Showing papers in "Journal of building engineering in 2015"

How many interviews are enough? Do qualitative interviews in building energy consumption research produce reliable knowledge?

Abstract: Research in building energy consumption often uses semi-structured interviews to produce qualitative data on consumer beliefs, attitudes, practices and skills. A survey of 54 recent papers in six prominent building and energy journals shows that the samples are typically small, but inferences are often made for interventions in the light of the findings, on the assumption that these are somehow transferable to wider populations. It is often asked ‘how many interviews are enough’ to produce reliable results. Theoretical literature on this theme has avoided a straightforward statistical critique, and justified the practice with appeals to precedent, the special nature of qualitative personal data, and a limited pool of empirical work. This paper reviews this literature and presents a statistical approach, based on binomial logic, to critiquing and supporting the practice of semi-structured interview research in the building and energy field. The approach developed offers a set of straightforward criteria which researchers can use to estimate the reliability of their findings and inferences from the qualitative data produced in semi-structured interviews.

Role of water/cement ratio on strength development of cement mortar

Abstract: The effect of water/cement ( w / c ) ratio on the mechanical properties such as compressive strength and split tensile strength of cement mortar cylinders and cubes was investigated experimentally for 28 days curing period as per IS standard. Based upon the experimental results, empirical equations have been developed to predict the strength of cement mortar mixes with various w / c ratios. It is observed that Abrams’ law is applicable for the cement mortar also. The cement mortar contains varying proportions of portland pozzolana cement (PPC) and river sand such as 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 with different w / c ratios. An empirical equation has been developed between split tensile strength and compressive strength of cement mortar. Results show that compressive strength and split tensile strength of cement mortar decreased with an increase in the w / c ratio. It is observed that minimum w / c ratio required to make the cement mortar workable is 0.5.

Assessment of the progress towards the establishment of definitions of Nearly Zero Energy Buildings (nZEBs) in European Member States

Abstract: The European Climate and Energy package foresees a substantial reduction of energy consumptions in buildings by 2020 The implementation of Nearly Zero Energy Buildings (nZEBs) as the building target from 2018 onwards represents one of the biggest challenges to increase energy savings and minimize greenhouse gas emissions The aim of this paper is to provide an overview of the European status towards the implementation of nZEBs The main open issues are presented together with categories, definitions, and calculation methodologies The paper reports the progress made by Member States (MS) towards the adoption of nZEBs definitions through the analysis of the available literature, National Plans, templates submitted to the Commission, as well as information from the EPBD Concerted Action (CA) and Energy Efficiency Action Plans (NEEAP) Different aspects to be outlined, such as balance, boundary, energy uses, and renewables are taken into account in the study Results show that progress is evident in many MS compared to first attempts to launch a national definition, but coherency cannot yet be found The current situation is discussed to contribute to the clarification and the establishment of agreed definitions The paper underlines the effort to integrate the nZEBs notion into National Codes and International Standards It also shows how this topic has gained a growing attention in the last decade, but the achievement of a common nZEBs concept is still far to be reached and implemented into construction practices and routines, especially at a refurbished level

Performance requirements for electrochromic smart window

Abstract: To accomplish specific energetic and environmental tasks in buildings large area electrochromic windows must exhibit acceptable levels in specific performance indicators. These parameters concern a number of electrical, thermal and optical properties which depend on the structural composition and configuration of the electrochromic device. In this paper a comprehensive and systematic analysis of the optimal performance requirements of electrochromic windows from the perspective of building energy efficiency and indoor comfort has been carried out. A comparison with the performance of a home-made fully solid-state electrochromic device tested in laboratory controlled conditions and of large-area electrochromic glazing currently available in the market is also made. The study points out the actual potential of the electrochromic technology for smart window applications and identifies some desirable performance improvements for optimizing building integration.

