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Figure from:Influence of thermal insulation on the energy balance for cold-formed buildings

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Table 4. Annual Energy Need for Cooling (Qena)

Table 4 Annual Energy Need for Cooling (Qena)

Related Figures (26)

Figure 1. Life Cycle Analysis of the Building
Figure 1. Life Cycle Analysis of the Building
where Qy;; is the total heat transfer for the heating mode, Qy¢, are the total heat gains for the heating mode, and 77¢n 1s the utilization factor for the internal and solar heat gains. The gain utilization factor (7H,¢n) takes into account that only part of the gains are utilized to decrease the energy need for heating, the rest leading to an undesired increase of the internal temperature. This factor is a function of the gain/loss ratio (¥ = Qgn/Qm) and a numerical parameter (z) that depends on the time constant of the building (building inertia), and is illustrated in Figure 2. The total heat gains (Qg,), over the given period, are given by the sum of the internal heat sources (Qin), and the sum of the solar heat gains (Q,.)), in MJ,
where Qy;; is the total heat transfer for the heating mode, Qy¢, are the total heat gains for the heating mode, and 77¢n 1s the utilization factor for the internal and solar heat gains. The gain utilization factor (7H,¢n) takes into account that only part of the gains are utilized to decrease the energy need for heating, the rest leading to an undesired increase of the internal temperature. This factor is a function of the gain/loss ratio (¥ = Qgn/Qm) and a numerical parameter (z) that depends on the time constant of the building (building inertia), and is illustrated in Figure 2. The total heat gains (Qg,), over the given period, are given by the sum of the internal heat sources (Qin), and the sum of the solar heat gains (Q,.)), in MJ,
In RCCTE, the length of the heating season depends on the location of the building in the country, according to Figure 3. It may vary from 4.3 months, for the least severe zone, to 6 months, in the most severe one. Similarly to Eq. (1), the quantification of the annual energy needs for heating (Nic) is given, per net area of the floor, in kWh/m’, as
In RCCTE, the length of the heating season depends on the location of the building in the country, according to Figure 3. It may vary from 4.3 months, for the least severe zone, to 6 months, in the most severe one. Similarly to Eq. (1), the quantification of the annual energy needs for heating (Nic) is given, per net area of the floor, in kWh/m’, as
The building frame consists of a steel structure formed by cold formed steel profiles, designed for a service life of 50 years according to the Structural Eurocodes [24]. The total internal net space is 361 m2. The ground floor is composed of a living-dining room, a small office, a kitchen, a small pantry, two bathrooms and stairs (see Figure 5). The first floor has 4 bedrooms, 4 bathrooms and stairs. The top floor has one master bedroom and one bathroom. The main facade of the house faces south.
The building frame consists of a steel structure formed by cold formed steel profiles, designed for a service life of 50 years according to the Structural Eurocodes [24]. The total internal net space is 361 m2. The ground floor is composed of a living-dining room, a small office, a kitchen, a small pantry, two bathrooms and stairs (see Figure 5). The first floor has 4 bedrooms, 4 bathrooms and stairs. The top floor has one master bedroom and one bathroom. The main facade of the house faces south.
The characteristics of the building components are described in the following paragraphs. The external walls are made of an outside layer of Oriented Strand Board (OSB) panels, 11 mm thick, and an inside layer of gypsum boards with a thickness of 15 mm. The gap between the two panels is filled with rock wool 140 mm thick. The internal walls are made of gypsum boards with a thickness of 15 mm and a layer of rock wool with a thickness of 70 mm. The slabs are made of composite panels with a top layer of OSB panels (15 mm), an intermediate layer of rock wool 70 mm thick, and a bottom layer of gypsum boards 13 mm thick. The ground floor is made of a light-concrete slab over a layer of gravel. The terrace floor is made of a top layer of OSB panels 18 mm thick, covered by 40 mm of cast
The characteristics of the building components are described in the following paragraphs. The external walls are made of an outside layer of Oriented Strand Board (OSB) panels, 11 mm thick, and an inside layer of gypsum boards with a thickness of 15 mm. The gap between the two panels is filled with rock wool 140 mm thick. The internal walls are made of gypsum boards with a thickness of 15 mm and a layer of rock wool with a thickness of 70 mm. The slabs are made of composite panels with a top layer of OSB panels (15 mm), an intermediate layer of rock wool 70 mm thick, and a bottom layer of gypsum boards 13 mm thick. The ground floor is made of a light-concrete slab over a layer of gravel. The terrace floor is made of a top layer of OSB panels 18 mm thick, covered by 40 mm of cast
4.2. Climatic Data concrete and a ceramic finish, an intermediate layer of rock wool 140 mm thick, and a bottom layer of gypsum boards 13 mm thick. The rock wool insulation panels completely clad the steel frame ensuring that the house achieves high thermal and acoustic behaviour according to regulatory requirements. The envelope of the house is covered by an Exterior Insulation and Finish System (EIFS). The quantities of the main materials estimated for the construction are indicated in Table 1.
