED) Infrastrutture Lombarde, from the Geo Map, the portal of the Municipality of Milan, and from the Italian Ministry of Education (MIUR). A comparison with the Italian situation was possible, when useful, consulting data recently reported by Fondazione Agnelli on an overview of the Italian educational system. Different projects on heating production and dispersion on a sample of four school buildings. The following buildings were selected for sample analysis: Villa Simonetta seat of the Musical School Claudio Abbado: an historical building belonging to the XV century. Any renovation or refurbishment or even maintenance work on it should meet the strict conditions imposed by strict protocols. The comprehensive School Stoppani: built in the first years of the last century is the typical school building belonging to the Giolittian Age. The Comprehensive School, Einaudi Pascoli: built in 1974 is a traditional example of low quality buildings constructed during and soon after the demographic post-war boom. The Citylife, Nursery School: built in 2018 is a virtuous and rare example in Italy of a Nearly Zero Emission Building The following characteristics were considered for the preliminary technical analysis: heated volume, material of construction, window characteristics, source of energy supply, source of energy diffusion, air exchange modality , thermal and electrical loads For any proposed intervention thermal and electrical energy savings were calculated together with Capital Expenditure (CAPEX) and Operating Expense (OPEX) The economic analysis was conducted according to different scenarios: voluntary vs reinforcement replacement, with or without incentives. The financial indicators considered for analysis were the Net Present Value (NPV), the Internal Rate of Return (IRR) and the Pay-Back Time (PBT). Results I) Pollutants concentration assessment: domestic heating is responsible for 25% and 30% and 14% respectively of PM10, PM2,5 and NOx emission in the area of Milan. While for PM10 and PM2,5 the mean concentration / year resulted to be within the limits established by the DIRECTIVE 2008/50/EC. Nevertheless, the number of days exceeding the maximum allowed concentration of PM10 (threshold 50 µg/m3) still remains always consistently above the requested limits in the last five years (35 days): 2015 (101 days), 2016 (73 days), 2017 (97 days), 2018 (79 days), 2019 (72 days). The thermal year (October – April) and in particular the trimester December- February are the most critical period for concentration of particulate (PM10 and PM2,5) due to the lower temperature and consequently the maximum emissions from heating system. The mean concentration / year of NO2 still consistently above the limit imposed by law in the Metropolitan Area of Milan. The maximum week concentration levels of NOx are typically registered in the Area of Milan in the second and third week of December (mean 2015-2020, 214 and 272 µg/m3 respectively). During the recent lock-down period (March-April 2020) imposed by the SARS-CoV-2 pandemia environmental concentration of PM10 and PM2,5, did not significantly change as compared to mean values in the same months of the previous years. On the contrary, NOx concentrations showed a consistent reduction with values significantly below the historic registrations of the last five years mainly due to the drastic limitation to traffic imposed. II) Technical characteristics of the school buildings in Milan: The mean age of school buildings in Milan is 54 years. The majority of school buildings (63%) were constructed according the plugging technique. Load bearing constructions account for 14,4% of buildings. Aluminum is the most frequently used material for doors and windows, (73%). Wood accounts for only 23%. Gasoline thermal plants are still in function only in a minority of school buildings (3%). Nevertheless, methane still represents the heating source in 82% of the sample. Alternative sources of energy for heating represents a small portion of the sample: heating districts 12%, renewables energy 3%. Radiators still remain the main source of heating diffusion (86%). Other poorly represented ways of heat diffusion are fan coils (7%), aerothermal systems (5%) and radial panels (2%). Air exchange is mainly provided by natural ventilation (93%). Only 40% of school building in Milan have already undergone any kind of technical assistances aimed at energy savings. III) Three projects on heating production and dispersion on a sample of four school buildings. 1 . Villa Simonetta seat of the Musical School Claudio Abbado. Intervention project: A) Substitution of a classic methane condensing furnace with a an electric heat pump . Electricity consumption + 56.181 €/year. Methane consumption – 62.287 €/year Cost for energy consumption: - 6.106 €/yr The high initial investment required for the installation of an electric heat pump system as compared to that required for a traditional methane supported plant (85.000 € versus 40.000 €) is economically not sustainable without incentives from the administration. In our specific case , considering a useful life of 15 years, the Net Preserve Value (NPV) in a Voluntary Replacement scenario of the intervention without incentives was – 28.492 € with a pay-back time (PBT) of 22 years . B) Substitution of radiators with fan coils Due to the cost of investment (34.340 €) and no energy saving , the economical scenario of an electric thermal plant associated to an air diffusing system is even worse than that above presented and should not be taken into account without incentives and without considering evident benefits on air pollution and ambiences comfort . C) Installation of a building integrated photovoltaic (PV) system. This innovative but highly expensive solution of building integrated PV tiles (3500 €/kW installed) seemed to be the best solution due to the limitations imposed by the Fine Arts. NPV (25 yrs) without incentives = -7.252 € - with incentive = 94.270€ - PBT without incentives 28 yrs - with incentive 11 yrs. Incentives are necessary for an economical viable results. D) Substitution of fluorescent with led lamps. This intervention allows a 60% reduction of electricity consumption (15.488 vs 62.264 kWh/yr) and is thus an easy to accomplish and economically viable solution for energy saving: without incentives. NPV (10 yrs) = 13.000 € - PBT = 19 months. 