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VIP as thermal breaker for internal insulation system
Energy and Buildings 85 (2014) 631–637
Contents lists available at ScienceDirect
Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild
VIP as thermal breaker for internal insulation system H. Sallée a , D. Quenard a,∗ , E. Valenti b , M. Galan c a
CSTB, Centre Scientifique et Technique du Bâtiment, 24 Rue Joseph Fourier, 38400 Saint Martin d’Hères, France PLATEC, ZA Bavière Dauphine, Colombe 38690, France c SAITEC, ZI 5 Bd Pascal, BP 177, Challans Cedex 85303, France b
a r t i c l e
i n f o
Article history: Available online 30 August 2014 Keywords: Vacuum insulation panels Thermal breaker Retrofitting Energy savings
a b s t r a c t Building renovation is a major challenge in Europe with more than 200 million of existing buildings to renovate. Generally, ETICS (External Thermal Insulation Complex System) is claimed as being the most efficient system especially for tackling thermal bridges and keeping thermal inertia. Nevertheless, this system cannot be applied to some existing buildings, especially those having a fac¸ade with a high architectural character. In this communication, a slim thermal breaker (STB) for indoor use, made of a VIP protected with PU foam and a finishing board, is presented. A mock-up has been built up in order to investigate the efficiency of the thermal breaker for partition wall. The experimental results and the simulation have shown that the use of this slim thermal breaker (STB) yields a reduction of around 30% of the whole U-value whereas a reduction of 50% is obtained using ETICS. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Building renovation is a major challenge in Europe with more than 200 million of existing buildings [1]. More than half of them were built before the first major oil crisis, in 1973, an era where there was little or no consciousness of the need to design for energy efficient performance. A large part of this existing stock need to be insulated and building envelope [2] is of high priority to achieve energy efficiency. Indeed, several studies [3,4] have shown that the most efficient way to curb the energy consumption in the building sector remains the reduction of the heat loss by improving the thermal insulation of the building envelope (roof, floor and wall). Generally, ETICS (External Thermal Insulation Complex System) [5] is claimed as being the most efficient system especially for tackling thermal bridges and keeping thermal inertia from external walls. Nevertheless, ETICS cannot be applied to some existing buildings, especially the 12 million of residential multi-storey buildings with distributed ownership. Indeed, these buildings often present interesting features from the architectural and structural point of view, often having a fac¸ade with some 3D architectural patterns, especially in cities. Furthermore, in existing building, thermal bridges represent a significant share of heat losses through building envelope. They account for about 5–10% of the total heat losses of building,
∗ Corresponding author. Tel.: +33 4 76 76 25 46. E-mail address: [email protected] (D. Quenard). http://dx.doi.org/10.1016/j.enbuild.2014.08.039 0378-7788/© 2014 Elsevier B.V. All rights reserved.
air-ventilation included, and more than 40% of heat losses through a vertical wall. They are also the source of a lot of pathologies due to high relative humidity and moisture condensation resulting to lower temperatures at the intersection between vertical walls and ceiling, floors or partition walls. In order to meet the requirements of the European Thermal Regulation, many thermal breakers [6] have been developed for new buildings but technical solutions for existing buildings are still missing. Super Insulating Materials, such VIP’s [7], appear as good candidates but due to their specific properties and technical characteristics they cannot be implemented directly on site without drastic recommendations and a continuous supervision during the works. Therefore, two types of slim thermal breaker (STB) have been developed by integrating a VIP panel in protective shell made of PU foam on one side and plasterboard or a high density PU on the other one. 2. Design of the slim thermal breaker (STB) The internal thermal breaker concept is presented in Fig. 2 and the geometrical characteristics (length and thickness) of this system have been defined through thermal modelling, carried out with the software HEAT 2D [8]. The simulation scheme considers the connection between an insulated external wall and a partition wall, both made with concrete. Two simplified thermal breakers are installed on both sides of the partition wall (Fig. 1). The cavity and the fastening rails (Figs. 3 and 7) are not taken into account in the simulation. The parametric analysis considered only two cases.
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H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 3. Scheme of the STB for ceiling implementation.
Heat loss reduction %
Fig. 1. Concept of the internal thermal breaker.
