ETHICS. WP 7: Design Guidance on energy and thermal improvements for non-residential buildings

Transcription

1 ETHICS Energy and Thermal Improvements for Construction in Steel RFSR - CT WP 7: Design Guidance on energy and thermal improvements for non-residential buildings Deliverable a) Report on the influence of various energy reduction measures on whole building performance regarding energy demand for heating, cooling and lighting 1

2 2

3 Contents WP7-Work programme and distribution of tasks with indication of participating contractors... 5 Interrelation with other work packages: WP 1, 2, 3, 4, Deliverables and milestones Introduction Operational energy Thermal Performance Energetic requirements for building quality and technical equipment The Importance of Detailing Air tightness Long Term Use Energy services Energy and Thermal Improvements for Construction in Steel - Parametric Study PAPER FROM RWTH Sources From WP Concept of the Parametric Study and Reference Building... 9 Air-tightness Thermal bridges Energy performance PAPER FROM LABEIN Sources From WP PAPER FROM CRM Sources from WP PAPER FROM CTICM Source from WP1 - ETX Building 1: Hall Clermont-Ferrand Building 2: Hall Martigues Result summary and conclusion Final comments and conclusions PAPER FROM AMLg Source from WP Energy consumptions of the Steel Centre building compared to the PEB requirements Parametric study on energy efficiency of the Steel Centre Conclusion from study of the CAAL building

4 4

5 WP7 Work programme and distribution of tasks with indication of participating contractors WP7.1 Evaluate the influence of air-tightness and thermal performance of modern steel cladding systems on the overall energy use (RWTH, ArcelorMittal Liège, CTICM) Transfer of the results of WP 1 and WP 2 on non-residential buildings. Active with this report. WP7.2 Carry out parametric study of whole building performance for typical industrial buildings for different climates including requirements for heating and cooling (CTICM, RWTH) Calculations for various air-tightness levels and steel cladding systems using standardized methods and numerical simulations (TRNSYS, e.g.). Active with this report. WP7.3 Identify innovative cladding systems with improved performance characteristics (CTICM, RWTH, CRM) Numerical simulations using FEM (Marc Mentat e.g). Active with this report. WP 7.4 Identify energy efficient solutions for steel intensive commercial buildings with optimised façade and floor systems (CRM, RWTH, ArcelorMittal Liège, VTT) Active with this report. WP7.5 Application of Energy Certification on non-residential buildings (VTT, RWTH, CRM, CTICM) Calculations and certification based on the valid national and European standards and regulations. Active with this report. WP7.6 Prepare guidance for architects on energy efficient solutions in steel (CTICM, ArcelorMittal Liège, CRM). Interrelation with other work packages: WP 1, 2, 3, 4, 5 Deliverables and milestones The deliverable are: Report on the influence of various energy reduction measures on whole building performance regarding energy demand for heating, cooling and lighting. This report. Report on recommendations for suitable energy and thermal improvement measures for nonresidential building in steel. Energy certificates for selected commercial and industrial buildings in steel. Guidance for Architects and Engineers on Energy Efficient Solutions in Steel for Commercial and Industrial buildings. 5

6 6

7 1. Introduction 1.1. Operational energy The operational phase includes 85-95% of the life-cycle energy usage of a building. The framework itself has insignificant influence on the operational energy, but the thermal efficiency of the building envelope in combination with a building service is important. Improvements in insulation can have an important influence on the total energy usage. The national differences are of course significant depending on the climatic conditions, and the operational energy is directly related to the type of activity within the building. Furthermore, particularly in office buildings, energy is also used for cooling. Steel systems in exterior walls can be very efficient if used correctly. Light-gauge steel framing combined with thermal insulation, wind barrier, vapor barrier and optional other boards can achieve a U-value below 0,15 W/m 2,K (= R > 7). Modern technology shows that light steel framings can be designed to achieve excellent thermal performance. National building regulations specify the heat flow parameters for different types of buildings. In industrial buildings, heating is often at a low level as processes might produce heat and indoor temperature requirements are relatively low Thermal Performance Thermal insulation through the building envelope is traditionally the Architect s responsibility but, the structural engineer must be intimately involved in the development of appropriate details and layout. Supporting systems for cladding may be more involved, again involving eccentric connection to the supporting steelwork. Steel members that penetrate the insulation, such as balcony supports, need special consideration and detailing to avoid thermal bridging. Thermal bridges not only lead to heat loss, but in extreme concern, may also lead to condensation on the inside of the building. One of the most effective ways of reducing primary energy consumption is by improved thermal performance of the building envelope, such as by reduced thermal transmission and improved air-tightness. Thermal insulation is characterised by its U value, which represents the heat loss through a unit area of the external elements of the facade or roof per degree temperature difference between inside and outside. In a residential building a U value of less than 0.25 kw/m 2 K is the unit generally adopted as a maximum value for façade elements of the building envelope, and a maximum of 0.15 kw/m 2 K is the unit for roofs. This can be achieved by using insulation placed externally to the light steel walls and roof so that the risk of cold bridging and condensation is minimised. Perforated or slotted sections are used in some countries to reduce cold bridging effects by up a to a factor of 10 and doing so, the insulation may be placed efficiently between the light steel components in order to minimize the wall or roof thickness. 7

