Additional Insulation Research Articles

Microvascular Decompression for Glossopharyngeal Neuralgia: Clinical Analyses of 30 Cases.

ObjectiveWe present our experience of microvascular decompression (MVD) for glossopharyngeal neuralgia (GPN) and evaluate the postoperative outcomes in accordance with four different operative techniques during MVD.MethodsIn total, 30 patients with intractable primary typical GPN who underwent MVD without rhizotomy and were followed for more than 2 years were included in the analysis. Each MVD was performed using one of four different surgical techniques: interposition of Teflon pieces, transposition of offending vessels using Teflon pieces, transposition of offending vessels using a fibrin-glue-coated Teflon sling, and removal of offending veins.ResultsThe posterior inferior cerebellar artery was responsible for neurovascular compression in 27 of 30 (90%) patients, either by itself or in combination with other vessels. The location of compression on the glossopharyngeal nerve varied; the root entry zone (REZ) only (63.3%) was most common, followed by both the REZ and distal portion (26.7%) and the distal portion alone (10.0%). In terms of detailed surgical techniques during MVD, the offending vessels were transposed in 24 (80%) patients, either using additional insulation, offered by Teflon pieces (15 patients), or using a fibrin glue-coated Teflon sling (9 patients). Simple insertion of Teflon pieces and removal of a small vein were also performed in five and one patient, respectively. During the 2 years following MVD, 29 of 30 (96.7%) patients were asymptomatic or experienced only occasional pain that did not require medication. Temporary hemodynamic instability occurred in two patients during MVD, and seven patients experienced transient postoperative complications. Neither persistent morbidity nor mortality was reported.ConclusionThis study demonstrates that MVD without rhizotomy is a safe and effective treatment option for GPN.

Techno-economical Analysis based on a Parametric Computational Evaluation for decision process on envelope technologies and configurations

Energy saving is crucial for existing buildings which is present a huge potential of improvement by a strong energy retrofitting. Often, the existing envelope components are not adequately insulated and deep refurbishment is required to comply current regulations to improve energy efficiency and address Nearly Zero Energy Building (NZEB) goals. The strategies to enhance buildings energy performance involve heating and cooling demands strongly dependent by envelope quality (i.e. insulation, thermal mass, internal gain storage capacity and solar heat gains exploitation). Commonly, the suggested main retrofit interventions on envelope are glazed surfaces replacement, Solar Heat Gain Coefficient (SHGC) reduction and thermal transmittance (U value) improvement by additional insulation layers or even components replacement. However, it is worthy to note that the resulting thickness of the external envelope and the payback time of the interventions are important supports for decision-making. The environmental issue related to CO2 emissions during the operational phase of the building is encompassed into the standard energy certification of the asset and the conversion factors to define fuels’ impacts are available and updated. However, the calculation excludes the environmental impact due to energy used for materials’ production and few official information sources provide accredited values, e.g. the Environmental Product Declaration (EPC). Going towards a Zero Energy Building, which reduces its environmental impact during the running phase, embodied energy claims an increasing weight. Thus, materials and components with low embodied energy should be favoured and endorsed. For this reason, the most influential rating systems worldwide available for building sustainability assessment (e.g. LEED, BREEAM, etc.) updated their checklists including criteria related to reduced energy for extraction, production and materials transportation on the field.The technological optioneering of envelope solutions to achieve both energy efficiency and economic affordability is inevitably based on and supported by multicriteria assessment frameworks. These frameworks should include energy, environmental and economic parameters to define the technological suitability in different climate conditions identifying accurate optimization points, e.g. thickness of the insulation layer or heat storage capacity, considering energy saving and management costs in the life cycle. When actual optimization processes are required, computational parametric tools support to ease the options’ performance comparison and to compute different combinations. Nowadays some tools are available into the main authoring software on the energy simulation market. Although different tools could be adopted, the need of transparency and custom workflows is crucial. In the present research, a specific multi-criteria methodological approach enables to outline a synoptic diagram for each considered climate to compare the envelope technological solutions by aggregating LCA (Life Cycle Analysis) and LCC (Life Cycle Cost) factors. For LCA, Embodied Energy (EE) of the envelope materials and Primary Energy (EP) used during the running phase have been considered. For LCC Investment Cost (C) of the materials to enhance a baseline performance and related operational costs of the building based on Net Present Value (NPV) and Discounted Payback Period (DPP) have been adopted.The present study focuses as first on the construction coherency of different technologies used to define the external envelope of a test room, able to manage the energy flows resulting from different external conditions. Subsequently the definition of the technological basket, a parametric analysis based on reducing thermal losses and increase solar gains has been performed defining the most suitable technologies and façade configuration in three representative climate conditions at national level by calculating heating and cooling demand and related primary energy.

