Dissertations / Theses on the topic 'Building performance gap'

Increasing studies imply that predicted energy performance of buildings significantly deviates from actual measured energy use. This so-called "performance gap" may undermine one's confidence in energy-efficient buildings, and thereby the role of building energy efficiency in the national carbon reduction plan. Closing the performance gap becomes a daunting challenge for the involved professions, stimulating them to reflect on how to investigate and better understand the size, origins, and extent of the gap. The energy performance gap underlines the lack of prediction capability of current building energy models. Specifically, existing predictions are predominantly deterministic, providing point estimation over the future quantity or event of interest. It, thus, largely ignores the error and noise inherent in an uncertain future of building energy consumption. To overcome this, the thesis turns to a thriving area in engineering statistics that focuses on computation-based uncertainty quantification. The work provides theories and models that enable probabilistic prediction over future energy consumption, forming the basis of risk assessment in decision-making. Uncertainties that affect the wide variety of interacting systems in buildings are organized into five scales (meteorology - urban - building - systems - occupants). At each level both model form and input parameter uncertainty are characterized with probability, involving statistical modeling and parameter distributional analysis. The quantification of uncertainty at different system scales is accomplished using the network of collaborators established through an NSF-funded research project. The bottom-up uncertainty quantification approach, which deals with meta uncertainty, is fundamental for generic application of uncertainty analysis across different types of buildings, under different urban climate conditions, and in different usage scenarios. Probabilistic predictions are evaluated by two criteria: coverage and sharpness. The goal of probabilistic prediction is to maximize the sharpness of the predictive distributions subject to the coverage of the realized values. The method is evaluated on a set of buildings on the Georgia Tech campus. The energy consumption of each building is monitored in most cases by a collection of hourly sub-metered consumption data. This research shows that a good match of probabilistic predictions and the real building energy consumption in operation is achievable. Results from the six case buildings show that using the best point estimations of the probabilistic predictions reduces the mean absolute error (MAE) from 44% to 15% and the root mean squared error (RMSE) from 49% to 18% in total annual cooling energy consumption. As for monthly cooling energy consumption, the MAE decreases from 44% to 21% and the RMSE decreases from 53% to 28%. More importantly, the entire probability distributions are statistically verified at annual level of building energy predictions. Based on uncertainty and sensitivity analysis applied to these buildings, the thesis concludes that the proposed method significantly reduces the magnitude and effectively infers the origins of the building energy performance gap.

This study aims at a preliminary characterization of system operation uncertainty. It bases this on an analysis of the energy consumption of 6 existing buildings on the Georgia Tech campus. The analysis is speculative in nature.

The building sector is responsible for almost a quarter of the total carbon dioxide emissions. The urgency to reduce the emissions is reflected in the stricter guidelines which have been set all over the world. To reduce the building sector’s emissions the energy consumption need to be reduced, which can be done in two ways: building new energy efficient buildings or retrofitting of current buildings. Due to the life expectancy of current building stock the largest savings before 2030 will be made through retrofits. For this reliable computational tools are required, and currently there is a gap between the predicted and actual performance of retrofitted buildings. This thesis is going to look into how the computational method is contributing to the performance gap. A building at the RMIT campus in Melbourne, Australia, which is going to be retrofitted through retrofits designed by Siemens, is used. A thermal simulation model of the building was built, and tuned to reflect the pre-retrofit building, and compared against the measured energy performance of the building. The retrofits were then implemented in the simulation model and the gap in the predictions between the simpler computational method used by Siemens in designing the retrofits, and the extensive simulation model was compared. The gap between the computational methods were analysed in order to see how Siemens calculation method contribute to the performance gap. The conclusions which have been drawn are that the simulation model is reflecting the energy use of the building well considering the access of data available during the study. Especially the electricity use is reflected well both in the total annual use, approximately 4 % gap to measured value, and the monthly variation over the year. The total natural gas use is under predicting the annual use, approximately 40 % gap to the measured value, but shows a good correlation to the monthly variation. The electricity use is relatively stable in the simulation model, where the natural gas was sensitive for direct changes to the heating system. The input parameters which have the largest impact in the electricity use are internal gain profiles and the electrical internal gains energy use. Siemens calculation method are contributing to the performance gap through the lack of interaction between the different retrofits, the light retrofit have a noticeable impact on the heating and cooling system of the building. To only use one single period in the regression models can also easily lead to incorrect predictions. The strength of the simulation model is its ability to see the retrofits influence on each other and the possibility for scenario analysis.
Byggnadssektorn är ansvarig för nästan en fjärdedel av de totala globala koldioxidutsläppen. Viljan att minska utsläppen kan ses i de allt striktare riktlinjer som sätts över hela världen. För att reducera utsläppen finns det två sätt: bygga nya energieffektiva byggnader eller ombyggnation av nuvarande byggnader. Livslängden på nuvarande byggnadsbestånd innebär att de största besparingarna innan 2030 kommer att ske inom ombyggnationer. För detta krävs tillförlitliga verktyg, och i nuläget finns det ett gap mellan byggnaders förutspådda och verkliga energiprestanda. I denna examensuppsatts kommer beräkningsmetodens inflytande över detta gap att undersökas. En byggnad på RMIT:s campus i Melbourne, Australien, som kommer att undergå en ombyggnation som designats av Siemens har använts. En termisk simuleringsmodell av byggnaden skapades och avstämdes mot den verkliga byggnaden, och jämfördes mot uppmätta värden av byggnadens energiprestanda. Ombyggnationerna var sedan implementerade och skillnaden mellan den förutspådda prestandan av byggnaden, genom den omfattande simuleringsmodellen och den enklare beräkningsmetoden som användes av Siemens, jämfördes. Genom att analysera gapet mellan de olika beräkningsmetoderna kunde slutsatser dras angående hur de kan bidra till gapet i energiprestanda. Slutsatserna från arbetet är att simuleringsmodellen ger en bra bild av energianvändningen av byggnaden, med hänsyn till informationen som varit tillänglig. Byggnadens totala uppmätta elektricitetsanvändning är speciellt väl överrensstämmande med simuleringsmodellens resultat både i den årliga användningen, ca 4 % skillnad från uppmätta värden, och variationen över ett år. Den totala användningen av naturgas enligt simuleringsmodellen är under de uppmätta värdena med en skillnad på ca 40 %, men med en god överrensstämmelse med den årliga variationen. Användningen av elektricitet i modellen är relativt stabil, användningen av naturgas är känslig för direkta ändringar till uppvärmningssystemet. Inputparametrarna som har störst inverkan på elanvändningen är interna, energiproducerande och konsumerande, enheters användningsprofil (PC, personer, ljus m.m.), el konsumtion, och latenta samt sensibla värme. Siemens beräkningsmetod bidrar till gapet mellan förutspådda och verkliga energiprestanda genom brist på samverkan mellan de olika delarna i ombyggnationen. Ombyggnationen som innebär uppgradering av byggnadens belysning innebär exempelvis märkbara skillnader i byggnadens uppvärmnings- och kylsystem. Användningen av endast en period i skapandet av regressionsmodeller för att förutspå vattenkokarnas och kylarnas användning leder även till en missledande framtida energiproduktion. Styrkan i simuleringsmodellen är möjligheten till samverkan mellan olika ombyggnationer påverkan på varandra samt möjligheten till scenarioanalys.

