Ventilative Cooling in Shopping Centers' Retrofit: The Mercado Del Val Case Study ☆

Abstract Nearly all retail locations use ventilation and cooling systems to ensure adequate air exchange for health reasons and indoor comfort temperatures. These systems can run for over 2,000 hours per year and we expect that average operating hours will continue to rise across Europe because of the continued trend towards longer opening hours and increased number of opening days. Shopping malls often enclose large open spaces and atria with high solar and internal gains that can drive ventilative cooling. This paper presents the ventilative cooling strategy proposed, analysed and implemented in one of the three demo cases of the project: Mercado del Val, the historic market of the city of Valladolid. Once we determined the climate suitability, we defined a ventilative cooling strategy that exploits openings in the facade and in the skylight to promote stack effect ventilation. Considering that indoor spaces of a shopping centre highly interacts among each other, a multizone based analysis of airflows is needed to evaluate the ventilative cooling strategy effectiveness and to assess potential energy savings. We sized openings area and location on the facade, taking into account design constraints, and we assessed their performances in terms of energy, thermal comfort and indoor air quality. Results show the potential cooling load reduction, with the achievement of acceptable thermal comfort due to the ventilative cooling in the shopping mall. The analysis performed supported the design decision process towards cost effective low energy shopping centre

Mixed-mode ventilation design and thermal comfort in transitional spaces

Transitional spaces are pivotal in non-residential architecture. Depending on the building typology, the proportion of such areas may vary between 10% up to 40% of the total volume. Because of their features transitional spaces are independent dynamic spaces with various physical conditions and behaviour which may that have different thermal comfort requirements. Being integral part of the non-residential architecture, their HVAC design and controls follow however guidelines intended for indoor space. No current comfort guidelines that are specific for this peculiar building zones exists. Nevertheless, if designed with appropriate energy saving strategies as mixed-mode ventilation solution and flexible controls of HVAC, these peculiar building spaces can help achieve more energy efficient buildings. With the aim of a deeper understanding of these peculiar building zones, this PhD dissertation focuses on three aspects related to transitional spaces: mixed-mode ventilation design, thermal comfort and actual thermal performance. Information about 17 non-residential building, which integrate a transitional space in their architecture and mixed-mode ventilation strategy, were analysed and collected in a small databased. Within the building typologies considered, shopping centres resulted to be a very interesting one for the implementation of mixed-mode ventilation strategies. From the analysis of recent examples of shopping centres conversion from fully mechanical into mixed-mode operation, a design procedure was proposed. The conversion from fully mechanical into mixed-mode operation is further encouraged by the findings related to thermal comfort in shopping centers common areas. Within the studies about thermal comfort in transitional spaces, an investigation of human response within shopping centres common areas was missing. With the scope of understanding actual comfortable ranges in these spaces, around 700 customers were interviewed about their state of comfort while measuring environmental parameters. For this scope a specific questionnaire and a Mobile Environmental Monitoring cart (MEMO) were developed. The measurements were performed in spring and summer 2016 in three different Italian shopping centres, fully-mechanical operated. The results show a wider range of indoor thermal comfort conditions than in typical indoor spaces. The necessity of a tailor-made model to assess thermal comfort in transitional spaces is also disclosed. The model could correlate indoor comfort temperatures with outdoor temperatures on the basis of the direct observation of users’ thermal sensation. In order to expand the database of evidence and the creation of such model, further field studies are required, gathering together a conspicuous number of data which cover all the seasons. These findings unlock important energy use implication. If shopping centre HVAC systems are operated in a more flexible way and natural ventilation potentialities are exploited, the final goal of achieving more energy efficient buildings without sacrificing users’ comfort seems closer. With the objective of verifying the level of comfort provided by a mixed-mode solution in a transitional space, the thermal comfort and airflow performance of an atrium located in a warm temperate climate were investigated. The measurements campaign lasted over four-weeks in summer 2017. The thermal comfort evaluation of the atrium users’ was performed under different operational modes. The results showed that users’ state of comfort was independent from the way the atrium was conditioned. Specific to this case, the result opens possibilities for the use of just natural ventilation to provide comfortable conditions in summer. This would reflect in a consistent reduction of the operation costs for cooling. In the perspective of the reduction of building energy consumption without compromising thermal comfort, the results of this thesis confirm and booster the interest towards mixed-mode operated building. The potentialities of transitional spaces expressed in the thesis need to be taken into account in non-residential building design. The nature of the results for shopping centers transitional spaces can be extended to all those non-residential buildings that have transitional spaces with similar features