8 1.3. Energetic requirements for building quality and technical equipment The architectural design decisively influences the later amount of a building s energy consumption. This primarily concerns the electricity needed for heating and cooling, lighting and possibly necessary mechanized ventilation, other requirements are as follow: Thermal bridges should be avoided, Glazing systems should have a low heat transmission factor (less than 1.2 W/m².K), effective solar shading, on south facing facades, Effective ventilation at night. It is also necessary that the constructions envelope is air-tight The Importance of Detailing Air tightness In addition to achieving good U values, thermal performance will also depend upon the airtightness of the building. Good air tightness can be achieved in light steel construction but is dependent not only on the quality design and detailing but, as much, on the quality of construction of the building envelope. The primary points of leakage are around openings, light fixtures, pipes, and the junctions of walls, roofs and foundations Long Term Use The design life of non-residential buildings is typically years in terms of building envelope but the structure should have a much longer life. However, there is a functional need for buildings to be flexible in use and adaptable to future demands, which steel technologies can provide through use of relocatable partitions, longer span flooring and open roof systems. In this approach, the envelope performance is of prime importance on the energy cost and an efficient thermal performance of the envelope including both thermal looses and air/water tightness are consequently important. Galvanized steel components are durable and long life, as evidenced by long term measurements of buildings in different climatic conditions. A design life of over 100 years is predicted for steel components within the building envelope Energy services The methodology of calculation of energy performances of buildings should integrate the following aspects: a. Thermal insulation (of building shell and installations), Insulation and ventilation (e.g. wall cavity and roof insulation, double/triple glazing of windows, etc.), b. Air tightness of the building envelope, c. Heating and cooling systems (e.g. efficient boilers, installation/efficient update of district heating/cooling systems, etc.), d. Hot water (e.g. installation of new devices, direct and efficient use in space heating, washing machines, etc.), e. Air-conditioning installation, f. Position and orientation of the building, solar shading on south facade. Other areas where energy efficiency measures may be identified and implemented are: i. Lighting (e.g. new efficient bulbs and ballasts, digital control systems, etc.), ii. Cooking and refrigeration (e.g. new efficient devices, heat recovery systems, etc.), 8

9 iii. iv. Other equipment and appliances (e.g. new efficient devices, time control for optimized use of room). Others areas not in direct relation with buildings as mechanical efficiency, transportations, etc. For frame and envelope building constructors, points a and b in the list above are the main responsability and guidance are developed in the following sections. 2. Energy and Thermal Improvements for Construction in Steel Parametric Study 2.1. PAPER FROM RWTH Sources From WP1 General Information In WP1 and WP2 detailed investigations were made regarding air-tightness and heat transfer. The characteristics were quantified and solutions for improvements were presented. This report presents the effects of these details on the whole building performance for nonresidential buildings. Concept of the Parametric Study and Reference Building The relevance of details (thermal bridges and air-tightness) on the whole building performance is strongly dependent on the dimensions of the building. Therefore a basic model of a typical industrial building is taken (Figure 01), which is varied in its dimensions. Figure 01: Basic Model for parametric study Array of Dimensions: - width: 10 m b 50 m, reference: 30 m - length: 20 m l 100 m, reference: 45 m - height: 5 m h 25 m, reference: 8 m The dimensions of the building components (windows, roof lights, doors) correspond to the variations of the main dimensions. The details, marked with A to O, are considered in different qualities for air-tightness and thermal bridge effect (ψ-value). 9

10 Air-tightness The air-tightness of the whole building is quantified by the air change-rate (n in h -1 ), that is obtained at a given pressure difference (typically 50 Pa). The value can be determined by a blower-door test (see WP 1). On the other hand, the n 50 value is the sum of the leakages of all details, therefore a theoretical estimation is possible, if the performance of the details is known. Quality levels of air leakage The overall air-tightness of the buildings is determined by the joints as given in Figure 01 and additionally the junctions of the panels in the regular area. Concerning the openable joints of doors and windows, the air-tightness characteristics were taken from the requirements (Table 01) and for the panels in the regular area and other connections the air leakage coefficients were varied according the results achieved in WP 1 in three different classes (L1, L2, L3, see Table 2). Table 01: Air leakage rates of openable windows and joints Joint a-value [ m³/(h m) ] Detail Junction Standard G 1, H, I 1 Window 2.25 (at 100 Pa) J, K Large Door 12 (at 50 Pa) G 2, I 2 Door 2 (at 10 Pa) Table 02: Air leakage rates of junctions and other joints Joint a-value [ m³/(h m) ] Detail Junction L1 L2 L3 A, B, C, E, F Ridge, Eave, Verge, Corner Regular junctions wall and roof elements Figure 02, 03 and 04 show the effect on the air-tightness of the whole building (n 50 -value). For tight and very tight junction (L1, L2) for every dimension the n 50 value is far below the requirements. And also for un-tight junctions (L3, a = 1 m³/(hm) at 10 Pa) for buildings with a quite medium compactness (A/V below 0.4 to 0.5) a n 50 -value below 1.5 h -1 can be achieved. 10

11 air change rate at pressure difference p = 50 Pa n 50 [ 1/h ] A / V [ m -1 ] calculated values maximum, natural ventilation maximum, mechanical ventilation reference building Figure 02: Air-tightness at junctions according class L1 3.0 air change rate at pressure difference p = 50 Pa 2.5 n 50 [ 1/h ] A / V [ m -1 ] calculated values maximum, natural ventilation maximum, mechanical ventilation reference building Figure 03: Air-tightness at junctions according class L2 11