There is widespread acceptance of the need to reduce energy consumption within the built environment. Despite this, there are often large discrepancies between the energy performance aspiration and operational reality of modern buildings. The application of existing mitigation measures appears to be piecemeal and lacks a whole-system approach to the problem. This Engineering Doctorate aims to identify common reasons for performance discrepancies and develop a methodology for risk mitigation. Existing literature was reviewed in detail to identify individual factors contributing to the risk of a building failing to meet performance aspirations. Risk factors thus identified were assembled into a taxonomy that forms the basis of a methodology for identifying and evaluating performance risk. A detailed case study was used to investigate performance at whole-building and sub-system levels. A probabilistic approach to estimating system energy consumption was also developed to provide a simple and workable improvement to industry best practice. Analysis of monitoring data revealed that, even after accounting for the absence of unregulated loads in the design estimates, annual operational energy consumption was over twice the design figure. A significant part of this discrepancy was due to the space heating sub-system, which used more than four times its estimated energy consumption, and the domestic hot water sub-system, which used more than twice. These discrepancies were the result of whole-system lifecycle risk factors ranging from design decisions and construction project management to occupant behaviour and staff training. Application of the probabilistic technique to the estimate of domestic hot water consumption revealed that the discrepancies observed could be predicted given the uncertainties in the design assumptions. The risk taxonomy was used to identify factors present in the results of the qualitative case study evaluation. This work has built on practical building evaluation techniques to develop a new way of evaluating both the uncertainty in energy performance estimates and the presence of lifecycle performance risks. These techniques form a risk management methodology that can be applied usefully throughout the project lifecycle.

The UK Government has placed the need to reduce national energy demands and carbon emissions at the forefront of the political agenda, with a commitment made to meet EU targets of 20% reductions in greenhouse gas emissions and primary energy consumption, alongside a 20% improvement in overall energy efficiency, across all EU Member States, by 2020. Building performance has been identified as a key area where significant progress towards meeting these ambitions can be made. It is fundamental to ensure that the building fabric of a property functions correctly in order to achieve high levels of thermal effectiveness, which should result in lower energy demands and carbon emissions. However, research to date shows that a gap exists between predicted and actual performance levels. This research utilises the dwelling Heat Loss Coefficient (HLC) as a common output in design stage and post-construction evaluation techniques, that can be used to compare predicted and measured fabric performance. The Standard Assessment Procedure (SAP), coheating tests, air pressure tests and thermal imaging are used to evaluate in-situ buildings. Sensitivity analysis and controlled conditions experiments are utilised in order to investigate the reliability of the assessment techniques used. The key findings from the study include the demonstration, through novel coheating test, that post-installation mechanically ventilated heat recovery (MVHR) system efficiency levels can have a pronounced effect on the measured HLC, and, in conjunction with use of assumed theoretical efficiency levels, can cause divergence in theoretical and measured data of 10-15%. This can largely be resolved through correct design, installation and commissioning. Environmental conditions, both notional and site-specific, can also cause divergence in the HLC data, including wind speed (15%) and solar gains (10-26%). In addition, it has been shown that, when considering thermal bridging values, inaccurate calculation at the design-stage and poor attention to detail during construction could cause underperformance in this element by up to 50%. This is of significance as there are currently no mandatory procedures to assess post-construction compliance with thermal bridging levels specified within the UK Building Regulations.

