IBPSA England Newsletter
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The electronic Newsletter of IBPSA England (2021 No. 2)

Dear IBPSA England members,
Welcome to the June issue of the IBPSA England eNews letter. In this issue, we are first sharing the sad news of the passing away of Professor Godfried Augenbroe - a pioneer for building simulation research (Item 1). The issue moves on with the research stories from two young members of IBPSA-England - Ben Roberts (Item 2) and Nishesh Jain (Item 3). The issue proceeds with software news on LBNL's release of Modelica Buildings Library versions 8.0.0 and 7.0.1 (Item 4).  To conclude, the usual "Ask a Modeler" column from IBPSA-USA and a calendar of future BPS-related events. 

Happy reading!
Renjith Jayapalan Nair 
IBPSA England eNews Editor

P.S. The IBPSA eNews is published on a quarterly basis, namely at the end of the following months: March, June, September, and December. If you would like to share Building Performance Simulation related information with all IBPSA England delegates, please don't hesitate to send an email to r.jayapalan-nair@lboro.ac.uk

Item 1:  Remembering Professor Godfried Augenbroe (1948-2021)

Professor Godfried “Fried” Augenbroe passed away on Friday, May 14, 2021, after his fight with cancer. Godfried Augenbroe was a pioneering thought leader, researcher and educator. He is internationally recognized for a career that spanned more than 35 years. Augenbroe served on the scientific boards of five international journals and published three books and over 200 refereed papers. Augenbroe had close ties to the UK. He held visiting professorships at the University of Newcastle (2000-2003) and Loughborough University (2001-2011), and regularly visited some of his former students who worked in academia across the UK. 
Augenbroe’s research ranged from explorations in building performance, computational building simulation, and intelligent building systems to indoor air quality, uncertainty and risk, and system monitoring and diagnostics. In the nineties, he coordinated four major EU-funded consortia of academic and industrial partners in the fields of design tool interoperability (COMBINE, 1990-1995), energy performance simulation, outsourcing and project planning (e-HUBS, 2002-2005). He served on the board of the IBPSA World. At GeorgiaTech, he was director of the High-Performance Building laboratory. His work was recognized by the community through a number of awards, such as the JOULE Researcher of the Year award from the EU-CEC in 1995, IBPSA-USA Lifetime Achievement Award 2008, the National Science Foundation (NSF) EFRI-SEED award “Risk conscious design and retrofit of buildings for low energy”, 2010-2014, and, IBPSA Distinguished Achievement Award 2015.

But most of all, he has mentored more than 35 PhD and a large number of MS students, who all recognize his deep mentorship to them, and consider him to be more than a mentor. 

Item 2:  IBPSA-England Young Blood Forum: Research Story - 1

"Ventilation and shading to reduce overheating in UK homes: an evaluation using matched pair test houses with synthetic occupants"
Dr Ben Roberts,
Research Associate,
Building Energy Research Group,

Loughborough University

Summertime overheating in UK homes presents a growing risk to occupant health and well-being. Ventilation and shading strategies to keep homes cool without using air-conditioning are needed, and these could make use of existing features of the homes: operable windows, internal shading, internal doors, or a combination of these. However, there is a gap in knowledge about what occupants should do, and when, to reduce indoor temperatures in summer and what effect these interventions might have in typical UK homes. 

This research utilised the Loughborough Matched Pair test houses, which are operated by the Building Energy Research Group at Loughborough University. The test houses were used to conduct side-by-side comparisons of different ventilation and shading strategies. Synthetic occupancy devices operated windows, internal shading, internal doors and mimicked the internal heat gains of occupants and appliances to follow the CIBSE TM59 schedules. Sensors measured indoor temperatures, and the weather conditions. Tracer gases were released to determine ventilation rates.

Overheating was assessed using the CIBSE TM59 criteria. The synthetically occupied houses were monitored for an entire summer period, which featured a heatwave. It was found that night ventilation of bedrooms and a ground floor room with internal doors open was the most effective ventilation strategy to keep homes cool in summer. However, the ventilation and shading strategies trialled during the heatwave did not prevent the houses from overheating, and so alternative cooling strategies are needed.

Ventilation experiments revealed that keeping the curtains open in bedrooms allowed for higher ventilation rates compared to when curtains were closed. This has implications for the design of ventilation openings. Measured infiltration was lower than predicted by all infiltration estimation methods, which has implications for both overheating prediction and indoor air quality.

Predictions of overheating are commonly made using dynamic thermal models and the CIBSE TM59 methodology, but the accuracy of the predictions is largely unknown. If overheating is not correctly predicted, buildings are at a higher risk of overheating because overheating mitigation strategies may not be identified and implemented at the dwelling design stage. To quantify the uncertainty in overheating prediction, a two-phase multi-modeller empirical validation and inter-model comparison exercise was conducted using the Loughborough Matched Pair test houses as a case study during the period they were synthetically occupied following the TM59 schedules. Models consistently predicted higher maximum temperatures and larger diurnal swings than were measured. Ultimately, the uncertainty in the predictions of overheating was sufficiently large that it was difficult to reliably ascertain whether the houses would overheat in an overheating risk assessment, due to the inter-model variability.

This research demonstrated the value of matched pair houses for understanding the effect that different ventilation and shading strategies had on reducing overheating in summer. It also demonstrated and quantified the reliability of the overheating predictions of dynamic thermal models. These and other results will be valuable to house builders, those concerned with assuring the health and well-being of UK citizens, and the academics, engineers, and consultants that use dynamic thermal models to assess summertime overheating.

