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IEA I NTERNATIONAL E NERGY A GENCY E NERGY C ONSERVATION IN B UILDINGS AND C OMMUNITY S YSTEMS Annex Definition Annex35 HybVent Hybrid Ventilation in New and Retrofitted Office Buildings Aalborg University, May 2017 IEA-BCS Annex 35: HybVent ANNEX 35 HYBRID VENTILATION IN NEW AND RETROFITTED OFFICE BUILDINGS 1. DESCRIPTION OF TECHNICAL SECTOR AND DEFINITIONS 1.1. Description of Technical Sector Immediately after the energy crisis in 1973 attention was focused on thermal insulation, airtightness of buildings and heat recovery to decrease energy consumption of heating and cooling of buildings. Buildings were designed to be isolated from the outdoor environment with an indoor environment controlled by artificial lighting, mechanical ventilation and heating and cooling systems. Today, in the design of new buildings and retrofit of old buildings, the attention has turned towards a more integrated design with focus not only on thermal insulation, airtightness and heat recovery but also on optimal use of sustainable technologies as passive solar gains, daylighting and natural ventilation. Buildings are designed to interact with the outdoor environment and they are utilizing the outdoor environment to create an acceptable indoor environment whenever it is beneficial. The extent to which sustainable technologies can be utilized depends on outdoor climate, building use, building location and design. Under optimum conditions sustainable technologies will be able to satisfy the demands for heat, light and fresh air. In some cases supplementary mechanical systems will be needed and in other cases it will not be possible to use sustainable technologies at all. In thermally well insulated office buildings, which are more and more frequent in IEA countries, ventilation (and cooling) account for more than 50% of the energy requirement, and a well-controlled and energy-efficient ventilation system is a prerequisite of low energy consumption. Natural ventilation and passive cooling are sustainable, energy-efficient and clean technologies as long as they can be controlled. These technologies are well accepted by occupants and should therefore be encouraged wherever possible. Unfortunately, the design of energy-efficient ventilation systems in office buildings has often become a question of using either natural ventilation and passive cooling or mechanical ventilation and cooling. This prevents a widespread use of sustainable technologies because a certain performance cannot be guaranteed under all conditions. In fact in the majority of cases a combination of systems would be beneficial depending on outdoor climate, building design, building use and the main purpose of the ventilation system. The number of office buildings to be retrofitted in most IEA countries is now much larger than the potential for new buildings. In many cases there is a large potential for use of sustainable technologies either as a supplement to the existing mechanical systems or as a replacement for conventional systems. 02/05/2017 2 IEA-BCS Annex 35: HybVent Therefore, there is certainly a need for development of innovative hybrid ventilation systems. Suitable design tools as we know them for mechanical systems are not available for hybrid ventilation systems. Valid design tools would give architects and engineers the necessary confidence in system performance, which in many cases, is the decisive factor for choice of system design. The scope of this annex is therefore to obtain better knowledge of the use of hybrid ventilation technologies and to focus on development of control strategies for hybrid ventilation, on development of methods to predict hybrid ventilation performance in office buildings and on implementation and demonstration of hybrid ventilation in real buildings. Thorough control of hybrid ventilation in new as well as in retrofitted buildings requires a completely integrated approach to building design, its technical systems (lighting, heating), occupant behaviour, topography of surroundings, climatic and meteorological conditions, etc. The integrated approach is the basic strategy applied in this annex. Therefore, in development of methods to predict hybrid ventilation performance preference is given to combined models, describing as far as possible all involved phenomena to give realistic results, even if simplifying assumptions are required. The fact that input data are not known with perfect accuracy is also taken into account. It has no meaning to develop a sophisticated method if the uncertainty of input data results in output data which are not more reliable than output from a simpler method. 