There is a need to reduce unsustainable use of fossil fuels. Increased usage of renewable energy by combined use of photovoltaic solar panels (PV) with battery storage is one way. Another way is to increase awareness of energy usage and reduce the energy performance gap by building energy-efficient buildings. Buildings have a long lifetime and high energy usage will have an impact for a long time. Barriers, drivers and non-energy benefits (NEBs) for investments in battery storage in photovoltaic systems (PV) in the context of farmers in Sweden with PV systems was investigated by a questionnaire study. The questionnaire was sent to farmers in Sweden who already have photovoltaics installed and about 100 persons answered, a response rate of 59%. Among the drivers for investments in battery storage in PV systems in agriculture it was found that the highest-ranked driver, i.e., to use a larger part of the electricity produced oneself, turns out to be the highest priority for grid owners seeking to reduce the need for extensive investments in the grid. The primary NEBs found were the possibility to become more independent of grid electricity. A method for the building process, called ByggaE, which aims to reduce the energy performance gap, has been developed and described. The method is based on two main processes with activities. Documents that support the activities can be found and stored in the energy documentation, a digital map structure. The two main processes are: The client’s activity to formulate requirements and ways to verify these requirements. The main process for other actors is to identify, handle and follow up risks or critical parts. An overall relation between the energy efficiency gap and the energy performance gap has been identified. Realistic assumptions and follow-up related to the assumptions are found to be important to reduce both the energy efficiency gap and the energy performance gap.
För att uppnå klimatmålen är det nödvändigt att minska den ohållbara användningen av fossila bränslen. Ett sätt är att öka användning av förnybar energi genom att kombinera solel med batterilager. Ett annat sätt är att öka medvetenheten om energianvändningen med dess negativa påverkan på miljön och uppfylla energikraven för nya byggnader bättre. Eftersom byggnader har lång livslängd ger onödigt hög energianvändning påverkan under lång tid.   Hinder, drivkrafter och andra icke energirelaterade fördelar med att investera i batterilager till solel har undersökts i en enkätstudie bland svenska lantbruk. Det kom in 100 svar från lantbrukare som har solel, vilket motsvarar en svarsfrekvens på 59 %. Den viktigaste drivkraften för att investera i batterilager till solelanläggningen är en högre egenanvändning av el. Detta visade sig också vara högst prioriterat av elnätsägare för att minska behovet av kostsamma investeringar i elnätet. Den största icke energirelaterade fördelen med batterilager är större oberoende av elnätet.   En kvalitetsäkringsmetod för byggprocessen har utvecklats och beskrivits. Syftet med metoden, som kallas ByggaE, är att minska skillnaden mellan verklig energianvändning och energikrav i nya byggnader. Metoden bygger på två huvudprocesser med aktiviteter. Beställarens huvudprocess är att formulera krav och metoder att kontrollera och följa upp dessa krav. De andra aktörernas huvudprocess är att identifiera, hantera och följa upp risker eller kritiska moment som kan påverka energianvändningen. Dokument som stödjer aktiviteterna lagras i en digital mappstruktur.   Det är viktigt med realistiska antaganden och uppföljning som relaterar till dessa antaganden för att fler lönsamma energieffektiviseringsåtgärder ska bli genomförda och för att de energiprestanda som krävs eller förväntas ska bli uppfyllda.

The market shift towards high-performance buildings has been brought into question by growing concerns about the actual energy efficiency of these projects. Research studies have been pointing increasingly to performance gaps between the predicted (or modelled) and actual (or measured) energy consumption of certified ‘green’ buildings. Discussions about reasons for performance gaps have been recurring in the building industry and research alike. This thesis investigates the energy performance gap of three high-performance LEED-certified buildings in British Columbia: the Centre for Interactive Research on Sustainability (CIRS), the Jim Pattison Centre of Excellence in Sustainable Building Technology and Renewable Energy Conversation (JPCE) and the District Education Centre (DEC). For each case study, an energy performance evaluation reveals differences between modelled and measured energy consumption. Based on an extensive literature review, the reasons for identified performance gaps are explored through expert interviews with key stakeholders that were involved in the design, construction or operation of each of these projects. The energy performance evaluation reveals significant performance gaps in all three case studies, with one project out-performing and two under-performing the design predictions. The research highlights a lack of consistent metered-energy data at the system level. Based on these findings this study attempts to evaluate key sources of performance issues, in the context of the three case-study buildings. It shows that performance-gap reasons indicated in the literature occurred at all phases of the building lifecycle: starting at the planning/design and modelling phase, through the construction, commissioning and handover phases, to the building operation and occupancy phase. The results suggest that performance gaps are closely related to shortcomings in energy design concepts, development procedures, and operational practices that were applied in the three buildings. The research emphasizes the importance of creating a greater transparency of development procedures and collaborative approaches to successfully design, build and operate high-performance buildings. The challenges faced by project teams to integrate innovative technologies calls for robust design solutions and methodologies that can be easily translated into implementation strategies and operation procedures that meet building management capacities.
Science, Faculty of
Resources, Environment and Sustainability (IRES), Institute for
Graduate