80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0
EPS (e mm) e R 10 - 0.31 20 - 0.63 30 - 0.94 40 - 1.25 50 - 1.56 60 - 1.88 70 - 2.19 80 - 2.5 VIP (e mm) e R 10 - 1.25 20 - 2.75 30 - 3.5
0
200
400
600
800
1000
1200
VIP or EPS length mm Fig. 2. Design of the slim thermal breaker (STB) – length & thickness of the VIP.
Table 1 Material description & properties. Materials
Thickness (cm)
Thermal conductivity (W m−1 K−1 )
Concrete wall (Figs. 1 and 2) Concrete blocks filled with poured concrete (Mock-Up) EPS insulation Plasterboard VIP PU foam High density PU
20
2
15
1.7
8 1.3 2 2 1.3
0.032 0.3 0.008 0.022 0.028
Fig. 4. Photography of the STB for ceiling implementation.
thickness) of the VIP panel and consequently the price of the STB, a VIP thickness of 20 mm and 700 mm length has been selected. These values yield a reduction of the linear transmission coefficient about 55% of the heat loss through the thermal bridge. Indeed, an increasing of the VIP length by 10 cm only reduces the heat loss only by 1.5%. 3. Manufacturing and implementation testing
The first one is made of traditional EPS foam with a thickness varying from 10 to 80 mm (thin lines in Fig. 2) whereas the second one is made of a composite multilayer system: a PU foam layer, a VIP and a plasterboard. The properties of the three materials are given in the Table 1. Three VIP thicknesses have been tested: 10, 20 and 30 mm (thick lines in Fig. 2). In Fig. 2, the reduction of the linear transmission coefficient , initially equal to 0.77 W m−1 K−1 , is presented versus the type, the length and the thickness of the insulating materials. The computation shows that a pseudo-asymptotic value is reached with a length of about 1100 cm. With 8 cm of EPS or 3 cm of VIP the heat loss reduction is around 65%. In order to reduce the sizes (length &
Two types of slim thermal breaker (STB) have been developed, one for ceiling applications (cornice type – Figs. 3 and 4) and another for floor implementation (Figs. 5 and 6). Considering the fragility of VIP, mainly the risk of punching during handling and implementation, both thermal breaker concepts have been designed as a multilayer composite systems. They are made of a VIP which is protected on the hindered side by PU foam and on the visible side either by plasterboard for the ceiling STB (Figs. 3 and 4) or by high-density PU foam for the floor STB (Figs. 5 and 6), in order to offer a traditional surface finishing. The geometrical characteristics and the thermal properties of both STB are summarised in Table 2. The thermal resistances of
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
633
Fig. 5. Scheme of the STB for floor implementation.
Fig. 7. Implementation of the STB for ceiling.
Table 2 Thickness and thermal properties of the STB types. STB type
Thickness (mm)
Equivalent thermal conductivity (mW m−1 K−1 )
Thermal Resistance (m2 K W−1 )
Floor 1 Floor 2 Ceiling 1 Ceiling 2
54.3 54.1 53.5 53.3
9.7 9.7 9.4 8.8
5.60 5.58 5.69 6.06
but it can be considered as a positive aspect for the STB presented in this paper. 4. Experimental mock-up
Fig. 6. Photography of the STB for floor implementation.