4.2. Climatic Data concrete and a ceramic finish, an intermediate layer of rock wool 140 mm thick, and a bottom layer of gypsum boards 13 mm thick. The rock wool insulation panels completely clad the steel frame ensuring that the house achieves high thermal and acoustic behaviour according to regulatory requirements. The envelope of the house is covered by an Exterior Insulation and Finish System (EIFS). The quantities of the main materials estimated for the construction are indicated in Table 1.
According to the Portuguese /nstituto de Meteorologia [25], the annual average of the air temperature varies regularly over the year, reaching the highest values in August and the minimum values itr January. In the summer, the values of the average maximal temperature vary between 16°C in the highest mountain (inner central-northern region) and from 32°C to 34°C in the inner central-southert part of the country. The values of the average minimal temperature, during winter, vary between 2°C in the inner high lands and 12°C in the south. The rain values vary from the northern part to the southern part of the country. On average, about 42% of the annual rainfall occurs during the winte1 (December-February), while the lowest values happen during summer (July and August) with a share of 6% of the annual rainfall.
According to the Portuguese /nstituto de Meteorologia [25], the annual average of the air temperature varies regularly over the year, reaching the highest values in August and the minimum values itr January. In the summer, the values of the average maximal temperature vary between 16°C in the highest mountain (inner central-northern region) and from 32°C to 34°C in the inner central-southert part of the country. The values of the average minimal temperature, during winter, vary between 2°C in the inner high lands and 12°C in the south. The rain values vary from the northern part to the southern part of the country. On average, about 42% of the annual rainfall occurs during the winte1 (December-February), while the lowest values happen during summer (July and August) with a share of 6% of the annual rainfall.
Table 2. Thermal Transmittances of the Building Components 4.3.2. Operational Energy
Table 2. Thermal Transmittances of the Building Components 4.3.2. Operational Energy
The energy need for heating, per year, is represented in Figure 7.
The energy need for heating, per year, is represented in Figure 7.
The total life cycle operational energy represents about 80% of the total life cycle energy. It should be noted that the operational energy, in this case study, includes only the energy needs for heating and cooling. The time period needed for the operational energy to overcome the embodied energy is 16 years.
The total life cycle operational energy represents about 80% of the total life cycle energy. It should be noted that the operational energy, in this case study, includes only the energy needs for heating and cooling. The time period needed for the operational energy to overcome the embodied energy is 16 years.
Figure 11. Schemes of the Alternative Scenario 3: t,,, = 100 mm, t,2 = ty3 = 60 mm In order to assess the influence of the level of insulation, several alternative solutions are analysed. The first scenario corresponds to the original solution, where only the external walls have an outside layer of polystyrene with 3 cm, and represents the reference scenario. Scenario 2 corresponds to a lower level of insulation. Scenario 3 corresponds to an increased level of insulation, with the thickness of the layer in the external walls increased to 10 cm, and a layer of polystyrene added to the roof and to the terrace slab, as shown in Figure 11.
Figure 11. Schemes of the Alternative Scenario 3: t,,, = 100 mm, t,2 = ty3 = 60 mm In order to assess the influence of the level of insulation, several alternative solutions are analysed. The first scenario corresponds to the original solution, where only the external walls have an outside layer of polystyrene with 3 cm, and represents the reference scenario. Scenario 2 corresponds to a lower level of insulation. Scenario 3 corresponds to an increased level of insulation, with the thickness of the layer in the external walls increased to 10 cm, and a layer of polystyrene added to the roof and to the terrace slab, as shown in Figure 11.
Table 5. Level of Insulation for the Various Scenarios and Relative Thermal Transmittances Scenario 4 is identical to scenario 3 but with an improvement in the thermal behaviour of the windows. Finally, scenario 5 is similar to scenario 1 but without the shading effect from horizontal overhangs above the windows. The various scenarios are summarized in Table 5. These scenarios will change the amount of the material needed for each solution, which will be taken into consideration for the calculation of the embodied energy for each case. In the following paragraphs, the results obtained for each scenario are presented.