Bridging the gap between the predicted and actual energy performance of buildings is necessary to increase the energy performance of existing buildings and achieve the European Union’s energy efficiency targets in the “2030 climate & energy framework”. Construction is considered the sector with the most potential for energy saving. Specifically, buildings space heating has considerable potential for energy saving. Thermal transmittance is the fundamental parameter to characterise the heat losses of building envelopes. However, several research authors evidenced that assumptions regarding heat loss from a home pre-retrofit and post-retrofit were incorrect. In this sense, accurate on-site measurements are necessary to provide information on the actual thermal transmittance of façades. The purpose of this thesis is to contribute to reduce the energy performance gap of residential buildings. Therefore, the aim of the thesis is to enhance the accuracy of in situ measurements of the actual thermal transmittance of façades of existing residential buildings using the heat flux meter method to ensure successful decision-making during the energy renovation processes of existing buildings, and to confirm energy performance strategies for new nearly zero-energy buildings. The analysis of testing parameters for the in situ measurement process of the thermal transmittance are not fully specified by the standard ISO used extensively. Relating to calculation methods to conduct research on the thermal behaviour of façades, the standardised average method is widely used by authors. Very few initiatives used the standardised dynamic method because it is more complex than the average method. This research assesses the implications of using the different standardised calculation methods in order to verify which best fits theoretical values. Moreover, the usability of the standardised dynamic method is promoted and facilitated through a calculation procedure, defining a programmed spreadsheet accessible to practitioners. The dissertation proposes a classification system of façades to facilitate the selection of façades to conduct a systematic analysis of the thermal performance of façades in the housing sector. The classification of façades of existing residential buildings for subsequent analysis is based on the characterization of the opaque part of façades. The dissertation continues with the exploration of the boundaries of the requirements for using the standardised heat flow meter method to refine the testing conditions in low U-value façades. Façades with low thermal transmittance values are increasingly promoted due to comply with Directive 2010/31/EC targets. However, as several researchers shown, conducting accurate in situ measurement of low thermal transmittance façades is a challenging task. Investigating the limits of application of the HFM method for the in situ measurement of U-values in low thermal transmittance façades would allow to ensure compliance with policies to transition the existing building stock to nearly zero-energy buildings, and to confirm energy performance strategies for new nearly zero-energy buildings. To enhance the usability of the heat flux meter method, the dissertation compares different criteria for determining conditions for stopping the test during in situ experimental campaigns when measuring the thermal transmittance of existing buildings’ façades using the heat flow meter method. This will help to reduce practitioners’ uncertainty about the duration of experimental campaigns for obtaining accurate actual thermal transmittance of existing buildings’ façades. The dissertation concludes by outlining the main contributions of this research. The subjects that were raised during the research undertaken although they could not be addressed are commented and proposed as future work.
Reduir la diferència entre el rendiment energètic previst i real dels edificis és necessari per tal d’augmentar el rendiment energètic dels edificis existents i assolir els objectius sobre eficiència energètica de la Unió Europea en el “Marc sobre clima i energia per al 2030”. La construcció és considerada el sector amb més potencial d'estalvi energètic. Concretament, el condicionament tèrmic dels edificis mitjançant calefacció té un potencial d'estalvi energètic considerable. La transmitància tèrmica és el paràmetre fonamental per caracteritzar les pèrdues de calor a través de les envolvents de l’edifici. Tanmateix, diversos investigadors han demostrat que les hipòtesis sobre la pèrdua de calor dels edificis abans i després d’una rehabilitació no són correctes. En aquest sentit, es fa necessari realitzar mesures in situ amb elevada precisió per proporcionar informació sobre la transmitància tèrmica real de les façanes. El propòsit d’aquesta tesi és contribuir a reduir la bretxa del rendiment energètic en els edificis residencials. Per això, l'objectiu d'aquesta dissertació és millorar la precisió en la realització de mesures in situ de la transmitància tèrmica real de les façanes dels edificis residencials existents usant el mètode estandarditzat del mesurador de flux de calor (HFM), per assegurar l'èxit en la presa de decisions durant els processos de renovació energètica dels edificis existents i confirmar estratègies d'eficiència energètica per a nous edificis de consum d’energia quasi nul. L'anàlisi dels paràmetres d’assaig per a la mesura in situ de la transmitància tèrmica no està totalment especificada en l'estàndard ISO utilitzat extensivament. Pel que fa als procediments de càlcul, el mètode que s’utilitza de forma més àmplia pels investigadors és el mètode de mitjanes. Poques iniciatives utilitzen el mètode dinàmic degut a la seva complexitat. La investigació avalua les implicacions d'utilitzar els diferents mètodes de càlcul estandarditzats per verificar quin s’ajusta millor als valors teòrics de referència. A més, es fomenta i facilita la usabilitat del mètode dinàmic estandarditzat mitjançant un procediment de càlcul, definint un full de càlcul programat accessible per als professionals. La dissertació proposa un sistema de classificació de façanes per facilitar la selecció de façanes per a la seva posterior anàlisi del rendiment tèrmic de les façanes del sector de l'habitatge. La classificació de façanes d'edificis residencials existents es basa en la caracterització de la part opaca de les façanes. La dissertació continua explorant els límits dels requisits per a la utilització del mètode HFM per a refinar les condicions d’assaig en les façanes amb baixa transmitància tèrmica. Aquestes façanes es promouen cada vegada més per tal de complir amb els objectius de la Directiva 2010/31/CE. Tot i així, diversos investigadors han demostrat que realitzar mesures in situ precises en aquest tipus de façanes és un repte. Investigar els límits d'aplicació del mètode HFM per a la mesura in situ de la transmitància tèrmica en façanes amb baixa transmitància tèrmica permetrà assegurar el compliment de les polítiques de transició d'edificis existents a edificis de consum energètic quasi nul (nZEB), i confirmar estratègies d'eficiència energètica per a nous edificis nZEB. Per millorar la usabilitat del mètode HFM, aquesta tesi analitza diferents criteris per a determinar les condicions d’aturada de l’assaig durant les campanyes experimentals per mesurar in situ la transmitància tèrmica de les façanes. Els resultats ajudaran a reduir la incertesa sobre la durada de les campanyes experimentals per obtenir una transmitància tèrmica real precisa de les façanes dels edificis existents. La tesi conclou resumint les principals aportacions d'aquesta investigació. Els temes que s’han plantejat durant la investigació realitzada, i que no s'ha pogut abordar, es comenten i es proposen com a línies de treball futures