both STB panels have been measured using a Heat Flow Metre and reach a value around 6 which corresponds to a thickness of 24 cm for a traditional insulating material ( = 0.040 W m−1 K−1 ). At the tip of the ceiling STB there is a small cavity between the VIP and the plasterboard for fastening the STB to the ceiling. This cavity is needed for fastening but can be used to install lighting systems such as LED’s or wires for electricity or communication transfer. Implementation on site is another important issue with high performance and fragile materials like VIP. For a wide acceptance of workers on site, the fixing procedure of the new component should not change a lot from the traditional way of doing. That’s why a special attention has been paid to the interaction with the vertical insulation panel and with the fixing at ceiling. The same fixing rails have been used, as presented in Fig. 7 where an STB is installed in a corner between a vertical wall and a concrete block ceiling. The workers who implemented the STB (Fig. 7), expressed their satisfaction and confirmed that the handling and fixing of these new components did not need special skills and should be accepted by most of the workers who are used to install insulating composite panel made of EPS or PU protected by plasterboard. Of course, this is only the opinion of a very few number of workers
As it was not possible to perform experimental testing on site, a mock-up has been built in the CSTB testing hall. This mock-up is made of an external wall and two partition walls built with concrete blocks of 20 cm thick, filled with poured concrete. A wooden structure insulated with 10 cm of mineral wool closes the volume (Fig. 8). The height and the length of the mock-up were respectively 2.5 and 6 m. The distance between both partition walls was 2 m and the distance between the partition walls and the external wall was 1.8 m (Figs. 8 and 9). The indoor temperature was controlled using an electric heater to keep an internal temperature between 26 and 29 ◦ C whereas the external temperature was continuously measured during the experiment. This temperature was around about −2 ◦ C during the test. A 10 cm layer has been installed on the interior surface of the external wall of the mock-up (Fig. 9) and both ceiling and floor STB have been implemented on both side of one of the vertical partition walls. Actually, as it would have been too expensive to build a horizontal concrete floor, both STB have been tested vertically along the partition wall. The outdoor surface of the external wall was covered by a mortar rendering. In Fig. 10, on the right side of the steel pillar of the test hall, there are a brushed aluminium tape and a black tape. The brushed aluminium tape was slightly glued to the wall for measuring the apparent reflective temperature to take into account the contribution of radiation from the local environment. The black surface is strongly stick to the wall and is used to define the reference emissivity for the Infra-Red Camera, it is considered as a black body. The small white spots indicate the
634
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 8. The mock-up for testing made of concrete blocks filled with poured concrete & wooden structure.
Fig. 9. Description of the mock-up and positions of the numbered thermocouples.
thermocouples positions on the external surface. Twenty four thermocouples have been implemented on the surfaces of the external and partition walls as illustrated in Figs. 10 and 11. In Fig. 11, the IR image exhibits the role of the STB and gives a good approximation of the outside temperature given by the “blue” steel pillar of the test hall. The red vertical strip, on the right of the “blue” steel pillar, corresponds to the wall without STB.
Furthermore, the temperature profiles along the external wall, plotted in Fig. 12, given either by the thermocouples or the IR camera, show a good agreement. By analysing these profiles (Fig. 12), the impact of the STB is clearly pointed out. Indeed, the thermocouples on the external wall, aligned with the partition walls with and without the STB, show a temperature difference of about 2 ◦ C.
Table 3 Thickness and thermal properties of the STB types. Wall
Without STB
STB first partition wall
STB second partition wall
Mean U-value (W/(m2 K)) (one partition wall) U %
0.6 0.86 0%
0.5 0.43 16%
0.4 0.43 29%
ETICS 0.3 51%
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 10. Photography of the external wall of the mock-up build in the test hall.
Fig. 11. IR image of the external wall.
Fig. 12. Comparison of the temperature profiles given by the thermocouples & the IR camera.
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636
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 13. Comparison of the temperature profiles given by the thermocouples & the simulation.
Fig. 14. Comparison of the temperature profiles along the partition wall with & without the STB.
5. Simulation As to design the STB in Section 1, the simulation of heat transfer in the external and partition walls of the mock was carried out using the HEAT2D [8]. As discussed in Section 4, the simulation provides interesting information to explain experimental results such the temperature difference at the tip of the STB. Moreover, the comparison of the simulation and experimental profiles along the external wall shows a good correlation (Fig. 13). Considering that the comparison between the simulation and experimental results are reasonable, it’s therefore possible to compute the impact of the STB on the and U value of the wall and to compare with an external thermal insulation composite system. Calculated according the standard NF EN ISO 10211 [9], the results are presented
in Table 3. The reduction of the whole U value of the wall thanks to the STB is of about 30% compared to a reduction of 50% with ETICS. Moreover, the simulation allows describing in detail the temperature profiles in the internal partition wall. Indeed, a surprising effect occurred at the tip of the STB as presented in Fig. 14. Actually, the temperature at this position is lower with the STB than without. This effect is due to the penetration of the “cold wave” from the external wall as shown in Fig. 14 with the temperature profiles given by the thermocouples. This effect is well emphasised in Fig. 15 which shows the 2D results obtained by simulation. This effect is similar to the capillary rise effect when a non-permeable coating is installed on both side of a wall in contact with a wet ground.