2 . Antonio Stoppani comprehensive school. Intervention project A ) Installation of a Building Energy Management (BEM) system A BEM systems is aimed at monitoring and controlling services such as heating, ventilation and air-conditioning, ensuring the building operates at maximum levels of efficiency. The installation of a BEM system can guarantee high levels of thermal and electrical energy saving . In our case study, considering a thermal energy saving of 30% (37.500 m3 /year of methane) the bill for methane consumption was reduced from 91.360 €/ yr to 63.960 €/ yr. Considering an electrical energy saving of 50% the costs for electricity were reduced from 57.326 €/yr to 28.633 €/yr. NPV (10 years) = 418.250 € - PBT = 11 months. BEM system are thus to be considered highly viable solution for energy saving. B) Installation of traditional panel photovoltaic (PV) system. Less expensive traditional PV panels (1325 €/kW installed) seemed to be the best solution for this building. NPV (25 yrs) without incentives = 35.116 € - with incentive = 46.825 € - PBT without incentives 8 years - with incentive 5 yrs. 3 . Einaudi Pascoli Primary School. Intervention project A) District heating District heating systems are an alternative, safe and efficient solution for heating production. With district heating the production of heat is centralized and is assigned to a single high-efficiency plant. The Silla 2 central heating plant ( A2a Calore e Servizi ) is located in the north-west suburbs of Milan and its network could technically quite easily be connected in the future with the area of the school. One important economic advantage is represented by the absence of any initial and maintenance cost . This make possible an immediate 6,6% year cost reduction for thermal energy that account in our case study for a saving of 4.622 €/yr. B) Rain screen cladding insulation on partitions and rooftops The installation of a rain screen cladding is a solution aimed at improving the energy performances of buildings that are characterized by the poor features of materials of construction as in this case study. The most significant technical result was the reduced heat dispersion of the building expressed by a decreased transmittance value 1,4 → 0,163 W/ m2K and 1,63 → 0,162 W/m2K for partitions and roof tops respectively. This resulted in a 15,3 % thermal energy saving (13’641,7 € / year). Due to the high cost of the intervention (550.000 € in our case study) incentives are also necessary for rain screen cladding to sustain the economical feasibility of the project. C) Installation of an air handling unit An air handling unit (AHU) , is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning system. In this study the installation of a AHU was considered particularly necessary for the Pascoli comprehensive institute that is characterized by low values of natural air exchange due to the poor architectural design. The most relevant economic advantage derived from a AHU system is provided, in our case, by a 6,4% thermal energy saving obtained by the limitation of natural air exchange that is today possible only by opening windows and doors. This was calculated to be 5.700 €/yr. Conclusion The majority of school buildings in Italy and in the Metropolitan Area of Milan are characterized by problems related to environment and energy sustainability. Heating and heat maintaining are , among these, one of the most relevant issue. Since the construction of new school building is no longer a priority, the future challenge for central and local school administrations is represented by the necessity of financing new and extensive programs for the implementation of the existing architectural heritage. Among the different technical solutions that were considered in the present study, some resulted to be highly effective and economically viable. This was the case of BEM system installation and connection to heating districts. Others (electric heat pumps, PV plants, air handling units and rain screen cladding) require adequate incentives in order to results economically sustainable. Nevertheless, regardless any economic issue, the restoration of the old Italian school building heritage according to the recent severe national and European regulations has become the new mandatory challenge of national and local administrations of the educational system. Limitations The main limitation of this study is represented by the lack of any economic analysis to calculate secondary but not less important benefits on atmospheric pollution, safety and environmental increased comfort of the school ambiences. Moreover data regarding technical characteristics of school building were difficult to retrieve from the public administration and frequently incomplete and not up-to-date. The recent shut down period has deeply worsened this condition.