Role of building material in thermal comfort in tropical climates – A review

Abstract: Changing climatic scenario and raising temperature is likely to subject nearly 60% of the working populations in India to thermal discomfort in their workplaces. Half of the total energy produced in the developed world is used to heat, cool, ventilate and control humidity in buildings, to meet the increasing thermal comfort demands of the occupants. Indoor workplaces many times cannot offer thermal comfort to workers attributable to the location, processes involved and resource constraints that may pose a negative effect on worker's health, their ability to function effectively and also on their work productivity. In most situations, mechanical cooling devices offer solutions that are neither environment friendly nor energy sustainable. These mechanical devices are non-functional and cannot offer thermal comfort without energy input. Hence utilization of advanced building materials and passive technologies in buildings may offer the solution for thermal comfort demands, substantially reduce the energy demand, impact on the environment and carbon footprint of building stock worldwide. This also could offer a sustainable solution in the context of predicted raising temperatures and constraints in energy availability especially in the developing world. The review particularly identified certain materials such as VIPs, PCMs, ACC, polymer skin, with good thermal properties with a potential to be incorporated in different parts of the building envelope to enhance thermal comfort. Light colored external surfaces, reflective paints, window treatments and roof gardens are also discussed as preferred options to help reduce the heat load of the building.

Reducing embodied carbon during the design process of buildings

Abstract: To achieve low-carbon buildings, or buildings with low greenhouse (GHG) emissions, planning must begin during the design phase of a building project This paper evaluates the current methods as support for the design of low-carbon buildings and the significance of different design phases from the perspective of embodied carbon Through evaluation of relevant literature, interviews with practicing architects, and a building case study, we recommend to proceed gradually across all design phases for achieving low-carbon building design This should take place in a systematic way that describes the status, coverage, and accuracy of GHG assessments in each design stage Furthermore, we outline the framework with the use of the Royal Institute of British Architects (RIBA) stages of design, and for each stage, we identified the objectives, typical deliverables, and milestones necessary for ensuring carbon efficiency This will require integration of the roles and responsibilities of the relevant stakeholders, including the client, project manager, architect, structural engineer, and Heating Ventilation and Air Conditioning (HVAC) engineer

Understanding barriers affecting the selection of sustainable materials in building projects

Abstract: The selection of sustainable building materials has been identified as an important strategy in the design of a building. Although the sustainability imperative is gaining in importance, there are still major barriers preventing this’‘new style’ architectural practice becoming the norm. This paper examines the major barriers encountered in the selection of sustainable building materials among building construction professionals in Nigeria. A questionnaire survey was developed to capture the perception of construction professionals regarding the significance of the identified barriers as it affects the selection and use of sustainable building materials. Case studies of three completed building projects were conducted with design team to validate the result of the survey. Research results show that perception of extra cost being incurred and lack of sustainable material information are identified as the top barriers to sustainable materials selection. The paper concludes with suggestions and actions that can help overcome these existing barriers.

Energy retrofit of historic buildings: Environmental assessment of cost-optimal solutions

Abstract: This paper describes the implementation of an integrated cost optimality and environmental assessment involving alternative energy efficiency retrofit packages for a building that dates from the beginning of the 20th century. A building typical of the building stock in the centre of Coimbra (located in the central region of Portugal and recently classified as a UNESCO World Heritage Site) was used to illustrate the methodology presented. The results were also analysed for the same building in two other locations. A life-cycle (LC) model was implemented to assess different energy efficiency measures for an apartment. The economic assessment complied with European Directive 2010/31/EU. The results show that the lowest life-cycle environmental impacts were obtained for insulation thicknesses between 50 and 120 mm, which are also cost-optimal. It is also shown that insulation thicknesses of more than 80 mm do not improve energy efficiency or global cost reduction. This paper shows that, even though historic buildings in Portugal do not have to comply with building energy codes, significant energy savings can be achieved for them without changing their historic character. It was also concluded that economic and environmental costs can both be minimised by choosing the most suitable energy efficiency retrofit measures.

An experimental evaluation of prediction models for the mechanical behavior of unreinforced, lime-mortar masonry under compression

Abstract: This paper contributes to the understanding of lime-mortar masonry strength and deformation (which determine durability and allowable stresses/stiffness in design codes) by measuring the mechanical properties of brick bound with lime and lime-cement mortars. Based on the regression analysis of experimental results, models to estimate lime-mortar masonry compressive strength are proposed (less accurate for hydrated lime (CL90s) masonry due to the disparity between mortar and brick strengths). Also, three relationships between masonry elastic modulus and its compressive strength are proposed for cement-lime, hydraulic lime (NHL3.5 and 5), and hydrated/feebly hydraulic lime masonries respectively. Disagreement between the experimental results and former mathematical prediction models (proposed primarily for cement masonry) is caused by a lack of provision for the significant deformation of lime masonry and the relative changes in strength and stiffness between mortar and brick over time (at 6 months and 1 year, the NHL 3.5 and 5 mortars are often stronger than the brick). Eurocode 6 provided the best predictions for the compressive strength of lime and cement-lime masonry based on the strength of their components. All models vastly overestimated the strength of CL90s masonry at 28 days however, Eurocode 6 became an accurate predictor after 6 months, when the mortar had acquired most of its final strength and stiffness. The experimental results agreed with former stress–strain curves. It was evidenced that mortar strongly impacts masonry deformation, and that the masonry stress/strain relationship becomes increasingly non-linear as mortar strength lowers. It was also noted that, the influence of masonry stiffness on its compressive strength becomes smaller as the mortar hydraulicity increases.