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
637
in use of this new STB needs to be investigated through a larger number of workers on site. Acknowledgments The authors would like to thank ADEME for the financial support and highly appreciate the great interest of Samira Kherrouf (ADEME’s supervisor) in this project. Fig. 15. 2D simulation of the temperature map in the external & partition walls.
6. Conclusions and outlook Two types of new thermal breakers made with VIP has been designed, manufactured and tested. There are mainly devoted to internal applications as in this case, saving living surface is of tremendous importance especially downtown. The heat loss reduction which can be reached using both thermal breakers is around 60% of that obtained with ETICS. Nevertheless, the layout of these thermal breakers remains an important issues which should be solved either by using pre-designed STB in order to fit to the length or by using “fillers” to connect standard STB. Moreover, the fitness
References [1] BPIE, Europe’s buildings under the microscope: a country-by-country review of the energy performance of buildings, www.bpie.eu [2] Wuppertal Institute, Ecofys, ESV, Improving and implementing national energy efficiency strategies in the EU framework findings from energy watch, www.energy-efficiency-watch.org (June 2013). [3] G. Verbeeck, H. Hens, Energy savings in retrofitted dwellings: economically viable? Energy & Building 37 (2005) 747–754. [4] P.A. Enkvist, T. Naucler, J. Rosander, A cost curve for greenhouse gas reduction, Mc Kinsey Quarterly (2007). [5] European Association for ETICS (EAE) – www.ea-etics.eu (November 2013). [6] www.schoeck.com [7] R. Baetens, et al., Vacuum insulation panels for building applications: a review and beyond, Energy and Buildings 42 (2010) 147–172. [8] HEAT2D Software, www.buildingphysics.com/index-filer/heat2.htm [9] NF EN ISO 10211. Thermal bridges in building construction – heat flows and surface temperatures – detailed calculations.
Contents lists available at ScienceDirect
Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild
VIP as thermal breaker for internal insulation system H. Sallée a , D. Quenard a,∗ , E. Valenti b , M. Galan c a
CSTB, Centre Scientifique et Technique du Bâtiment, 24 Rue Joseph Fourier, 38400 Saint Martin d’Hères, France PLATEC, ZA Bavière Dauphine, Colombe 38690, France c SAITEC, ZI 5 Bd Pascal, BP 177, Challans Cedex 85303, France b
a r t i c l e
i n f o
Article history: Available online 30 August 2014 Keywords: Vacuum insulation panels Thermal breaker Retrofitting Energy savings
a b s t r a c t Building renovation is a major challenge in Europe with more than 200 million of existing buildings to renovate. Generally, ETICS (External Thermal Insulation Complex System) is claimed as being the most efficient system especially for tackling thermal bridges and keeping thermal inertia. Nevertheless, this system cannot be applied to some existing buildings, especially those having a fac¸ade with a high architectural character. In this communication, a slim thermal breaker (STB) for indoor use, made of a VIP protected with PU foam and a finishing board, is presented. A mock-up has been built up in order to investigate the efficiency of the thermal breaker for partition wall. The experimental results and the simulation have shown that the use of this slim thermal breaker (STB) yields a reduction of around 30% of the whole U-value whereas a reduction of 50% is obtained using ETICS. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Building renovation is a major challenge in Europe with more than 200 million of existing buildings [1]. More than half of them were built before the first major oil crisis, in 1973, an era where there was little or no consciousness of the need to design for energy efficient performance. A large part of this existing stock need to be insulated and building envelope [2] is of high priority to achieve energy efficiency. Indeed, several studies [3,4] have shown that the most efficient way to curb the energy consumption in the building sector remains the reduction of the heat loss by improving the thermal insulation of the building envelope (roof, floor and wall). Generally, ETICS (External Thermal Insulation Complex System) [5] is claimed as being the most efficient system especially for tackling thermal bridges and keeping thermal inertia from external walls. Nevertheless, ETICS cannot be applied to some existing buildings, especially the 12 million of residential multi-storey buildings with distributed ownership. Indeed, these buildings often present interesting features from the architectural and structural point of view, often having a fac¸ade with some 3D architectural patterns, especially in cities. Furthermore, in existing building, thermal bridges represent a significant share of heat losses through building envelope. They account for about 5–10% of the total heat losses of building,
∗ Corresponding author. Tel.: +33 4 76 76 25 46. E-mail address: [email protected] (D. Quenard). http://dx.doi.org/10.1016/j.enbuild.2014.08.039 0378-7788/© 2014 Elsevier B.V. All rights reserved.
