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Green Building Calculator

The GBE Green Building Calculator provides information regarding Energy Consumption, Carbon in use, Cost of building and Cost of running a building. It is an impartial, easy to use, value for money product that can make a real difference to the world around us.

Different building shapes, methods of construction, materials choices and resultant energy demand and consumption can be compared easily.

With XR Extinction Rebellion, Greta Thunberg’s behaviour change campaign, Architects Declare and Architects Climate Action Network, as well as Government bodies declaring and becoming involved in environmental design in a bigger way, architects and other professionals now have a quick way of creating greener buildings or easing their way into the ‘New Normal’.

Moreover, they will understand why 50mm of stone wool insulation, shown in the ageing textbooks, is no longer enough and sometimes has the wrong properties for the application. They will be able to do their own U value calculation independently of manufacturers or suppliers who will do them for free, without obligation.

The GBE Green Building Calculator has been created for:

  • Clients: to do their own project analysis
  • Self Builders: to check that quotes with specifications meet building targets, before they buy
  • Building Designers: Architects, Technicians and Technologists, CAD users, Surveyors, M&E Engineers, D&B Constructors, Small Builders
  • Design Students: to evaluate their studio designs to help ensure they are future-proof and competent
  • Advisors: EPC, BREEAM, SAP, SBEM Assessors, Home Energy Advisors, Energy Consultants, Overheating Assessors, Building Performance advisors, Carbon reduction consultants
  • Developer’s Team: Evaluating House type, Wall thicknesses, Plot widths, Site planning, Regulation compliance or improvement, Marketing on Carbon and Building Performance
  • Constructors & Contractors: Design & Build Contractors on Tender Design Development, Contracts with Design Portion, Energy Performance Contracting, Specialist Subcontractors; for cost of variation or substitution evaluations
  • Facilities & Property Managers: For in-house adaptation and churn activity
  • University Lecturers: to introduce the potential sophistication of building information analysis outside of BIM CAD

Easy to use

  • Multiple Choice Answers, dropdown menus, lookup tables, less typing, less risk of errors
  • Yes/No Inclusion or exclusion of elements in your project
  • Instructions at every step

The GBE Green Building Calculator provides a low-cost Energy Performance and Cost analysis tool for new building designs, for those not engaging in the PHPP planning tool, or SAP, SBEM, IES, etc. calculations.

Brian Murphy, Founder of Green Building Encyclopaedia (GBE) created the original version of the product and he has continued to update and expand it.

Some of the features

  • Whole Building and Room by Room Schedule of Accommodation, areas and volumes, hours of operation, design temperatures, inside and out
  • Room by Room heat loss calculator to determine radiator or underfloor heating requirements or to size the boiler
  • Bill of materials, quantities, labour and costs
  • Analysis of Form Factor and optimal U values to respond to them
  • Elements and secondary-elements are selected from ready-made lists to match the project; dimensions are added by the user and their areas are automatically calculated
  • Schedules of windows, rooflight and doors, as they come in a multitude of sizes
  • The ability for users to compare and choose between Building Regulations Part L, LETI, AECB CarbonLite, Passivhaus, EnerPHit, Environmental Assessment Methods, other national standards, etc. including: U values, Airtightness, Form factors, Elevation glazing percentage and orientation
  • Automatically see what thickness of different k-value insulation materials is needed to meet targeted U values
  • Allows users to populate and assemble elements by choosing a combination of functional components and then choosing the materials or products for each component
  • Costs of insulation, windows and energy savings to help users to persuade clients to spend money on insulation and higher performance windows and glazing
  • Allows users to cost plan their projects with a Bill of materials, quantities, labour and costs, based on building fabric only so far
  • Element Summary to compare calculated U values with selected or target U values
  • Calculates energy losses from each element and secondary-elements to give total losses or demands
  • Calculates each element and secondary elements total demands as a percentage of the whole
  • Allows comparisons to be made by the user to prompt reconsideration of earlier decisions

GBE Green Building Calculator provides a low-cost way into Environmental design and Specification. It improves on some aspects of BREEAM and Green Guide to Specification to avoid the greenwash.  GBE Green Building Calculator produces real calculations for real buildings with generic materials and real products.

GBE Green Building Calculator will be updated continuously during the first year, starting with a Retrofit interface followed by an Embodied Energy, Embodied Carbon, Sequestered Carbon Calculator. Other updates will include an Overheating avoidance calculator.

Multi-functional Green Building Calculator benefits

  • Does what you want, but thought that you could never do yourself
  • Does what you want but thought you had to pay an arm and a leg for
  • Hours of operation and room working temperatures can be set
  • Analyse the result of spending more money on more insulation and/or more expensive glazing
  • Instant Carbon-In-Use calculation
  • Brings together many calculations in one place, all interlinked so one change filters throughout
  • All the parts are in place, correct format linked to correct data sources so no more searching your ‘college-knowledge’
  • Broader service offering to clients
  • Less reliance on external consultants
  • More in-house skills
  • Saves you time

What it means to declarers

  • Engage more robustly with Climate Emergency.
  • Engage with RIBA Climate Challenge.
  • Enables Architectural competition entries to be supported by competent performance and carbon data.
  • Enables engagement with Architects Climate Action Network ambitions.