Within the European framework, most of residential buildings do not satisfy the minimum thermal specifications. In fact, the renovation rate across the EU is estimated at 1% per year. To fulfil with the goals stated by European Directives 2010/31/EU and 2012/27/EU, it is necessary to ensure a minimum energy performance gap. From a thorough literature review, it was detected that the thermal behavior of a building is often underestimated or neglected during its construction and operation stages. For this reason, an accurate non-destructive testing (NDT) should be required, improving the shortcomings given by the current modelling tools and diagnostic techniques. The purpose of this thesis was to develop a method for determining in-situ the thermal behavior of façades under steady-state conditions using quantitative internal infrared thermography (IRT). After drawing up a numerical model to estimate the thermal transmittance (U-value) as a key parameter of the built quality, the dissertation continued with a validation process that was executed in two typical Spanish walls from different construction periods. This allowed: (i) refining the proposed method; (ii) exploring the boundaries conditions; (iii) assessing the influence of tabulated values set by international standards for wall emissivity and convective heat transfer coefficients among other aspects. The results revealed lower deviations related to the theoretical U-values (1.24 to 3.97%) for test durations of 2-3 hours. Furthermore, the results demonstrated that the use of tabulated values might entail high deviations (40%) in heavy multi-leaf walls with low U-values. Broadly, construction project documents for existing buildings, especially the oldest ones, are not available. Hence, this method may provide information about the building envelope for future refurbishment. In the case of new buildings, the method might allow the thermal behaviour of building façades to be checked according to the design parameters. Despite this, a subsequent literature review highlighted that a gap in the standardization of this method for in-situ building diagnostics is still to fill. Considering this aspect, three studies were developed in order to enhance the applicability of the quantitative internal IRT within the construction industry field. Firstly, the most influential operating conditions were analyzed through an experimental room with a heavy single-leaf wall tested under a wide temperature difference range (3.8 < DT < 21ºC). Secondly, this dissertation performed tests in a public housing stock comprised of four unoccupied buildings (without electric and heating systems in operation), to assess the influence of non-transient thermophysical properties of the wall (i.e. heat capacity per unit of area) on the accuracy of the method. Thirdly, a data-processing method based on U-value time series analysis was proposed and validated through six building façades with heavy multi-leaf walls. The aim was to find a common criterion for stopping the test when it is not necessary more data to obtain a reliable result. Having investigated the aspects mentioned above, it can be extrapolated that: (i) the optimum temperature difference range is found to be between 7 and 16ºC; (ii) the variance in the thermal transmittance could mainly be predicted by changes in the outer air temperature; (iii) the quantitative internal IRT is more accurate in heavy multi-leaf walls with high heat capacities per unit of area, reaching maximum deviations of 0.20%; (iv) the test might be executed in only 30 minutes; (v) the method could allow the assessment of aspects related to the determination of U-value of unoccupied buildings for DT under 10ºC, especially in Spain or European countries with a Mediterranean climate where these test conditions might represent a limitation. Hence, the decision-making could be streamlined in real built environments, increasing the European renovation rate in the mid-term.
Dins el Marc Europeu, la majoria dels edificis residencials no satisfan les especificacions tèrmiques mínimes. De fet, la taxa de renovació a Europa és estimada en 1% anual. Per complir amb els objectius de les Directives Europees 2010/31/UE i 2012/27/UE, és necessari assegurar una bretxa energètica mínima. A partir d'un estat de l'art exhaustiu, es va detectar que el comportament tèrmic d'un edifici sovint és subestimat o negligit durant les etapes de construcció i operació. Per aquest motiu, una prova no destructiva i precisa hauria de ser requerida, per tal de millorar les deficiències donades per les actuals eines de modelització i diagnosi d'edificis. El propòsit de la tesi era desenvolupar un mètode per determinar in-situ el comportament tèrmic de les façanes sota condicions estacionàries mitjançant la termografia quantitativa interna (IRT). Després d'elaborar un model numèric per estimar la transmitància tèrmica (U-value) com a paràmetre clau de la qualitat construïda, la dissertació va continuar amb un procés de validació executat en dues parets típiques espanyoles de diferents períodes de construcció. Això va permetre: (i) refinar el mètode proposat; (ii) explorar les condicions de contorn; (iii) avaluar la influència dels valors tabulats establerts per les normatives internacionals per l'emissivitat de la paret i els coeficients de transferència de calor per convecció. Els resultats van revelar baixes desviacions respecte als valors teòrics de transmitància tèrmica (1.24 a 3.97%) per duracions de test entre 2 i 3 hores. A més a més, els resultats van demostrar que l’ús de valors tabulats podria implicar altes desviacions (40%) en parets compostes. En general, els projectes de construcció d'edificis existents antics no estan disponibles. Per tant, aquest mètode podria proporcionar informació sobre la façana per futures rehabilitacions. En el cas d’edificis nous, el mètode podria permetre verificar el comportament tèrmic de les parets d’acord amb els paràmetres de disseny. Malgrat això, una revisió bibliogràfica posterior va posar de manifest que encara hi ha una bretxa en la estandardització d’aquest mètode per la diagnosi in-situ. Considerant aquest aspecte, es van desenvolupar tres estudis per tal de millorar l’aplicabilitat de la termografia quantitativa interna dins el camp de la indústria de la construcció. En primer lloc, es va analitzar la influència de les condicions operatives en la determinació de la transmitància tèrmica mesurada a través duna cambra experimental amb una façana simple sota un ampli rang de diferència de temperatura (3.8 < DT < 21ºC). En segon lloc, es van dur a terme tests en un parc d’habitatges públics constituïts per quatre pisos desocupats (sense sistemes elèctrics ni de calefacció en funcionament), amb la finalitat d’analitzar la influència de les propietats termofísiques no transitòries (ex. la capacitat de calor per unitat d’àrea) en la precisió del mètode. En tercer lloc, es va proposar i validar un mètode de processat de dades basat en l’anàlisi de sèries de temps de la U-value mitjançant sis parets compostes. L’objectiu era trobar un criteri comú per aturar la prova quan no són necessàries més dades per obtenir un resultat fiable. Havent investigat els aspectes mencionats anteriorment, es pot extrapolar que: (i) el gradient de temperatura òptim es troba entre 7 i 16ºC; (ii) la variància en la transmitància tèrmica podria ser principalment atribuïda a canvis en la temperatura ambient de l’aire exterior; (iii) la IRT quantitativa interna és més acurada en parets compostes amb altes capacitats de calor per unitat d’àrea, aconseguint unes desviacions màximes del 0.20%; (iv) el test podria ser executat en només 30 minuts; (v) el mètode podria permetre l’avaluació d’aspectes relacionats amb la determinació de la U-value en edificis desocupats per T sota 10ºC, especialment a Espanya o països europeus amb un clima mediterrani on aquestes condicions de test podrien representar una limitació. Per tant, la presa de decisions es podria simplificar en entorns construïts reals. De fet, aquesta recerca podria conduir a una millor execució del procés de rehabilitació en edificis que s’espera que tinguin deficiències l’any 2050, augmentant així la taxa de renovació europea a mig termini. La dissertació conclou resumint les principals aportacions d’aquesta investigació. Els temes que s’han plantejat durant la recerca realitzada, i que no es van poder abordar, es comenten i es proposen com a línies de treball futures.