air-ventilation included, and more than 40% of heat losses through a vertical wall. They are also the source of a lot of pathologies due to high relative humidity and moisture condensation resulting to lower temperatures at the intersection between vertical walls and ceiling, floors or partition walls. In order to meet the requirements of the European Thermal Regulation, many thermal breakers [6] have been developed for new buildings but technical solutions for existing buildings are still missing. Super Insulating Materials, such VIP’s [7], appear as good candidates but due to their specific properties and technical characteristics they cannot be implemented directly on site without drastic recommendations and a continuous supervision during the works. Therefore, two types of slim thermal breaker (STB) have been developed by integrating a VIP panel in protective shell made of PU foam on one side and plasterboard or a high density PU on the other one. 2. Design of the slim thermal breaker (STB) The internal thermal breaker concept is presented in Fig. 2 and the geometrical characteristics (length and thickness) of this system have been defined through thermal modelling, carried out with the software HEAT 2D [8]. The simulation scheme considers the connection between an insulated external wall and a partition wall, both made with concrete. Two simplified thermal breakers are installed on both sides of the partition wall (Fig. 1). The cavity and the fastening rails (Figs. 3 and 7) are not taken into account in the simulation. The parametric analysis considered only two cases.
632
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 3. Scheme of the STB for ceiling implementation.
Heat loss reduction %
Fig. 1. Concept of the internal thermal breaker.
80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0
EPS (e mm) e R 10 - 0.31 20 - 0.63 30 - 0.94 40 - 1.25 50 - 1.56 60 - 1.88 70 - 2.19 80 - 2.5 VIP (e mm) e R 10 - 1.25 20 - 2.75 30 - 3.5
0
200
400
600
800
1000
1200
VIP or EPS length mm Fig. 2. Design of the slim thermal breaker (STB) – length & thickness of the VIP.
Table 1 Material description & properties. Materials
Thickness (cm)
Thermal conductivity (W m−1 K−1 )
Concrete wall (Figs. 1 and 2) Concrete blocks filled with poured concrete (Mock-Up) EPS insulation Plasterboard VIP PU foam High density PU
20
2
15
1.7
8 1.3 2 2 1.3
0.032 0.3 0.008 0.022 0.028
Fig. 4. Photography of the STB for ceiling implementation.
thickness) of the VIP panel and consequently the price of the STB, a VIP thickness of 20 mm and 700 mm length has been selected. These values yield a reduction of the linear transmission coefficient about 55% of the heat loss through the thermal bridge. Indeed, an increasing of the VIP length by 10 cm only reduces the heat loss only by 1.5%. 3. Manufacturing and implementation testing
The first one is made of traditional EPS foam with a thickness varying from 10 to 80 mm (thin lines in Fig. 2) whereas the second one is made of a composite multilayer system: a PU foam layer, a VIP and a plasterboard. The properties of the three materials are given in the Table 1. Three VIP thicknesses have been tested: 10, 20 and 30 mm (thick lines in Fig. 2). In Fig. 2, the reduction of the linear transmission coefficient , initially equal to 0.77 W m−1 K−1 , is presented versus the type, the length and the thickness of the insulating materials. The computation shows that a pseudo-asymptotic value is reached with a length of about 1100 cm. With 8 cm of EPS or 3 cm of VIP the heat loss reduction is around 65%. In order to reduce the sizes (length &
Two types of slim thermal breaker (STB) have been developed, one for ceiling applications (cornice type – Figs. 3 and 4) and another for floor implementation (Figs. 5 and 6). Considering the fragility of VIP, mainly the risk of punching during handling and implementation, both thermal breaker concepts have been designed as a multilayer composite systems. They are made of a VIP which is protected on the hindered side by PU foam and on the visible side either by plasterboard for the ceiling STB (Figs. 3 and 4) or by high-density PU foam for the floor STB (Figs. 5 and 6), in order to offer a traditional surface finishing. The geometrical characteristics and the thermal properties of both STB are summarised in Table 2. The thermal resistances of
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
633
Fig. 5. Scheme of the STB for floor implementation.