12 air change rate at pressure difference p = 50 Pa n 50 [ 1/h ] A / V [ m -1 ] calculated values maximum, natural ventilation maximum, mechanical ventilation reference building Figure 04: Air-tightness at junctions according class L3 Thermal bridges For the relevant details typical standard values and improvements concerning the -values were determined (Table 03.) Table 03: -values for standard and enhanced details Linear thermal bridge -value [ W/(m K) ] Detai l Junction L [m] Standard Enhanced A Ridge L B Eaves 2 l 0,310 0,100 C Verge 2 b 1,010 0,010 E 1 Cladding Drip 2 (l+b) 0,860 0,600 E 2 Ground Floor 2 (l+b) 0,160 0,160 F Corner 4 h 0,180 0,010 G 1 Window Head 2 l 0,970 0,620 G 2 Door Head 2,0 0,910 0,620 H 1 Window Sill 2 l 0,480 0,100 I 1 Door Jambs 8,0 0,800 0,080 I 2 Window Jambs 4,0 0,670 0,080 J 1 Head Large Door 4,0 0,680 0,620 K 1 Jamb Large Door 8,0 1,700 0,710 12

13 U TB [ W/(m².K) ] global additional value for transmission heat losses of thermal bridge junctions variation of dimensions national regulation 0,10 W/(m².K) reference building A / V [ m -1 ] Figure 05: Additional transmission by thermal bridges (standard details) U TB [ W/(m².K) ] global additional value for transmission heat losses of thermal bridge junctions variation of dimensions national regulation 0,10 W/(m².K) reference building A / V [ m -1 ] Figure 06: Additional transmission by thermal bridges (enhanced details) Figure 05 and 06 show, that improving the thermal bridges reduces the additional thermal transmission of the whole building envelope U TB about 0.1 W/m²K. For smaller buildings the difference will be more than 0.2 W/m²K. The effect on the overall energy performance will be shown later. Energy performance These results were now used in calculations of the energy performance, in which these calculations were done for the reference building. This work was done in a parametric study for four different locations, for different user profiles and four different characteristics regarding air-tightness and thermal bridges (Figure 07 to 10). 13

14 heating energy demand Q h ' [ kwh/(m³a) ] workshop, manufacturing Industrial building (reference dimensions) annual heating energy demand acc. DIN V Standard details, no airtightness test, n50 = 4,0 Enhanced details, no airtightness test, n50 = 4,0 Enhanced details, with airtightness test, n50 = 2,0 sports hall retail, department stores Enhanced details, ideal airtight, n50=0,14 storehouse, archives trade fair, congress Figure 07: Heating energy demand, location: Germany (Berlin) heating energy demand Q h ' [ kwh/(m³a) ] workshop, manufacturing Industrial building (reference dimensions) annual heating energy demand acc. DIN V Standard details, no airtightness test, n50 = 4,0 Enhanced details, no airtightness test, n50 = 4,0 Enhanced details, with airtightness test, n50 = 2,0 Enhanced details, ideal airtight, n50=0,14 sports hall retail, department stores storehouse, archives trade fair, congress Figure 08: Heating energy demand, location: Spain (Madrid) heating energy demand Q h ' [ kwh/(m³a) ] Industrial building (reference dimensions) annual heating energy demand acc. DIN V Standard details, no airtightness test, n50 = 4,0 Enhanced details, no airtightness test, n50 = 4,0 Enhanced details, with airtightness test, n50 = 2,0 Enhanced details, ideal airtight, n50=0,14 workshop, manufacturing sports hall retail, department stores storehouse, archives trade fair, congress Figure 09: Heating energy demand, location: UK (London) 14

15 heating energy demand Q h ' [ kwh/(m³a) ] workshop, manufacturing Industrial building (reference dimensions) annual heating energy demand acc. DIN V Standard details, no airtightness test, n50 = 4,0 Enhanced details, no airtightness test, n50 = 4,0 Enhanced details, with airtightness test, n50 = 2,0 Enhanced details, ideal airtight, n50=0,14 sports hall retail, department stores storehouse, archives trade fair, congress Figure 10: Heating energy demand, location: Finland (Helsinki) This investigation quantifies the effect of air-tightness and thermal bridges on the overall heating energy demand. Optimizing the details has a remarkable effect for light-weight building in steel. The absolute amount depends on the location and the use, but the relations within one data set (one specific use for one specific location) shows the same trend for all these variations. The energy demand for lighting and cooling is much more depending on building services, glazing and shading, building use etc., the quality of the building envelope is one aspect among others PAPER FROM LABEIN Sources From WP3 Work done in WP3 by LABEIN: Document ETX-029 Innovative techniques for improved thermal comfort has foreseen on a benchmark of several configuration of buildings including a real experimental building structure to investigate on the best solutions for energy saving. BENCHMARK BUILDING CHARACTERISTICS It is not possible to select a specific building configuration that is representative for the whole of Europe. Several approaches have been considered to find an appropriate configuration for benchmarking the various innovative techniques proposed in the ETHICS project to improve thermal comfort. Based on the conclusions made in previous European projects (EEBIS), where a reference zone was defined to investigate the performance of innovative steel intensive products, a more advanced configuration has been selected. The reference zone is defined as a representative section of a building. A reference zone is not necessarily a room within a building. It only corresponds to a representative building section with respect to the following ratios: façade to floor area, façade to, building volume and proportion of windows in the facade. 15

