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With a clear understanding of the trade-off between the various design options and their impact on environmental performance you can more easily navigate the complex relationship between design objectives, constraints and possible design options. Now you can make informed recommendations with confidence.

The Optimisation module provides access to:

  • Multi-objective optimisation tools for advanced cost-benefit analysis.
  • Uncertainty Analysis reports confidence levels in simulation outputs based on uncertainties in specific inputs.
  • Sensitivity Analysis reports on the design variables having the greatest/least impact on your key simulation results. Often carried out as a preliminary step, sensitivity analysis can be used to help identify any less important design variables so they can be removed from an optimisation analysis.


Example applications

optimisation poster

  • Cost-benefit studies to find the design options that best meet even complex design criteria at any stage of the design process.
    For example see: our poster on the optimisation of a passive building design from the CIBSE-ASHRAE Symposium in Dublin 2014
  • Select the most cost effective lighting, glazing, construction, renewable and HVAC systems even at early design stages.
  • Identify optimal control strategies giving the best combination of environmental and comfort performance for even complex HVAC, natural ventilation, mixed mode system types.

Key features

  • Test over 120 different design variables including glazing type and amount, thermal mass, HVAC, natural ventilation and lighting system type and associated control settings.
  • Select up to 2 design objectives, multiple constraints and up to 10 design variables from a wide range of key performance indicators and variable types..
  • Decide the priority to be placed on the design objectives after the analysis by checking the graphical results. For example in the above graph the red points show the "Pareto Front" of optimal solutions which give the lowest combination of construction cost and operational carbon emissions. The trade off between cost and carbon can be seen very clearly as well as the impact of the decision on lighting system choice. A quick look at this graph might help the designer to home in on the fluorescent lighting system with daylight control as the most cost effective system.

Technical specification

  • Constrained multi-objective optimisation software using the NSGA2 algorithm and EnergyPlus simulations to calculate energy/comfort/carbon emissions.
  • Behind the scenes, the Optimisation module uses advanced evolutionary algorithms through a natural selection process based on improving building performance to help meet the design objectives. The best characteristics are passed on to future generations and the process continues until the optimum designs have been identified.
  • Even "conflicting" design objectives such as "minimise cost" and "minimise carbon emissions" can be analysed simultaneously to provide a set of suggested designs which best meet both objectives.
  • The set of proposed solutions (on the "Pareto front") can be further analysed visually through the graphical outputs and numerically to identify the designs which best meet the design priorities placed on the objectives used. E.g. prioritise on construction cost or comfort performance or perhaps on the balance between cost and carbon emissions.
  • Multiple designs are assessed in parallel on the local machine, on a network simulation server or with an appropriate account on a remote high performance computer.
  • Links to the JESS online simulation service allows fast simulations to be run on the cloud.
  • Apply any selected design from the optimisation to be the new base design.
  • Export results for further analysis using a spreadsheet.


Uncertainty and Sensitivity Analysis

Example applications

  • Generate probabilistic simulation results by quantifying the variation in outputs alongside coresponding changes in inputs, providing stakeholders with a preliminary risk assessment for meeting design objectives.
  • Improve the optimisation process by identifying any unimportant variables for the optimisation objectives and excluding them from the optimisation search space.
  • Identify aspects of the building which have a high probability of creating operation stage performance issues and thereby help in the model calibration process.
  • Identify the most influential factors impacting energy use by comparing uncertainty due to various inputs such as those related to occupant behaviour and to construction quality.

Key features

  • High quality reports with histograms for each output and input explain the significance of the various uncertainty and sensitivity analysis results.
  • Various sampling methods and a wide range of probabilistic distributions are supported for the input parameters.
  • Any number of design variables can be included in the analysis for each of the selected outputs. 
  • Full statistical analysis carried out with reports for regression coefficients, p-values for statistical significance, standard deviation, median, min/max etc.

Sample outputs





Optimisation is included in the more advanced packages for engineers, Engineering Plus and Pro.


Optimisation also requires both the Simulation and Cost modules if the Carbon and Cost objective functions are to be applied in the optimisation.