1.2. Definitions Hybrid ventilation systems can be described as systems providing a comfortable internal environment using different features of both natural ventilation and mechanical systems at different times of the day or season of the year. It is a ventilation system where mechanical and natural forces are combined in a two mode system. The basic philosophy is to maintain a satisfactory indoor environment by alternating between and combining these two modes to avoid the cost, the energy penalty and the consequential environmental effects of yearround air conditioning. The operating mode varies according to the season and within individual days, thus the current mode reflects the external environment and takes maximum advantage of ambient conditions at any point in time. The main difference between conventional ventilation systems and hybrid systems is the fact that the latter are intelligent systems with control systems that automatically can switch between natural and mechanical mode in order to minimize the energy consumption. Hybrid ventilation should dependent on building design, internal loads, natural driving forces, outdoor conditions and season fulfil the immediate demands to the indoor environment in the most energy-efficient manner. The control strategies for hybrid ventilation systems in office buildings should maximize the use of ambient energy with an effective balance between the use of advanced automatic control of passive devices and the opportunity for users of the building to exercise direct control of their environment. The control strategies should also establish the desired air flow rates and air flow patterns at the lowest energy consumption possible. The figure below shows the definition of hybrid ventilation applied in Annex 35. 02/05/2017 3 IEA-BCS Annex 35: HybVent Definition of Hybrid Ventilation Hybrid Ventilation is a two-mode system which is controlled to minimize the energy consumption while maintaining acceptable indoor air quality and thermal comfort. The two modes refer to natural and mechanical driving forces Purpose of Ventilation All hybrid systems have to provide air for indoor air quality purposes, but in addition some also provide air for thermal conditioning and thermal comfort during working hours Purpose of Control System The purpose of the control system is to establish the desired air flow rate and air flow pattern at the lowest energy consumption possible Figure 1. Annex 35 definitions of hybrid ventilation and purpose of ventilation and control system. 2. OBJECTIVES The objectives of Annex 35 are to develop control strategies for hybrid ventilation systems in new and retrofitted office and educational buildings to develop methods to predict hybrid ventilation performance in hybrid ventilated buildings to promote energy and cost-effective hybrid ventilation systems in office and educational buildings to select suitable measurement techniques for diagnostic purposes to be used in buildings ventilated by hybrid ventilation systems 3. MEANS 3.1. Subtasks The following three subtasks will be carried out in order to reach the objectives: Subtask A: Development of control strategies for hybrid ventilation Subtask B: Theoretical and experimental studies of performance of hybrid ventilation. Development of analysis methods for hybrid ventilation Subtask C: Pilot studies of hybrid ventilation 3.1.1. Subtask A: Development of Control Strategies Integration of a natural and a mechanical ventilation system in a common hybrid ventilation system requires development of new control strategies. The objective of this subtask is to develop strategies that can control hybrid ventilation systems at any time and for a certain combination of internal loads, outdoor conditions and comfort requirements can ensure that the immediate demands to the indoor environment are fulfilled in the most energy efficient manner. 02/05/2017 4 IEA-BCS Annex 35: HybVent The participants shall achieve this objective, by means of a typical case in their own country and climate, by theoretical studies, laboratory experiments and pilot studies of the performance of different control strategies in a hybrid ventilated office or educational building. The main focus shall be on development of strategies for switching between ventilation modes and for combining central automatic and individual manual control. The cost-effectiveness of different ventilation and control strategies shall be investigated by comparing capital cost and operational costs against a typical refurbishment or new building. Assessment philosophies and analysis methods of hybrid ventilation concepts shall be developed in the framework of Energy Performance Standardisation Regulations. 