UCL Energy Institute


BLP LCC for sustainability


Principal investigator: Tadj Oreszczyn
Duration of project: 1 April 2010 - 30 June 2012
Sponsor: Technology Strategy Board (TSB)

The project is led by BLP in partnership with Willmott Dixon, UCL Energy Institute and University of Cambridge Centre for Sustainable development.

Research project funded by the Technology Strategy Board (TSB), aiming to the creation of a new software package, under the name ‘Butterfly’. This low carbon design and decision tool will simplify and improve decision making at the design stage by incorporating for the first time in one tool the life cycle, embodied and operational energy performance and carbon metrics as well as a Code for Sustainable Homes calculator. It will calculate life cycle cost and the environmental impact of the design and components for both new build and refurbished residential buildings.


BLP: building topology and life cycle cost modelling, component durability with the ability to draw on a wider network based on British and ISO standards work on life cycle costing.

UCL Energy Institute: running and operational energy and CO2 modelling.

Cambridge University Centre for Sustainable Development: embodied energy and CO2 modelling.

Willmott Dixon: Sustainable construction, costs and modelling, user input.

The Butterfly process

The energy model will be based on SAP underpinned with improved empirical data and for the first time incorporate factors such as rebound, health and comfort. The toolkit will be pre-loaded with default building models and an extensive library of optional building elements, assemblies and energy data that users can select to model specific buildings. Butterfly can also import data from CAD.


The proposed toolkit is uniquely innovative. No other package deals with both existing and new dwellings, is completely transparent about data and assumptions, offers such a wide range of default building models and the ability for user modifications at building, construction type, element, system and component level.


Butterfly will provide a means to evaluate constructions which meet sustainability benchmarks based on life cycle costs, energy and sustainability metrics to demonstrate value for money.

The research and development for the BLP LCC for sustainability toolkit aims to:

  • Integrate a range of existing tools: life cycle costs, energy calculators (SAP and EnergyPlus), sustainability measures (CfSH) and U-values.
  • Provide an interface to give designers and specifiers detailed performance data with minimal inputs yet offer flexibility to model buildings however constructed. This will be achieved by basing the toolkit on a default set of standard building types for concept stage assessments. Users can edit these models using an extensive integral library of elements, assemblies, component and energy parameter data for bespoke modelling at detailed design stage and operational phases. Metrics include: capital costs, operational costs, running and embodied energy costs and CO2 emissions. These will be calculated automatically with numerical and graphical presentation.
  • Incorporate ‘what-if’ and sensitivity analysis to allow users to compare alternative systems and component choices at concept, design and in-use phases.
  •  Develop an existing dwelling module with the same functionality as for new build including consideration of retrofit modifications and a function to appraise demolition versus retrofit.
  • Collaborate with software and database developers to take the computational strain and allow users to focus on modelling buildings with transparency of assumptions and underlying data.
  • Remove barriers such as cost, time and lack of data by packing disparate information into a single application to enable users to demonstrate the cost, energy and CO2 emission benefits of sustainable design options.
  • Offer a toolkit for open and collaborative working based on shared knowledge

Develop a model which can be applied to other building types, countries and markets.


The toolkit promotes optimisation of cost and energy at all stages of the building process (manufacturing, design, construction, maintenance and retrofit) for the ultimate benefit of the end user and more broadly for society. It will help to simplify the approach to two of the key issues facing our industry, reducing carbon and energy use and the drive towards Building Information Modelling, both of which are key Government targets.

  • Butterfly is targeted at the construction market which is currently grappling with energy evaluations, carbon emissions and costs to determine best value and optimise design for issues such as: what level CfSH, construction and energy strategy for long term best value and carbon savings?
  • Is retrofit or demolish and rebuild the best option for existing buildings?
  • What is the optimum construction solution balancing operational energy savings against embodied energy for any given component, element or system?

It enables best value for money to be assessed in context of capital and operating costs and also determines best value reduction in carbon over the life of the building. This step change in connectivity will overcome the shortcomings of current SAP and SBEM energy models which only access improvements against operational energy and therefore often result in an inappropriate focus on heating systems and appliance investments rather than taking into account whole life energy and carbon emissions.

This project will assist the sector driven by government agenda to meet sustainability targets and ensure value for (public) money is achieved. The proposed 2013 edition of Part L f the Building Regulations for England and Wales will make the toolkit attractive to the private housing building market. It will save time, money and waste for the builder and will give the developer and consumer an audited design with measurable sustainability claims.

sustainability carbon performance