Jlm Jan Hensen

Literature review on thermal comfort in transient conditions

Abstract The conventional theory of thermal comfort in conditions characteristic for dwellings and offices (for example, that of Fanger) assumes steady-state conditions. Yet thermal conditions in buildings are seldom steady, due to the interaction between building structure, climate, occupancy, and HVAC system. This article reviews work on thermal comfort specifically undertaken to examine what variations in indoor temperatures may be acceptable. Following an account of mans thermoregulatory system, some experimental findings on periodic and on ramp (or drift) variation in room temperature are presented. It is concluded that the results for cyclic variations uphold the present ASHRAE standard, but those for drifts may not.

Thermal comfort: research and practice.

Thermal comfort--the state of mind, which expresses satisfaction with the thermal environment--is an important aspect of the building design process as modern man spends most of the day indoors. This paper reviews the developments in indoor thermal comfort research and practice since the second half of the 1990s, and groups these developments around two main themes; (i) thermal comfort models and standards, and (ii) advances in computerization. Within the first theme, the PMV-model (Predicted Mean Vote), created by Fanger in the late 1960s is discussed in the light of the emergence of models of adaptive thermal comfort. The adaptive models are based on adaptive opportunities of occupants and are related to options of personal control of the indoor climate and psychology and performance. Both models have been considered in the latest round of thermal comfort standard revisions. The second theme focuses on the ever increasing role played by computerization in thermal comfort research and practice, including sophisticated multi-segmental modeling and building performance simulation, transient thermal conditions and interactions, thermal manikins.

On the Application of Uncertainty and Sensitivity Analysis with Abstract Building Performance Simulation Tools

Building performance simulation (BPS) is a powerful measure to educate the building design process. However, its use in practice is to a large extent limited to the detailed design stage dedicated to the code compliance analysis of worked out design proposals. BPS is not much used to support the conceptual design stage. To date BPS tools are regarded as pure analysis tools, which do not provide design information. It is hypothesized that, when integrating uncertainty analysis techniques to existing BPS tools, following an incremental research approach, valuable design information can be provided. The article gives an update on the process to extend the capabilities of a tool specifically developed to support the conceptual design stage about uncertainty assessment. The resulting prototype should be capable of providing information about the variation of specific building performance metrics (simulation output) based on the propagated uncertainties of the building specification (simulation input). The main focus was herby the representation of material properties and their impact on the performance uncertainty of the building concept. The results also indicate the degree of impact, sensitivity, of the building specification parameters on the variation of the performance metrics as a result of their uncertainty.

Impact of Available and Perceived Control on Comfort and Health in European Office Buildings

The objective of this study was to find out how perceived control and access to control options like operable windows and thermostats affect the comfort and health of European office workers. For this, the Health Optimisation Protocol for Energy-efficient Buildings database was re-analysed. Statistical analyses were conducted to find out what the impact is of available controls on perceived control of building occupants. Furthermore, the effect of perceived control on comfort and health (building-related symptoms) of building occupants was determined. Overall, no significant correlations were found between available controls and perceived control. Solar shading, however, was an exception. On the other hand, between perceived control and comfort or health, multiple significant correlations were found. Occupants are more comfortable in buildings in which the amount of perceived control over temperature, ventilation and noise is high. Perceived control also has an impact on the incidence of building related symptoms, also if one looks at combinations of perceived control (e.g. control over temperature and ventilation).

Distributed building performance simulation : a novel approach to overcome legacy code limitations

This paper describes the development of as well as implementation strategies for distributed simulation of building systems by run-time coupling of existing software. The approach differs from the traditional way of developing software in which additional models are added by incorporating new modules into an existing program. This paper focuses on the actual coupling mechanism. A case study is presented that illustrates the need and potential of the approach. The conclusion is that a distributed simulation environment is more flexible, practical, and powerful than the sum of the individual software programs.

Performance Assessment of an Operating Theatre Design Using CFD Simulation and Tracer Gas Measurements

This paper advocates application of the performance-based approach to arrive at improved, innovative and more functional buildings. It does so by describing the development of a performance assessment methodology for the assessment of the efficiency of a ventilation system in an operating theatre. This assessment is performed in the design and use phase to adhere to the performance-based approach definition. The developed methodology was tested in a real case study with an innovative down-flow plenum. The focus was on the low infection rate functional requirement. The results from the case study indicated that the assessment methodology functions and that the innovative down-flow systems, that was the topic of the case study, adhered to the requirements set. Some parts of the methodology, however, allow openings for further research. On the other hand, a similar assessment can be extended to other requirements, such as thermal comfort, hypothermia, etc.

Modelling and simulation of a jet fan for controlled air flow in large enclosures

Jet fans are applied for control of air flow and support of pollutant dispersal in large enclosures. In The Netherlands, application is well known for car parks as part of the fire safety design. In the design phase often the Computational Fluid Dynamics (CFD)-technique is used to verify the fire safety level afforded by the application of jet fans. However, very little is known on the modelling requirements of jet fans in CFD. This includes paucity on experimental data that can be applied for validation of the jet fan model. In this study results are presented as measurements for a specific type of jet fan in a large enclosure and of validation of modelling characteristics of the jet fan in CFD. Both free and near-wall positioning have been investigated and a modelling proposal is made. For the modelling of the jet fan, point-of-departure is a low complexity, as the model generally will have to be included in large computational domains. Applicability of the developed approach and assessment of efficiency of jet fan positioning in large enclosures is shown through a case study.

Towards an integral approach of building and HVAC system

Abstract The dynamic thermal interaction between a building and the HVAC systems which service it is still difficult to predict. As this thermal interaction becomes more critical in practice, related knowledge and evaluation tools become increasingly important. It is argued why these need to be based on an integral approach of the overall problem. A research project aimed at development and/or enhancement of building performance evaluation tools for this field of interest is outlined. The work involved expansion of an existing building energy simulation environment on the fluid flow and plant simulation side. Application of this integral simulation system is demonstrated by means of a case study.

International survey on current occupant modelling approaches in building performance simulation

It is not evident that practitioners have kept pace with latest research developments in building occupant behaviour modelling; nor are the attitudes of practitioners regarding occupant behaviour modelling well understood. In order to guide research and development efforts, researchers, policy-makers, and software developers require a better understanding of current practice and acceptance of occupant modelling. This paper provides results, analysis, and discussion of the results of a 36-question international survey on current occupant modelling practice and attitudes in building performance simulation. In total, 274 valid responses were collected from BPS users (practitioners, educators, and researchers) from 37 countries. The results indicate that most assumptions made about occupants vary widely and are considerably simpler than what has been observed in reality. Most participants cited lack of time or understanding as their primary reason for not delving deeply into occupant modelling, but responded that they are receptive to further training.

Selecting an appopriate tool for airflow simulation in buildings

With the advancement of technology, and with the widespread availability of simulation tools, we are forced to consider which simulation tool would be appropriate for a particular problem. This seemingly trivial decision is in reality not very easy to make. Very often this leads to the practice of using the most sophisticated tool available for every problem. The levels of resolution and complexity of simulations are directly related to the accuracy of the simulation and to the total cost of the simulation process. A simple tool may be cheaper, but there is a high risk of inaccuracy. An advanced tool could be more accurate, but it needs a huge amount of resource in terms of computing power, labour, and the advanced knowledge to perform the simulation and interpret the results. This paper proposes a guideline for selecting a simulation tool for airflow prediction. Sensitivity analysis is selected as the tool for decision making. A case study is used to highlight the proposed method.