Green Building Calculator

Create Greener Buildings

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,
  • Drop Down List,
  • Lookup tables,
  • Less typing,
  • Less risk of errors
  • ‘Yes’ Inclusion or ‘No’ exclusion of elements in your project
  • Instructions at every step: for rows, columns and cells

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 calculator and he has continued to update and expand it.

Version 1.0.0. took 440 hours to create and launch, many more hours will go into adding more functionality over the following months.

Some of the features of Version 1.0.0.

  • 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; or to insulate to meet the boiler size.
  • Bill of materials, quantities, labour and costs to enable cost planning
  • 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.

Versions 2 to 15

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 consider alternative scenarios
  • Enable users to offer ‘Deep-retrofit-first’ to their existing clients 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’, Cost cutting and ‘Substitution’ exercises.
  • Helps users 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 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.
  • Outputs feel like more than one person’s efforts

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 Employer’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:

The order is subject to GBC user feedback:

  • More Generic Material datasets
  • More Product Datasets
  • MEP Services added
  • Life Cycle Analysis & Environmental Product Declaration results
    • ‘Renewables’ (LCA and EPD data sets)
  • Waste minimisation and recycled content
    • GBE’s WasteCost®Lite calculator
  • Thermal bridge & Psi values
    • GreenGauge Advanced Details
  • Embodied Energy, Embodied Carbon, Sequestered carbon
    • ICE for (EE EC Database v1.6 > v3)
  • Thermal Mass Calculator
  • Decrement Delay Calculator (overheating prevention)
  • Condensation Check
  • Landscape Elements
  • Civils & Infrastructure Elements
  • Plastics Avoidance or use of recycled content
  • Furniture Fixtures & Equipment
  • BIM Apps for numerous CAD software
  • Whole Project Budget calculations (Fees, overheads, profits, preliminaries, etc.)
  • EU and International versions


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

  • It is open-book, not a black box
  • Close to open source principles adopted, no macros allowed
  • 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

In due course a BIM app will be inevitable, there may need to be an interface outside of Excel and inside CAD/BIM software.

Future Development

  • GBE will maintain a stakeholder group to ensure we make what you want and need
  • Having a large number of users will help with:
    • error detection, feedback loops, encouraged by free upgrade versions
    • developing GBE Green Building Calculator with more features and stronger datasets
  • We will encourage customisation requests to be shared; ideas will be considered for development into the core file for the greater good
  • Users will be invited to review the 15 version’s order of development, in case users want something sooner, by popular demand

Early User Feedback

“Green Building Calculator is an amazing product. Both novices and advanced users will appreciate this calculator. It is just the tool that the industry and practitioners need!”

DJ Maloney via LinkedIn


If you have not seen this calculator yet, here it is people! What a fantastic tool this is created by BrianSpecMan Murphy at GBE Get stuck in

DJ Maloney via LinkedIn

#sustainabledesign #sustainableconstruction #sustainablesolutions #thefutureisbright #retrofitting


Green Building Calculator brings material properties, embodied carbon and costs all in one place

Brian’s Green Building Calculator (GBC) is a tool designed for the Specifier to select the optimum product to achieve Green.

Martin West RIBA MSt cantab of Syndicate West Architects (former Director of RHWL)


  • Student: £4.88
  • 1 – 3 person practice: £48.88
  • Larger practice: £98.88
  • Self-Builders: Wales TAN6 OPD: £4.88
  • Self-Builders: Others: £48.88

Price of 15 versions will increase progressively with increased functionality

Crowd funding is an option GBE have considered to speed up 15 version development.

Bespoke versions


  • Student and lecturers price as above
  • 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
  • Price on Application (free software option: Version 1)

Support: Users

  • Email helpline:
    • Email questions and responses will be added to new page or FAQ
  • Coming soon:
  • Live Zoom: introduction, 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.

Support: Bespokers

  • Support by Email, Telephone Helpline or Video call package
    • Questions and responses will be added to new page or FAQ

Support: Manufacturers and Suppliers (Dataset providers)

  • Stakeholder steering group: including manufacturers and suppliers
  • Email helpline:
    • Email questions and responses will be added to new page or FAQ
  • Zoom meeting to introduce opportunity to be included in Green Building Calculator
  • GBC Product Import Spreadsheet:
    • Download latest (once completed) for free
    • Completed by you, at your speed, at your expense
    • Audited by GBE for correction or completion by you or by GBE
    • Products, Accessories and Systems
    • Sizes, properties and certification
    • Appropriate Competent Applications
    • Specification Clauses
    • Suppliers
    • Correlation to any BIM Models & Product Data Files
  • Coming soon:
  • Guidance for completion of Import Spreadsheet
  • Live Zoom: introduction, including demonstration.
  • 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

Green Building Calculator Awards

Green Building Calculator

© GBE GBC NGS ASWS Brian Murphy aka BrianSpecMan *
11th June 2020 – 26th June 2020