Modelling of double ventilated facades according to CEN Standard 13790 method and detailed simulation

The European Energy Performance of Buildings Directive (EPBD) encourages the use of technologies in buildings that can potentially improve their energy performance. Double ventilated façades can often have a positive contribution to this objective and their effect has to be quantified during the calculation of the overall energy performance of the buildings. The updated EN ISO 13790 Standard is part of the new set of CEN Standards that have to be delivered to support the EPBD requirement for a general framework for the methodology of calculation of the total energy performance of buildings. It contains a method to calculate the contribution of the double ventilated façades to the annual heating and cooling requirements of buildings. At the same time (validated) detailed simulation tools, which are also allowed in this Standard, offer an alternative way to quantify the effect of the double ventilated façades on the buildings' energy performance. This paper examines a case study where the ESP-r simulation program and the method described in the Standard were used for a common building specification to investigate the impacts from a double ventilated façade on the energy performance of the building. It discusses the potential differences that might appear when a detailed simulation tool (ESP-r) is used with constrained (according to the Standard) inputs and also unconstrained inputs, compared to the outputs obtained from the method described in the Standard. Some parametric studies are included to show whether the same trends are obtained using both the method in the Standard and the detailed simulation approach

Integrated comparative validation tests as an aid for building simulation tool users and developers

Published validation tests developed within major research projects have been an invaluable aid to program developers to check on their programs. This paper sets out how selected ASHRAE Standard 140-2004 and European CEN standards validation tests have been incorporated into the ESP-r simulation program so that they can be easily run by users and also discusses some of the issues associated with compliance checking. Embedding the tests within a simulation program allows program developers to check routinely whether updates to the simulation program have led to significant changes in predictions and to run sensitivity tests to check on the impact of alternative algorithms. Importantly, it also allows other users to undertake the tests to check that their installation is correct and to give them, and their clients, confidence in results. This paper also argues that validation tests should characterize some of the significant heat transfer processes (particularly internal surface convection) in greater detail in order to reduce the acceptance bands for program predictions. This approach is preferred to one in which validation tests are overly prescriptive (e.g., specifying fixed internal convection coefficients), as these do not reflect how programs are used in practice

History and development of validation with the ESP-r simulation program

It is well recognised that validation of dynamic building simulation programs is a long-term complex task. There have been many large national and international efforts that have led to a well-established validation methodology comprising analytical, inter-program comparison and empirical validation elements, and a significant number of tests have been developed. As simulation usage increases, driven by such initiatives as the European Energy Performance of Buildings Directive, such tests are starting to be incorporated into national and international standards. Although many program developers have run many of the developed tests, there does not appear to have been a systematic attempt to incorporate such tests into routine operation of the simulation programs. This paper reports work undertaken to address this deficiency. The paper summarizes the tests that have been applied to the simulation program ESP-r. These tests have been developed within International Energy Agency Annexes, within CEN standards, within various large-scale national projects, and by the UK's Chartered Institution of Building Services Engineers. The structure used to encapsulate the tests allows developers to ensure that recent code modifications have not resulted in unforeseen impacts on program predictions, and allows users to check for themselves against benchmarks

Development and performance evaluation of a minimum input model calibration methodology for residential buildings

Energy simulations of existing dwellings are often impeded by the complexity of assigning appropriate model inputs. While data-driven calibration is an effective method to reduce variance between measured and simulated datasets, significant effort is required for monitoring and auditing. A new minimum input calibration method is proposed, where the number of inputs is greatly reduced through a three-step sensitivity analysis creating an input set with the most influential parameters on internal temperatures. The reduction in input parameters simplifies calibration and reduces the likelihood of unrealistic solutions. The proposed method is verified on two dwellings where conventional calibration techniques were compared to the minimum input calibration method using sub-hourly internal temperatures. Compared to baseline models, the variance of minimum input models reduced from 9.9% and 9.7% to 3.3% and 3.8% (CVRMSE (%)). Results indicate that minimum input model calibration can sufficiently predict thermal performance and could be applied to retrofit optimization. Acronyms: BoM: Bureau of Meteorology; BPS: building performance simulation; CD: cooling dominant; CDH: cooling-degree hours; CVRMSE: coefficient of variation of the root mean square error; D: discrete; ECM: energy conservation measure; HD: heating dominant; HDH: heating-degree hours; MAE: mean absolute error; MBE: mean bias error; MIM: minimum input model; MIS: minimum input set; MOAT: manual one at a time; N: normal distribution; NRMSE: normalized root mean square error; RMSE: root mean square error; RMY: reference meteorological year; SHGC: solar heat gain coefficient; U: uniform distribution

