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Dynamic Performance Assessment of Multidimensional Heat Transfer in Buildings Caracterización Térmica Dinámica de la Transferencia De Calor Multidimensional en Edificios
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EPBD directive 2002 and its recast 2010 have led to significant efforts in Member States to improve the energy performance of buildings. Important aspect of this goal is the compliance of building energy performance assessment which needs developed procedures in order to be able to achieve stringent energy targets in practice. Transmission characteristics have a significant role in energy efficient buildings. QUALICHeCK project conducted a review of thermal bridges in energy calculation and compliance procedures in nine European countries (Austria, Belgium, Cyprus, Estonia, France, Greece, Romania, Spain, Sweden). Results showed that there are four main types of methods to take thermal bridges into account in transmission heat loss calculation: the detailed calculation based on linear thermal transmittance values, simple basic rules, default transmittance values, and mean U-values. Regarding the compliance, review showed that often there are no specific thermal bridge related compliance procedures. General conclusion of this study was that compliance frameworks needs to be extended in order to be able to assess as built energy performance. It is common approach in many countries that control mechanisms stop with building permit phase.
Thermal insulation in buildings is getting more and more performing with modern energy efficiency regulations in developed countries. Not only insulation requirements are imposed to new-built buildings, but also to refurbishment activities of the existing building stock, where availability of space is often limited. These requirements lead to increased insulation thicknesses in building envelope constructions in modern days, leading to opportunities industries to develop integrated super insulation solutions, as internal insulation solutions. Materials such as Aerogels allow for a substantial reduction of the required space.
However, the implementation of these materials at large scale requires of the development of construction systems to guarantee that the overall energy performance of these meets the possibilities of super-insulated materials. Research outcomes integrated in this paper provide solutions through the assessment of thermal bridge effects in light construction systems for aerogels, and full scale experimental campaigns conducted at the Kubik by Tecnalia test facility.
The outstanding results are that metallic profile systems should be avoided if these need to be laid across the insulation layer, as the overall heat transfer is increased by almost 40%, and that this issue can be reduced by incorporating non-metallic plastic composite profiles in these systems, or by using systems where profiles are directly anchored at floor slabs. All this is demonstrated on full scale tests in which the overall energy performance of these systems is shown along with a relevant reduction in space requirements.
In this paper, an assessment is made on a pre-fabricated timber framed hemp-based building envelope system. The hemp-lime mixture within the envelope is produced by mixing the hemp shiv with a lime formulated solution, which acts as a binder, and provides thermal insulating and moisture buffering capacity to the resulting construction.
Hemp, by its natural origin, is a fixative of CO2 and can result in a negative carbon footprint helping to reduce the global impact of a building. In addition the hemp- lime layer absorbs and expels heat and humidity in relation to the environment and acts as a thermal storage by reducing the flow of energy through the wall. The presented system targets at the generation of an innovative building system focused on the expansion of the market for structural products, sustainable, ecological and low carbon footprint.
As part of its development its thermal insulation and moisture buffering properties have been assessed, and case studies and outcomes of full scale experimental studies are presented.
External Thermal Insulation Composite Systems (ETICS) are increasingly used for the energy-efficient retrofit of buildings.
This paper evaluates the in-situ thermal performance of a prefabricated composite panel made of PIR and concrete, by full scale testing of a prototype installed at the KUBIK test facility. Experimental results from measurement show a reduction in the thermal resistance of the ETICS assembly compared to theoretical design values. A number of phenomena have been identified causing multidimensional heat flow of conductive and convective nature, such as thermal bridges at floor slabs and anchors, and thermal bypass of the insulation causing airflow behind the ETICS.
Until very recently, technical systems such as solar thermal systems, and other HVAC elements have been conceptualized based uniquely in their thermal performance levels, and its integration with other architectural elements (envelopes, slabs,…) limited to mechanical fixation. However, with steadily increasing use of technologies for the reduction of the non-renewable energy needs in buildings, already developed in the last decades, deeper architectural integration is needed, also considering on cost and assembly process optimization to ensure wide market adoption. In this context, two main trends appear: Integration and hybridation of solar systems in building envelopes. Integrated solutions are created when modular and dimensionally variable glazed collectors are integrated in curtain wall structures or in external cladding systems. Hybrid solutions such as External thermal insulation systems and sandwich panels are generated where unglazed collectors are integrated as part of renders, claddings, etc. to obtain neutral aesthetical impact. Architectural, constructional and thermal results are discussed, not only based on design assessments, but also on manufacture, assembly and assessment results from experimental data.
Young's modulus as well as solid thermal and electrical conductivitiy of aerogels have been observed to scale with density. No quantitative explanations were available up to now for these experimental findings. To establish a quantitive relationship between morphological and topological features of fractal gel networks, a simulation procedure is introduced that allows to produce three-dimensional gel structures, from which two important parameters can be extracted: i) the fraction α of interconnected mass of the gel network and ii) the ratio γ of Pythagorean distance to minimum path length on the gel backbone. Surprisingly the product α γ , which enters important macroscopic parameters such as elasticity or solid thermal (and electrical) conductivity, was found to scale with an exponent that is only a function of the mass fractal dimension D. Also, an analytical relation between modulus and conductivity can be derived.
A key aspect in assessing the thermal standard of building envelopes is the quantification of the heat loss though thermal bridging, which can be expressed in terms of the linear thermal transmittance Ψ. Values of Ψ may be obtained from tabulated values for standard building details, from numerical modelling or from measurement. Where the internal structure of the building envelope is unknown, which is very often the case, measurement is the only option. This study shows how the infrared thermography technique (ITT) can be used as a non-invasive and easy-to-use method to provide quantitative measures of the actual thermal bridging performance. The novelty of this approach includes evaluation of the actual heat flow rate caused by thermal bridge qTB and Ψ-value by means of the ITT solely, without any supporting methods. Another important aspect of the methodology is that it accounts for the correlation between the surface temperature and the convective and radiative heat transfer coefficients. Values for these coefficients are assessed for the whole range of the surface temperatures recorded on the thermogram resulting in improve accuracy. The qTB and Ψ-value calculated using the presented methodology fully mirrors the real thermal performance of the thermal bridge. The methodology has been tested under laboratory conditions in a steady state in a hot box with excellent agreement.
The aim of the first subtask of IEA EBC Annex 58 was to give an overview and evaluation of previous and ongoing in situ test activities based on a literature review and existing reports. An inventory was made of full scale test facilities for the evaluation of energy performances of building components and systems, available at different institutes all over the world. The book gives a description of 25 existing test facilities or test sites according to their main functionalities: objectives, lay-out of the infrastructure, typical equipment and operation, examples of measuring campaigns and analysis methods. The descriptions were provided by the participants of IEA-Annex 58. The inventory provides examples and background to building researchers responsible for the design and construction of new test facilities or for the management of existing ones.