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Your Questions


My directors have asked me to look into the Green Building Calculator and I was wondering whether you could please help me with a few queries I have?

GBE Answers


Thank you for your Director’s enquiry, very happy to answer.

  • In your description it says that it provides cost information of different materials.
  • Where does this information come from?
  • Is this something that we will have to get from manufacturers and input it manually or does it connect to a database?
  • Initially the file is populated by your own enquiries from manufacturers and suppliers
  • At Tender stage it can be populated by your tenderer/contractor as a pricing document
  • This information could be used to populate your own rough prices look up table
  • Green Building Calculator (GBC) had originally considered Spon pricing books but the discussions we have had suggest these are not reliable enough and may be contributing to Quantity Surveyors (QS)’s poor cost planning and the ‘race to the bottom’ our industry is experiencing.
  • GBC will seek Manufacturer’s and Suppliers support to populate the product spreadsheets with cost data.
  • GBC have access to Life Cycle Analysis (LCA) datasets that also include cost data, these will be considered for inclusion in GBC but we will seek confirmation from manufacturers
  • 20 years ago there was a QS who wanted to build the Green Building Price Book, he is now retired, we have discussed what he planned then, if GBC takes off and generates revenue then GBC will reengage with his ambition and embed it in GBC.
  • How it compares with the PHPP software?
  • I understand that this calculator explores different heating options and doesn’t rely solely on a heat recovery system like Passivhaus, but in terms of the other calculations it does, how does it compare?
  • Does it have the same extent of calculations?
  • My practice is unclear on which licence to purchase.
  • This is not equivalent to PHPP, however you can get an impression of what Passivhaus (PH) or EnerPHit (or AECB’s Carbon Lite & CL Retrofit) will do to your building’s U values, Insulation thicknesses, if you choose it as your energy target.
  • Whilst PH is a great route to low energy in use, GBC knows many may not go that way and may focus on lowering embodied energy (EE) embodied carbon (EC) raising sequestered carbon (SC) and lowering in use carbon (IUC).
  • GBC have developed the whole building & elemental calculators to determine the demand heat source(s) size
  • GBC have also developed the room by room calculator to work out radiator/Under floor heating (UFH) coil sizes or start with boiler size and work out insulation thicknesses to match the boiler.
  • This version of GBC calculator does not have a Services Design Function yet (GBC Version 16 unless we bring it forward, we probably will)
  • GBC have met the man who can help to build this module, GBC will engage with him once version 2 is published.
  • GBC is adding a Services Bill of materials/quantities/costs, EE EC & LCA in version 2 (bringing parts from v3 and v6 much sooner)
  • PHPP software compares the calculated version to the Passivhaus criteria (so gives a benchmark).
  • In your description it says it does a comparison with different standards.
  • Does this mean that it will provide the various criteria for Passivhaus,  BREEAM etc?
  • After a Form factor calculation you are promoted to set your U value targets, then you choose between Regulations, which should be local to the project (e.g. UK’s England & Wales, Scotland or Northern Ireland or other national standard) and design standards: UK Green Building Council (UK GBC), Zero Carbon Hub (ZCH), PH EnerPHit, Carbon Lite (CL), Carbon Lite Retrofit (CLR), Building Research Establishment Environmental Assessment Method (BREEAM), etc. targets
  • You choose and set targets, the U values permeates the calculator, when you assemble your building elements it tells you Pass, Unregulated Pass or Fail; and GBC will warn of failure with red coloured conditional formatting.
  • This may equate to your benchmarking?
  • You can then adjust insulation thicknesses to get Pass all round.
  • You should use PHPP for PH calculations not GBC.
  • This calculator will help with BREEAM area calculations and speed up some of the tedious fruitless calculations.
  • These calculations are useful as part of the design process, rather than totalling up and changing nothing.
  • Version 2 will have LCA calculations in it. (Brought forwards) 
  • This is based on your own specific or bespoke elemental assemblies, so it is not restricted to the 1200 or so in Green Guide to Specification (GGtS).
  • You get an instant answer without waiting for Building Research Establishment (BRE) to do their bespoke calculations for you.
  • In time GBE Product datasets will have useful data to support Passivhaus, BREEAM, etc.
  • Is version 3 the latest one on the market?
  • It has a lot of attractive functions!
  • Version 1 was released June-July 2020
  • Version 2 will be Spring-Summer 2021
  • Version 2 is being developed with Embodied Energy, Embodied Carbon, Sequestered Carbon, LCA, Bill of materials, Quantities, etc.
  • Version 2 should be the one that is needed by many
  • Version 3 functions are mostly included in the latest scope of version 2
  • Do let me know which functions are of interest from version 3 if any have been missed out.