Review: reconstruction of 3D building information models from 2D scanned plans

Abstract: 3D digital modeling, Building Information Modeling (BIM) and numerical simulation are widely recognized as essential components of building design support tools, but require a significant amount of digital data to truly achieve their potential. Currently, they are mostly applied in the design and construction of new buildings but rarely in renovation projects, since few digital data are available for the majority of existing buildings. It is therefore urgent to devise reliable and effective approaches to the generation of 3D digital (BIM) models of existing buildings. This recognition is widely shared and has resulted in a substantial amount of research work and significant innovations in various fields: 3D laser scanning, images processing, etc. With the aim of bringing some significant contribution to this state-of-the-art, this paper provides a critical review of the methods and tools for generating 3D building models from 2D drawings, developing along two complementary lines: a wide-spectrum assessment of 3D generation techniques, and a more focused, in-depth review of 2D drawings-based approaches (from image processing to BIM creation and validation). The review follows a well-defined methodology and builds on the work of more than 100 relevant references. It includes substantial discussions to highlight the strengths, weaknesses and preferential applications of the reviewed research works, and provides a research agenda. The study particularly highlights that the state-of-the-art is fragmented: most research works focus on specific, limited steps of the 3D models generation process, but no solution has yet been able to tackle the whole generation chain. An additional conclusion is that the selection of the most effective approach largely depends on the intended application, and on project-specific constraints. Also, the study highlights that significant benefits could be drawn from combining existing approaches.

Thermal analysis by DSC of Phase Change Materials, study of the damage effect

Abstract: This paper deals with an experimental study of Phase Change Materials (PCMs) by DSC and focuses particularly on the influence of PCMs damage on their thermodynamic properties. First, different series of tests were performed on non-damaged PCMs (reference) using different masses and heating rates in order to optimize the choice of the experimental parameters used in DSC test. Accordingly, the specific heats at solid, liquid phases and the latent heats of PCMs were obtained. In addition, a fast approximate approach was suggested for the determination of the heat capacity of PCMs from a direct exploitation of the heat flux curves obtained by scanning PCMs at different heating rates. Finally, damaged PCMs were investigated and their thermal properties (specific heat and phase change enthalpy) were compared to the reference PCMs. It was shown from the obtained results that low heating rates are more suitable for PCMs scanning during DSC measurements in order to ensure a thermodynamic equilibrium within the sample. Furthermore, the results highlighted that damage of PCMs can lead to the loss of their specific heat capacity of about 28% compared to the non-damaged PCMs.

Use of synthetic fibers in self-compacting lightweight aggregate concretes

Abstract: In this work, fiber reinforced SCLWAC (self-compacting lightweight aggregate concrete) mixtures were studied, in which synthetic fibers were used. Eight different SCLWACs were prepared, in which, as aggregates, different combinations of fine and coarse expanded clay were tried, also partially replaced by either quartz sand or aggregate coming from concrete recycling. SCLWACs were characterized at the fresh state by means of slump flow, V-funnel and L-box tests, and after hardening by means of compression, splitting tension and bending tests, and drying shrinkage measurements. Strength class of LC 45/50 was obtained by using synthetic macrofibres when the oven dry density of SCLWAC was about 1600 kg/m 3 , while if the oven dry density of SCLWAC was lower than 1250 kg/m 3 a strength class of LC 25/28 was reached as well. Tensile and flexural strength values were consistent with concrete strength class, while the elastic modulus was quite low with respect to normal weight self-compacting concrete (SCC). The post-cracking behavior of SCLWAC was strongly improved by the addition of synthetic macrofibers, which provided strain-hardening effect similar to that achievable by means of steel fibers, even if characterized by a sensibly lower weight. In conclusion, SCLWACs showed excellent combination of mechanical and functional properties.