Fig. 7. Implementation of the STB for ceiling.
Table 2 Thickness and thermal properties of the STB types. STB type
Thickness (mm)
Equivalent thermal conductivity (mW m−1 K−1 )
Thermal Resistance (m2 K W−1 )
Floor 1 Floor 2 Ceiling 1 Ceiling 2
54.3 54.1 53.5 53.3
9.7 9.7 9.4 8.8
5.60 5.58 5.69 6.06
but it can be considered as a positive aspect for the STB presented in this paper. 4. Experimental mock-up
Fig. 6. Photography of the STB for floor implementation.
both STB panels have been measured using a Heat Flow Metre and reach a value around 6 which corresponds to a thickness of 24 cm for a traditional insulating material ( = 0.040 W m−1 K−1 ). At the tip of the ceiling STB there is a small cavity between the VIP and the plasterboard for fastening the STB to the ceiling. This cavity is needed for fastening but can be used to install lighting systems such as LED’s or wires for electricity or communication transfer. Implementation on site is another important issue with high performance and fragile materials like VIP. For a wide acceptance of workers on site, the fixing procedure of the new component should not change a lot from the traditional way of doing. That’s why a special attention has been paid to the interaction with the vertical insulation panel and with the fixing at ceiling. The same fixing rails have been used, as presented in Fig. 7 where an STB is installed in a corner between a vertical wall and a concrete block ceiling. The workers who implemented the STB (Fig. 7), expressed their satisfaction and confirmed that the handling and fixing of these new components did not need special skills and should be accepted by most of the workers who are used to install insulating composite panel made of EPS or PU protected by plasterboard. Of course, this is only the opinion of a very few number of workers
As it was not possible to perform experimental testing on site, a mock-up has been built in the CSTB testing hall. This mock-up is made of an external wall and two partition walls built with concrete blocks of 20 cm thick, filled with poured concrete. A wooden structure insulated with 10 cm of mineral wool closes the volume (Fig. 8). The height and the length of the mock-up were respectively 2.5 and 6 m. The distance between both partition walls was 2 m and the distance between the partition walls and the external wall was 1.8 m (Figs. 8 and 9). The indoor temperature was controlled using an electric heater to keep an internal temperature between 26 and 29 ◦ C whereas the external temperature was continuously measured during the experiment. This temperature was around about −2 ◦ C during the test. A 10 cm layer has been installed on the interior surface of the external wall of the mock-up (Fig. 9) and both ceiling and floor STB have been implemented on both side of one of the vertical partition walls. Actually, as it would have been too expensive to build a horizontal concrete floor, both STB have been tested vertically along the partition wall. The outdoor surface of the external wall was covered by a mortar rendering. In Fig. 10, on the right side of the steel pillar of the test hall, there are a brushed aluminium tape and a black tape. The brushed aluminium tape was slightly glued to the wall for measuring the apparent reflective temperature to take into account the contribution of radiation from the local environment. The black surface is strongly stick to the wall and is used to define the reference emissivity for the Infra-Red Camera, it is considered as a black body. The small white spots indicate the
634
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 8. The mock-up for testing made of concrete blocks filled with poured concrete & wooden structure.
Fig. 9. Description of the mock-up and positions of the numbered thermocouples.
thermocouples positions on the external surface. Twenty four thermocouples have been implemented on the surfaces of the external and partition walls as illustrated in Figs. 10 and 11. In Fig. 11, the IR image exhibits the role of the STB and gives a good approximation of the outside temperature given by the “blue” steel pillar of the test hall. The red vertical strip, on the right of the “blue” steel pillar, corresponds to the wall without STB.