L’età media degli edifici scolatici in Italia è abbastanza vecchia ed è stimata essere di 52 anni. La maggior di queste è stato costruito dopo la Seconda guerra mondiale con un picchio di incidenza (30% dell’intero campione) è stato concentrato nel periodo di tempo 1961-1976 durante il periodo di espansione economica e demografica in Italia. Due precedenti periodi di costruzioni sono in relazione con il periodo Giolittiano all’inizio del XX secolo e con il periodo fascista tra le due Grandi Guerre. Un recente studio ha stimato che il 16 % degli edifici scolastici ha seri problemi strutturali. Mancanze dovute a sostenibilità ambientali e energetiche sono ancora più frequenti e incidono sulla maggior parte del campione. Il riscaldamento e il mantenimento del calore sono tra queste una dei più rilevanti problematiche. Questo causa elevati costi operativi che posso consistentemente essere ridotti adottando semplici provvedimenti tecnici. Il riscaldamento residenziale è uno delle cause maggiori dell’inquinamento atmosferico. I principali inquinamenti atmosferici sono PM10, PM2,5 e NOx. Qualsiasi progetto di risparmio energetico di edifici scolastici dovrebbe tenere in considerazione le nuove rigide limitazioni sull’ inquinamento dell’aria stabilito dalla legge e anche indicato dalla Comunità Europea. Il principale obbiettivo dello studio è di condurre una analisi tecnico-economica sui costi principalmente dovuti dal riscaldamento su un campione di quattro edifici scolastici milanesi e di proporre conseguentemente tre interventi migliorativi sugli stessi. Sebbene una qualsiasi ristrutturazione del progetto su un edificio a le proprie caratteristiche, l’idea era di creare quindi tre differenti modelli che possono essere applicabili in futuro per altri edifici con caratteristiche simili… guardare abstract in inglese !
Heating and polluting characteristics of school building in Milan. An analysis for improvement of energy consumption in three different models according to age and structural features
Da Pozzo, Giulio
2019/2020
Abstract
Introduction and brief notes on extant knowledge The mean age of school buildings in Italy is rather old and is estimated to be 52 years. The majority of them was constructed after world war II with a peak incidence (30% of the entire sample) that is concentrated in the time frame 1961-1976, during the years of the economic and demographic expansion in Italy. Two earlier peaks of construction are related to the “giolittian age” at the beginning of the 20th century and to the “fascist age” between the two world wars. A recent reports have estimated that 16% of school building have serious structural problems. Deficiencies related to environment and energy sustainability, are even more frequent and affects the majority of the sample. Heating and heat maintaining are, among these, one of the most relevant issue. This is responsible for elevated operating costs that could be significantly reduced by adopting simple technical measures. Domestic heating is a major source of severe atmospheric pollution. The principle local pollutants are PM10 and PM2,5 and NOx . Any project for energy saving of a school building should take into account the new strict limitations to air pollution established by law and also indicated by the European Community . Aim of the Study The main objective of the study was to perform a technical evaluation and an economic analysis on costs, mainly derived from heating, on a sample of four school buildings in Milan and to propose accordingly three restorations projects. Although any single restoration project for any single building has its own peculiarities, the idea was to create then three different models that could in the future be applicable to other constructions with similar characteristics. Secondary aims were to perform an analysis of the technical characteristics of the school buildings in Milan that have an influence on heating and an assessment of the pollutants concentrations in the Metropolitan Area of Milan in the last years including the recent COVID-19 shut down period. Methods Pollutants concentration assessment: Unpublished data requested and obtained from ARPA Lombardia, were personally analyzed. These were referred to the pollutants detection station of Brera, located in the city Centre. This choice was motivated by the need to reduce at minimum the influence of pollutants produced by traffic. As the matter of fact Brera is located in the Area C, a limited traffic zone. Technical characteristics of the school buildings in Milan Data for this analysis were obtained from the Technical Area for heating and cooling of the Municipality of Milan . Missing information were retrieved from Certificazione Energetica degli Edifici (CENED) Infrastrutture Lombarde, from the Geo Map, the portal of the Municipality of Milan, and from the Italian Ministry of Education (MIUR). A comparison with the Italian situation was possible, when useful, consulting data recently reported by Fondazione Agnelli on an overview of the Italian educational system. Different projects on heating production and dispersion on a sample of four school buildings. The following buildings were selected for sample analysis: Villa Simonetta seat of the Musical School Claudio Abbado: an historical building belonging to the XV century. Any renovation or refurbishment