3.1.2. Subtask B: Development of Analysis Methods The objective of this subtask is to achieve a better understanding and a better control of the hybrid ventilation process, which is a prerequisite for a successful application of hybrid ventilation and, based on this knowledge, to develop analysis methods for hybrid ventilation design. The participants shall achieve the objective by investigating the different elements of the air flow process in hybrid ventilation from air flow around buildings, air flow through openings, air flow in rooms to air flow between rooms in a building. The development of analysis methods shall focus partly on combining existing analysis methods and partly on developing new analysis methods for air flow control and thermal conditioning in hybrid ventilated buildings. The work shall focus on two major developments. The first development is a model that should be able to predict statistical occurrences of energy and air flow rates in hybrid ventilated buildings. The model shall be developed by combining available physical models of the phenomena involved with stochastic models. This procedure includes a sensitivity study and error analysis as well as comparisons with experiments and simulations with other models. The second development is an analysis model that combines existing thermal simulation models with existing air flow models. In this way the thermal dynamics of the building can be taken into account in predicting the performance of hybrid ventilation, which is very important both with regard to the driving forces and the air flow requirements. 3.1.3. Subtask C: Pilot Studies of Hybrid Ventilation The objective of this subtask is through pilot studies to implement hybrid ventilation systems and demonstrate their performance. The participants shall achieve this objective by analysis of hybrid ventilation components and systems. The participants shall monitor pilot studies to collect data on performance (IAQ, thermal comfort and energy consumption) and to evaluate corresponding control strategies and analysis methods. The pilot studies shall include both retrofitted and new build designs and shall highlight similarities and differences in climatic issues (including seasonal differences), institutional and cultural issues (developers and occupants), and technology transfer issues. The pilot studies shall concentrate on success stories of hybrid ventilation but also critically highlight problematic cases. New diagnostic measurement techniques may be developed and reported. 02/05/2017 5 IEA-BCS Annex 35: HybVent 3.2. Participating Countries An overview of participating countries and their subtask affiliation is shown in Table 1. Table 1. Overview of participation in Annex 35. Country Australia Belgium Canada Denmark Finland France Germany Greece Italy Japan Norway Sweden The Netherlands United Kingdom U.S.A. 3.3. Subtask A Subtask B X X X X X X X X X X X X X X X X X X X X X X X X Subtask C X (X) X X X X X X X X Programme of Work An overview of programme of work is shown in Table 2. Table 2. Overview of programme of work. Task Research Method State-of-the-art Review Subtask A Definition of requirements and evaluation criteria for control strategies Development of strategies for switching between and combining ventilation modes Development of strategies for combination of automatic and manual individual control Control system design Demonstration and evaluation of control strategies Survey of available analysis methods Achieve better understanding of the physics of hybrid ventilation (air flow control) Integration of air flow and thermal simulation models Development of probabilistic analysis method Application and evaluation of analysis methods Survey of existing systems and solutions to specific problems Market survey of components Survey of building codes Analysis of hybrid ventilation components and systems Analysis of barriers for hybrid ventilation application Cost-benefit analysis of hybrid ventilation Demonstration of hybrid ventilation performance Technology transfer Development of Analysis Methods Subtask C Pilot Studies 02/05/2017 Implementation and Demonstration Survey of existing strategies Local versus central control Development of Control Strategies Subtask B Theoretical and Experimental Studies 6 IEA-BCS Annex 35: HybVent 3.3.1. Subtask A The participating countries in subtask A shall based on existing buildings perform a stateof-the-art review of existing control strategies and algorithms applicable for hybrid ventilation, including a critical view on the integration with BEMS and on individual contra whole building control. They shall also based on existing buildings provide a market survey of commercially available control systems, automatic control devices, algorithms, etc. The results shall be summarized and included in the state-of-the-art report. In the development of new control strategies the focus will be on different issues in the participating countries and will cover a range of hybrid ventilation system and building designs. Australia will investigate the impact of occupant individual control of heating, cooling and lighting on energy consumption in an office building. Denmark will focus on development and evaluation of control strategies and automatic control systems for open plan offices that allow control of local indoor climate. France will focus on theoretical definition, experimental evaluation and implementation of fuzzy control strategies and automatic tuning techniques of controllers in office and educational buildings. Norway will develop and evaluate control strategies for a hybrid ventilation system with