Thermal and structural performance of a new fiber-reinforced polymer thermal break for energy-efficient constructions

The thermal bridges constitute critical regions in building envelopes and they are created due to the interruption of the insulation layer. One of the many structural thermal bridges in building envelopes is created in balcony junctions because of the required structural continuity of the concrete slab. The detrimental effects of such thermal bridges are minimized, by using thermal breaks that interrupt the heat flow towards the external environment by adding an intermediate insulation layer between the internal floor and the balcony slab. For the majority of these thermal breaks, the load transfer from the balconyâs cantilever to the main structure occurs through stainless steel bars, which penetrate the insulation layer and still have a high thermal conductivity. The current research proposes a new thermal break composed of fiber-reinforced polymer composite materials (FRP) that have much better thermal properties than the conventional materials and investigates its short- and long-term structural and thermal behavior. The tensile force from the cantilever moment is transmitted by an aramid-FRP (ARFP) loop, whose thermal conductivity is about 170 times smaller than that of stainless steel. The compression component of the moment is transferred by a short glass-FRP (GFRP) element while the shear compression diagonal is transmitted by a FRP-PU hexagonal foam sandwich. The insulation layer is composed of a thin layer of aerogel granulate. All the components are assembled in a polymer box. The thermal performance of the above-mentioned thermal break was validated by estimating its impact on the energy balance of a traditional building, using three different building envelopes (a MINERGIE envelope, a MINERGIE-P envelope and an optimum envelope). Furthermore, 3d finite element steady-state thermal simulations were performed in order to define the true losses through the optimized thermal break. Finally, the thermal behavior of the thermal break was compared with that of traditional thermal breaks. The structural validation of the FRP thermal break included the mechanical characterization of the components through static, long-term and durability experiments. The static experiments of the components comprised tensile experiments (AFRP loop) and compression experiments (FRP-PU hexagonal foam sandwich and GFRP bar). The long-term behavior was evaluated through tensile and compression creep experiments, while its simulation and prediction were achieved by applying traditional creep methods and two new proposed models that were able to predict the secondary creep stage (Gradient regression and Gradient regression with NHPP). The durability was evaluated by their immersion in alkaline environment, simulating that of the concrete. Finally, the total behavior of the balcony junction was examined through full scale beam experiments that led to the analytical modelling of the system

Energy saving potentials in historic buildings’ renovations ::to which extent is the heating demand limit value (SIA 380/1) reachable and at which costs?

The renovation of historic buildings is essential to meet the Swiss objectives for energy consumption in 2050. These buildings offer a great saving potential, however, the heritage preservation has to be considered in the renovation scenarios. While essential for the historic conservation, this consideration restricts the renovation possibilities to achieve the heating demand requirements according to the SIA 380/1 standard. This study introduces a framework for identifying the suitable historic buildings’ renovation schemes considering life cycle costs, energy and life cycle environmental impacts. With a case study, the feasibility of achieving the energy performance SIA 380/1 standard is then discussed

Aramid/glass fiber-reinforced thermal break - thermal and structural performance

Energetically weak points in thermally insulated building envelopes are formed by thermal breaks that are implemented to structurally connect external balconies to internal slabs. Current thermal breaks comprise stainless steel bars that penetrate the insulation layer and thus cause significant thermal losses. A new thermal break composed of highly insulating aramid and glass fiber-reinforced polymer ( AFRP and GFRP) components and aerogel granulate insulation materials was developed and the first prototypes of the load-bearing components were experimentally investigated. The use of AFRP leads to an excellent thermal performance with linear thermal transmittance values of below 0.15 W/m K. The experimental prototype investigations confirmed the targeted ductile failure mode through concrete crushing in the component-concrete interfaces. The serviceability limit state conditions are met for a targeted balcony cantilever span of 4.0 m. The material-tailored components can be manufactured by fully automated processes such as filament and tape winding and pultrusion to economically produce large quantities within a short time. (C) 2015 Elsevier Ltd. All rights reserved