Factors governing the development of moisture disorders for integration into building performance simulation

Abstract: Excessive levels of moisture in buildings lead to building pathologies. Moisture also has an impact on the indoor air quality and the hygrothermal comfort of the building's occupants. A comprehensive list of the possible types of damage caused by moisture in buildings is discussed in the present paper. Damage is classified into four types: damage due to the direct action of moisture, damage activated by moisture, damage that occurred in a moist environment and deterioration of the indoor environment. Since moisture pathologies strongly depend on the hygrothermal fields in buildings, integrating these factors into a global model combining heat air and mass transfers and building energy simulation is important. Therefore, the list of moisture damage types is completed with a proposal of factors governing the risk of occurrence of each type of damage. The methodology is experimented on a simple test case combining hygrothermal simulations with the assessment of possible moisture disorders.

Economic and environmental savings of structural buildings refurbishment with demolition and reconstruction - A Portuguese benchmarking

Abstract: Europe is a consolidated continent, characterized by a wide range of ancient buildings that urgently need refurbishments, especially in seismic zones such as Portugal, where structural reinforcement is imperative. However, demolishing and reconstructing also contributes to real estate renovation. In these cases it is simpler to build earthquake safe buildings that comply with current standards of comfort and quality. The question now is whether refurbishment (and what type) is environmentally and/or economically profitable or needed compared with new construction. To answer this question, this work used the life cycle approach in two complementary approaches: a literature review that theoretically compares different LCA works for refurbished and new buildings; and a real LCA and LCC case study for a classified ancient Portuguese building located in Lisbon, where real refurbishment is compared with hypothetical demolition, followed by complete reconstruction on the same site, respecting the same architecture, constraints and demands, and using reinforced concrete and clay brick walls. This issue is very urgent in Portugal, because of its extensive stock of ancient buildings needing refurbishment works. Moreover, there are few studies reporting whether the refurbishment can be economically and environmentally more efficient, according to the Portuguese economic environment. Thus, this study mostly contributes to this debate, first at a national level, and then as a new case study reporting this kind of benchmarking, and its significance is related to the actual results measured at the construction site for the traditional refurbishment works made in Portugal. This comparison showed that structural refurbishment seems to be environmentally more positive. Nevertheless, in the case-study gains were not as high as commonly suggested, mainly because of the massive use of structural steel and shotcrete required for the seismic and structural strengthening of the ancient building. Finally, as far as the economic approach is concerned, this paper concludes that in those conditions rebuilding would make more economic sense than refurbishing. These conclusions indicate that an integrated decision-making process is needed and also stress the development of new financial facilities for refurbishment and, especially, the development of less costly solutions that could save scarce resources and incentives.

A parametric approach for achieving optimum daylighting performance through solar screens in desert climates

Abstract: Daylighting provision gives a significant contribution to the enhancement of the indoor environment. However, in desert climates spaces are exposed to direct solar radiation, leading to a non-uniform daylight distribution and excessive heat gain. The literature proves that the use of a shading device may solve these problems. In this daylighting study, a parametric approach was implemented where all combinations of five screen parameters (window to wall ratio, louvers count, louvers tilt angle, screen depth ratio, and screen reflectivity) were computed. This generated 1600 different screen configurations based on the predefined range of each parameter. Two consecutive phases were performed in which the Illuminating Engineering Society (IES) metrics, Spatial Daylight Autonomy (sDA300/50%), Annual Sunlight Exposure (ASE1000/250 h), Daylight Availability as well as Annual Daylight Glare Probability (DGP), were examined. Diva-for-Rhino plug-in for Rhinoceros was used to interface Radiance and Daysim while Grasshopper plug-in for Rhinoceros was used to generate 1600 solar screen's configurations parametrically and to automate the simulation process. The simulated case study was a generic south-oriented classroom located in Cairo' desert in Egypt. A parallel computing procedure, by which multiple Radiance simulations can be run, was used to find optimal solutions. These solutions were characterized by maximum daylit area without excessive solar penetration. The general tendency of each parameter and the interaction between them was examined. Simulation results demonstrated the trend of converging solutions starting from 1:1 depth ratio with downward tilted angles. Finally, the influence of increasing screen reflectivity in enhancing daylighting performance was illustrated.

