1. Energy and Environmental Modelling at Building and Urban Scale
Submitting InstitutionCardiff University
Unit of AssessmentArchitecture, Built Environment and Planning
Summary Impact TypeTechnological
Research Subject Area(s)
Information and Computing Sciences: Artificial Intelligence and Image Processing
Built Environment and Design: Building
Economics: Applied Economics
Summary of the impact
The Welsh School of Architecture (WSA) is recognised internationally for
its research in developing advanced computational numerical models for
simulating the energy and environmental performance of the built
environment. These models have been used by leading design practices in
the design of major buildings and urban developments. This impact case
study presents three models from this research activity that have been
widely taken up by industry worldwide, namely, the `building energy' model
HTB2, the urban scale `energy and environment prediction' framework EEP
and the `building environment' model ECOTECT.
HTB2 has been used by leading international practices in
the design of over 100 exemplary low energy buildings, including Dubai's
award-winning Lighthouse tower, and EMPA, the first zero
energy office building in Switzerland.
EEP modelling framework for urban simulation has been
used to assess the energy performance of existing large estates, for
example, for use in housing retrofit programmes, and, to plan low-carbon
developments, such as the Gateway City in Ras al Khaimer. It is
now accessible through Google SketchUp, a common design tool
used by architects.
Ecotect underwent significant development at the WSA before its
sale to Autodesk in 2008, and by 2010 had over 2000 licenced users
Application of the models, often linked (e.g. HTB2 is the numerical
engine for EEP and is accessible within the ECOTECT framework), has
resulted in extensive environmental benefits, through reductions
in global CO2 emissions. Additionally, there has been a marked
impact on practitioners and professional practices, through new
guidelines for major international developments (e.g. Pearl Island
Qatar and the Chongqing Ba'nan Low Carbon Development).
The three simulation models introduced above, HTB2 (Senior
Lecturer Don Alexander [1983-], Prof Phil Jones [1978-], Research Fellow
Simon Lannon [1988-] and Dr Peter Lewis [1971-96]), EEP
(Lannon and Jones [1999-]), and Ecotect (Research Fellow Dr
Andrew Marsh [2001-06]), are outputs from a research programme at the WSA
that has spanned four decades, intensifying over the last 10 to 15 years
as attention to sustainability and low carbon energy performance of
buildings has increased. These tools are specifically developed to inform
the design process at an early stage, when major decisions are made and
impact is greatest, as well as checking at the more developed detailed
design stages. These tools now benefit the building industry, and their
underpinning research is explained below:
HTB2  is simulation software that predicts the thermal
energy performance of buildings under varying weather and occupancy
conditions. The software was developed solely within the WSA, with major
developments in the last 15 years. Alexander has been responsible for its
recent development and distribution, with contributions from Lannon and
Jones. The flexibility and ease of modification of HTB2 
has made it eminently suited for use in the rapidly evolving field of
energy efficiency and the sustainable design of buildings. The model has
kept pace with changes in the design and construction industry through a
continuing process of extension, testing, and modification. Since 1988,
reflecting the growing importance of energy efficient buildings,
developments include: chilled and heated surface environmental systems, a
range of infiltration and ventilation models, and detailed simulation of
advanced glazing systems and multiple skin facades [3,4]. It has been
combined with the HVAC model BEACON (funded through a Hong Kong Government
Grant) to produce the model BEEP, aimed at the Hong Kong commercial
The motivation for creating EEP, arose from a need to
extend performance-based assessment from single buildings to urban scale.
Research into urban modelling at the WSA began in 1994, funded through an
EPSRC grant [GR/K19181: To Develop a Model for Energy and Environmental
Planning for Sustainable Cities, 1994-98] continuing with further EPSRC
funding [GR/L81536: Development and completion of the EEP model,1998-2001]
and followed by EPSRC / MRC funded research [G9900679: Housing
Neighbourhoods and Health 2001-3 ]. The main research aim was to integrate
energy simulation tools with Geographical Information Systems (GIS), with
additional models addressing transport, air pollution and health to
support analysis of complex urban processes. This software framework
allows different simulation tools to communicate and share data, for
example, simple energy tools can be used, such as the UK SAP annual energy
predictor, as used in UK Building Regulation calculations, or, more
complex energy models such as HTB2. EEP was initially developed to
consider the existing built environment and allow planners and designer to
address major urban retrofit projects [5,6]. After further research and
development, the software now offers a comprehensive urban modelling tool
for planning and designing new urban developments, predicting energy use,
CO2 emissions and the potential for collecting solar energy. The latest
version has replaced the original GIS framework with Google's SketchUp
and Google Earth, to provide pre-processing computational
environments that are commonly used by designers , and enabling the
simultaneous simulation of 100's of buildings using advanced models such
as HTB2, to provide annual hourly data on energy and thermal performance.