heat recovery and focus on controlling air flows in a three storey office building, on individual floors and in individual rooms, respectively. The United Kingdom's input will based on the state-of-theart review of control devices, systems and strategies; parametric analysis will be carried out using computer ventilation modelling to estimate their performance. Belgium, Denmark, The Netherlands will work on a classification of hybrid ventilation systems and assessment philosophies and analysis methods of hybrid ventilation concepts will be developed in the framework of Energy Performance Standardisation Regulations. The results shall be documented in technical reports and be public available on the homepage of Annex 35. All countries shall summarize their findings and contribute written material to the final report as agreed. 3.3.2. Subtask B The participating countries in subtask B shall perform a state-of-the-art review of the available analysis methods for prediction of hybrid ventilation performance. These methods include analytical/empirical methods, zonal and multizone methods, probabilistic methods and computational fluid dynamics. The results shall be summarized and included in the state-of-the-art report. The participating countries will focus on achieving a better understanding of the air flow process and on development of new analysis methods related to hybrid ventilation. Hybrid ventilation air flow process Individual elements of the air flow process in hybrid ventilation will be investigated as well as the air flow process of whole systems. Greece will work on translation of meteorological data from weather stations into urban data. Belgium will study wind pressures around buildings and the impact on predicted performances, while Denmark will based on theoretical studies investigate the impact of air flow and local climate around buildings on the optimum location of air inlets and outlets. Denmark and Italy will by systematic tests of hybrid ventilation components as air inlets 02/05/2017 7 IEA-BCS Annex 35: HybVent and outlets obtain the necessary performance data for component characterization. Italy and Germany will investigate, optimize and model solar chimney performance and Italy will develop a model for ventilated roofs and facades. Australia and Canada will investigate air flow patterns, energy transport and air flow control in a hybrid ventilated building with solar chimneys and under floor plenum for passive cooling. Greece and Sweden will develop models for buoyancy driven flow in stairwells. Sweden will study and develop models for inter-zonal buoyancy driven and forced air flows through both vertical and horizontal openings. Sweden will develop tracer gas methods that are capable of evaluating such flows. Finland, Germany, Japan and Sweden will, based on simulation studies with different simulation techniques, analyse and develop hybrid ventilation concepts for office and educational buildings. Finland will focus on development of concepts for office buildings in Finish climates, while Germany and Sweden will focus on educational buildings, and Japan on improvement of hybrid ventilation concepts based on the task-ambient ventilation principle. Multizone methods Both Australia , Finland and U.S.A. will develop analysis methods that combine an existing thermal simulation model with an existing multizone air flow model. In Australia it will be a further development of the program CHEMIX where as in the U.S.A. it will be an integration of the multizone air flow model COMIS into the thermal building simulation model Energy Plus. Zonal methods Canada, France and Italy will develop and improve zonal models for the prediction of thermal comfort, indoor air quality and thermal stratification in hybrid ventilated buildings. The main emphasis will be placed on the special boundary conditions and ventilation systems that prevail in hybrid ventilated buildings as well as implementation of the prediction of different control strategies. Probabilistic methods Denmark will develop a probabilistic analysis method for hybrid ventilation that can predict the probability of critical incidents as unsatisfactory air flow, poor indoor air quality or large energy consumption for a specific design. Italy will develop a probabilistic approach to inlet and outlet performance based on computer calculations and experimental evaluation of the results. Australia will apply a probabilistic approach to study output uncertainties, due to uncertainties in input parameters, of the solutions obtained from simple analytical methods. Simple analytical methods Australia and Denmark will develop new and simple analytical methods for the design of hybrid ventilation in single and multizone buildings. Germany and United Kingdom will investigate and demonstrate the applicability of developed analysis methods by parametric analysis and comparisons with measurements in existing buildings. Greece will incorporate developed models in the Building Performance TOOLBOX. Norway will develop and implement simple analytical models in the simulation program SCIAQ while Sweden expand the NatVent program to include hybrid ventilation predictions. 