Post-World War II Italian school buildings: typical and specific seismic vulnerabilities

Abstract: Structures belonging to the same type and built in the same period may share similar geometrical and spatial characteristics. When these features also affect the seismic response of the buildings, they are referred to as typical seismic vulnerabilities. When a building presents one or more of these typical vulnerabilities, some general and qualitative considerations on its seismic behaviour can be made a priori, considering their actual influence on the seismic behaviour of other similar cases. In this work, we propose and apply a specific procedure based on a priori considerations to a specific building type: the post-World War II Italian Schools. To this purpose, we first improved our knowledge about this type of building, pointing out typical and specific seismic vulnerabilities by studying the standard architectural principles suggested by the main manuals and laws of that time. Then, in order to find how these typological features affect the global seismic behaviour of the examined structures, we analysed a real case study representative of the entire building type. Pushover and Nonlinear Dynamic analyses have been carried out, considering four different models, representing three different configurations that may result from different combinations of the most significant typical vulnerabilities. The result of this work confirms that in the case of post-World War II Italian school buildings, typological vulnerabilities such as wide atriums, eccentric stairs and tall windows, along with irregularity in plan configuration, can strongly affect the global seismic behaviour of the school buildings.

Mechanical properties of self-consolidating concrete containing lightweight recycled aggregate in different mixture compositions

Abstract: The fresh and mechanical properties of self-consolidating concrete (SCC) with different mixture compositions and lightweight coarse aggregate were investigated in this study. The investigation included 28 normal-weight SCC (NWSCC) mixtures with varied coarse-to-fine (C/F) aggregate ratios (0.7–1.2), coarse aggregate size (10–20 mm), binder content (450–500 kg/m 3 ), air content (5–7%), and different supplementary cementitious materials (SCMs) (metakaolin, silica fume, and ground granulated blast-furnace slag). The investigation also included 11 semi-lightweight normal vibrated concrete (SLWNVC) and semi-lightweight self-consolidating concrete (SLWSCC) mixtures with a density ranging from 1933 to 2077 kg/m 3 . These mixtures were developed with different binder content (450–500 kg/m 3 ), SCMs (metakaolin and fly ash), and varied C/F aggregate ratios (0.7–1.5). The results indicated that using metakaolin greatly enhanced the mixture viscosity, particle suspension, and mechanical properties of NWSCC and SLWSCC mixtures. In NWSCC mixtures the mechanical properties were not significantly affected by increasing the aggregate size. However, increasing the binder content of NWSCC from 450 to 500 kg/m 3 improved all the mechanical properties, and adding 5% entrained air resulted in an 8%, 10%, 11%, and 8% reduction in the 28-day compressive strength, flexural strength, splitting tensile strength, and modulus of elasticity, respectively. The results also indicated that it is not recommended to develop SLWSCC mixtures with a C/F aggregate ratio above 1.5 since the fresh and mechanical properties of the mixtures were greatly reduced above this amount.

Evaluation of properties of gypsum plaster-superplasticizer blends of improved performance

Abstract: The effect of SMF-based superplasticizer on the performance of β-hemihydrate plaster has been studied. A 0.6 wt% SMF content contributes 69% enhancement in the compressive strength of modified paste as compared to reference sample. The influence of superplasticizer on the hydration characteristics and morphology of the gypsum crystals have been studied by XRD, TGA, SEM and Electrical Conductivity techniques. These studies showed that superplasticizer accelerates the rate of hydration and leads to the formation of a dense and well compacted texture of crystals, thereby imparting high strength and better water resistance to the gypsum matrix than the reference material.

Recycled natural wastes in metakaolin based porous geopolymers for insulating applications

Abstract: The effectiveness of two amorphous silica based wastes, rice husk ash and volcanic ash powders, used to act as structural reinforcement and partial replacement of metakaolin in porous matrices for thermal isolation was assessed. Both wastes produced colloidal phase that contributed to improve the reactivity and homogeneity of the matrices enhancing the mechanical strength. Rounded pores were obtained in relation with significant reduction of the interpore partitions under controlled addition of the blowing agent. The bulk thermal conductivity decreased from 0.6 to less than 0.15 W m −1 K −1 with the increase of the concentration of blowing agent. The final matrix presented pore size distribution and pore connectivity that allows analytical description and prediction of their effective thermal conductivity.Results demonstrated that clear relations can be established among the viscosity of the pastes, chemical composition, amount of blowing agent and the volume expansion/pore size distribution.