At a Make a Difference (MaD) Hangout #3 presentation:

  • Q&A Session:
  • Does this tool engage with Scope 3?
  • I did not understand the question so could not answer
  • I explained what it does, what data it uses and how it does it.
  • Another delegate said it does
  • Over the following days emails we got to the bottom of the question
  • I gave a better answer by email
Cutting Carbon/Greenhouse/GHG emissions is what IPCC and GHG Protocol are trying to do.
It is a globally accepted framework for systematically trying to lower carbon emission.
Using GHG Protocol, big corporates measure-control-report carbon emissions.
Let us assume that there is company named ABC.
Scope 1 – ABC Company’s own emissions from boiler, turbine, heater, incinerator, air-conditioner, freeze, freezer, etc.
Scope 2 – ABC Company’s own emissions from electricity, gas, etc which is energy purchase
Scope 3 – They are not ABC company’s own carbon emissions, but carbon emissions from its supply chain partners:
  1. Up value chain – Miners-Manufacturers-Suppliers-Transporters, from where material comes to ABC company, so purchasing side.
  2. Down value chain – Customers-Manufactures-Consumers-Transporters-Franchise-Waste. This is the place where ABC company’s goods are sold/consumed.
I hope this helps a bit.

Scope 1:

  • Is Cradle to gate emissions (EN 15804 A1-A3) from company ABC’s in-use energy and in-use carbon, premises-side of the consumer unit
  • (I think I would exclude turbine from your list since it generates energy rather than consume it)
  • I guess it will include improvements due to voltage optimisation premises-side of the consumer unit.
  • I believe LCA of products focusses on impacts and emissions from the production of product to sell,
  • but probably does not try to distinguish between production and accommodation consumption and emissions and just regards it as an overhead of production.
  • I say this on the assumption they do not do sub-metering between factory and office on the same site.
  • I believe that LCA and EPD data is the source and it converts everything to GHG = CO2equivalents.
  • GBC V2 includes LCA EPD datasets for the products used to make a building.

Scope 2:

  • Is emissions in primary energy delivered to your premises. (Part of EN 15804’s A3)
  • To some extent is out of ABCs control (but they can choose a Green Energy Tariff)
  • Depends upon: fuel choice (e.g. Renewable energy v Fossil energy)
  • and varies upon production inefficiency (fuel to steam to generator to electricity),
  • conversion inefficiency (PV DC via Inverter to AC or transformers and voltage drops)
  • and transmission losses (along sunk, overhead or buried cables)
  • I guess it does not address voltage optimisation premises-side of the consumer unit.
  • I believe LCA of products focusses on impacts and emissions from the production of product to sell,
  • it inevitably adds primary energy choices and emissions to the calculations.
  • The LCA will choose main electricity average figure for ABCs country
  • France has a high nuclear % Uk has a significant RE % and reducing fossil %
  • Unless ABC have onsite RE, have access to offsite RE installations or buy Green Tariff and choose it to calculate accordingly.
  • I do have a table for emissions from mains electricity across all EU countries individually
  • (not yet incorporated into GBC V2 calculations but could be added with less than an hours work)
  • I might do that today.