Analysis of heat-conducting inclusions in exterior walls of residential building

The study is aimed at detecting the zones of major heat losses in exterior walls of residential buildings and developing recommendations on their elimination. The “ELCUT” software program calculated the temperature fields of the external wall under the design temperature of the outside air. The calculation was carried out for three options: the thermal characteristics of the materials of the layers of the outer wall correspond to the design parameters; thermal characteristics of the materials of the layers of the outer wall correspond to the actual measured values; Thermal technical characteristics of the materials of the layers of the outer wall correspond to the actual indicators and additional insulation is made. It is established that with additional insulation, the irregularity of the temperature field on the external surface of the wall is eliminated and normalized thermal resistance complies with the requirements.

Habitat characteristics of the hoary marmot: assessing distribution limitations in Montana

AbstractSpecies that live in ecosystems with extremely different seasonal conditions must balance the constraints of each season to survive. Alpine species that do not migrate seasonally are especially adept at balancing the constraints created by short growing seasons and long, harsh winters. We investigated the habitat characteristics of hoary marmots in western Montana to provide a better understanding about habitat selection at the southern extent of this species’ distribution. Hoary marmots are an alpine obligate of special concern in western Montana; given that climate change is impacting alpine ecosystems at a rapid rate, this species may be especially vulnerable at the southern edge of their range. We conducted occupancy surveys in three study areas along a latitudinal gradient in 2014 and 2015 to assess the importance of specific habitat characteristics to their presence on the landscape. Slope, aspect, and presence of shrubs were all important habitat characteristics. Marmots preferred shallow slopes and southern aspects, similar to findings from other studies on hoary marmots and other marmot species. Our results provide evidence that marmots may strike a balance between the environmental conditions they require during summer and winter. Shallow slopes typically accumulate deeper snow in winter that provide the best insulating snowpack. However, a preference for southern aspects allows for more snow‐free areas in spring, providing a slightly longer growing season than northern aspects. Hoary marmots may be selecting areas with shrubs because shrubs can accumulate deeper snow and the additional insulation can increase subnivian temperatures. Other studies suggest that marmot survival is influenced by snowpack, indicating that marmot distribution may be more closely tied to winter conditions rather than summer conditions. This highlights the difficulty of working on marmots and other alpine obligates, as most studies occur only during the short growing season. Given the current and projected increases in temperature and reduction in snowpack in Montana, areas that provide the winter conditions hoary marmots require may become more limited. Effectively conserving, monitoring, and managing alpine obligates under an uncertain climate future will require a closer look at how winter conditions drive habitat selection and distributions on the landscape.

Impact Verification of Aerogel Insulation Paint on Historic Brick Facades

Increasing the sustainability of existing buildings is being motivated by reduction of their energy demands. It is the above all the building envelope and its refurbishment by substitution or addition of new materials that makes the opportunity for reduction of energy consumption. A special type of refurbishment is conservation of historical buildings. Preservation of historic buildings permits also application of innovative methods and materials in addition to the original materials if their effects are known and the gained experience ensures their beneficial effect. On the market, there are new materials with addition of silica aerogel in various forms of products. They are also potentially useful in conservation of monuments. However, the effects of aerogel application in these cases are not known. For refurbishment is commercially available additional transparent insulation paint - Nansulate Clear Coat which is containing aerogel and can be used for structured surfaces such as bricks. A series of experiments examined the thermo-physical manifestation of an ultra-thin insulation coating of Nansulate Clear Coat containing silica aerogel on a brick facade. The experiments of active and passive thermography have observed effects of application on the small-scale samples of the brick façade of a protected historical building. Through a series of experiments were measured thermal insulation effect and influence on the aesthetic characteristics such as change in colour and gloss. The treated samples were compared to a reference. Results have shown no thermal-insulating manifestation of the recommended three layers of insulation paint. The three layers recommended by the manufacturer did not significantly affect the appearance of the brick facade. Color and gloss were not significantly changed. Experiments showed the absence of thermal insulation effect of Nansulate transparent triple coating. The thermal insulation effect could likely be reached by more layers of application, which, on the other hand may be unacceptable on the heritage conservation because of number of applications, time demand and financial costs. The effects of multiple layers on heritage attributes were not researched. Extrapolating the measured results, it can be expected that application of more than three layers of paint can significantly affect the aesthetic characteristics of the monument such as gloss and colours of historic brick facades. Due to specific material consistence of historic architecture and new insulation paint materials on the market, it is recommended to provide independent laboratory testing and on-site tests on facades of historic buildings in cooperation with the Monument Protection Board.