Optimizing roof insulation for roofs with high albedo coating and radiant barriers in India

Abstract: To make roofs energy efficient, typically two types of techniques are followed: surface treatments (cool roofs, radiant barriers) and thermal property modifications (roof insulation). The interplay between these two techniques has been studied using energy simulations. A single storey, daytime operational, office building of 200 m2 area has been simulated for five climatic zones in India. A total of 88 different roof combinations have been studied for each climatic zone. An economic analysis using Internal Rate of Return has been performed to identify a suitable roof insulation thickness for a roof with high albedo, and radiant barrier combination. The incremental benefits in energy savings reduces by adding insulation after a limit. For a roof with albedo of 0.6 and radiant barrier emittance of 0.2, the optimized roof R-value is 0.49 m2 K/W in hot and dry and composite climates, 0.31 m2 K/W in warm and humid and temperate climates, and 1.02 m2 K/W for cold climates.

Interoperability from building design to building energy modeling

Abstract: Interoperability issues have been well acknowledged as an impediment to improve productivity in the Architecture, Engineering and Construction (AEC) industry. The current information exchange from building design to building energy modeling has numerous problems, including object parametric information deficiencies, geometric misrepresentations and re-input data confusion. These problems lead to major money, time and effort losses. This paper presents an automated solution through the design of a novel Extensible Style Sheet Language Transformation (XSLT), which includes a series of instructions to facilitate the information exchange between building design and energy modeling fields. The proposed solution has been implemented with Microsoft Visual C# Studio 2013. The effectiveness of the solution has been tested in three real case studies. The test results demonstrated that the proposed solution could rectify the overall geometric and material misrepresentations inherent to the current information exchange process.

Analysis of energy requirements versus comfort levels for the integration of phase change materials in buildings

Abstract: This paper investigates the importance of the design parameters when looking at possible energy savings and comfort enhancement in a building using Phase Change Materials (PCMs). Computer based simulations are performed using a simulation software for modelling a house and its thermal behaviour over a year. It is found that by varying the heating set point and the phase change (melting) temperature range of the PCM, significant changes can be observed. Some poor scenarios show that the integration of PCM can increase both the discomfort (up to 6% more discomfort hours) and the energy requirements (up to 25% more energy needed). On the other hand, appropriate scenarios bring significant energy savings (up to 33% less energy needed) and comfort enhancement (up to 31% less discomfort hours). This highlights the strong need for a clever design when integrating PCM into buildings. The goal is to find a trade-off between energy savings and comfort enhancement. The PCM with a phase change temperature range between 21 °C and 26 °C shows the best results. The study is based on climate conditions for Auckland City in New Zealand but most of the conclusions drawn can be applied to any climate.

A field study of indoor thermal comfort in the subtropical highland climate of Bogota, Colombia

Abstract: This paper undertakes the first field study of indoor thermal comfort in Colombia. The objective of this study was to compare thermal comfort data gathered in office buildings in Bogota, Colombia with the predictions made by three well established standards: ISO 7730:2005 (PMV model), ANSI/ASHRAE Standard 55:2013 (adaptive model) and EN Standard 15251 (adaptive model). The study comprised the administration of a thermal assessment survey to 115 participants and the simultaneous measurement of indoor and outdoor physical variables in 3 offices having different ventilation regimes (natural ventilation, mechanical ventilation and mixed-mode i.e. both natural ventilation and air-conditioning). The findings show that the PMV model incorporated in the ISO 7730 as well as in the ASHRAE standard (which is the standard currently adopted in Colombia for regulating indoor environmental parameters) is able to describe comfort conditions in the mechanically ventilated (MV) office. In the case of the naturally ventilated office (NV), results indicate that the PMV model is not successful at estimating occupants' thermal sensations, and underestimates occupants' perception of discomfort. The EN 15251 adaptive model underestimates thermal discomfort in the NV and MM offices. The ASHRAE adaptive model shows similar patterns underestimating discomfort in the NV office. The findings provide robust evidence that the lack of perceived or actual control in low-energy naturally ventilated buildings strongly reduce occupants' thermal comfort and thus invalidate adaptive model predictions.