16 A building structure has been erected that can be fitted with several building works, including envelope systems, roof, slabs and other elements. Figure 10: Complete steel structure Also the Energy Plus software was used to simulate the behaviour of the building fitted with different work elements and configurations. Two identical reference zones (materials, construction systems, geometries, window fractions, usages, services, climates ) were used in order to identify the different energy demands depending on two characteristics: - Orientation - Location with regards to the building lay-out Orientation is an important parameter that affects solar radiation, wind, etc The location with regards to the building lay-out is meant to account for non-regular parts of the building such as rooms in the corner of a building (where two external walls and two orientations meet). The main building characteristics to account in the simulations are as follows: - Geometry - Basement and foundations - Steel structure - Reference flooring system - Reference facade system - Roof system - Internal partitions - Heating and ventilating systems (HVAC) 16

17 One of the main investigation was on the thermal inertia of the building with a specific study to characterise the performance of a steel building versus concrete building with the following base: Steel Vs. Concrete Several studies have been carried out to compare the effect of thermal inertia for both concrete and steel framed buildings. The general conclusions drawn in those studies are that for a rather similar building (cast-in-place concrete structure Versus. steel framed structure both with identical shape, orientation, building envelope and HVAC systems), which are simulated using identical weather conditions, usage and percentage of openings, they perform almost identically. This suggests that any steel-framed building has sufficient thermal inertia to generate the same benefits from thermal mass as a concrete building. Furthermore, it is shown that the glazing-to-wall ratio is a far more significant factor affecting the energy consumption of the building. Conclusions from other studies are focused on the effect of having thermal mass in the building envelope, which is not always beneficial. The positive or negative impact depends on the overall U-value of the external walls, the ratio of window-to-façade, the solar radiation intensity at the location, the use of the building, and the control of HVAC systems. In addition, the impact of thermal mass in the building envelope is less important compared to how the glazing ratio, U-Value and HVAC controlling systems affect the energy consumption of the building. It is necessary to balance the positive effect of thermal inertia with the embodied energy of the construction materials used in a specific building. We note here, regarding the overall benefits to obtain thermal inertia when a material has a high levels of embodied energy content and considering over the life of the building. Some passive strategies have been set for thermal efficiency based on the following base: Combined with thermal inertia, there are a number of passive strategies that influence the thermal performance of any steel intensive building. It is interesting to assess and quantify the effect of those strategies before focusing on thermal inertia and how they interact. By doing so, we will be able to obtain a more precise idea about the affection of thermal inertia over the whole building energy consumption. The benchmark building characteristics previously defined have been used to produce a number of models that will be used to assess how the following aspects affect the energy demand of a steel intensive building: - Façade thermal transmittance - Roof thermal transmittance - Window characteristics These aspects strongly affect the energy consumption of a building. However, they are focused on elements (building envelope) claimed to have a limited effect over the building thermal inertia. The goal of analysing these aspects independently is to control their effect before the thermal inertia specific study is conducted. A variety of configurations are simulated and the conclusions obtained in this section are extrapolated to further sections of 17

18 the document. Refer to document: ETX-029 Innovative techniques for improved thermal comfort from LABEIN for calculation details. The program Energy Plus has been used to carry out the series of simulations, which allows dynamic analysis to calculate the energy demand of the benchmark building in a transient mode. The general conclusion for overall energy evaluation of commercial buildings is summarised as follow: For facades: - Reducing the thermal transmittance of the façade (increasing its insulating properties) produces a clear reduction on the heating demand. However the amount of heat lost through the building envelope throughout the winter time is limited when the thermal transmittance reduces below a certain figure. - The opposite pattern is found in the cooling mode. The cooling demand slightly increases as the thermal transmittance reduces. This is due to the fact that increasing the insulating properties of the building envelope reduces the loss of internal gains to the exterior and generates a higher cooling demand to keep constant internal temperatures. This effect is expected to be very much climate dependant. - The most efficient façade thermal transmittance for a specific building is very dependant of the climatic conditions. In the case of the simulations, a mild climate has been considered (southern Europe) and the use of higher envelope insulation does not really present serious advantages. If the weather pathern had more drastic summer/winter and day/night temperature variations, the benefits provided by decreasing the thermal transmittance of the building envelope would be more noticeable. - The economical and environmental impact of increasing the insulating properties of the building facade is recommended before making a decision based on energy demand saving. For roofs: - The mild climatic conditions selected for the simulations make the cooling demand more important than heating. - Reducing the thermal transmittance of the roof produces the same effect as for the facades. However, the variations in the roof U-Value has less overall effect due to the fact that the roof has a lower surface area than the facades. For Widows: - The heating demand increases when the window solar factor increases. The lower the solar factor, the lower the solar gains and the larger the heating demand. - For the same reason, the cooling demands decreases when the window solar factor increases. - The selection of the most appropriate windows needs to take into consideration both, the heating and the cooling demand. Not only the energy demand but the environmental and economical cost should be considered when selecting the windows. 18