Furthermore, the temperature profiles along the external wall, plotted in Fig. 12, given either by the thermocouples or the IR camera, show a good agreement. By analysing these profiles (Fig. 12), the impact of the STB is clearly pointed out. Indeed, the thermocouples on the external wall, aligned with the partition walls with and without the STB, show a temperature difference of about 2 ◦ C.
Table 3 Thickness and thermal properties of the STB types. Wall
Without STB
STB first partition wall
STB second partition wall
Mean U-value (W/(m2 K)) (one partition wall) U %
0.6 0.86 0%
0.5 0.43 16%
0.4 0.43 29%
ETICS 0.3 51%
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 10. Photography of the external wall of the mock-up build in the test hall.
Fig. 11. IR image of the external wall.
Fig. 12. Comparison of the temperature profiles given by the thermocouples & the IR camera.
635
636
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
Fig. 13. Comparison of the temperature profiles given by the thermocouples & the simulation.
Fig. 14. Comparison of the temperature profiles along the partition wall with & without the STB.
5. Simulation As to design the STB in Section 1, the simulation of heat transfer in the external and partition walls of the mock was carried out using the HEAT2D [8]. As discussed in Section 4, the simulation provides interesting information to explain experimental results such the temperature difference at the tip of the STB. Moreover, the comparison of the simulation and experimental profiles along the external wall shows a good correlation (Fig. 13). Considering that the comparison between the simulation and experimental results are reasonable, it’s therefore possible to compute the impact of the STB on the and U value of the wall and to compare with an external thermal insulation composite system. Calculated according the standard NF EN ISO 10211 [9], the results are presented
in Table 3. The reduction of the whole U value of the wall thanks to the STB is of about 30% compared to a reduction of 50% with ETICS. Moreover, the simulation allows describing in detail the temperature profiles in the internal partition wall. Indeed, a surprising effect occurred at the tip of the STB as presented in Fig. 14. Actually, the temperature at this position is lower with the STB than without. This effect is due to the penetration of the “cold wave” from the external wall as shown in Fig. 14 with the temperature profiles given by the thermocouples. This effect is well emphasised in Fig. 15 which shows the 2D results obtained by simulation. This effect is similar to the capillary rise effect when a non-permeable coating is installed on both side of a wall in contact with a wet ground.
H. Sallée et al. / Energy and Buildings 85 (2014) 631–637
637
in use of this new STB needs to be investigated through a larger number of workers on site. Acknowledgments The authors would like to thank ADEME for the financial support and highly appreciate the great interest of Samira Kherrouf (ADEME’s supervisor) in this project. Fig. 15. 2D simulation of the temperature map in the external & partition walls.
6. Conclusions and outlook Two types of new thermal breakers made with VIP has been designed, manufactured and tested. There are mainly devoted to internal applications as in this case, saving living surface is of tremendous importance especially downtown. The heat loss reduction which can be reached using both thermal breakers is around 60% of that obtained with ETICS. Nevertheless, the layout of these thermal breakers remains an important issues which should be solved either by using pre-designed STB in order to fit to the length or by using “fillers” to connect standard STB. Moreover, the fitness
References [1] BPIE, Europe’s buildings under the microscope: a country-by-country review of the energy performance of buildings, www.bpie.eu [2] Wuppertal Institute, Ecofys, ESV, Improving and implementing national energy efficiency strategies in the EU framework findings from energy watch, www.energy-efficiency-watch.org (June 2013). [3] G. Verbeeck, H. Hens, Energy savings in retrofitted dwellings: economically viable? Energy & Building 37 (2005) 747–754. [4] P.A. Enkvist, T. Naucler, J. Rosander, A cost curve for greenhouse gas reduction, Mc Kinsey Quarterly (2007). [5] European Association for ETICS (EAE) – www.ea-etics.eu (November 2013). [6] www.schoeck.com [7] R. Baetens, et al., Vacuum insulation panels for building applications: a review and beyond, Energy and Buildings 42 (2010) 147–172. [8] HEAT2D Software, www.buildingphysics.com/index-filer/heat2.htm [9] NF EN ISO 10211. Thermal bridges in building construction – heat flows and surface temperatures – detailed calculations.