02/05/2017 8 IEA-BCS Annex 35: HybVent The results shall be documented in technical reports and be available on the homepage of Annex 35. All countries shall summarize their findings and contribute written material to the final report as agreed. 3.3.3. Subtask C The participating countries in subtask C shall perform a state-of-the-art review of hybrid ventilation systems with examples of existing systems and solutions to specific problems. They shall provide a market survey of commercially available components, systems, etc. and investigate the suitability of hybrid ventilation in different building types and urban locations for the climatic conditions of their country. Finally, they shall provide a survey of the building codes of their country with special focus on items that have an impact on the applicability of hybrid ventilation. The results shall be summarized and included in the state-of-the-art report. The participating countries shall provide a pilot study with a hybrid ventilation system according to the definition applied in this annex. The performance (IAQ, thermal comfort, energy consumption, etc.) of the hybrid ventilation system with the corresponding control strategies shall be monitored during a one year period. Measurement data shall also be provided for evaluation of analysis methods and/or control strategies. Participants shall provide an analysis of barriers for hybrid ventilation application as well as a cost-benefit analysis of the alternatives to ventilation system design. The individual research group relating to each pilot study is responsible for the collection of data on the performance, analysis of the results and providing a technical report describing the building, measurements and findings. This report shall be available on the homepage of Annex 35. All countries shall summarize their findings and contribute written material to the final report as agreed. 3.3.4. Planned effort in Annex 35 The planned effort in Annex 35 is summarized in Table 3. It shows country contribution to each subtask according to the planned work described in sections 3.3.1 to 3.3.3. 02/05/2017 9 IEA-BCS Annex 35: HybVent Table 3. Planned effort in Annex 35 (staff months) AU B CAN DK FIN F D G I J N x x x x x x 54 18 11 40 24 9 Contribute to state-ofthe-art and final report x x x x x x x Air flow process 5 2 35 12 20 7 S NL UK US Subtask A Contribute to state-ofthe-art and final report Development of control strategies x 4 x x Subtask B Multizone methods 4 x x 19 10 18 x x ? 8 Zonal methods 36 36 36 Probabilistic methods 5 60 Simple analytical methods 5 3 9 24 9 6 10 2 9 Subtask C Contribute to state-ofthe-art and final report Pilot study analysis and measurements 3.4. x x 3 3 x x x x x 11 16 8 37 28 14 13 6 ? 6 Annex Management The annex shall be managed by the Operating Agent and the leaders of the subtasks A-C (The Technical Advisory Committee). All subtasks will provide material for the two final reports which will have two editors each. The organization of Annex 35 is illustrated in Figure 2. Technical Advisory Committee TL Development of Control Strategies OA TL Development of Analysis Methods TL Pilot Studies E E E E Reporting Principles of Hybrid Ventilation State-of-the-art Review Figure 2. Organization of Annex 35 with subtasks, final reports and a Technical Advisory Committee. 02/05/2017 4 10 IEA-BCS Annex 35: HybVent 3.4.1. The Operating Agent The Operating Agent is responsible for the overall performance, time schedule, reporting, knowledge transfer, etc. of Annex 35. 3.4.2. Subtask Leaders The leaders of subtasks A-C are responsible for the quality and the management of the work within their subtask. The subtask leader shall be a participant who provides a high level of expertise to the subtask and undertakes in his or her country substantial research and development in the field of the subtask. Subtask leaders shall be proposed by the Operating Agent, and designated by the Executive Committee acting by unanimity. Changes in the leadership may be agreed to by the Executive Committee, acting by unanimity of the participants. The subtask leaders of subtasks A-C will: 1) Co-ordinate the work performed under the subtask 2) Assist the Operating Agent in preparing the detailed programme of work 3) Direct technical workshops and provide the Operating Agent with written summaries of workshop results 4) Edit technical reports resulting from the Subtask and organize their publication 3.4.3. Technical Advisory Committee The participants shall establish a Technical Advisory Committee (the “Technical Advisory Committee”) consisting of the leaders of subtasks A-C and the Operating Agent or their respective designees. The Technical Advisory Committee shall assist the Operating Agent in the co-ordination of the annex and advise the Operating Agent on the performance of the annex. 