19 - Future works should consider the assessment of various solutions with identical solar factor and variable thermal transmittances. It is expected that the predominant effect of the windows over the building energy demand are the solar gains produced by the openings rather than the heat transfer due to convection and conduction through them. Investigation was conducted on thermal inertia and ventilation strategy in commercial building with the following conclusions: As shown in the simulations, the total building energy demand falls when the floor slab thermal mass increases. Night time ventilation must be conducted in a way such that this effect does not lead to increase the heating demand. This could happen in cases when the ventilation decreases the building temperature too much and it is necessary to heat up the building at the early working hours, especially in the summer. In order to have efficient night time ventilation, it is necessary to adjust the number of air changes per hour and the period of time when this ventilation is active. It is recommended to calculate the period of time when the night time ventilation must end before achieve the building set point temperature. It is also recommended that the night time ventilation is produced through natural means. It is important to avoid mechanical ventilation, which would lead to increase the building energy consumption. Other comfort aspects to be accounted for when implementing night time ventilation, such as draft, noise. Further work identified throughout the modelling process is listed in the following lines: - Need to optimize the air volume entering the building and the most appropriate schedule to do so. - Correct design of openings to get the most efficient air circulation. - If natural ventilation is not possible, the correct choice of the mechanical ventilation system and calculation of its energy consumption is important to the design solution. - CFD analysis to provide adequate internal comfort conditions Due to the fact that the analysis did not consider the possibility of using mechanical ventilation, the results show that the larger the air changes are, the larger the demand reduction is. In this respect, and to illustrate what it was stated before, increasing the air changes from 8 to 12 per hour produces a small demand reduction. However, to be able to increase the number of changes from 8 to 12, the need for mechanical ventilation becomes necessary. Therefore, it is important to evaluate whether the electricity consumption of the fans is larger than the reduction in the energy demand. Solar shading Solar shading systems are defined as construction elements that provide shade to the building they are attached to in order to increase the passive building performance. They allow diffuse radiation (mainly visible lighting) to enter the building and prevents from heating up the interior. 19

20 The use of steel intensive solar shading systems (SSS) is increasing due to the flexibility that this material provides to architects and designers. There is however not much scientific background about how these systems influence the thermal, visual and acoustic performance of the building they are attached to and how they should be designed to obtain the optimum working conditions. Flexible Flexible 1-direction Flexible 2- directions Rigid Open Area Less than 25% 25-50% More than 50% Figure 12: Example of solar shading works elements made of steel plates and grilles. A conclusion for shading parameter obtained from the simulations, the total building energy demand falls when the floor slab thermal mass increases. In addition to that, the following conclusions are made: - In order to reduce the energy demand through solar shading systems, the most adequate strategy is to use solar shadings in the southern facades and vertical elements parallel to the openings in the western and eastern facades. - The solar systems used in these simulations are vertical elements parallel to the façade in the western and eastern façade, and horizontal elements for the south facade. - The effect of placing the solar shading systems at variable distances from the façade has not been evaluated. - The use of solar shading systems produces the following effect over the building energy demand: o Heating: Increases o Cooling: Decreases o Lighting: Increases - These tendencies are more noticeable when the percentage of openings within the solar shading system decreases and it becomes more opaque. 20

21 - For commercial use (office building), the most significant demand for the whole building consumption is the cooling demand. Therefore, the most efficient configuration is the one that reduces the most the cooling demand (lower percentage of openings within the solar shading system) PAPER FROM CRM Sources from WP1 In WP1, the CRM4 building has been simulated with the national tool PEB given by the regional government (Région Wallonne of Belgium). This software offers two models: the simple energy models (were only U values and the surface of elements are encoded) and the geometrical model where the complete details can be drawn. The simple energy model has been used. Therefore the precise details of the envelope, and the thermal bridges (at the panel junctions) were not modelized. As a simple parametric study, two parameters have been changed: air tightness and thermal insulation. 13 values of air tightness have been simulated for the CRM4 building. The effect seems rather linear (Figure 11). An n50 air tightness of 0.6 vol/h (level of passive buildings) would reduce the heating net consumption of 10%. An n50 air tightness of 7.7 vol/h (the average for buildings in Belgium) would lead to an increase of 10%. Figure 11: Effect of air tightness on the CRM4 building energy demand 5 types of insulation level were simulated for the CRM4 building (table 04): Table 04: Parametric elements details Global insulation Element details level K149 Uwall 1.50 Uwindows 6.00 Uroof 1.00 K56 Uwall

22 Uwindows for horizontal, 2.5 for door Uroof 0.35 K45 Uwall 0.30 Uwindows for door Uroof 0.29 K33 Uwall 0.14 Uwindows for door Uroof 0.14 K20 Uwall 0.07 Uwindows for door Uroof 0.07 Note: The K factor refers to the global transmittance of the building. This may be considered as for the U value if not fully the case. It depends of the U values of the buildings works but also of the compactness of the building. The effect of the thermal insulation of the CRM4 is shown on Figure 11. The insulation level of CRM4 was calculated to K56. The K20 would include a decrease of 55% in the heating but an increase of 54% in the cooling. The total consumption (heating + cooling) would be decreased by 8%. The calculated heating demand (99kWh/m2) is close to the measured heating consumption (91kWh/m2) but the cooling demand (75kWh/m2) estimated exceeds the 61kWh/m2 measured. So the total consumption at K20 should be decreased by more than 8% in the reality. It was difficult to reach low K values with classical U values for envelope elements. For example, the U values at the K56 line correspond more to a K45 domestic house. Some nonrealistic values (Uwindows=0.4) have even to be chosen to reach the K20 level. One explanation comes from the low density of the building (ratio of volume on the envelope surface, V/At): 1.56m. The CRM4 building was designed with a large patio. The K values take the density into account. So the CRM4 K level is penalized by its high perimeter factor. A lower density of the CRM4 would lead to a low K value for the same U values of the surfaces. This could have been realised with an atrium (protected space) instead of the patio (not protected space). Figure 11: insulation effect 22