Scope 3:

  • is ABC’s Gate to site emissions (EN 15804’s A4 and any of B1-B6, C1-C4)
  • To some extent outside of ABCs control, influenced through supply chain development, by setting targets for continuing relationship
  • and relates to their supply chain companies own Scope 1 2 (& 3) emissions
  • GBC V2 accommodates and calculates EN 15804 A1-D when any EPD has the information
  • So I believe GBC V2 is Scope 3 compliant if the manufacturers have the data in their EPDs.

I reviewed a bit more on GHG Protocol website.

  • LCA (Life Cycle Assessment) and Supply Chain (Scope 3) are two different approaches to the same solution of carbon emission reduction.
    • Interesting
  • I think, your calculator takes care to reduce carbon emission by carefully selecting product as well as design, so focusing on the right approach of LCA.
    • Good to hear
  • Secondly, supply chain (scope 3) may be irrelevant in your case, as the product (i.e. building) is to be used by the person who buys/rents it. So basically, it is almost at the end of the supply chain (i.e. consumption).
    • Interesting
  • I do not have access to the calculator, but if this calculator has end of life (when building is demolished in future) carbon footprint, then I think you have addressed scope 3.
    • Green Building Encyclopaedia has many screenshots of GBC V2 if you want to see inside.
    • The LCA function has EN 15804 C1-C4 and D so can do the calculation if the data is on the manufacturers EPDs
    • I think that the RICS Document allows a theoretical calculation for C1-C4 and D but I need to investigate it.
  • You seem to have done an amazing job in creating something very difficult.
    • Thank you very much for your kind words, it is not so difficult, as time consuming, it has taken 10 months so far.
    • It would put most people off
    • It would take a big project with a long programme to carry its development as an overhead

At a Construction Excellence Award Panel:

  • Q&A Session: Q1
  • Does the Calculator Address Indoor Air Quality?

GBE and Indoor Air Quality

  • Green Building Calculator Version 2 Does not address Indoor Air Quality
  • Later versions could address it
  • At the time of this panel GBC do not know if Indoor air Quality can be calculated
  • But it will be investigated
  • Sentinel Haus accreditation carries out a physical test within a dwelling, sampling the air in a sealed building over a set period of time.
  • If it is possible to assess the IAQ based on the amount of materials at the internal surfaces based on their ingredients and VOCs then GBC will endeavour to calculate it in later Versions.

At a Construction Excellence Award Panel:

  • Q&A Session: Q2
  • Does the calculator use other external data sources?

GBC sourcing external data

  • Green Building Calculator Version 2 Does not yet access external data sources.
  • Later versions will engage with CAD BIM and share dimensions and Bill of Material data.
  • At this stage GBC is being developed with small practices in mind.
  • Larger practices will have CAD BIM and Appropriate Apps.
  • Smaller practices will probably not afford the high end high cost solutions.
  • GBC intends to remain a low cost solution for the majority.
  • Recent survey reports that a significant number of practices have not and probably will not adopt BIM.
  • If they are not doing Government Work there is no requirement.
  • There is a big financial investment to switch from CAD to BIM and hardware to support it.
  • There needs to be Carbon solutions for these practices too.
  • As open data sources grow GBC will seek opportunities to obtain Product datasets from such data sources

GBC as an external Data Source

  • GBC may become a data source in its own right.
  • Green Building Product Data Sets
  • Green Building Elemental Assemblies
  • Green Building Price Book

At a Construction Excellence Award Panel:

  • Q&A Session: Q3
  • Can the Calculator be subdivided and used separately?
GBC CPD Poster 2 Slide23

GBC as a Design and Decision Tool

  • The reasons for creating this calculator include:
    • To enable designers to regain better control of their project
    • To take back control of cost planning away from low cost focussed QSs
    • To enable well informed responses to Cost Cutting disguised as Value Engineering
    • To Reduce the Performance Gap caused by substitution
    • To count energy and carbon
  • Only if your have all the core functions in Version 2 can you have:
    • Cost planning, Tendering, Controlled Price adjustments
    • In use Energy, In use Carbon, In use Cost
    • Embodied Energy, Embodied carbon, Sequestered carbon
    • Pay back periods, Carbon back periods
    • Well informed Value Engineering instead of dumb Cost Cutting
    • Control over the Performance Gap
  • So subdivision has no useful purpose