This Engineering Doctorate aims to understand the factors that generate variability in small power consumption in commercial office buildings in order to generate more representative, building specific estimates of energy consumption. Current energy modelling practices in England are heavily focussed on simplified calculations for compliance with Building Regulations, which exclude numerous sources of energy use such as small power. When considered, estimates of small power consumption are often based on historic benchmarks, which fail to capture the significant variability of this end-use, as well as the dynamic nature of office environments. Six interrelated studies are presented in this thesis resulting in three contributions to existing theory and practice. The first contribution consists of new monitored data of energy consumption and power demand profiles for individual small power equipment in use in contemporary office buildings. These were used to inform a critical review of existing benchmarks widely used by designers in the UK. In addition, monthly and annual small power consumption data for different tenants occupying similar buildings demonstrated variations of up to 73%. The second contribution consists of a cross-disciplinary investigation into the factors influencing small power consumption. A study based on the Theory of Planned Behaviour demonstrated that perceived behavioural control may account for 17% of the variation in electricity use by different tenants. A subsequent monitoring study at the equipment level identified that user attitudes and actions may have a greater impact on variations in energy consumption than job requirements or computer specification alone. The third contribution consists of two predictive models for estimating small power demand and energy consumption in office buildings. Outputs from both models were validated and demonstrated a good correlation between predictions and monitored data. This research also led to the development and publication of industry guidance on how to stimate operational energy use at the design stage.

Buildings contribute a significant part to the electricity demand profile and peak demand for the electrical utilities. The addition of renewable energy generation adds additional variability and uncertainty to the power system. Demand side management in the buildings can help improve the demand profile for the utilities by shifting some of the demand from peak to off-peak times. Heating, ventilation and air-conditioning contribute around 45% to the overall demand of a building. This research studies two strategies for reducing the peak as well as shifting some demand from peak to off-peak periods in commercial buildings: 1. Use of gas heat pumps in place of electric heat pumps, and 2. Shifting demand for air conditioning from peak to off-peak by thermal energy storage in chilled water and ice. The first part of this study evaluates the field performance of gas engine-driven heat pumps (GEHP) tested in a commercial building in Florida. Four GEHP units of 8 Tons of Refrigeration (TR) capacity each providing air-conditioning to seven thermal zones in a commercial building, were instrumented for measuring their performance. The operation of these GEHPs was recorded for ten months, analyzed and compared with prior results reported in the literature. The instantaneous COPunit of these systems varied from 0.1 to 1.4 during typical summer week operation. The COP was low because the gas engines for the heat pumps were being used for loads that were much lower than design capacity which resulted in much lower efficiencies than expected. The performance of equivalent electric heat pump was simulated from a building energy model developed to mimic the measured building loads. An economic comparison of GEHPs and conventional electrical heat pumps was done based on the measured and simulated results. The average performance of the GEHP units was estimated to lie between those of EER-9.2 and EER-11.8 systems. The performance of GEHP systems suffers due to lower efficiency at part load operation. The study highlighted the need for optimum system sizing for GEHP/HVAC systems to meet the building load to obtain better performance in buildings. The second part of this study focusses on using chilled water or ice as thermal energy storage for shifting the air conditioning load from peak to off-peak in a commercial building. Thermal energy storage can play a very important role in providing demand-side management for diversifying the utility demand from buildings. Model of a large commercial office building is developed with thermal storage for cooling for peak power shifting. Three variations of the model were developed and analyzed for their performance with 1) ice storage, 2) chilled water storage with mixed storage tank and 3) chilled water storage with stratified tank, using EnergyPlus 8.5 software developed by the US Department of Energy. Operation strategy with tactical control to incorporate peak power schedule was developed using energy management system (EMS). The modeled HVAC system was optimized for minimum cost with the optimal storage capacity and chiller size using JEPlus. Based on the simulation, an optimal storage capacity of 40-45 GJ was estimated for the large office building model along with 40% smaller chiller capacity resulting in higher chiller part-load performance. Additionally, the auxiliary system like pump and condenser were also optimized to smaller capacities and thus resulting in less power demand during operation. The overall annual saving potential was found in the range of 7-10% for cooling electricity use resulting in 10-17% reduction in costs to the consumer. A possible annual peak shifting of 25-78% was found from the simulation results after comparing with the reference models. Adopting TES in commercial buildings and achieving 25% peak shifting could result in a reduction in peak summer demand of 1398 MW in Tampa.