Mixed-mode ventilation design and thermal comfort in transitional spaces

Transitional spaces are pivotal in non-residential architecture. Depending on the building typology, the proportion of such areas may vary between 10% up to 40% of the total volume. Because of their features transitional spaces are independent dynamic spaces with various physical conditions and behaviour which may that have different thermal comfort requirements. Being integral part of the non-residential architecture, their HVAC design and controls follow however guidelines intended for indoor space. No current comfort guidelines that are specific for this peculiar building zones exists. Nevertheless, if designed with appropriate energy saving strategies as mixed-mode ventilation solution and flexible controls of HVAC, these peculiar building spaces can help achieve more energy efficient buildings. With the aim of a deeper understanding of these peculiar building zones, this PhD dissertation focuses on three aspects related to transitional spaces: mixed-mode ventilation design, thermal comfort and actual thermal performance. Information about 17 non-residential building, which integrate a transitional space in their architecture and mixed-mode ventilation strategy, were analysed and collected in a small databased. Within the building typologies considered, shopping centres resulted to be a very interesting one for the implementation of mixed-mode ventilation strategies. From the analysis of recent examples of shopping centres conversion from fully mechanical into mixed-mode operation, a design procedure was proposed. The conversion from fully mechanical into mixed-mode operation is further encouraged by the findings related to thermal comfort in shopping centers common areas. Within the studies about thermal comfort in transitional spaces, an investigation of human response within shopping centres common areas was missing. With the scope of understanding actual comfortable ranges in these spaces, around 700 customers were interviewed about their state of comfort while measuring environmental parameters. For this scope a specific questionnaire and a Mobile Environmental Monitoring cart (MEMO) were developed. The measurements were performed in spring and summer 2016 in three different Italian shopping centres, fully-mechanical operated. The results show a wider range of indoor thermal comfort conditions than in typical indoor spaces. The necessity of a tailor-made model to assess thermal comfort in transitional spaces is also disclosed. The model could correlate indoor comfort temperatures with outdoor temperatures on the basis of the direct observation of users’ thermal sensation. In order to expand the database of evidence and the creation of such model, further field studies are required, gathering together a conspicuous number of data which cover all the seasons. These findings unlock important energy use implication. If shopping centre HVAC systems are operated in a more flexible way and natural ventilation potentialities are exploited, the final goal of achieving more energy efficient buildings without sacrificing users’ comfort seems closer. With the objective of verifying the level of comfort provided by a mixed-mode solution in a transitional space, the thermal comfort and airflow performance of an atrium located in a warm temperate climate were investigated. The measurements campaign lasted over four-weeks in summer 2017. The thermal comfort evaluation of the atrium users’ was performed under different operational modes. The results showed that users’ state of comfort was independent from the way the atrium was conditioned. Specific to this case, the result opens possibilities for the use of just natural ventilation to provide comfortable conditions in summer. This would reflect in a consistent reduction of the operation costs for cooling. In the perspective of the reduction of building energy consumption without compromising thermal comfort, the results of this thesis confirm and booster the interest towards mixed-mode operated building. The potentialities of transitional spaces expressed in the thesis need to be taken into account in non-residential building design. The nature of the results for shopping centers transitional spaces can be extended to all those non-residential buildings that have transitional spaces with similar features.L’architettura degli edifici non residenziali comprende per la maggiore degli spazi di transizione la cui destinazione d’uso non è quella prevalente cui l’edificio è destinato. La porzione di tali spazi varia dal 10% al 40% del volume totale dell’edificio a seconda della tipologia di edificio non residenziale. Molte volte l’utilizzo delle aree comuni (spazi di transizione) è indipendente rispetto al resto dell’edificio. Le condizioni di dinamicità che li caratterizzano potrebbero comportare diversi standard di comfort rispetto al resto dell’edificio ma essendone parte integrante, il modo e il grado di comfort garantito è lo stesso che per le zone prettamente indoor. Al momento infatti non esistono delle linee guida per il condizionamento specifico di queste zone. Tuttavia, se fossero progettate con adeguate strategie per il risparmio energetico, come ad esempio la ventilazione ibrida, o ad esempio ci fosse un controllo più flessibile dell’impianto di ventilazione e condizionamento, queste zone offrirebbero un grosso potenziale per l’ottenimento di edifici più efficienti. L’obiettivo di questo lavoro di dottorato è quello di approfondire la conoscenza di questi spazi in relazione a tre aree che sono: il design di soluzioni di ventilazione ibrida, il comfort termico e le reali prestazioni di soluzioni di ventilazione ibrida. Al fine di studiare diverse soluzioni di ventilazione ibrida per edifici non residenziali che integrano uno spazio di transizione nella loro architettura, le informazioni tecniche relative a 17 edifici non-residenziali sono state raccolte in un piccolo database. Tra le tipologie di edifici non-residenziali considerate, i centri commerciali sono risultati esserne di grande interesse per l’implementazione. Analizzando recenti esempi di conversione di centri commerciali da funzionamento totalmente attivo a soluzioni ibride, è stato possibile ricavare una procedura di design per il retrofit in tale direzione. L’utilizzo di soluzioni ibride di ventilazione negli spazi di transizione dei centri commerciali è ulteriormente incoraggiato dai risultati relativi al comfort termico in tali spazi. Da un’analisi della letteratura relativa agli studi di comfort negli spazi di transizione ne è risultata la mancanza di uno studio relativo ai centri commerciali. Con lo scopo quindi di colmare questa mancanza è stato condotto uno studio in tali zone intervistando più di 700 clienti in relazione al loro stato di comfort e misurandone al contempo i parametri ambientali sperimentati. Ai fini dello studio è stato infatti sviluppato uno specifico questionario e un carrellino per il monitoraggio ambientale (MEMO). Le misure sono state condotte nella primavera e nell’estate del 2016 in tre differenti centri commerciali locati in Italia. I risultati dimostrano come per questi spazi, i range di comfort siano più ampi rispetto ai tipici spazi indoor. E’ inoltre emersa la necessità di un modello specifico per la caratterizzazione del comfort termico in questi spazi. Il modello, attraverso l’osservazione diretta della sensazione termica degli utenti, potrebbe correlare le temperature comfort interne con le temperature esterne. Tuttavia al fine della creazione di tale modello sono necessari altri studi in modo da collezionare un cospicuo numero di dati che ricoprano tutte le stagioni. Questi risultati aprono a importanti implicazioni dal punto di vista energetico. Se gli impianti di ventilazione e condizionamento dei centri commerciali fossero gestiti in maniera più flessibile e le potenzialità della ventilazione naturale fossero sfruttate, l’obiettivo finale di avere edifici energeticamente efficienti senza inficiare sul comfort termico degli utenti sembrerebbe più vicino. Con l’obiettivo di verificare il livello di comfort che una soluzione di ventilazione ibrida può garantire sono state studiate le prestazioni termiche di un atrio locato in un clima caldo-temperato. Le misure sono state effettuate per un periodo di quattro settimane in estate e il comfort termico degli utenti è stato valutato sotto differenti strategie di condizionamento estivo. Lo stato di comfort degli utenti si è dimostrato indipendente dal modo in cui l’atrio veniva condizionato. In relazione a questo caso, tale risultato apre possibilità al solo utilizzo della ventilazione naturale per garantire condizioni di comfort in estate. Questa soluzione permetterebbe un consistente taglio dei costi di raffrescamento. Nella prospettiva di riduzione dei consumi energetici degli edifici senza comprometterne il comfort interno, i risultati di questo lavoro di tesi confermano e sostengono l’interesse verso edifici con sistemi di ventilazione ibrida. In tal senso, le potenzialità degli spazi di transizione espresse in questo lavoro, devono essere prese in considerazione nella progettazione degli edifici non-residenziali. I risultati relativi ai centri commerciali possono essere estesi a tutti gli edifici residenziali che hanno degli spazi di transizione con caratteristiche simili

