Skip to main content

Thermal Bridge Psi (Calculator) G#25033

By 1 August 2019August 13th, 20192017, 2017, Archive, Blog, Calculators, Diary, News, Other's Stuff

GBE Thermal Bridge Psi Calculator

GBE > Encyclopaedia > Files > Calculators > G#25033

GBE Thermal Bridge Psi Calculator

Greengauge launches library of calculated thermal bridge details

  • It is in response to the pressure to achieve excellent SAP results, which is being driven by increases in the SAP scores demanded by Building Regulations Approved Document L “Part L”, and also by sustainability targets set by clients and local authorities.
  • This service was launched by building physics consultancy Greengauge, will bring calculated thermal bridge details within reach for many designers and assessors who currently rely on standard details.

Advanced Details

  • Advanced Details, is a searchable web-based database offering high-performance details for a full range of standard junctions. Compared to the standard details, using the service can cut the DER by 10%, and by 25% compared to using default psi values – without the need to make significant changes to the design. This could be especially valuable if, as anticipated, changes to SAP bring in higher default values.
  • The database offers ultra-high-performance options for many junctions. Greengauge director Toby Cambray explained: “As experienced Certified Passivhaus Designers, we understand the importance of minimising thermal bridging and we wanted to make it as easy as possible for everyone to do this. Our solution is a comprehensive, user-friendly library of details.”
  • The pressure to achieve excellent SAP results is being driven by increases in the SAP scores demanded by Part L, and also by sustainability targets set by clients and local authorities. With the anticipated changes due in SAP 2016, this challenge may get tougher, as Toby Cambray warns.
  • “In the recent consultation for the next version of SAP there are several changes proposed that will increase the penalties for failing to consider thermal bridging,” he says. “Many of the default psi-values (non-linear thermal bridge heat loss) are increasing, and it is proposed to increase the default Y-value by 33%, penalising designs where thermal bridge calculations are not available.”
  • The large dataset is accessed via a carefully designed search tool, which enables users to find the exact result they’re looking for, very fast.
  • Details can be gathered together in the project manager tool, which can also calculate Y-values to help steer the overall design. Passivhaus designers will be pleased to know it lists the external Ψ-values they need for PHPP, the passivhaus energy model alongside the internal figures used in SAP and DEAP.

Quote: User

  • “It saves me loads of time reducing the thermal bridging in my projects, and I’ve come to rely on it.”
  • Gary Evans Building Performance Consultant at Generate Building Performance Solutions Ltd
  • Gary has been helping to test the service.
  • M 07534 800 442 T 020 3930 8387
  • E


  • The full service was formally launched at Ecobuild 2017 (Stand B177), where the team was offering some fantastic introductory deals.

GBE Link

GBE Provider

  • Greengauge, is a Building physics consultancy of designers, physicists, engineers and programmers with one aim: to make better buildings.
  • Director: Toby Cambray
  • Greengauge Building Energy Consultants
  • 01225 862605

GBE Review

  • On the face of it it sounds like a good service.
  • Pros and Cons.
  • In theory less thermal bridging means more efficiency
  • I have recently been receiving emails from a consultancy offering to reduce building costs by avoiding generic and using specific psi values
  • I am worried that this approach offers developers the opportunity to change nothing at the detail, improve thermal bridge calculation inputs, use less insulation elsewhere and build cheaper
  • Since ZCH identified a major Performance Gap, the combination of less insulation and other causes of the performance gap means we get worse buildings more profitably.
  • This may not be what you intended but it may be a consequence of better easily accessible information.
  • Can you reassure me that is not the case or am I misreading the possibilities?

There are other details missing:

  • I have visited a number of speculatively built homes and received enquiries about loft water tank insulation
  • The insulation is missing below the tank platform as expected to avoid the tank freezing.
  • The tank is insulated top and sides
  • The uninsulated ceiling links to the ventilated loft space with no insulation barrier at the perimeter of the tank platform
  • I have seen it on one house and I am confident I will see it in the whole estate, because the ill-informed or skilled and don’t care, or have no time to care installers will have done the same in each.