or even maintenance work on it should meet the strict conditions imposed by strict protocols. The comprehensive School Stoppani: built in the first years of the last century is the typical school building belonging to the Giolittian Age. The Comprehensive School, Einaudi Pascoli: built in 1974 is a traditional example of low quality buildings constructed during and soon after the demographic post-war boom. The Citylife, Nursery School: built in 2018 is a virtuous and rare example in Italy of a Nearly Zero Emission Building The following characteristics were considered for the preliminary technical analysis: heated volume, material of construction, window characteristics, source of energy supply, source of energy diffusion, air exchange modality , thermal and electrical loads For any proposed intervention thermal and electrical energy savings were calculated together with Capital Expenditure (CAPEX) and Operating Expense (OPEX) The economic analysis was conducted according to different scenarios: voluntary vs reinforcement replacement, with or without incentives. The financial indicators considered for analysis were the Net Present Value (NPV), the Internal Rate of Return (IRR) and the Pay-Back Time (PBT). Results I) Pollutants concentration assessment: domestic heating is responsible for 25% and 30% and 14% respectively of PM10, PM2,5 and NOx emission in the area of Milan. While for PM10 and PM2,5 the mean concentration / year resulted to be within the limits established by the DIRECTIVE 2008/50/EC. Nevertheless, the number of days exceeding the maximum allowed concentration of PM10 (threshold 50 µg/m3) still remains always consistently above the requested limits in the last five years (35 days): 2015 (101 days), 2016 (73 days), 2017 (97 days), 2018 (79 days), 2019 (72 days). The thermal year (October – April) and in particular the trimester December- February are the most critical period for concentration of particulate (PM10 and PM2,5) due to the lower temperature and consequently the maximum emissions from heating system. The mean concentration / year of NO2 still consistently above the limit imposed by law in the Metropolitan Area of Milan. The maximum week concentration levels of NOx are typically registered in the Area of Milan in the second and third week of December (mean 2015-2020, 214 and 272 µg/m3 respectively). During the recent lock-down period (March-April 2020) imposed by the SARS-CoV-2 pandemia environmental concentration of PM10 and PM2,5, did not significantly change as compared to mean values in the same months of the previous years. On the contrary, NOx concentrations showed a consistent reduction with values significantly below the historic registrations of the last five years mainly due to the drastic limitation to traffic imposed. II) Technical characteristics of the school buildings in Milan: The mean age of school buildings in Milan is 54 years. The majority of school buildings (63%) were constructed according the plugging technique. Load bearing constructions account for 14,4% of buildings. Aluminum is the most frequently used material for doors and windows, (73%). Wood accounts for only 23%. Gasoline thermal plants are still in function only in a minority of school buildings (3%). Nevertheless, methane still represents the heating source in 82% of the sample. Alternative sources of energy for heating represents a small portion of the sample: heating districts 12%, renewables energy 3%. Radiators still remain the main source of heating diffusion (86%). Other poorly represented ways of heat diffusion are fan coils (7%), aerothermal systems (5%) and radial panels (2%). Air exchange is mainly provided by natural ventilation (93%). Only 40% of school building in Milan have already undergone any kind of technical assistances aimed at energy savings. III) Three projects on heating production and dispersion on a sample of four school buildings. 1 . Villa Simonetta seat of the Musical School Claudio Abbado. Intervention project: A) Substitution of a classic methane condensing furnace with a an electric heat pump . Electricity consumption + 56.181 €/year. Methane consumption – 62.287 €/year Cost for energy consumption: - 6.106 €/yr The high initial investment required for the installation of an electric heat pump system as compared to that required for a traditional methane supported plant (85.000 € versus 40.000 €) is economically not sustainable without incentives from the administration. In our specific case , considering a useful life of 15 years, the Net Preserve Value (NPV) in a Voluntary Replacement scenario of the intervention without incentives was – 28.492 € with a pay-back time (PBT) of 22 years . B) Substitution of radiators with fan coils Due to the cost of investment (34.340 €) and no energy saving , the economical scenario of an electric thermal plant associated to an air diffusing system is even worse than that above presented and should not be taken into account without incentives and without considering evident benefits on air pollution and ambiences comfort . C) Installation of a building integrated photovoltaic (PV) system. This innovative but highly expensive solution of building integrated PV tiles (3500 €/kW installed) seemed to be the best solution due to the limitations imposed by the Fine Arts. NPV (25 yrs) without incentives = -7.252 € - with incentive = 94.270€ - PBT without incentives 28 yrs - with incentive 11 yrs. Incentives are necessary for an economical viable results. D) Substitution of fluorescent with led lamps. This intervention allows a 60% reduction of electricity consumption (15.488 vs 62.264 kWh/yr) and is thus an easy to accomplish and economically viable solution for energy saving: without incentives. NPV (10 yrs) = 13.000 € - PBT = 19 months. 