23 2.4. PAPER FROM CTICM Source from WP1 ETX 062 In this section, the results of thermal and energy calculation are presented for five examples of steel buildings including the two buildings diagnosed by CTICM within the Work under WP1. CTICM has performed energy efficiency parametric variations on these buildings in way to give orientation on the best financial benefits for refurbishments operation. Building in France Use Area (m²) Hall: Clermont-Ferrand Industrial 802 Hall: Martigues Industrial 1630 Hall: Orleans Industrial 450 Jeanne de Champagne Residential 2370 Clinique Majorelle Hospital 510 For the first building (Hall, Clermont-Ferrand), in addition to performance assessment of the building in its initial state, some solutions are proposed to improve the building thermal performances. The solutions involve thermal insulation and air-tightness of the envelope. For the other buildings, only the impact of the air-tightness and thermal bridges are studied Evaluation of heat transfer through thermal bridges The evaluation of thermal bridges can be carried out experimentally by using standardised test methods on two identical building elements, the first one with and the second one without a thermal bridge. This method is limited to those building elements that can be tested. Thus, the accuracy of the assessment is rather uncertain, it is time consuming, expensive and laborious, only applicable for important projects or for checking the reliability of simulation calculations. Catalogues give several examples of thermal bridges for fixed parameters (e.g. dimensions and kind of material). So they are less flexible than calculations. In France, like in many European countries, tabulated values of are given for typical cases. But they often do not match with the actual details of any building project. Thermal bridges can therefore be evaluated by using numerical methods. However all software needs should be used with minimum care for the defining the boundary conditions. Numerical calculations of the heat transfer through a thermal bridge require the use of methods with numerical resolution, such as finite element or finite difference methods. The European Standard EN ISO describes the calculus method for 2D and 3D thermal bridges and superficial temperatures. In this study we use the FE code ANSYS. Calculations have been made using volume elements SOLIDO70 to simulate normal proportion material element, and shell elements SHELL57 to simulate steel thin panels. 23

24 Figure 13: Example of FE calculation of 3D thermal bridge Hypotheses of calculation parametric data - results The calculation hypotheses are given in the following tables for the boundary conditions and the thermal conductivities (Table 05). Table 05: Boundary conditions and thermal conductivity of materials Title Surface heat transfer coefficient (W/m²K) Horizontal Upwards Downwards flow flow flow Surface thermal resistance (m²k/w) Horizontal Upwards Downwards flow flow flow Temper ature Internal External Material Thermal conductivity (W/m.K) Insulation 0.04 Concrete 2.00 Steel 50 Building thermal performances The building thermal performances (heating need and heating consumption) are calculated with the visual TTH 2005 software. In France, other approved software can, be used (BBSSLAMA, Perrenoud software, etc.). The software allows the calculation of regular coefficients: Ubât, Uât-réf, Cep, Cep-réf, Tic and Tic-réf. The input calculation data are the U-value for various walls, thermal bridge coefficients and the equipment used for HVC. This regular calculation is based on conventions and the results do not coincide necessarily with the real performance of the building. Building 1 Clermont-Ferrand is given as a example, details on other building can be read in the report of WP1. 1. Building 1: Hall Clermont-Ferrand The building is located in the France department 63 and has a floor areaof 802 m². The external dimensions are as follows: length: m, width: m, height: m, and volume of 6610 m3 including the envelope. The building is heated during the winter period. The roof has suffered water leaks during the former years and has recently be refurbished with an extra roof composed of an 100 mm of glass wool insulation and over-cladding steel sheeting. The roof air vents, as seen on the picture, have been disconnected and new 24

25 mechanical vents have been constructed on the lateral facade of the building. This building is 15 years old, medium quality and corresponds to the needs of air tightness testing in the project. Figure 14: The complex of the buildings at Polytech, Clermont-Ferrand: France Figure 15: West façade with rolling door Figure 16: North facade Original building - Concrete facade and steel cladding About 30% of the facade is non-insulated concrete, that leads to high heat losses. The linerar thermal bridge due to a steel column is about 0.6 W/m.K. Concrete Wall Steel column Figure 17: Concrete facade wall of the building as is and thermal modelization For the double skin cladding, the thermal bridge due to steel column is about 1 W/m.K. 25

26 Insulation Figure 18: Steel cladding facade wall of the building as is The roof s thermal performance are improved by the installation of an over-roofing with 100 mm of insulation. Figure 19: Addition over-roof of the existing building Table 06: Envelope thermal performances Designation U-value (W/m²K) Air-tightness : Facade Steel cladding 0.38 I4 = 5.81 m 3 /h/m² (4 Pa) Concrete 2.82 Roof 0.26 Ground floor 0.46 i li i Thermal bridges: TB (W/m².K) SHON 0.60 Thermal performances of the building: Gas heating 26

27 Heating need Heating consumption kwh/m²/an Figure 20: Energy consumption evaluation of the building over a year period Solutions to improve the thermal performances of the building are described as follows: Isolation of concrete wall: Cladding with external insulation (PSX 10 cm, λ = 0.03 W/m.K) and plaster (fixing by pins). This solution reduces thermal bridging of about 99% (0.005 W/m.K instead of 0.6 W/m.K). The U-value is reduced by about 90% (0.30 W/m².K instead of 2.82 W/m².K). Concrete Wall External insulation Figure 21: Improvement proposal: External insulation and cladding of the concrete wall Improving Isolation of concrete wall: 0.30 W/m².K Gain/initial state (%) 30% 25% 20% 15% 10% 5% 0% Heating need Heating consumption Uwall 1= 0.3 W/m².K I4 = 5.81 m3/h/m² Figure 22: Potential gain for energy consumption: Thermal insulation Improving the envelope air-tightness: I4 = 3; 2; 1 m 3 /h/m² (4 Pa) Gain/initial state (%) 50% 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Case 1 I4 = 3 Heating need Heatin consumption 1 Case I4 = 2 Case 3 I4 = 1 Figure 23: Potential gains for energy consumption: Ait tightness 27