Knowing from the past – Ingredients and technology of ancient mortar used in Vadakumnathan temple, Tirussur, Kerala, India

Abstract: In the present study, lime mortar samples from the restoration site of Vadakumnathan temple, Kerala, India have been analyzed. Samples from three different locations of the temple such as ancient wall, gopuram and arch have been taken. Traditional methods such as chemical analysis, acid loss analysis and organic test were conducted on mortar samples. Modern instrumental techniques such as electronic particle size distribution, X-ray Diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Infrared Spectroscopy (FT-IR) were employed in the study. The binder used in the mortar is calcium high with 30% of clay mineral. A binder to aggregate ratio in the range of 1:1.5–2.5 has been established from acid loss analysis. Particle of the aggregate are mostly silt in nature, hence nominal sand would have been grinded to reduce the particle size and to induce pozzolanic reaction. The presence of carbohydrate, protein and fats are identified by organic test that are in agreement with FT-IR analysis and TGA. Calcite, aragonite and calcium complexes of silicate and aluminates in form of hydro thermal product namely gyrolite and okenite are present in wall and gopuram samples. The formation of hydrothermal products confirms that the mortar was produced by hot lime technology. In TGA, the decomposition of CaCO 3 to CO 2 between 600 and 770 °C reveals the transformation of calcite from complex forms of CSH (gyrolite and okenite) and CAH. The presence of degraded products such as syngenite and gypsum in arch sample shows that the lime mortar is in complete deterioration where as mortar remained in good condition in gopuram and wall samples.Texture along with elemental analysis (EDX) confirms the results of chemical analysis.

The influence of waste crumb rubber in reducing the alkali–silica reaction in mortar bars

Abstract: The objective of this experimental work was to study the effect of crumb rubber on decreasing the expansion caused by Alkali–Silica Reaction (ASR) in mortar specimens prepared with highly reactive aggregate. In this regards, mortar bars containing 0%, 16% and 24% crumb rubber by volume as fine aggregate replacement were prepared for the accelerated mortar bar test (AMBT). Results from this study indicated that the use of 16% and 24% crumbed rubber as fine aggregate replacement decreased the ASR expansion in mortar bars by 43% and 39%, respectively. However, the compressive strength of the mortar cubes containing 16% and 24% crumb rubber reduced by 20% and 47% at 28 days, respectively. While Thermo-Gravimetric Analysis (TGA) showed no reaction between rubber particles and pore solution of concrete, the Scanning Electron Microscopy analysis from mortar bar sections containing crumb rubber confirmed the positive impact of physical damping of crumb rubber particles on reducing the ASR in the mortar specimens.

A case study: The energy performance gap of the Center for Interactive Research on Sustainability at the University of British Columbia

Abstract: This work is a case study of the energy performance gap in a LEED Platinum-certified university building. Comparing the whole-building energy modeling results with the overall measured energy consumption, the building shows approximately 60% higher energy consumption during its first year of operation than the initial model prediction. The building is heavily instrumented and a large amount of detailed data is logged, providing a unique opportunity to compare energy model prediction to actual building performance and operations. Energy performance gaps of this magnitude are commonly found and the reasons are not yet well understood. There are many potential sources for discrepancies: different usage of the building in model and reality, design, construction and commissioning deficiencies, software limitation and modeling errors and different weather in reality than in the model are the factors typically considered. To better understand the nature of the performance gap, potential sources of discrepancy between model and measurement have been eliminated in a series of steps, to evaluate their significance in the case of this particular building, starting with eliminating the most intrinsic prediction challenge to any energy model – the weather – and continuing toward increased controllability and interdependence: occupancy, lighting and equipment loads, envelope performance, mechanical systems and ventilation. The present paper shows that in the case of the CIRS building the major sources of the performance gap are that the building has been built and is operated differently from what was expected. A major component of the CIRS energy concept is heat exchange with a neighboring building; however, because of design and commissioning deficits, the heat exchange falls short of the design intent. Furthermore, a waste water treatment plant located in the building is on the building's meters and included in the measured data, but not in the energy model. The transformers' electricity consumption was not in the energy model either and they were significantly inefficient. Part of the building's unanticipated usage is large lighting and plug loads.