2 . Antonio Stoppani comprehensive school. Intervention project A ) Installation of a Building Energy Management (BEM) system A BEM systems is aimed at monitoring and controlling services such as heating, ventilation and air-conditioning, ensuring the building operates at maximum levels of efficiency. The installation of a BEM system can guarantee high levels of thermal and electrical energy saving . In our case study, considering a thermal energy saving of 30% (37.500 m3 /year of methane) the bill for methane consumption was reduced from 91.360 €/ yr to 63.960 €/ yr. Considering an electrical energy saving of 50% the costs for electricity were reduced from 57.326 €/yr to 28.633 €/yr. NPV (10 years) = 418.250 € - PBT = 11 months. BEM system are thus to be considered highly viable solution for energy saving. B) Installation of traditional panel photovoltaic (PV) system. Less expensive traditional PV panels (1325 €/kW installed) seemed to be the best solution for this building. NPV (25 yrs) without incentives = 35.116 € - with incentive = 46.825 € - PBT without incentives 8 years - with incentive 5 yrs. 3 . Einaudi Pascoli Primary School. Intervention project A) District heating District heating systems are an alternative, safe and efficient solution for heating production. With district heating the production of heat is centralized and is assigned to a single high-efficiency plant. The Silla 2 central heating plant ( A2a Calore e Servizi ) is located in the north-west suburbs of Milan and its network could technically quite easily be connected in the future with the area of the school. One important economic advantage is represented by the absence of any initial and maintenance cost . This make possible an immediate 6,6% year cost reduction for thermal energy that account in our case study for a saving of 4.622 €/yr. B) Rain screen cladding insulation on partitions and rooftops The installation of a rain screen cladding is a solution aimed at improving the energy performances of buildings that are characterized by the poor features of materials of construction as in this case study. The most significant technical result was the reduced heat dispersion of the building expressed by a decreased transmittance value 1,4 → 0,163 W/ m2K and 1,63 → 0,162 W/m2K for partitions and roof tops respectively. This resulted in a 15,3 % thermal energy saving (13’641,7 € / year). Due to the high cost of the intervention (550.000 € in our case study) incentives are also necessary for rain screen cladding to sustain the economical feasibility of the project. C) Installation of an air handling unit An air handling unit (AHU) , is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning system. In this study the installation of a AHU was considered particularly necessary for the Pascoli comprehensive institute that is characterized by low values of natural air exchange due to the poor architectural design. The most relevant economic advantage derived from a AHU system is provided, in our case, by a 6,4% thermal energy saving obtained by the limitation of natural air exchange that is today possible only by opening windows and doors. This was calculated to be 5.700 €/yr. Conclusion The majority of school buildings in Italy and in the Metropolitan Area of Milan are characterized by problems related to environment and energy sustainability. Heating and heat maintaining are , among these, one of the most relevant issue. Since the construction of new school building is no longer a priority, the future challenge for central and local school administrations is represented by the necessity of financing new and extensive programs for the implementation of the existing architectural heritage. Among the different technical solutions that were considered in the present study, some resulted to be highly effective and economically viable. This was the case of BEM system installation and connection to heating districts. Others (electric heat pumps, PV plants, air handling units and rain screen cladding) require adequate incentives in order to results economically sustainable. Nevertheless, regardless any economic issue, the restoration of the old Italian school building heritage according to the recent severe national and European regulations has become the new mandatory challenge of national and local administrations of the educational system. Limitations The main limitation of this study is represented by the lack of any economic analysis to calculate secondary but not less important benefits on atmospheric pollution, safety and environmental increased comfort of the school ambiences. Moreover data regarding technical characteristics of school building were difficult to retrieve from the public administration and frequently incomplete and not up-to-date. The recent shut down period has deeply worsened this condition.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/166810