Effectiveness of an intensive green roof in a sub-tropical region

The overall assessment of an intensive green roof located in a sub-tropical region has been undertaken. The results showed a fairly good agreement between the published and measured solar radiation data and also confirmed July and January as the hottest and coldest periods, respectively, for the region. The soil was established as a silt type with good planting medium properties for green roofs. The overall thermal performance showed that the green roof provided an average temperature reduction of 3.3°C (i.e. 50% temperature reduction) through the roof in July. Equally, its performance was remarkable during the coldest period of January. A maximum differential temperature of 15.5°C was achieved with the soil contributing to 24% of the temperature difference through the roof. Further studies are, however, needed to cover a wider area of influence such as effects of different types of construction materials, plants, locations and soil. In view of the limitation of the theoretical model, it would also be useful to consider some of the factors which were either neglected or assumed to be constant in any future comparative studies

Encapsulation of validation tests in the ESP-r simulation program

It is well recognised that validation of dynamic building simulation programs is a long-term complex task. There have been many large national and international efforts that have led to a well-established validation methodology comprising analytical, inter-program comparison and empirical validation components, and a significant number of tests have been developed. As simulation usage increases, driven by such initiatives as the European Energy Performance of Buildings Directive, such tests are starting to be incorporated into national and international standards. Although many program developers have run many of the developed tests, there does not appear to have been a systematic attempt to incorporate such tests into routine operation of the simulation programs. This paper reports work undertaken to address this deficiency. The paper summarizes the tests which have been applied to the simulation program ESP-r. These tests have been developed within the International Energy Agency Annexes, within CEN standards, within various largescale national projects, and by the Chartered Institution of Building Services Engineers. It will then describe work undertaken to encapsulate validation tests within the simulation program. The resulting structure allows developers to ensure that recent code modifications have not resulted in unforeseen impacts on program predictions, and allows users to check for themselves against benchmarks

Development and evaluation of a comfort-oriented control strategy for thermal management of mixed-mode ventilated buildings

The paper presents the development, implementation and performance investigation via simulations and experiments of a comfort-oriented control strategy for natural ventilation and mechanical air conditioning management of a mixed-mode building. The proposed comfort-oriented control strategy determines whether it would be possible to operate in natural ventilation mode or in mechanical heating/cooling. The control algorithm calculates first the optimal opening percentage of the windows according to adaptive thermal comfort criteria. If natural ventilation cannot guarantee the thermal comfort requirements and mechanical conditioning is required, the algorithm dynamically optimises the heating or cooling set-point targeting a defined Predicted Mean Vote (PMV) index objective. The performance of the proposed controller was tested via simulations and experiments by using a residential mixed-mode building as a case study. The house features operable windows, a reverse-cycle ducted air conditioner and a comprehensive experimental control and monitoring infrastructure. A comparison with a baseline control strategy was performed to evaluate the comfort and energy performance improvement potential of the proposed control algorithm. The comfort-oriented controller was proven to outperform the baseline controller in terms of maintaining comfort in accordance with targets set by the current comfort standards, such as deviation from a PMV set-point or the middle of the adaptive thermal comfort band. The building energy consumption was also reduced in cooling dominated conditions. The experimental tests demonstrated that this logic can be integrated in an embedded controller, and its performance is in line with the expected one from the simulation results

Implementation of a new bi-directional solar modelling method for complex façades within the ESP-r building simulation program and its application

This paper provides an overview of a new method for modelling the total solar energy transmittance. It is implemented in the ESP-r building simulation program to model complex façades such as double glazed façades with external, internal or integrated shading devices. This new model has been validated and tested for several cases. The new model required changes to the solar control simulation algorithm and the user interface, so a new “Advanced optics menu” was also introduced into ESP-r. The paper presents the interface development and application of the new technique to different simulation configurations (especially different complex façades with shading devices) in a standard office building