The successful delivery of low-carbon housing (both new and retrofitted) is a key aspect of the UK s commitment to an 80% reduction in carbon emissions by 2050. In this context, the inclusion of small-scale building-integrated renewable energy technologies is an important component of low carbon design strategies, and is subject to numerous regulation and incentive schemes (including the Renewable Heat Incentive (RHI)) set up by government to encourage uptake and set minimum performance benchmarks. Unfortunately there are numerous examples of in-use energy and carbon performance shortfalls for new and retrofitted buildings this is termed the performance gap . Technical and human factors associated with building subsystem performance, which are often not considered in design tools used to predict performance, are the root cause of performance uncertainty. The research presented in this doctoral thesis aims to develop and apply a novel probabilistic method of evaluating the performance uncertainty of solar thermal systems installed in the UK. Analysis of measured data from a group of low carbon retrofitted dwellings revealed that the majority of buildings failed to meet the designed-for carbon emissions target with an average percentage difference of 60%. An in-depth case study technical evaluation of one of these dwellings showed significant dysfunction associated with the combined ASHP/solar thermal heating system, resulting in a performance gap of 94%, illustrating that the performance gap can be regarded as a whole-system problem, comprising a number of subsystem causal factors. Using a detailed dataset obtained from the UK s largest field trial of domestic solar thermal systems, a cross-cutting evaluation of predicted vs. measured performance similarly revealed a discrepancy with a mean percentage difference in predicted and measured annual yield of -24%. Having defined the nature and extent of underperformance for solar thermal technology in the UK, causal factors influencing performance were mapped and the associated uncertainty quantified using a novel knowledge-based Bayesian network (BN). In addition, the BN approach along with Monte Carlo sampling was applied to the well-established BREDEM model in order to quantify performance uncertainty of solar thermal systems by producing distributions of annual yield. As such, the modified BN-based BREDEM model represents a significant improvement in the prediction of performance of small-scale renewable energy technologies. Finally, financial analysis applied to the probabilistic predictions of annual yield revealed that the current UK RHI scheme is unlikely to result in positive returns on investment for solar thermal systems unless the duration of the payments is extended or electricity is the primary source of heating.

We are coming to realize that there is an urgent need to reduce energy usage in buildings and it has to be done in a sustainable way. This thesis focuses on the performance of the building envelope; more precisely thermal performance of walls and super insulation material in the form of vacuum insulation. However, the building envelope is just one part of the whole building system, and super insulators have one major flaw: they are easily adversely affected by other problems in the built environment.  Vacuum Insulation Panels are one fresh addition to the arsenal of insulation materials available to the building industry. They are composite material with a core and an enclosure which, as a composite, can reach thermal conductivities as low as 0.004 W/(mK). However, the exceptional performance relies on the barrier material preventing gas permeation, maintaining a near vacuum into the core and a minimized thermal bridge effect from the wrapping of barrier material round the edge of a panel. A serpentine edge is proposed to decrease the heat loss at the edge. Modeling and testing shows a reduction of 60% if a reasonable serpentine edge is used. A diffusion model of permeation through multilayered barrier films with metallization coatings was developed to predict ultimate service life. The model combines numerical calculations with analytical field theory allowing for more precise determination than current models. The results using the proposed model indicate that it is possible to manufacture panels with lifetimes exceeding 50 years with existing manufacturing. Switching from the component scale to the building scale; an approach of integrated testing and modeling is proposed. Four wall types have been tested in a large range of environments with the aim to assess the hygrothermal nature and significance of thermal bridges and air leakages. The test procedure was also examined as a means for a more representative performance indicator than R-value (in USA). The procedure incorporates specific steps exposing the wall to different climate conditions, ranging from cold and dry to hot and humid, with and without a pressure gradient. This study showed that air infiltration alone might decrease the thermal resistance of a residential wall by 15%, more for industrial walls. Results from the research underpin a discussion concerning the importance of a holistic approach to building design if we are to meet the challenge of energy savings and sustainability. Thermal insulation efficiency is a main concept used throughout, and since it measures utilization it is a partial measure of sustainability. It is therefore proposed as a necessary design parameter in addition to a performance indicator when designing building envelopes. The thermal insulation efficiency ranges from below 50% for a wood stud wall poorly designed with incorporated VIP, while an optimized design with VIP placed in an uninterrupted external layer shows an efficiency of 99%, almost perfect. Thermal insulation efficiency reflects the measured wall performance full scale test, thus indicating efficiency under varied environmental loads: heat, moisture and pressure. The building design must be as a system, integrating all the subsystems together to function in concert. New design methodologies must be created along with new, more reliable and comprehensive measuring, testing and integrating procedures. New super insulators are capable of reducing energy usage below zero energy in buildings. It would be a shame to waste them by not taking care of the rest of the system. This thesis details the steps that went into this study and shows how this can be done.
QC 20120228

The aim of the diploma thesis is to evaluate the energy assessment and elaboration of energy performance certificates of the building. The building is an apartment building in Vítkov. The theoretical part deals with centralized heat supply. The calculation part contains a more detailed description of individual relationships and calculation procedures that are used to process energy performance certificates of the building. Furthermore, proposals for measures to improve the energy performance of buildings. In this part there is also a proposal of individual equipment of the new boiler room and thermographic measurement. In the project part there is an energy assessment assessing the building in two variants with individual heat sources. The evaluation is carried out from an energy, economic and environmental aspect.