Marsh began the development of Ecotect, an integrated
building analysis software package, initially through his PhD, before
joining the WSA in 2001. During his 5 year tenure to 2006, as a Research
Fellow, he collaborated with colleagues on the development and application
of building simulation tools, carrying out major developments of Ecotect,
and integrating it with other modelling software, including HTB2,
and the WSA's Computational Fluid Dynamic (CFD) airflow model
WINAIR . This research included testing numerical models
against physical scale models of complex estates, allowing modelling of
internal and external spaces on the same scale . This version of Ecotect
has since made significant worldwide penetration into architectural
practice and teaching since its purchase by Autodesk Inc. in 2008.
References to the research
All outputs below are available on request from HEI.
1 HTB2: Heat Transfer in Buildings (Version2), User manual 2.0c.12/11/97,
Alexander D K, WSA
2 Lewis, PT, Alexander, DK, 1990. HTB2: A Flexible Model
for Dynamic Building Simulation. Building and Environment, 25 1.
3 Alexander D K, Mylona A and Jones P J, The Simulations of
Glazing Systems in the Dynamic Thermal Model HTB2, IBPSA, (Canada),
(2005) p 11-18. ISBN 2-553-01152-0
4 Sun, L, Jones, P Alexander, DK, 2008. Energy Efficiency
of Double-skin Façade in Office Buildings of Shanghai. Proceedings COBEE
2008, July 13-16, Dalian China.
5 Jones P J and Patterson J, Modelling the Built Environment
at Urban Scale Landscape and Planning Journal (2007) pages 39-49.
6 Jones, P, et al, Retrofitting existing housing: how far, how
much? Special Issue of Building Research & Information, Urban
Retrofitting (Editors: Dixon and Eames), August/September 2013. (Paper
also an output for EPSRC Retrofit 2050 project). DOI: 10.1080/09613218.2013.807064
7 Phil Jones, Simon Lannon, Hendrik Rosenthall, Energy
Optimisation Modelling for Urban Scale Master Planning, 44th
ISOCARP Conference 2009.
8 Jones P, et al. Intensive Building Energy Simulation at Early
Design Stage, IBPSA, August 2013.
9 Jones P, Alexander D.K., Marsh A.J., Burnett J., Evaluation of
Methods for Modelling Daylight and Sunlight in High Rise Hong Kong
Residential Buildings, Indoor and Built Environment, 13, pp249-258, 2004.
10 Bleil de Souza C, Knight IP, Marsh AJ &
Dunn GN. 2006. "Modelling Buildings For Energy Use: A Study Of The Effects
Of Using Multiple Simulation Tools And Varying Levels Of Input Detail."
International Conference on Electricity Efficiency in Commercial Buildings
(IEECB 2006), Frankfurt, Germany April 2006.
Details of the impact
Impact has been achieved through in-house application of software to
design projects in collaboration with external partners, and through the
use of such software by third parties at both international and national
levels. As a result, construction professionals have been able to simulate
more accurately the energy performance of buildings and large-scale urban
developments and retrofit programmes. This has orchestrated significant environmental
benefits. In the UK alone over a quarter of all CO2 emissions derive
from the fuel used in homes. However tighter energy efficiency standards
for homeowners can cut domestic CO2 emissions by 80%. Moreover, globally a
considerable proportion of CO2 emissions and energy use is attributable to
buildings - approximately 40% according to the international Energy
Agency. Improved energy efficiency in buildings, as evidenced by the
examples below, is considered to be capable of reducing global emissions
by at least 1.8 billion tonnes of C02 (United Nations Environment
Additional impacts, stemming directly from Cardiff's research, are economic
savings associated with a more efficient design process and reducing
householders' annual energy expenditure (conservative estimates suggest
this would save £100-200 per household on fuel alone). Furthermore, there
is substantial impact on practitioners and professional services,
including the provision of consultancy for global engineering firms and
the development of enhanced design practices and guidelines that have been
Impact during the REF period:
Improved energy and environmental design and performance of
residential, commercial and industrial buildings: The WSA has
distributed HTB2 widely and free of charge to many
commercial organisations worldwide. Its application has enabled the
simulation of energy performance at an early design stage on many hundreds
of construction projects, which is an essential part of the low carbon
sustainable design process. Examples include:
The DIFC Lighthouse, a 400 metre tower in Dubai,
in collaboration with Atkins Global, `providing a full building
physics and system analysis' , identifying design options for,
reducing internal heat loads, façade design, and HVAC systems.
Simulations of the building design, which began construction in 2008
(but deferred during the economic downturn), identified solutions for
achieving a 65% reduction in energy use compared to Dubai standards. The
design won an international Holcim Foundation sustainable
construction award .
HTB2 was used to help explore design options with Atkins
Global for large scale building developments in the Middle East
and China, including the Al Akaria 300,000m2 mixed
use and retail complex in Jeddah (2011), and an office tower with
multi-floor atria in Tianjin (2008) .
- The WSA's involvement in developing the HK-BEAM
assessment methodology led to R&D investment and collaborative
development of the HTB2 software with Hong Kong
Polytechnic University . HTB2 has been used in
conjunction with the HVAC model BEACON , and in 2010,
HTB2 was the 2nd most commonly used software
tool in Hong Kong . The product has been targeted specifically to
meet the need for advanced environmental modelling software in China's
rapidly expanding construction sector (4).