Experimental investigations of wooden beam ends in masonry with internal insulation

Today’s stringent requirements on building energy performance and gradually increasing price of energy enforce complex refurbishment measures. Improvement of thermal insulation of building enclosure is the first logical step for climatic conditions of semi-continental climate. Refurbishment of many buildings with cultural value is possible only by accepting additional thermal insulation of external walls from interior side. Floors in such buildings are often supported by wooden beams placed in pockets embedded in brick walls. This paper deals with temperature and relative humidity in the air cavity behind wooden beam ends. To study this phenomena real scale experiments in University Center for Energy Efficient Buildings (UCEEB) of the Czech Technical University in Prague have been monitored for two years. Measured results indicated the fundamental difference between different types of joist pocket treatment. The relative humidity in open pockets approached to 100 % in cold season and corresponding mold growth index reached a maximum higher than one (germination of mold spores). Sealed pockets reached practically zero mold growth index throughout the experiment, although relative humidity in the pocket tended to exceed 80 % during cold seasons.

Achieving a low carbon housing stock: An analysis of low-rise residential carbon reduction measures for new construction in Ontario

Residential buildings contributed 14% of Canada's greenhouse gas emissions in 2014, making this sector pivotal to climate change mitigation. In 2016, the provincial government of Ontario, Canada mandated a net-zero carbon standard for new “small buildings” by 2030, meaning the low-rise residential sector must undergo major changes to meet this target. Through an energy modelling analysis of a typical single-family home in Ontario, this study demonstrates the potential carbon emissions savings of different reduction strategies, including changes to the building envelope and mechanical system. The most effective strategies include increasing building airtightness, installing additional exterior insulation, and switching to an air source heat pump for heating and cooling. These strategies were then analysed based on the incremental cost above a house built to the building code baseline. In terms of cost per kilogram of carbon mitigated, the most efficient strategies are further insulating the basement, adding additional exterior insulation, and increasing the efficiency of the heat recovery ventilator. Finally, a policy discussion demonstrates that carbon reductions implemented at the design stage must be verified and monitored post-occupancy using policy tools such as energy reporting and small-scale performance studies.

Low Density Cellular Concrete Made of Reftinskaya SDPP Fly Ash

There is experience of the production and use of low density autoclaved aerated concrete. It is shown that fly-ash from Reftinskaya State District Power Plant efficiently substitutes the quartz sand aerated concrete technology. Its use opens up additional opportunities for AAC with the density of 300-400 kg/m3. In order to optimize the structure and properties it has been suggested to introduce the gypsum aerated concrete additive into the autoclave in the amount of 3-5% by weight of the dry components. The introduction of gypsum ensures the creation of a uniform homogeneous structure, resulting in the increased strength properties and reduced drying shrinkage. The resulting aerated concrete has thermal conductivity of 0.075-0.100 W/m·K, it allows using and creating single-layer fencing structures without additional insulation. The low-density gas-ash concrete production allows extending the scope of cellular concrete application and increasing its competitive advantages over other walls and insulating materials.

Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction.

We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.

Modeling the costs and benefits associated with the evolution of endothermy using a robotic python.

Endothermy provides considerable benefits to an organism but requires large energy investment. To understand potential driving forces that would lead to the evolution of endothermy, it is important to understand the energy costs and potential benefits of intermediate steps between ectothermy and homeothermic endothermy as well as the influences of environmental conditions on energetic costs. However, efforts to examine intermediate conditions are greatly limited by the predominant natural dichotomy between ectothermy and endothermy. Facultative endothermy by brooding pythons provides a fortunate study system where endothermy is beneficial but not essential. As one cannot control the extent of energy investment in heat production by a female python, we created an artificial snake with controllable heating capability. This enabled us to determine the energetic costs of maintaining a clutch at a preferred temperature, and to determine the relative thermal benefit of limited energy-producing capability (i.e. 50% of the required energy to maintain the preferred developmental temperature). We manipulated the pseudoserpent's clutch size (5, 10, 15 eggs), diel ambient temperature cycle (2, 4, 6°C) and insulation (with and without) at each of these power levels: unlimited power, half required power and no power. We found no significant effect of clutch size on either power requirements or developmental temperature. Energy requirements increased with the amplitude of the diel cycle and decreased with the addition of insulation, while the quality of the thermal environment decreased with the amplitude of the diel cycle. Interestingly, the quality of the thermal environment also decreased with the addition of insulation. We discuss these results within the context of the reproductive model of the evolution of endothermy.