Table 5. Level of Insulation for the Various Scenarios and Relative Thermal Transmittances Scenario 4 is identical to scenario 3 but with an improvement in the thermal behaviour of the windows. Finally, scenario 5 is similar to scenario 1 but without the shading effect from horizontal overhangs above the windows. The various scenarios are summarized in Table 5. These scenarios will change the amount of the material needed for each solution, which will be taken into consideration for the calculation of the embodied energy for each case. In the following paragraphs, the results obtained for each scenario are presented.
Table 7 and Figure 12 summarize the balance between life cycle embodied energy and life cycle operational energy for the five scenarios. The influence of the degree of insulation results in variations of + 22.7% and —18.7% of the operational energy, with corresponding variations of the embodied energy of -15.4% and +18.3%. Globally, the solution with the best insulation minimizes the total energy (-11%). Finally, the operational energy becomes dominant for a service life in excess of 11.7 to 22.9 years and represents, over the service life of 50 years, 73.2% to 85.2% of the total life cycle energy, depending on the scenario.
Table 7 and Figure 12 summarize the balance between life cycle embodied energy and life cycle operational energy for the five scenarios. The influence of the degree of insulation results in variations of + 22.7% and —18.7% of the operational energy, with corresponding variations of the embodied energy of -15.4% and +18.3%. Globally, the solution with the best insulation minimizes the total energy (-11%). Finally, the operational energy becomes dominant for a service life in excess of 11.7 to 22.9 years and represents, over the service life of 50 years, 73.2% to 85.2% of the total life cycle energy, depending on the scenario.
Figure 12. Balance of Life Cycle Embodied Energy and Life Cycle Operational Energy The parametric study shows that for a standard service life of residential buildings of 50 year reducing the operating energy is more important than reducing the embodied energy. Furthermore, tt solution that minimizes the operating energy also minimizes total lifecycle energy. It is also well-known that a simplified quasi steady-state approach can be used for a comparatiy analysis but does not simulate real daily conditions (namely thermal inertia of the building an ventilation are not properly considered in the analysis). Additionally, examination of Table 6 shows consistent trend for the heating period, but reveals some discrepancies for the cooling period. In ord to validate the results obtained with the simplified approach and to overcome some of the limitatior indicated, a dynamic simulation analysis is performed for the 5 scenarios indicated in Table 5, and described in the next paragraphs. 5.3. Dynamic Simulation Approach
Figure 12. Balance of Life Cycle Embodied Energy and Life Cycle Operational Energy The parametric study shows that for a standard service life of residential buildings of 50 year reducing the operating energy is more important than reducing the embodied energy. Furthermore, tt solution that minimizes the operating energy also minimizes total lifecycle energy. It is also well-known that a simplified quasi steady-state approach can be used for a comparatiy analysis but does not simulate real daily conditions (namely thermal inertia of the building an ventilation are not properly considered in the analysis). Additionally, examination of Table 6 shows consistent trend for the heating period, but reveals some discrepancies for the cooling period. In ord to validate the results obtained with the simplified approach and to overcome some of the limitatior indicated, a dynamic simulation analysis is performed for the 5 scenarios indicated in Table 5, and described in the next paragraphs. 5.3. Dynamic Simulation Approach
Table 8. Average Operational Temperatures
Table 8. Average Operational Temperatures
Figure 13. Temperatures Variation Inside and Outside the Building
Figure 13. Temperatures Variation Inside and Outside the Building
Table 9. Average Operational Temperatures 5.3.3. Heating season
Table 9. Average Operational Temperatures 5.3.3. Heating season
Figure 14. Temperatures Variation Inside and Outside the Building
Figure 14. Temperatures Variation Inside and Outside the Building
Table 11. Annual Heating Energy According to EnergyPlus
Table 11. Annual Heating Energy According to EnergyPlus
Figure 15. Temperatures Variation Inside and Outside the Building (Winter Season)
Figure 15. Temperatures Variation Inside and Outside the Building (Winter Season)
Table 12. Annual Cooling | Energy According to RCCTI Uy
Table 12. Annual Cooling | Energy According to RCCTI Uy
Table 13. Annual Cooling ] Energy According to | EnergyPlus
Table 13. Annual Cooling ] Energy According to | EnergyPlus