Ventilative cooling to avoid overheating in low energy buildings

Simulazioni dinamiche tramite Software VELUX EIC IDA ICE 4.1 per l analisi e la soluzione del problema dell'overheating di due low energy buildings tramite l'utilizzo di sistemi di raffrescamento passivo (solar shading and night ventilation) in rispetto dei consumi energetici e dell' ambiente interno (thermal environment). Le simulazioni sono state effettuate per il clima di Copenaghe

Systemic solution-sets

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Bulk airflow measurements in a large naturally ventilated atrium in a mild climate

In recent years, concerns about global warming and greenhouse gas emissions have motivated designers to reduce building energy consumption through the implementation of passive solutions without compromising users’ thermal comfort. This evidence has stimulated a renewed interest in designers for the exploitation of natural ventilation as means of passive cooling solutions. The adoption of ventilative cooling is particularly suitable for large spaces (non-residential buildings) as a measure to reduce the HVAC system high cooling loads. Due the inability to control and ensure a constant airflow rate through natural ventilation most of the times designers choice goes towards mixed-mode buildings. Mixed-mode buildings are designed in such a way that the HVAC system acts as backup to prevent uncomfortable conditions when natural ventilation is not sufficient to guarantee a comfortable environment. Unfortunately, information about the actual performance of mixed-mode buildings is difficult to obtain due the difficulties to set up measurements in naturally ventilated buildings that highly depend on building geometry and outdoor conditions (weather, pollution and noise). This limitation leads designers to follow a traditional design approach based on mechanical air conditioned systems. With the aim of reducing the lack of information about the actual performance of mixed-mode non-residential buildings, this paper presents a full-scale bulk air flow measurements for a large naturally ventilated atrium in a mild climate. The methodology and the results presented in this paper refers at the first step of a more complete and complex work which aims at assessing the performance of the large mixed-mode atrium. The general performance of the atrium are tested through a long term measurement campaign which is indeed ongoing. The final aim is to quantify the effect of ventilative night cooling in term of cooling energy reduction and indoor thermal environment