Final energy savings and cost-effectiveness of deep energy renovation of a multi-storey residential building

In this study we present a method for analysis of cost-effectiveness of end-use energy efficiency measures and demonstrate its application for modelling a wide range of energy renovation measures for a typical 1970s multi-family building in Sweden. The method integrates energy balance and bottom-up economic calculations considering total and marginal investment costs of energy efficiency measures as well as net present value of total and marginal savings of the measures. The energy renovation measures explored include additional insulation to basement walls, exterior walls, and attic floor, improved new windows, efficient electric appliances and lighting, efficient water taps, glazed enclosed balcony systems, and exhaust air ventilation heat recovery systems. The measures are analysed first individually and then designed to form economic packages. Our results show that improved windows give the biggest single final energy savings while resource-efficient taps is the most cost-effective measure for the building. We find that the cost-effectiveness of the energy renovation measures is sensitive to real discount rates and energy price increases. Cost-optimal final heat savings varies between 34% and 51%, depending on the choice of real discount rate and energy price increase. The corresponding electricity savings varies between 35% and 43%. This study shows a method and the significance of various technical and economic-related parameters in achieving deep energy savings cost-efficiently.

(Invited) Carbon Nanotubes from Synthesis, Assembly to Electrochemical Sensors

The unique physical properties of individual Carbon Nanotubes (CNTs) surpass the properties of many advanced materials available today. Due to their large surface area, chemical stability, and electrical conductivity, they are the most promising candidates for a large number of electroanalytical applications. A material for these applications requires high purity CNT assemblies like fibers and films, that have good electrical conductivity, in some case additional insulation coatings. This talk will report the synthesis of catalyst free CNTs, their assembly into ribbons at 15.9 m/s speed, fiber processing and polymer coating into a micro-cable format. CNT micro-cable was used for detection of toxic metals contaminants in H2O, that are considered as the most significant potential threats to human health by ATSDR and EPA. Polystyrene coated CNT fiber was used as the working electrode; bare CNT thread was used as the auxiliary electrode; and a pseudo-reference electrode was fabricated by electroplating CNT fiber with Ag that is subsequently anodized in chloride solution to form a layer of AgCl. The Ag/AgCl coated CNT fiber electrode provides stable potential comparable to the conventional liquid-junction type Ag/AgCl reference electrode, while bare CNT fiber auxiliary electrode provided a stable current comparable to a Pt wire auxiliary electrode. This all-carbon CNT fiber three electrode cell is evaluated for simultaneous detection of trace levels of heavy metal ions by anodic stripping voltammetry (ASV). Hg2+, Cu2+ and Pb2+ in H2O were detected successfully, and the detection limits are 1.05 nM, 0.53 nM and 0.57 nM for Hg2+, Cu2+ and Pb2+, respectively. These electrodes significantly reduce the dimensions of the conventional three electrode electrochemical cell and have the potential to become low cost and disposable sensor.

Evaluating flashover performance of insulators under fire fighting conditions

EHV and UHV high voltage transmission lines frequently pass through high vegetation areas as well as national forests where there is a significant risk of wildfire by natural or manmade causes. Firefighters use aerial vehicles to douse fires by dumping large amount of fire retardant liquid that is conductive, thus increasing the risk of insulator flashover and power interruptions. In this paper, an ammonium polyphosphate based fire retardant liquid was evaluated to understand its effect on insulator flashover properties. Composite and ceramic insulators, suitable for 115 kV transmission lines, were studied by the solid layer test method. Tests were conducted with and without external wetting by fog. Results indicate that there is a high probability of flashover if the entire insulator is coated with the fire retardant liquid. Statistical methods were applied to extend the validity of testing results to predict flashover voltages at higher voltage levels of 230, 345 and 500 kV. It is shown that standard insulator dimensions used for EHV and UHV lines in fire prone areas could be deficient and additional insulation required to improve the flashover performance to acceptable levels in such locations has been determined.