GBC Subdivision

  • GBC may become a data source in its own right.
  • But only certain parts make sense in that respect:
    • Green Building Product Data Sets
    • Green Building Elemental Assemblies
    • Green Building Price Book
  • It is unlikely that GBC will be subdivided and sold separately

GBC Core and Modules

  • Version 1 was never a complete Green Building Calculator without EE EC SBC & LCA
  • Version 2 has Embodied Energy, Embodied Carbon, Sequestered Carbon and Life Cycle Analysis
  • It is envisages that Versions 2 is the minimum core set of calculators
    • It could be envisaged that this core set could be a minimum package
  • Later Versions will:
    • Reinforce the core calculators
    • Improve the datasets
  • Other later Versions will provide:
    • Additional non-core calculators
    • Further datasets to support these non-core calculators
  • It is envisages that the core will be the sold as a minimum package
  • Non-core calculators and datasets may be sold as extra modules

At a Construction Excellence Award Panel:

  • Q&A Session: Q4
  • How is the data sources used verified as quality data?

GBC and Data Quality

Embodied Carbon

  • Previous versions of Whole Building calculator were based on ICE database 1 to 2
  • Early version of ICE data base includes data from old LCA following inconsistent methods giving rogue results
  • After EN 15804 standard was published all LCA and EPD could follow a consistent method for consistent
  • Now with over 10,000 EN 15804 compliant LCA and EPD
  • ICE database 3 contains many of these EPDs
  • So the Embodied carbon data sub-set is more robust and reliable

Life Cycle Assessment

  • After EN 15804 standard was published all LCA and EPD could follow a consistent method for consistent
  • Now with over 10,000 EN 15804 compliant LCA and EPD
  • EPDs are peer reviewed for consistency
  • LCA Data has been extracted to EPD to test the calculator during development
  • Other LCA data sets will be obtained as they continue to be released into the market and updated on a regular update programme

At a Construction Excellence Award Panel:

  • Q&A Session: Q5
  • What software is GBC created with?

GBC Software

  • GBC version 1 & 2 have been developed in MS Excel
  • For familiarity, easy of use, consistency and competency
  • GBC is following Open Source principles of uncomplicated software
  • GBC have every intentions to keep it that way in all future Versions
  • Any BIM APP may not follow this rule, but if it can it will

At a Construction Excellence Award Panel:

  • Q&A Session: Q6
  • Has GBC been used in real projects and what feedback have you had so far?

GBC Use and Feedback

  • The pre-curser to GBE Whole Building Calculators were used by 50 students at Post Graduate level Architecture year 5 to assess their studio projects, successfully
  • All the part time students took these calculators back to their offices and used then on live projects.
  • One ex student runs his own practice and has used it on all of his projects
  • One of the ex students approached GBC during an Architectural Competition and asked for some help with calculating U values and embodied energy and embodied and sequestered carbon for exiting concrete panels and replacement timber panels and insulation materials options.
  • The same Ex student has approached GBC about doing whole building analysis for them
  • GBE have been working with a 3 person practice to develop the scope of GBE Version 1 & 2
  • Version 1 was released in June 2020
  • The same practice obtained a copy but COVID lockdown happened and all their projects are on hold.
  • So still waiting for a solid break from COVID
  • 66 copies of version 1 are out there no negative feedback so far.

At a Construction Excellence Award Panel:

  • Q&A Session: Q7
  • Which job functions do you envisage using GBC?

GBC Users

  • Self Builders, Architectural Technicians, Architects, Surveyors, Interior Designers, Engineers,
  • Specification Writers, Environmental consultants, EAM Assessors
  • Design and Build, Contractor Design Portion and Energy Performance Contractors
  • Potentially: Cost Planners, Quality Surveyor, Value Engineers

Alternative Calculators are out there for:

  • Structural Engineers, Service Engineers, Highway Engineers, Civils and Infrastructure Engineers

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14th September 2020 – 23th May 2021


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