Psi
Psi, also written with the Greek letter ψ has many different uses including in psychology, quantum mechanics and computing as well as in the design and construction of buildings.
In terms of building design the Psi or Ψ value is the property of a thermal bridge junction between two elements and expresses the rate of heat flow per unit length of at thermal bridge. It might be considered as an adjustment figure for performance and is considered when calculating or allowing for U values and het loss in building fabric.
Psi should not be confused with PSI, which might also be found in the construction field and stands for pounds per square inch (PSI). PSI is a measurement of pressure in the Imperial system of measurement, commonly used to measure the pneumatic pressure of gasses or the hydraulic pressure of liquids. PSI is also used as a measure of tensile strength, as a resistance to pulling forces, and elastic modulus strength, defined as resistance to deformation ie the stiffness of materials.
NB Part L 2021 Where to start, A guide for housebuilders and their advisors, Masonry construction, published by the Future Homes Hub in June 2022, states Psi-value or linear thermal transmittance is: ‘the measure of heat loss along a non-repeating thermal bridge calculated as per guidance in BR 497 (2nd edition 2016) and IP 1/06 (2006); expressed in terms of W/mK.’
See also: Linear thermal transmittance.
[edit] Related articles on Designing Buildings
Featured articles and news
RTPI leader to become new CIOB Chief Executive Officer
Dr Victoria Hills MRTPI, FICE to take over after Caroline Gumble’s departure.
Social and affordable housing, a long term plan for delivery
The “Delivering a Decade of Renewal for Social and Affordable Housing” strategy sets out future path.
A change to adoptive architecture
Effects of global weather warming on architectural detailing, material choice and human interaction.
The proposed publicly owned and backed subsidiary of Homes England, to facilitate new homes.
How big is the problem and what can we do to mitigate the effects?
Overheating guidance and tools for building designers
A number of cool guides to help with the heat.
The UK's Modern Industrial Strategy: A 10 year plan
Previous consultation criticism, current key elements and general support with some persisting reservations.
Building Safety Regulator reforms
New roles, new staff and a new fast track service pave the way for a single construction regulator.
Architectural Technologist CPDs and Communications
CIAT CPD… and how you can do it!
Cooling centres and cool spaces
Managing extreme heat in cities by directing the public to places for heat stress relief and water sources.
Winter gardens: A brief history and warm variations
Extending the season with glass in different forms and terms.
Restoring Great Yarmouth's Winter Gardens
Transforming one of the least sustainable constructions imaginable.
Construction Skills Mission Board launch sector drive
Newly formed government and industry collaboration set strategy for recruiting an additional 100,000 construction workers a year.
New Architects Code comes into effect in September 2025
ARB Architects Code of Conduct and Practice available with ongoing consultation regarding guidance.
Welsh Skills Body (Medr) launches ambitious plan
The new skills body brings together funding and regulation of tertiary education and research for the devolved nation.
Paul Gandy FCIOB announced as next CIOB President
Former Tilbury Douglas CEO takes helm.
UK Infrastructure: A 10 Year Strategy. In brief with reactions
With the National Infrastructure and Service Transformation Authority (NISTA).