4. RESULTS AND END PRODUCTS The results of Annex 35 will be summarized in two final reports and specific results of individual subtasks will be reported in technical reports and papers. 4.1. State-of-the-art Review This report will describe the state-of-the-art of hybrid ventilation technologies, of control strategies and algorithms and of analysis methods. The report will provide examples of existing systems and show solutions to specific problems (fresh air supply, excess heat removal, etc.) in particular office buildings located in different outdoor climates. It will, based on the existing buildings, also include a market survey of commercially available hybrid ventilation components. The report will focus on the impact of differences in climate (including seasonal differences as winter heating and summer cooling), building design, building use and internal loads on energy performance, indoor air quality and thermal comfort. 02/05/2017 11 IEA-BCS Annex 35: HybVent 4.2. Principles of Hybrid Ventilation This report will describe the principles of hybrid ventilation, including solutions for energy-efficient, comfortable and cost-effective hybrid ventilation and recommendations on control strategies and analysis methods. The report will be written on the basis of experience gained in annex subtasks as well as achievements from previous research (stateof-the-art review). 4.3. Annex Beneficiaries The “Principles of Hybrid Ventilation” report will be written for architects and engineers, and parts of it will be available for a large public. Therefore, architects should participate in the planning and review process of the report. This guide will provide advice for good practice for application of hybrid ventilation in new and retrofitted buildings. The emphasis will be on characteristic cases, which do not require specific studies. The technical reports and analysis methods will be available for engineering offices, helping them to provide advice to architects and to design systems, especially concerning cases not treated in the “Principles of hybrid ventilation” report. 5. TIME SCHEDULE The duration of the Annex will be four years (August, 1998 - July, 2002) and the project period is divided into three phases - a fact finding phase, a working phase and a reporting phase. The following figure shows the time schedule for the different annex activities and the major milestones. Figure 3. Time Schedule and Milestones 02/05/2017 12 IEA-BCS Annex 35: HybVent 6. FUNDING AND COMMITMENT The work has been divided into three subtasks and each participant shall work in at least one of the subtasks. All participants are also required to deliver information and written materiel to the final reports as agreed in the annex. The minimum commitment in the annex for each participant is described in paragraphs 3.2 and 3.3. Each participant shall individually bear the costs incurred in the activities. Funding includes working costs as well as travelling costs for participating in a minimum of two expert meetings per year in any of the participating countries during the four-year annex period and eventual overhead costs. Any participating country has access to the workshops and results of all subtasks. The participating country must designate at least one individual (an active researcher, scientist, or engineer, here called expert) for each subtask they participate in. It is expected that the same expert attends all expert meetings and acts as technical contact regarding the national subtask contribution. For the Operating Agent funding shall allow for extra 4 months per year for annex activities, including the attendance of 2 ExCo-meetings per year. For the subtask leaders funding shall allow for extra 2 months per year for annex activities. 7. ANNEX 35 LEADERSHIP 7.1. Operating Agent The Operating Agent for the Annex shall be Per Heiselberg, Aalborg University, Department of Building Technology and Structural Engineering, Aalborg, Denmark. 7.2. Subtask Leaders Leader of subtask A shall be Gerard Guarracino, E.N.T.P.E / L.A.S.H - D.G.C.B, CNRS, Building Sciences Laboratory, Vaulx en Velin Cedex, France. Leader of subtask B shall be Yuguo Li, CSIRO, Division of Building Construction and Engineering, Highett Vic, Australia. Leader of subtask C shall be Marco Citterio, ENEA, Energy Saving Department ERG SIRE, Rome, Italy. 7.3. Report Editors Editors of the state-of-the-art report shall be Tor Arvid Vik, SINTEF, Architecture and Building Technology, Trondheim, Norway and Angelo Delsante, CSIRO, Division of Building Construction and Engineering, Highett Vic, Australia. Editors of the report “Principles of Hybrid Ventilation” shall be ….. Possibly AIVC will contribute in the distribution of information etc……… 02/05/2017 13 IEA-BCS Annex 35: HybVent 8. ANNEX PARTICIPANTS The participants in this annex are the following: Australia, Belgium, Canada, Denmark, Finland, France, Germany, Greece, Italy, Japan, Norway, Sweden, The Netherlands, United Kingdom and United States. 02/05/2017 14