Effect of wall construction materials over indoor air quality in humid and hot climate

Abstract: In the present research work, a mix of 15 modern and old office buildings were sampled and classified in accordance with their building construction materials, along with the indoor ambience conditions. From this hourly study, it was found that the season was not the more important parameter, despite there being a tendency towards a similar kind of ambience during the rainy season. On the other hand, it showed a clear difference between modern and old buildings with plaster coating, during the period of occupation. Specifically, a better indoor ambience prevailed in the old buildings. At the same time, when marble and plaster coatings were analysed in the old buildings, a clear difference in indoor ambience was felt at the time of opening the office. This shows that a better indoor ambience prevailed during the dry period in the old buildings when marble coatings were used. Finally, the same effect, but not as pronounced, seen in the indoor ambience during the opening of the office, was obtained in new buildings that had marble coating. Finally, the procedure obtained could be the much sought-after solution to the problem stated by researchers in the past and future research works relating to this new methodology could help us define the optimal improvement in real buildings to reduce energy consumption, and its related carbon dioxide emissions, at minimal economical cost.

New optimisation methodology to uncover robust low energy designs that accounts for occupant behaviour or other unknowns

Abstract: The use of software to aid in the design of buildings or to show compliance is now commonplace. This has led several authors to investigate the potential for using such software to automatically optimise a design, or to generate a variety of near-optimal designs. One area where this approach has been found useful is in minimising annual energy demand. It is known that any estimate of demand will depend not only on the architecture and constructions used, but on the preferences and behaviours of the occupants. This suggests which design is truly optimal will also depend on occupant behaviour. In this paper optimisation is carried out for an array of different occupant behaviours based on real records. It is found that the resultant designs are more robust in terms of predicted heating energy use and overheating than when only a single behaviour is considered. It is recommended that in future all such optimisations are made using a realistic spectrum of behaviours, and that the approach is expanded to include other elements of design that might show variance during construction, for example, U-values and air tightness. This, it is hoped, will reduce some of the risks of designing and asking people to occupy very low energy buildings. Importantly, it is found that the near-optimal building designs found under variable occupancy present different characteristics than when only a single statement of occupancy is used. Being cognisant of this reduces the potential for inappropriate designs to be created that rely on a serendipitous arrangement of design and occupancy parameters that might not be met on site or by the occupants.

The influence of well geometry on the daylight performance of atrium adjoining spaces: A parametric study

Abstract: The aim of present study is to assess the impact of atrium width and clerestory height on amount of Average Daylight Factor (ADF) in different floors of vertical top-lit atria and determining the appropriate geometrical sizes for the four-storey, four-sided atrium to provide sufficient daylight in office spaces. The ADF s predicted using the modelling software IES-Radiance are validated by scale model measurements. Study on the relationship between atrium width ( W ) and daylight availability in the adjoining spaces of atrium indicates that, the variations trend of ADF in the different floors of atrium are not similar; as the maximum ADF occurs when the width of atrium provides an optimum distance between the office rooms in each floor and the clerestory opening; this distance is significantly related to the sky view angle, altitude angle and optimum distance that daylight can penetrate in the office rooms. Furthermore, it is found that growing the height of clerestory windows increases the amount of ADF in the atrium and its adjoining spaces. It concluded that the minimum acceptable ratio of clerestory height ( h ) to atrium height ( H ) for providing the sufficient level of ADF in the atrium adjacent spaces is h / H =3/8.

Influence of superplasticizer, temperature, resting time and injection pressure on hydraulic lime grout injectability. Correlation analysis between fresh grout parameters and grout injectability

Abstract: The grout injection technique is commonly used for the consolidation of old stone masonries. In particular, the multi-leaf masonries which generally exhibit low compactness in the inner core and very few links between the internal and external leaves. Grouts are concentrated suspensions that can be seen as mixtures of binder with water, and special admixtures. To ensure an adequate flow of the grout and a correct filling of the internal voids inside the masonry, it is essential to assure good fresh grout properties. Thus, the evaluation of the performance of the grout injectability is firstly started by checking the intrinsic properties of the grout (namely rheological parameters) and then by controlling the injectability, through injection tests in porous media that simulate old masonries. The main goal of this paper is to provide indications and valuable data about the combined effect of superplasticizer dosage, environmental temperature, resting times (i.e. the time after the grout mixing had ended) and injection pressure on grout injectability, aiming at a successful injection process. The lack of information about the influence of the referred parameters on the injectability of hydraulic lime grouts enhances the importance of a detailed research on the subject.