Aramid/glass fiber-reinforced thermal break - Structural system performance

Energetically critical points in thermally insulating building envelopes are caused by penetrations of building interior concrete slabs through the envelope insulation layers to create external balconies. A new highly insulating balcony thermal break element has been developed which enables both structural continuity and thermal insulation in the envelope's insulation layer. The element is composed of combined structural and thermally insulating AFRP/GFRP loop and sandwich components. The system behavior of the thermal break embedded between a building interior and an exterior balcony concrete slab has been investigated. The experimental results obtained for full-scale concrete beams showed that a statically determined truss model can be used to calculate the section forces in the thermal break components. The balcony deflections can be estimated by adding the deflections caused by a concentrated rotation in the thermal break to those of a continuous concrete slab. The failure modes are ductile due to prevailing concrete failures. The maximum balcony span of the system is approximately 2.5 m and is limited by the anchoring resistance of the AFRP loops in the adjacent concrete slabs. (C) 2016 Elsevier Ltd. All rights reserved

Hygrothermal assessment of historic buildings' external walls ::preliminary findings from the RIBuild project for Switzerland

To meet the national regulation on building energy needs while preserving the architectural heritage, the renovation of protected historic buildings implies to insulate internally their facades. However, it is a technically risky solution. This work is part of the European project RIBuild that develops guidelines to ensure moisture-safe solutions. For that purpose, historical buildings were monitored to confront the current state-of-the-art of hygrothermal simulations with in-situ measurements. To enforce these calculations, stones used in Swiss traditional construction were characterised, and materials' modelling were investigated. The results of the study will be integrated into a probabilistic web-tool

Development of a service life database of building elements based on an international data collection

This paper presents a new service life database (DUREE database) for building elements, based on international service life data. The database includes 7‘000 service life data, for more than 2‘000 building elements. In addition, the fitting of the data to a lognormal distribution is presented. The study contributes to the increasing demand of probabilistic building LCA and LCC and provides the possibility to define statistical distributions, with a systematic way, for a large number of building elements and different levels of details (LOD), appropriate for BIM-based assessments

Uncertainty of building elements’ service lives in building LCA & LCC ::what matters ?

The existing methods of evaluating the environmental life cycle assessment (LCA) and life cycle costs (LCC) performance of a building concept have been widely used, since they offer the possibility to consider the system globally and avoid, thus, the hidden impacts. However, many studies have indicated the possible uncertainties of the input parameters and recommended the use of probabilistic methods, to deal with these issues. The current study continues towards this direction and presents a systematic way to take into account the uncertainties of the building elements’ service life within a stochastic framework, by defining the corresponding probability density functions, based on a new service life database. Applying this methodology for the calculation of the LCA & LCC for multifamily houses in Switzerland revealed that the replacement stage contributes with a share of up to 36% on the GHG emissions. Furthermore, through a global sensitivity analysis, the uncertainty on the replacement rate of six building elements was found to mainly influence the LCA & LCC uncertainty, i.e. compact façade (external insulation), windows, roofing, flooring, internal layout and ceiling covering. Finally, it was found that the reference service life of the building significantly influences the LCA and LCC uncertainty. In order to increase the reliability on the building LCA and LCC results, it is recommended to take into account probabilistically the service lives of the building elements, which mostly influence the LCA uncertainty

Uncertainty and sensitivity analyses for evaluating the building element's replacement in building LCA

This paper presents a systematic way to consider the uncertainties of the building elements’ service lives within a stochastic framework, by defining the corresponding probability density functions, based on a service life database. This methodology is appropriate for screening and detailed building LCA, since the service life database offers the possibility to define the probability density functions of the service lives, in different level of details

Thermal performance evaluation of fiber-reinforced polymer thermal breaks for balcony connections

The potential effects of high-performance fiber-reinforced polymer thermal breaks for balcony connections on the thermal losses and heating needs of a typical residential building in Switzerland were investigated. In an optimized form, these new thermal breaks have a linear thermal transmittance of psi <= 0.10 W/mK.The reduction of the total transmission losses via these optimized thermal breaks through the building envelope remained modest. If however losses through the thermal bridges are related to those through the opaque envelope elements only, the latter were reduced by up to 18% for an optimum envelope. If furthermore these losses are related to the heating needs of a building with an optimum envelope, their magnitude is reduced by 41% if psi is decreased from 0.30 (recommended value from SIA) to 0.10 W/mK. In attempting to approach the goal of zero-energy buildings with zero heating needs, the thermal losses through thermal breaks can thus have a significant effect. (C) 2013 Elsevier B.V. All rights reserved