Current Status

Experimental Façade
The main part of the GPEE project is the creation of experimental facades, installed and metered at a selected site in Poland. Two of them will be placed on building A6 at the Technical University of Lodz. On the fourth floor of the chosen building two measuring rooms with experimental facades will be created (isolated thermally from the rest part of the building) and two referential rooms will be prepared for identical utilization purposes (with the existing facade). The rooms will be oriented on the east and on the west. On picture 1 with green rectangle the location of the discussed rooms and facades is marked.

Experimental Façade

Experimental FaçadeFigure 1. East and west elevation of the building on campus A of TUL. Green rectangle shows localization of experimental façade.

In that building, on the all five floors, there are classes and laboratories of the Faculty of Process and Environmental Engineering. According to EN 15251 the building can be assign to category III in terms of thermal comfort requirements. It can be averaged that classes and offices are occupied for 48h per week by 40 employees and changing number of students. The building was built with the frame construction of the façade, ventilated flat roof and basement (slab on ground). The construction was finished in 1972 and modernized after 30 years, in 2002.

Architectural concept of the façade
For the purposes of operational research analyses and energy calculations a modular construction of the facade was assumed. The following features, describing energy characterization, can be assigned to every module:

  • Properties due to processes of the reflection, absorption and transmission of solar radiation reaching the outer surface of the facade,
  • Properties due to the processes of photo-electric conversion of solar energy,
  • Properties due to the processes associated with the permeability of visible light to the interior,
  • Properties due to the processes associated with heat exchange surfaces in the flow path and the ground.

Initially, an unit of the module 0.3 × 0.3 m was accepted, what at covering the façade area of 3 x 3 m was giving the total number of modules equal 100. Due to technical limitations associated with dimensions of photovoltaic panels and due to large mutual impact of individual panels on temperature distribution, after all the division into modules with dimensions 0.6 x 0.6 m was accepted.

Daylight utilization
Ensuring an adequate amount of daylight and visual comfort in buildings, is strongly associated with the proper design of windows size, shape, type and location (above the level of the floor), as well as the appropriate design of rooms depth and proportions. To determine the solution of the most efficient use of daylight various sizes and geometries of windows have been analysed. The lighting condition has an impact on the activity of people occupying the room - speed, accuracy and effort are mainly influenced by the lighting condition in a room. In a wider range it has also a great influence on the health, well-being and life quality of the people who are working in the room. Therefore, it is important to create a visual comfort inside the room by providing suitable qualitative and quantitative characteristic of lighting. It should be emphasized that comfort depends on many parameters, but it is also very subjective. In work package 3 “Double criterion optimization of integrated Renewable Energy Systems (RES) and daylight utilization” visual comfort for combination of different sizes and geometry of windows, are analyzed based on indexes.

For the preliminary analysis three solutions were taken into account, for which the concept of the entire façade is presented in the following figure:

Different types of evaluated window geometriesDifferent types of evaluated window geometries

The numerical calculation has been done using “Daysim” software. Results have been received for the behaviour of shadow movement inside the room depended on the geometry of the window and for the light intensity distribution in the room. Evaluating the impact for visual comfort the calculations were executed for east and west orientation of the windows.

Thermal insulation
Energy performance of the building external envelope depends predominately on the construction and boundary conditions. To develop guidelines for the selection of physical properties of external walls that will meet the requirements of the zero-emission buildings, different cases of external and internal conditions should be taken into consideration. Due to isothermal energy storage potential, the modification of building materials by phase change material (PCM) can contribute to stabilization of temperature which can be beneficial in different ways:

1. Stabilization of temperature of internal surface of the wall will result in stabilization of internal environment conditions. Layer with phase change material should be placed on the internal surface of the wall and melting temperature of the material should be close to internal air temperature.

2. Stabilization of temperature of the building material inside the component can help to avoid the risk of condensation of water vapour.

3. Application of PCM as external layer of the wall will attenuate the impact of the external environment on internal conditions. Melting temperature of the material is expected to be close to average external temperature during considered period of time.

Transparent / photovoltaic components
To provide a zero-emission building is a very complex issue and requires application of active systems to obtain energy from the sun. The selection of appropriate building integrated photovoltaic systems depends on many factors, like the efficiency of the PV panel, cost and area needed per kW or availability on the market. The GPEE project research is performed for office buildings. Therefore, additional aspects such as attractive appearance of the façade and possibility of conversion of the diffuse radiation should be considered.

A preliminary project of the photovoltaic position on façades assumes vertical arrangement of two columns containing six horizontal PV panels. The selected PV module is situated in rails and can be positioned horizontally or vertically.

Figure 14. Visualisation of the photovoltaic façadeFigure 14. Visualisation of the photovoltaic façade

Life Cycle Assessment (LCA) of the façade
Innovative solutions for zero- emission façade design enable significant reduction of heat loses. However, considering all phases of the life cycle of a façade, some solutions being energy- efficient in the maintenance phase, may have a significant environmental impact on the production or disposal stage. Therefore, the Life Cycle Assessment (LCA) is needed in order to measure the sustainability of any design of the façade. The result of LCA should be considered with energy performance of the façade panel in the design procedure. In the GPEE project, the LCA calculations will be performed for 6 different façade panel solutions. The results of the LCA analysis for each panel will be than taken into consideration in the optimization procedure, allowing to choose the best design for zero-emission façades.

The first step needed to perform the LCA is the choice of the assessment method that corresponds best to the scope of the research and gives a clear result for further analysis. Different tools for LCA were considered (SimaPRO (Ecopoints, Ecoindicator), Carbon footprint, MIPS factors, EIOLCA, Gabi). The MIPS technique, which gives the LCA results as a single score was chosen for this assessment, since taking into account the optimization procedure, the result of the LCA should be expressed as score, proportional to the panel surface.

MIPS stands for Material Intensity per Service Unit and is a concept originally developed at the Wuppertal Institute, Germany. It is a clear and transparent tool for LCA calculations, based on a continuously updated database of material intensity (MI) factors, measured by experts, describing environmental impacts of different materials, energy production etc. LCA results are given in kg of natural resources consumed in the whole lifetime of a material (during its production, distribution, use and disposal).

Four opaque façade solutions and two transparent ones were considered in the analysis, including panels with glass finish or photovoltaic one, standard mineral wool insulation or insulation equipped with extra layer of PCM (phase change materials). The transparent solutions considered are single skin and double skin façade windows. The panel 3-D schemes of some opaque panels are presented in figure 15.

Figure. 15. 3-D schemes of analyzed panels solutions. MW stands for mineral wool insulation, PCM- phase change material, PV- photovoltaic finish.Figure. 15. 3-D schemes of analyzed panels solutions. MW stands for mineral wool insulation, PCM- phase change material, PV- photovoltaic finish

According to the general outcomes of the analysis, the panel with photovoltaic finish proves to be the most suitable opaque solution from the environmental point of view, as far as the façade is well exposed to the sunlight radiation. Due to the long life cycle of a building, the decisive factor for LCA is energy demand for heating (even for very efficient insulating systems). As a result, improving the energy performance of any façade design proves to be the most efficient way to reduce the environmental impact.

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