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Case Studies

Trusted by many of the world’s most prestigious companies and universities

  • "I have watched the steady progression of DesignBuilder for the last 10 years or so, and having seen recent improvements in DesignBuilder’s HVAC and LEED modeling I decided to attend their training. I was both surprised and pleased to find how easy to use DesignBuilder is compared to the other similar tools I’ve tried, especially given the power and flexibility offered by the underlying EnergyPlus, Radiance and CFD engines. I’m really pleased that after a week’s training I feel ready to produce accurate results and outputs for loads and sizing calculations and energy analysis. The ability to also undertake fully-integrated daylighting and CFD analysis from the same model you use for loads and thermal simulations is also a very big plus point."
    David Ellis PE, Virginia 22102, USA
  • " We have had a very positive experience with DesignBuilder this semester as it was the first year we shifted from our previous simulation software to DesignBuilder. Our students seem to spend less time on learning the software and more on actually understanding the results and being able to analyse them."
    Dr Shahaboddin Resalati - Senior Lecturer in Sustainable Architecture and Building Physics Architectural Engineering Group, School of Architecture, Oxford Brookes University, UK
  • " The graphical user interface of DesignBuilder is comprehensive and intuitive, allowing us to model complex buildings simply and quickly. The data management structure (data hierarchy and inheritance) allows us to assign model data quickly and accurately, improving our efficiency. The power and flexibility of EnergyPlus, the underlying simulation engine, enables us to model a building in fine detail where required so that we can accurately analyse its performance. This is particularly helpful when calibrating the model with actual energy consumption to obtain a reliable close match when assessing potential improvements and energy conservation measures."
    Alessandro Righi, architect and researcher at IUAV - Laboratory technical physics
  • " We utilised DesignBuilder software to carry out detailed natural ventilation assessments on buildings at our UK gas plants in order to demonstrate compliance with hazardous area regulations. First of all I would like to praise the initial support received from DesignBuilder staff, who were extremely knowledgeable and provided a welcoming point of contact for support and advice. Having used the majority of the alternative building simulation software packages on the market, I found without a doubt DesignBuilder the most user friendly and enjoyable to use. The modelling program itself is fantastically simple allowing even complex buildings to be developed quickly and easily. The user interface of the calculation part of the software is well thought out and the results outputs are graphical and concise. Within a few hours I had got to grips with the software and obtained the results I desired. It has allowed Shell to present compliance to regulating authorities, who were also impressed with the visualisation displays and graphical outputs. I fully endorse DesignBuilder, and in particular how easy it was to learn and use compared to similar building simulation software on the market. "
    Iain Begg, Senior HVAC Engineer, Shell Projects and Technology Group, Aberdeen, Scotland
  • " DesignBuilder’s clear, well-structured layout and intuitive help system makes it a much simpler tool to learn and use, and compared to other simulation packages the creation of professional-looking geometry is much easier. The ease of use extends to other areas of the program such as thermal bridging analysis and setting up HVAC systems, and the capability to easily model adjacent ground conditions is very useful. A very important aspect of our work is optimisation, and DesignBuilder seems to be the only software that currently provides this functionality. We are encouraged that the development team have taken some of our functionality and user efficiency suggestions on board for the next release. We are already using DesignBuilder for research, and for the above reasons we think it is a tool that our students will find easier to use so we will be using it for teaching next academic year. "
    Professor Ljubomir Jankovic, Birmingham School of Architecture, Birmingham City University
  • " We decided to go out and measure some natural light levels in buildings that we have access to.... One building was our own office, and the other was a green building we worked on which will be tenanted in 2 weeks so we had a chance to take readings in the same environment for which we simulated. I am happy to say that the DesignBuilder results are very close to what we measured... What impresses me is that if we measure a value of 250 lux at 3m from the facade, DB returns similar values. This means that if we say that 40% of a building's usable area will have lux levels of 250 or above, then the measured results correlate with that. ... It certainly makes us confident in the results we give to clients."
    Warren Gray, Mechanical Engineer, Solid Green Consulting
  • " First of all I would like to thank you very much for the outstanding online training that you made possible for our team. I was very happy that we could join with three people in an online training that offered us as an outstanding value. ... The course with DesignBuilder is going very well and we have some great feedback from the students.... Your data entry GUI makes it easy for students not only to “accept defaults” but to experiment. In addition your online help is extremely thorough and you present not only the theoretical background but also offer great links to the reference. You might not realize what a powerful learning tool this is; but it is. We think you have created something very valuable and we are looking forward very much to where your company goes from here... Thanks again for your great support."
    Dr Manfred J. Zapka, University of Hawaii
  • " Gold stars all round .... Many thanks again for the high quality of customer service I receive from all at DesignBuilder, it is quite refreshing and a credit to your company."
    Mark O’Neill, DM Hall LLP, Glasgow, Scotland

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