- Design modelling of the naturally ventilated and heated REGAIN
business incubator building in Ebbw Vale, owned by the Local Government,
used HTB2 to model energy use, and Ecotect
to analyse the day-lighting performance (2010 to 2012). The building won
the 2012 Low Carbon Award from Constructing Excellence Wales, who said:
"The design was heavily influenced by analytical data from Cardiff
University School of Architecture's Centre for Research into the Built
Environment. This enabled the design of the glazing and building
envelope to be optimised to maximise heat retention, and solar gain
while minimising overheating." 
HTB2 has been used by Kopitsis Bauphysik AG for
dynamic simulations of over 100 buildings over the past 15 years,
including Switzerland's first zero energy office, EMPA EAWAG
(2005) and the Rem Koolhaas Laboratory in Zurich (2012) .
Improved urban-scale sustainable planning and design: The
development of EEP has enabled city planners and other
professionals to achieve low carbon sustainable design and master-
planning, for new urban scale developments and large scale housing
retrofit programmes. The EEP framework has been developed
to quickly provide information for fundamental decision-making relating
to energy performance, at early concept design stage, being able to
simulate large numbers of mixed use buildings simultaneously. Examples
The Pearl, Qatar, an artificial island of residences for 40,000
people. Working with Building Energy Partnership, the EEP
framework was used to produce guidelines for plot developers to
reduce energy consumption. The project is due for completion in 2015 but
already has more than 5,000 residents. The guidelines require the
developers to achieve energy savings 50% lower than the ASHRAE 90.1-2004
international standard for energy efficient buildings .
- Working with Hyder Hong Kong, EEP was used to
provide early stage energy predictions in master planning Gateway
City, Ras al Khaima (UAE), for 200,000 people, to reduce its
carbon footprint. EEP was also used on a Hyder
study for a future urban cluster in Hanoi, Vietnam.
- The latest version of EEP, linked to Google
SketchUp, was used to provide Low Carbon Master-plan Guidance for
the Ba'nan Project in Chongqing. This guidance contained the results of
the simulation of different construction options and their potential
impacts on operational energy use, and the potential for using building
integrated solar energy.
EEP has been used in collaboration with the community
interest company Warm Wales, to assess over £50 million of
energy saving measures on large scale housing energy retrofit projects
in Wales, including the Welsh Government's Arbed programme .
Some 50,000 houses in Wales have been upgraded, resulting in CO2
emission reductions of 10 to 40% taking hundreds of families out of
`fuel poverty', and improving indoor living conditions
Commercial impact: As of 2010, Ecotect had over
2,000 licensed users . Ecotect was bought in 2008 by
Autodesk Inc., the industry leader in computer aided design software. The
acquisition marked a step change in the funding and impact of the
software, significantly enhancing market penetration. New clients include:
- Architects working on NASA's Ames Research Centre, Silicon Valley, a
$20.6 million facility, used Ecotect to predict the cost
impact of design decisions, including the integration of daylight.
- China Construction Design International, one of Asia's leading
multidisciplinary design firms, with more than 2,000 offices and
employees throughout the People's Republic of China.
Sources to corroborate the impact
- Testimony from Director, WS Atkins & Partners Overseas confirms
the use of Cardiff software in the Atkins construction projects listed.
- Holcim Foundation website http://www.holcimfoundation.org/T858/A08AMbr.htm
(accessed 13 04 2012) confirms Dubai Lighthouse Tower as Bronze
award-winner for sustainable construction, 2008, Africa and Middle East.
- BEAM Society, 2010. BEAM Plus for new Buildings. Page 6-37 of http://www.beamsociety.org.hk/fileLibrary/BEAM%20Plus%20NB%20Version%201.1.pdf
(accessed 13 04 2012) confirms HTB2 used as preferred software in
- Testimony from Technical Director of Atal Building Services
Engineering Ltd confirms that HTB2 was the second most commonly used
software tool in Hong Kong in 2009.
- Yik, F.W.H., Lee, W.L. and Lee, S.H. (2009) `The state of use of
building energy simulation tools in Hong Kong and preview of a proposed
tool'. In: Proceedings of Joint Symposium 2009, Design for Sustainable
Performance, HKIE (BSD) / CIBSE (HK Branch) / ASHRAE (HK Chapter) / HK
Polytechnic University, Nov. 25, Hong Kong confirms HTB2 is the second
most commonly used tool in Hong Kong.
- Constructing Excellence Wales Awards 2012. Confirmation of Cardiff's
contribution to the design of the Low Carbon winner.
http://www.cewales.org.uk/awards/award-winners-2012/ (Accessed 5
- Testimony from Director of Kopitsis Bauphysik AG confirms that
HTB2 has been used on a range of buildings by Kopitsis Bauphysik in
Switzerland and other international locations.
- Testimony from Partner of Building Energy Partnership confirms
that the software was used for thermal analysis and design guidelines
for the Pearl, Qatar.
- Testimony from CEO of Warm Wales confirms that they used EEP
in the assessment of a range of energy reducing options for large scale
retrofit housing projects in Wales.
- US Department of Energy description of Ecotect, including figures for
number of licences in 2010 before acquisition (assessed 5 November