  • Because the Building Regulation only cares about k, R and U values and now psi, etc. values
  • ZCH did not understand summer overheating.
  • Building regulations do not understand or control summer overheating.
  • I have logged in and taken a quick look
  • This tool only offering ‘normal’ insulation at ceiling or rafter, perpetuates business as usual.
  • (I have not explored all the details)
  • So it can help ensure the 20% of homes that already overheat may increase in percentage.

Architects are good if you give them a drawing

  • The dashboard approach is good
  • But not showing drawings of the elemental assemblies and their junctions and thickness modifications
  • Leaves them a little uncomfortable
  • (I am not sure what the dashboard is telling me)
  • If I could see a drawing I would be much more confident.
  • I would want to see an Architect using this for the first time unaided and watch and try to understand whats going on in their head.
  • If you are comfortable with these kind of comments than I would be happy to write something.
  • happy for it to be a question and answer session for you to clarify issues or answer questions.

GreenGauge Response

  • You raise some very important points, and I’d really like to discuss them with you, not just for a possible article.
  • I like to think we’re very much on the leading edge in terms of sustainability, but I’m also sometimes annoyed by the ‘greener than thou’ attitude of some people that work in a similar space
  • I think to be ultimately sustainable we need to take the whole industry with us, but this is fraught with the sort of issues you mentioned.

GBE Response

  • I do not normally link energy efficiency with green except as a sub-topic or if your using green tariff supply.
  • I only know one greener than thou but he had little business acumen and dropped out of the market.
  • I know a lot of people who choose ‘green’ because they are often higher performance and make competent buildings.
  • But mainstream dose not normally do competent building, hence the performance gap
  • Passivhaus on the other hand is growing in strength and might become mainstream in a decade

2 years later meeting to discuss future of this software

© GBE NGS ASWS Brian Murphy aka BrianSpecMan *
8th February 2017 – 1st August 2019

GBE Thermal Bridge Psi Calculator

GreenGauge Energy Consultancy Logo

  • Greengauge Building Energy Consultants
  • Director: Toby Cambray
  • 01225 862605

Advanced Details Thermal Bridge Calculator Logo

© GBE NGS ASWS Brian Murphy aka BrianSpecMan *
1st August 2019

GBE Thermal Bridge Psi Calculator
See Also:

GBE Shop:

GBE Equations

  • Thermal Mass
  • Decrement Delay
  • U values
  • Psi values
  • R values

GBE Datasets

GBE Calculators

Others Stuff:


GBE Proposal

GBE Jargon Buster

Initials, Abbreviations, Acronyms:

  • AECB
  • C
  • CO2
  • CO2e
  • D&DT
  • EC
  • EE
  • PHPP
  • Psi
  • SAP
  • SBEM
  • SC
  • TSB
 Words or phrases:
  • Building Embodied Carbon
  • Building Embodied Energy
  • Building Energy Demand
  • Building Fuel demand and Carbon generated
  • Building U Value
  • CAPEM Compass
  • Carbon lite
  • Design & Decision Tools
  • Element area U Value
  • Elemental section U Value
  • Embodied Carbon (EC)
  • Embodied Energy (EE)
  • Embodied Water
  • Fuel Carbon
  • ICE Database (Jargon Buster) G#1018 N#1037
  • Innovate UK
  • Passivhaus
  • Psi values
  • RetScreen
  • Scale Changer
  • Sequestered Carbon (SC)
  • Shared Earth Building Embodied Carbon
  • Thermal Bridge (Jargon Buster) G#9351
  • Thermal Break (Jargon Buster) G#9357
  • WasteCost®Lite
  • Technology Strategy Board (TSB)
  • U value
  • WasteCost®Lite (by GBE)
  • Water Calculator (by AECB)

GBE Links

© GBE NGS ASWS Brian Murphy aka BrianSpecMan *
1st August 2019

Leave a Reply