Environmental assessment of deep energy refurbishment for energy efficiency-case study of an office building in New Zealand

The purpose of this study was to determine the environmental impacts associated with a deep energy efficiency refurbishment using life cycle assessment. A prototypical refurbished model of an office building located in Auckland, New Zealand was used as a case study. The refurbishment included major changes to the building envelope with additional insulation, modified wall-window ratio, solar shading as well as technical replacement of the lighting and HVAC system. The study included identification of environmental hot spots of a deep energy refurbishment, and consideration of the effect of different electricity mixes in New Zealand on the total environmental impact of the refurbished building when compared to the un-refurbished existing building over different operation periods. An environmental payback period was calculated for each impact category. The results of this study indicate that deep energy refurbishment is associated with significant environmental impacts mainly due to the use of energy-intensive construction materials. However, the refurbishment yields net reductions in most impact categories if the building has a longer operational period. The environmental impacts of a building's operation are mainly associated New Zealand's electricity generated from coal. As future scenarios of New Zealand's electricity mix have a reduced share of electricity generated from coal, the environmental benefits of avoided electricity consumption are also reduced. The study concludes that measures to promote energy efficiency refurbishment in office buildings where a significant proportion of the operational energy is provided from renewable energy sources, should be carefully considered because they may not reduce overall environmental impacts.

Prediction of temperature distribution in a horizontal high pressure food processing vessel and its impact on process uniformity

The temperature distributions in HPP vessels should be of particular concern for pressure assisted thermal sterilization (PATS) processes because in PATS temperature plays a major role in microbial inactivation. Numerical simulations were carried out to predict thermal transport in a horizontal HPP vessel with and without insulation. The results showed that the temperature of water added to compensate for the compression of water in the pressure vessel and the addition of insulation on the inner surface of vessel had significant impact on the temperature distribution and on the predicted inactivation of Clostridium botulinum spores. It was concluded that adding insulation to the vessel lead to higher temperature levels but more non-uniform temperature distribution as compared with without insulation. It was also observed that the water added to compensate for compression did not impact the flow pattern in the vessel significantly due to low inlet velocity but the temperature of added water had a significant impact on the temperature and Clostridium botulinum spore inactivation distributions. The temperature distribution was close to uniform when the temperature of the inlet water was the same as the initial temperature for the process. Practical applications The results obtained from this research will be useful in the evaluation of process performance in terms of process validation and process filing with regulatory agencies to develop guidelines for producing high pressure processed foods using PATS, which are safe to consume. The results will also be important for food processors and equipment manufacturers to understand the effects of non-uniform thermal treatment on foods processed using PATS.

Reducing thermal energy demand in residential buildings under Spanish climatic conditions: Qualitative control strategies for massive shutter positioning

The effects of dynamic controls on external massive shutter positioning are studied as refurbishment measure to reduce energy demand in residential buildings. This kind of shading device can not only regulate solar radiation, but it also provides additional thermal insulation that reduces heat conduction when closed. Based on their capability for controlling both processes, a comparison of different qualitative shutter positioning control strategies are proposed to minimize thermal energy demand. To this aim, a simulation model based on the constructive characteristics of an experimental building has been developed with TRNSYS. The results show that when more input variables are considered greater thermal demand reduction is achieved. However, the most relevant input variables for reducing thermal demand are solar radiation and real demand of the building. A large reduction in thermal energy demand is also displayed in the comparison between massive shutters, and non-massive blinds, increasing from 23% to 35%. Surprisingly, this improvement can be achieved using simple radiation-based control strategies, whereas the inclusion of heat conduction as control variable only improves the results by 0.2%. Therefore, there is no need to increase the complexity of the shading control of the massive shutters to take advantage of their insulation properties. The thermal energy reduction is comparable to the effect of refurbishment of an ordinary double-glazed window (U=2.46 W/(K·m2)) with high-efficiency triple-xenon glazing (U=0.59 W/(K·m2)).