Business opportunities

  • Addressing Climate Emergency can become part of user’s ‘New Normal’.
  • Enable users to offer ‘Deep-retrofit-first’ to their existing clients.
  • Enables users to offer ‘Deep-retrofit-first’ and attract new Climate Emergency focused customers.

What it means to your Practice activities

  • Gives users access to equivalent tools that would otherwise be unaffordable.
  • Facilitates behaviour change by providing data for comparison and justification of better long term choices.
  • Enables defence of good decisions in ‘Value Engineering’ and ‘Substitution’ exercises.
  • Help make better well-informed evidence-based decisions at every stage
  • Allows easy consideration and comparison of better than ‘Business as Usual’ and ‘Legal Minimum’ regulations.
  • Allows easy consideration and comparison of better Passivhaus, CarbonLite, LETI energy standards over regulations.

What it means to one person and small practices

  • Users can become autonomous and do some additional consultancy services themselves.
  • Enables users to understand their designs better than they may have done before
  • Enables users to do much more than they could before.

What it means to students and graduates

  • Allows students to enhance their philosophy and snappy graphics with future-facing know-how to become climate emergency competent and eminently employable Students and graduates can acquire new skills for their CV that many Practices do not yet have.
  • Enables ‘year-outs’, graduates and young professionals to bring new services to Practice’s attention.
  • Enable ‘Grey Hairs’ to keep up with induction graduate’s expectations.

What it does not do

It does not replace AECB’s CarbonLite & CL Retrofit or Passivhaus’s PHPP and EnerPHit but enables many to experience what they do to a building that is future-proofed and comfortable.

Users wanting to do Passivhaus need to get formal training before they can focus more on the thermal bridge and air tightness details, calculations, etc.

Version 3 and beyond

Versions 3 and beyond will develop, seek support to develop or seek licences to include:

  • Life Cycle Analysis & Environmental Product Declaration results
  • ‘Renewables’ (LCA and EPD data sets)
  • Waste minimisation and recycled content – GBE’s WasteCost®Lite calculator
  • GreenGauge Advanced Details (Thermal bridge & Psi values)
  • ICE for (EE EC Database v3) and Sequestered Carbon calculator
  • Thermal Mass Calculator
  • Decrement Delay Calculator (overheating prevention)
  • Condensation Check
  • Landscape Elements
  • Civils & Infrastructure Elements
  • Furniture Fixtures & Equipment


GBE has developed this product as a MicroSoft Excel calculator because:

  • It is open-book, not a black box
  • All worksheets and cells are visible to see the calculations in action and double check the results
  • It allows user access, interrogation, greater understanding and learning opportunities
  • Many users are already familiar with MS Excel which means that more people can access a quick way into building performance analysis

For GBE Green Building Calculator integrity:

  • Worksheets are locked and input cells only are editable
  • No damage should be possible to the calculator functions

Future Development

  • GBE will maintain a stakeholder group to encourage customisation to be shared; ideas will be considered for development into the core file for the greater good
  • Having a large number of users will help with feedback loops, developing GBE Green Building Calculator with more features and stronger datasets
  • Users will be invited to review the 12 version’s order of development, in case users want something sooner, by popular demand


  • Student: £4.88
  • 1 – 3 person practice: £48.88
  • Larger practice: £98.88

Price of 12 versions will increase progressively with increased functionality

Crowd funding is an option to speed up 12 version development.

Bespoke version: Price on Application.

Unlocked versions for user development: Price on Application with NDA.


  • Price on Application (free software option: Version 1)
  • Lectures regarding functionality, building performance, low carbon building, datasets, equations, calculations, results, future development
  • Zoom Live or recorded demonstrations
  • Post pandemic (COVID-19): In-University lectures, demonstrations, analysis of results


Live Zoom: coming soon – including demonstration, coaching and training.

Recorded Zoom: available from Vimeo/YouTube after live events.

Powerpoint CPD: GBE Green Building Calculator + GBC Future Development.

Telephone Helpline: To be announced, if found necessary.

Green Building Encyclopaedia

Green Building Encyclopaedia (GBE) is a growing information resource about creating healthy, environmental and efficient buildings – giving you the know-how to be able to engage robustly with these and other issues and still have the freedom to make them beautiful.

GBE includes design advice, guidance and technical detail regarding the selection, design or specification of building methods, materials, services, systems, products and whole buildings.

The GBE Green Building Calculator is abbreviated to: GBE GBC

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