28 Isolation of concrete wall and improving the envelope air-tightness: Concrete wall: U = 0.30 W/m².K; I4= 3 m 3 /h/m² Gain/initial state (%) 60% 55% 50% 45% 40% 35% 30% 25% 20% 15% Heating need Heating consumption 10% 5% 0% Uwall 1= 0.3 W/m².K I4 = 3 m3/h/m² Figure 24: Thermal insulation and air tightness improvement: Possible potential gains 2. Building 2: Hall Martigues This building is typical of current building techniques for industrial buildings. This is a steel construction hall: length: m ; width of two bay, each of 15.7 m ; height of 9.98 m ; floor area: 1630 m², Volume: m3;; The building is located in the department 13 of France Figure 25: Two pictures of the building, external aspect and internal disposition The construction of the facade is made with Insulation panels: 90 mm thick and the calculated thermal transmittance is: U = 1.23 W/m².K 28

29 Figure 26: Wall composition of the facade: as is The construction of the roof is made with Insulation layer of 80 mm thick and the calculated thermal transmittance is: U = 0.50 W/m².K Figure 27: Roof composition of the original building Table 07: Envelope thermal performances of the original building Designation U-value (W/m²K) Air-tightness Facade 1.23 I4 = Roof 0.50 m 3 /h/m² (4 Pa) Ground floor 0.46 i li i Thermal bridges TB (W/m².K) SHON 0.34 Thermal performances of the building: Gas heating 29

30 Heating need Heating consumption kwh/m²/an Figure 28: Energy consumption of the original building: Solutions to improve the thermal performances of the building Improving the envelope air-tightness: I4 = 3; 2; 1 m 3 /h/m² (4 Pa) Thermal performances Reducing thermal bridges (TB): TB = 0.2; 0.1 W/(m².K); I4 = m 3 /h/m² (4 Pa) Thermal performances Gain/initial state (%) 80% 70% 60% 50% 40% 30% 20% Heating need Heatin consumption Gain/initial state (%) 6% 4% 2% Heating need Heating consumption 10% 0% Case 1 I4 = 3 1 Case I4 = 2 Case 3 I4 = 1 Figure 29: Improvement of air tightness. Potential energy consumption gains: 0% TB 1= 0.2 TB = 20.1 Figure 30: Improvement of thermal bridges : Potential energy consumption gains Note: The I4 factor refers to air tightness in normal condition as n50 is the equivalent factor for extreme condition. The results of these improvements are described as follows: Gain/initial state (%) 80% 70% 60% 50% 40% 30% 20% Heatin need Heatin consumption 10% 0% I4 1= 3 I4 = 21 TB = 0.2 TB = 0.1 Figure 31: Overall reduction due to thermal bridges and air tightness improvement: 30

31 For the 3 other buildings, details can be found in the specific report of WP1. A general summary is presented as follow Result summary and conclusion Table 08: Building 1: Hall Clermont-Ferrand Heating needs (kwh/m²/y) Heating consumption (kwh/m²/y) Initial building - Concrete wall and steel cladding : I4 = 5.81 M 3 /h/m² Improvement 1: External thermal cladding : % -23.5% mm: Uwall = 0.3 W/m².K Improving air tightness: I4 = 3.0 M 3 /h/m² -21% % Improving air tightness: I4 = 2.0 M 3 /h/m² -29 % % Improving air tightness: I4 = 1.0 M 3 /h/m² -37 % -39 % Improving both U and air tightness: U=0.3 W/m².K: I4 = 3.0 M 3 /h/m² Table 09: Building 2: Hall Martigue Heating needs (kwh/m²/y) % -46 % Heating consumption (kwh/m²/y) Initial building - steel cladding : I4 = M 3 /h/m² Improving air tightness: I4 = 3.0 M 3 /h/m² % -50 % Improving air tightness: I4 = 2.0 M 3 /h/m² -50 % -57 % Improving air tightness: I4 = 1.0 M 3 /h/m² -57 % -64 % Improving U and no improvement on air tightness: U=0.2 W/m².K: I4 = M 3 /h/m² Improving U and no improvement on air tightness: U=0.1 W/m².K: I4 = M 3 /h/m² Improving both U and air tightness: TB=0.2 W/m².K: I4=3m3/h/m² Improving both U and no improvement on air tightness: TB=0.1 W/m².K: I4=3m3/h/m² Table 10: Building 3: Hall Orléns Heating (kwh/m²/y) -2 % -2.7 % -4.5 % -4.7 % -45 % -55 % -64 % -70 % needs Heating consumption (kwh/m²/y) Initial building - steel cladding : I4 = 5.0 M 3 /h/m² Improving air tightness: I4 = 3.0 M 3 /h/m² -16 % -18 % Improving air tightness: I4 = 2.0 M 3 /h/m² % % Improving air tightness: I4 = 1.0 M 3 /h/m² -34 % -37 % Improving U and no improvement on air tightness: U=0.5 W/m².K: I4 = M 3 /h/m² Improving U and no improvement on air tightness: U=0.3 W/m².K: I4 = M 3 /h/m² -9 % -8 % -13 % -12 % 31