Development of a device providing resource-saving start-up of induction motors under reduced voltage

Electromechanical and thermal transients at start-up of squirrel-cage induction motors in reduced voltage conditions are the object of research. One of the most troubled places in these processes is sufficient difficulty diagnosing of resource consumption of induction motors with heavy start-up in reduced voltage conditions and timely facilitation of such regimes with a view to resource saving. To determine the diagnostic parameters of starting modes for induction motors at reduce of supply voltage it is necessary to identify the dependence of start-up duration depending on the parameters of the «motor – working machine» system and their impact on the thermal insulation wear in motor during period after start-up. Therefore, the main way to increase the operational reliability of induction motors is to develop technical device for diagnostics of additional thermal insulation wear in induction motor. We use such methods as: analysis method and mathematical modeling method. It is grounded that pulse of squared starting current can take as diagnostic parameter of additional thermal insulation wear of induction motor. Investigation of thermal insulation wear shows that the thermal transient at the start-up is adiabatic. Main thermal insulation wear is during period after start-up. The dependence of additional thermal insulation wear on the pulse of squared electric current of induction motor allows to select pulse set point of squared starting current of proposed device, which will facilitate the starting mode of the motor. A structural diagram of the device for diagnostics of additional thermal insulation wear in squirrel-cage induction motor during period after start-up is proposed.

Study of heat shielding qualities of brick wall angle with additional insulation located on the outside fences

The results of theoretical studies of heat-shielding properties of the angle of external wall a residential building are presented. The brick wall thickness of 510 mm was considered. The studies were performed for the I-st temperature zone of Ukraine. Heat insulation was located on the external side of enclosure. Thermal protection problems of the angle are consideration of the impact of heat-conductive inclusion on adjusted heat transfer resistance of enclosure. Conductive inclusion on the external angle area is its configuration. An additional layer of insulation in the angle area is necessary to use for bringing the level of thermal protection of angle area to the standards. The results of calculations of two-dimensional temperature fields were used for the analysis of thermal protection. Two options for additional insulation were studied. The first option: continuous strip insulation covering the external wall angle. Another one provides division of additional insulation layer into two parts and displacement them from the angle within the design scheme. Studies were performed for different thickness of additional insulation. There was additionally taking into account the value of insulation displacement from the angle for the second option. The optimal location and size of additional insulation were determined. The minimum amount of additional insulation under which the thermal protection requirements are performed was accepted like optimality criterion.

Prefabrication as Large-scale Efficient Strategy for the Energy Retrofit of the Housing Stock: An Italian Case Study

In this work a multi-story residential building located in Cinisello Balsamo, near Milan, was considered as case study for the application of two new prefabricated building systems for the energy retrofit. The first one, developed within EASEE, a European project funded by 7th Framework Program, consists in a preassembled insulated panel for the retrofit of facades, based on two TRC thin precast layers rigidly connected to an EPS core. The panels can be easily applied on the external side of existing facades without the use of scaffoldings, providing an additional efficient insulation as well a new external cladding. The second one consists in a preassembled timber panel for existing pitched roofs. The process includes the substitution of the existing roof with modular integrated panels with a high content of recycled materials that can be easily fixed on the existing structures (timber frames, concrete, masonry, etc.). The combination of the two prefabricated construction systems, applied on the case study, allowed the reduction of the building energy demand by 82%.

Numerical evaluation of natural vibration frequencies of thermo-modernized apartment buildings subjected to mining tremors

Prefabricated, with load-bearing walls, apartment buildings represent a significant group of objects, especially occurring in the countries of Central and Eastern Europe. They were built in 50’s, 60’s and 70’s of 20th century. Nowadays, the new European Union environmental regulations forced such buildings’ modernization, mainly regarding energy efficiency. Usually, in order to improve their energy properties and, as the result, to reduce the energy losses, the external walls thermal insulation is performed. This is one of the fastest and cheapest method increasing the thermal resistance of walls of buildings constructed using relatively old technology. Extra thermo-modernization layers of the prefabricated walls (consisting of materials such as styrofoam, reinforced mortar, glass fibre textile mesh) bring additional mass to the building and could change its stiffness. The dynamic properties of the structure could be changed as the result. Changes in the natural frequencies of vibrations are the most important among them–calculations of these values are necessary especially in the case of buildings located in paraseismic or seismic areas. In the paper the influence of the additional multilayer thermal insulation of the external walls on the natural vibration frequencies of high (12 storey) actual apartment buildings subjected to mining tremors is investigated. Numerical calculations were carried out using finite element method software. Various approaches to the modelling of prefabricated load bearing walls before and after thermo-modernization were analyzed and discussed. A simple one layer model of walls with equivalent stiffness as well as multi-layer one were taken into consideration. Finally, the simple model reducing multi-layer panel to one layer panel with equivalent (substitute) Young modulus and equivalent (substitute) Poisson’s ratio was recommended for the practical calculations of the dynamic properties of buildings. Numerically evaluated natural vibration frequencies of the buildings before and after thermo-modernization were verified by the experimental data obtained for actual structures.