La performance d’un système doit être bien définie, atteignable et surtout mesurable. Ce n’est pas le cas aujourd’hui pour la ventilation. D’une part, les performances des systèmes de ventilation sont habituellement exprimées sur des considérations énergétiques ou tout simplement sur une estimation trop approximative des débits de ventilation. Les performances liées au confort thermique et à la qualité de l’air intérieur sont abordées séparément à travers des outils d’évaluation dédiés. D’autre part, les outils d’évaluation existants sont aujourd’hui limités dans leur mise en pratique pour des mesures in situ, notamment lorsqu’il s’agit de ventilation naturelle et mixte. L’objectif de cette thèse est alors d’examiner et d’expérimenter les techniques expérimentales existantes à échelle réelle afin de proposer des améliorations sur les méthodes d’évaluation et de commissionnement. La thèse aborde la performance de la ventilation en prenant en compte l’efficacité de ventilation comme performance intrinsèque et le confort thermique comme performance globale.La première partie est consacrée à l’évaluation in situ des performances intrinsèques de ventilation (taux de ventilation, âges moyens de l’air et efficacité de renouvellement d’air), en se basant sur des techniques de gaz traceurs. Après une analyse théorique des différents indicateurs de performance de ventilation et de leurs techniques de mesure correspondantes, une étude expérimentale a été menée dans une salle de cours sous différentes stratégies de ventilation (mécanique, naturelle et mixte). Les analyses ont démontré l’importance de la mise en application des techniques de décroissance de gaz traceurs sur l’incertitude des taux de renouvellement d’air avec notamment une forte influence des temps de mesure et des concentrations de gaz utilisées. Une méthodologie a été adaptée puis testée pour la mesure de l’efficacité de renouvellement d’air en ventilation mécanique, naturelle et mixte en s’affranchissant de mesures en bouches d’extraction (technique habituellement utilisée et préconisée par les normes).La deuxième partie est consacrée à l’évaluation expérimentale in situ du confort thermique sous différentes configurations de ventilation. Différentes méthodes, standards et techniques d’évaluation ont été testés et comparés avec la perception des occupants. Les résultats ont démontré la présence de plusieurs inadéquations lors de la mise en pratique des méthodes et normes existantes. Principalement, il s’agit de l’inadéquation des méthodes statiques (PMV PPD) pour l’évaluation du confort en présence de conditions thermiques fluctuantes, y compris en ventilation mécanique. Les analyses d’incertitudes liées aux erreurs de mesure ont démontré l’incohérence des normes actuelles dans la classification des catégories de confort
The performance of a system must be well defined, attainable and above all measurable. This is not the case today for ventilation. On the one hand ventilation performance is usually declined on energy efficiency considerations or simply on a rough estimation of ventilation rates. The performance related to thermal comfort and IAQ are addressed separately through dedicated evaluation tools. On the other hand, the existing evaluation tools today are nowadays limited in their practical applications for in situ measurements, in particular in the case of natural and mixed ventilation. The aim of the present thesis is to examine the existing experimental technics, at full scale building in order to propose improvements on evaluation methods and commissioning protocols. The present thesis deals with ventilation performance taking into account ventilation efficiency as intrinsic performance and thermal comfort as overall performance.The first part is devoted to the in situ assessment of intrinsic ventilation performance (ventilation rates, mean age of air, and air exchange efficiency), based on decay tracer gas techniques. After a theorical analysis of the various performance indexes and their corresponding measurement techniques, an experimental study was carried out in a classroom under different ventilation strategies (mechanical, natural & mixed mode). The analysis proved the importance of the application of the tracer gas decay on ventilation rates accuracy with in particular a strong influence of measurement times and used tracer gas concentration. A methodology has been adapted and tested for the measurement of the air exchange efficiency in natural and mixed mode ventilation, by avoiding measurements in exhaust vents (a technique usually used and advocated by current standards).The second part is devoted to in situ assessment of thermal comfort under different ventilation strategies. Different methods, standards and evaluation techniques were tested and compared with occupants’ perception. The results demonstrated the presence of several inadequacies during the implementation of existing methods and standards. Mainly, it concerns the inadequacy of static methods (PMV PPD) for thermal comfort assessment in the presence of fluctuating thermal conditions, even with mechanical ventilation. Uncertainty analysis related to measurement errors has demonstrated the incoherence of current standards in the classification of comfort categories

Diploma Thesis „Polyfunctional building“. The work deals implementation project of polyfunctional building in Jihlava. Object is situated on Jihlava suburb in emerging part called „Horní Kosov“. Land is gently sloping from west to east. It continues for Buková street. The building has six floors and a basement. The basement is made from monolithic reinforced concrete. It is used as garages. Floors are made of ceramic bricks with isolation . First floor contains four commercial premises and main entry for housing part. Seventeen flats are situated from second to sixth floor. Sizes of apartments are 1+kitchen corner to 4+kitchen corner with terraces and balcony. Roofing is solved with simple flat roof. Heating will be ensured with central heating. Every apartment, commercial premises, shared premises are going to have it’s own gas boiler. Polyfunctional building is connected on a local road – Buková street, which is connected to new communication. Within multifunctional building twenty parking slots is designed at the basement. Next fourteen parking slots is designed outside.

Yes
This empirical research explores local skill capacity gap in the petroleum industry in Ghana using a mixed method approach to study four public organisations. Matched samples of employees (226) were surveyed, while HR directors (9) were purposively sampled and interviewed. The findings suggest a wide local skill gap. Originality, this is one of the very few studies to explore the shortcomings of local skill capacity in public sector organisation. Research implications, more matched-sample studies are necessary to understand IOC’s local skill capacity further. Practically, the study is of significance to the policymakers. The main contribution of the research amongst others is to conceptualise the concept of HRM in Ghana’s context.