32 Improving both U and air tightness: TB=0.5 W/m².K: I4=3M 3 /h/m² Improving both U and no improvement on air tightness: TB=0.3 W/m².K: I4=1 M 3 /h/m² % -23 % -45 % -48 % Table 11: Building 4: Jeanne de Champagne Heating needs (kwh/m²/y) Heating consumption (kwh/m²/y) Initial building - steel cladding :I4 = 3.0 M 3 /h/m² Improving air tightness: I4 = 2.0 M 3 /h/m² -14 % -18 % Improving air tightness: I4 = 1.0 M 3 /h/m² -28 % -33 % Improving air tightness: I4 = 0.5 M 3 /h/m² -35 % -42 % Improving U and no improvement on air tightness: U=0.1 W/m².K: I4 = M 3 /h/m² Improving U and no improvement on air tightness: U=0.05 W/m².K: I4 = m 3 /h/m² Improving both U and air tightness: TB=0.1 W/m².K: I4=2m 3 /h/m² Improving both U and no improvement on air tightness: TB=0.05 W/m².K: I4=1 m 3 /h/m² Table 12: Building 5: Clinique Majorelle Heating needs (kwh/m²/y) -6 %! -8 % -13 % % % -25 % -42 % -48 % Heating consumption (kwh/m²/y) Initial building - steel cladding : I4 = 3.0 M 3 /h/m² Improving air tightness: I4 = 2.0 M 3 /h/m² -10 % -11 % Improving air tightness: I4 = 1.0 M 3 /h/m² % -21 % Improving air tightness: I4 = 0.5 M 3 /h/m² -25 % % Improving U and no improvement on air tightness: U=0.15 W/m².K: I4 = 3.0 M 3 /h/m² Improving U and no improvement on air tightness: TB=0.05 W/m².K: I4 = 2.0 M 3 /h/m² Improving both U and air tightness: TB=0.15 W/m².K: I4=2m3/h/m² Improving both U and no improvement on air tightness: TB=0.05 W/m².K: I4=1 m3/h/m² -7 % -6 % % -12 % -16 % % -32 % % Final comments and conclusions Observing the summary of improvement and efficiency of the possible improvements and building situation it is calculated that: Improvement should first be made on the lowest performance factor. Improvement on this factor will generate relative high thermal benefits, 32

33 For industrial building it seem that improving air tightness is more efficient than improving U factor, but nevertheless shall be case of application, Improving U factor can be made by over-cladding and over roofing, or by replacing the external layer of thermal insulation by a more efficient one, Improving air tightness can be made by checking all possible air leak paths, including building and cladding joints. These joints are usually clearly located and improving is usually made by introducing sealants and other soft linear joints and fixing improving with rubber sealants. Improving both factors at the same time will save on work and cost because the operations are made on the same building elements. In any case, both thermal insulation and air tightness are consequence of a skilled workmanship on site PAPER FROM AMLg Source from WP1 This report describes the energy consumption parameters of the Steel Centre (ArcelorMittal Office Building in Liège Belgium), in comparison with the PEB requirements. In a second part, a parametrical study of the building is presented; the goal is to study the influence of airtightness and thermal parameters on the building energy performance Energy consumptions of the Steel Centre building compared to the PEB requirements. For an office building, the requirements of the PEB are: - Maximum U-values depending on the wall type and R min for floors in contact with the ground - Global insulation level K limited to K45. - Primary energy consumption level compared to an equivalent reference building E w, limited to Minimum ventilation airflow, depending on the number of people, and from the area of the room. The results for the Steel Centre building are: U-value (W/m²K) CAAL PEB (U-max) Brick wall not OK Opaque area not OK Roof not OK Window OK Intermediate floor OK Base floor not OK R (m²k/w) CAAL PEB (U-max) Base floor 1.26 Rmin = 1 OK - The global insulation level is K 42 < K45 OK - The primary energy consumption level E w equal to 99 > E w 80 not OK - The ventilation air flow criterion is respected. 1 U-value taking into account the thermal resistance of the ground 33

34 All PEB requirements are not fulfilled. Indeed, when CAAL building (Steel Centre) was designed and erected, PEB was not in application. At that time, the Steel Centre was conform to Belgian Standards, and was even considered as energy performant building. A feature to point out is the façade of the building: the steel curtain walls of the façade are mainly consisting of insulated glazing. The requirements for these façade elements are the one for windows (U max = 2.5 W/m²K), other for façades (U max = 0.4 W/m²K). There is thus an ambiguity in the way of considering the types of façade elements Parametric study on energy efficiency of the Steel Centre A parametric study was performed on the Steel Centre PEB model, in order to highlight the key parameters improving the energy efficiency of an office building. The following parameters were modified in 6 case study improvements: - U-values of walls - Lighting - Air-tightness of the envelope - External sun shading - Ventilation system The results of the Steel Centre (U-values and R) were taken as reference case parameters: Table 14 : Wall U-value (W/m²K) Curtain wall 1.49 Brick wall 0.49 Opaque area 0.51 Roof 0.35 Intermediate floor, over hanged part Thermal resistance R (m²k/w) Base floor, in contact with the ground 1.26 The extra heat losses caused by thermal bridges are not taken into account in this reference model. The air-tightness was not measured so the PEB default value was used: v50 = 12m³/hm² of external envelope. There is double flux ventilation, equipped with a 90% heat recovery system. The efficiencies of the reversible heat pumps are equal to 3.85 for heating production and 6.16 for the cooling production. However, the PEB software calculates this last parameter. The cooling COP (efficiency coefficient of the heat pump) is then set to 5. The set point temperature is the default value of the PEB, equal to 19 C. The installed lighting power is set to the default value given by the PEB software of 20 W/m². 2 PEB : U max intermediate floor : 0.6 W/m²K 34