Item 3:  IBPSA-England Young Blood Forum: Research Story - 2

"Reducing the performance gap using calibrated simulation models"
Nishesh Jain
KTP Research Associate,
University College London - DesignBuilder Software


There is considerable evidence to suggest that buildings underperform post-completion compared to the expected performance predicted at the design stage. The difference between the actual operation and the design intent is termed the ‘performance gap’. While the energy performance gap in buildings is a well-known phenomenon, its in-use interpretation is quite vague. Also, in the context of the performance gap, energy performance is generally the most emphasised. The gap, however, is not limited to energy – it also applies to indoor environmental quality (IEQ) parameters such as temperature and air quality. Moreover, the pursuit of energy efficiency may have the unintended consequence of compromising IEQ, requiring a more holistic approach to performance assessment.

This PhD thesis “Reducing the performance gap using calibrated simulation models” contributes to an improved understanding, quantification, and resolution of performance gap related issues by using a simulation-based approach that enables systematic identification and classification of its root causes. A new measurement and verification (M&V) framework that is underpinned by building performance simulation and calibration is proposed. This framework can identify and separate: 

  • the technical issues that cause the performance gap between design intent and actual operation, and
  • the deviations of operating conditions from the design that are driven by the building’s function and occupancy. 

This is achieved by integrating the conventional post-occupancy performance assessment approach with building performance modelling and evidence-based model calibration. The new calibration-based framework proposed in this study is applied to five case study buildings across four building sectors – offices, schools, hospitals, and apartment blocks. DesignBuilder, a widely respected graphical user interface to EnergyPlus, was used to develop the simulation models and to undertake the calibrations. 

In a wider context, the research illustrates the importance of taking a more holistic approach, balancing the current predominant focus of energy efficiency with maintaining acceptable levels of IEQ. To help industry practitioners apply this research in practice, the framework and methods from this research are explained in a CIBSE publication ‘CIBSE TM63: Operational performance: Modelling for evaluation of energy in‐use’, which is a part of a series of publications ‘CIBSE TM61-64: Operational performance of buildings’.

Item 4:  Software News: LBNL released the Modelica Buildings Library versions 8.0.0 and 7.0.1.

Version 8.0.0 is a major release that contains the first version of the Spawn of EnergyPlus coupling that has been developed by LBNL and NREL in collaboration with Modelon and Objexx Engineering.
The following major changes have been done in Version 8.0.0:
  • The package Buildings.ThermalZones.EnergyPlus contains the first version of the Spawn of EnergyPlus coupling that is being developed at lbl-srg.github.io/soep. The Spawn coupling allows to model HVAC and controls in Modelica, and graphically connect to EnergyPlus models for thermal zones, schedules EMS actuators and output variables. This allows for example to model HVAC systems, HVAC controls and controls for active facade systems in Modelica, and use the EnergyPlus envelope model to simulate heat transfer through the building envelope, including the heat and light transmission through the windows for the current control signal of the active shade.
  • The  package Buildings.Experimental.DHC contains models for district heating and cooling systems that are being developed for the URBANopt District Energy System software.
  • The new media Buildings.Media.Antifreeze.PropyleneGlycolWater allows modeling of propylene-glycol water mixtures.
  • A new cooling coil model Buildings.Fluid.HeatExchangers.WetCoilEffectivenessNTU has been added. This model is applicable for fully-dry, partially-wet, and fully-wet regimes. In contrast to Buildings.Fluid.HeatExchangers.WetCoilCounterFlow and to Buildings.Fluid.HeatExchangers.WetCoilDiscretized, this model uses the epsilon-NTU relationship rather than a spatial discretization of the coil. This leads to fewer state variables and generally to a faster simulation.
  • New simplified door models for bi-directional air exchange between thermal zones are implemented in Buildings.Airflow.Multizone.
  • Various other models have been improved or added, in particular for modeling of control sequences using the Control Description Language that has been developed in the OpenBuildingControl project at obc.lbl.gov.
  • For a detailed list of changes in version 8.0.0, see the 8.0.0 release notes.
Version 7.0.1 is a bug fix release that is compatible with 7.0.0. The following changes have been done:
  • Corrected memory violation on Windows for weather data file with long header lines.
  • Corrected various misplaced, or missing, declarations of the "each" statement.
  • Corrected access to protected classes.
  • Reformulated replaceable class to avoid access of components that are not in the constraining type.
  • Added missing parameter declarations for records.
For a detailed list of changes in version 7.0.1, see the 7.0.1 release notes.
Both versions have been tested with Dymola 2021 and 2022, JModelica (revision 14023), and OPTIMICA (revision OCT-stable-r12473_JM-r14295).

For download, go to simulationresearch.lbl.gov/modelica

Originally announced on June 9, 2021 by Michael Wetter via Bldg-sim mailing list

Ask a Modeler

What is the Best Approach to Simulating Geometrically Complex Buildings?

- Not Always Right-Angled
Adam Ozinsky,
Environmental Designer,
Atelier Ten

Answer on the IBPSA-USA website:

We want to hear your interesting, entertaining, or just plain odd questions about life and building performance simulation. Submit your questions to be answered by prominent building performance simulation experts. Note that questions requiring an immediate response should be submitted to the community of experts at unmethours.com. If you are interested in replying to a question as a featured expert or have any other feedback about Ask a Modeler please email askamodeler@ibpsa.us.

  • ASHRAE Virtual Annual conference, 28-30 June 2021 – ashrae.org
  • CIBSE Technical Symposium, 13-14 July 2021 – cibse.org
  • Building Simulation 2021 conference, 1-3 September 2021 [Bruges, Belgium] – bs2021.org
A calendar with events organised by other regional affiliates of IBPSA can be found in the bi-annual IBPSA World newsletter: www.ibpsa.org/ibpsa-newsletter/

If you would like to share Building Performance Simulation related information with all IBPSA England delegates, please don't hesitate to send an email to r.jayapalan-nair@lboro.ac.uk

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