Accurate Ψ-value and psi calculations for Part L compliance

What Are Thermal Bridging Calculations?

A thermal bridging calculation measures the additional heat loss at junctions in the building envelope.

This is expressed as a Ψ-value (psi value) in W/mK.

Unlike a U-value, which measures heat loss through an area, a psi value measures heat loss along a junction line.

Typical examples include:

• where the external wall meets the ground floor
• roof eaves details
• window and door openings
• steel beam penetrations
• junctions around flat roof upstands

These values are then entered into SAP or SBEM calculations to improve the overall Y-value and energy performance result.

What our clients say

We have recommended Barlings KWA to many of our clients for their air testing and energy assessment services. William and Kerry are extremely helpful and always deliver the work accurately and on time

Joe Campion

Why Are They Important?

Even when wall, roof, and floor U-values are good, poor junction details can create significant additional heat loss.

Thermal bridges may contribute a substantial proportion of total fabric heat loss and can also increase the risk of:

• surface condensation
• mould growth
• cold spots
• occupant discomfort
• thermal efficiency

By calculating the junctions accurately, we can often improve the SAP result compared with default assumptions.

• new dwellings
• extension details
• commercial Part L projects
• bespoke junction details
• steel frame interfaces
• retrofit insulation projects
• SAP and SBEM compliance
• condensation risk checks

This is especially useful where standard manufacturer details are not available.

We regularly work with architects, developers, and building control teams to help projects move forward quickly.

Our Service Includes

At Barlings KWA Ltd, we provide:

• bespoke junction psi calculations
• linear thermal transmittance (Ψ) values
• condensation temperature factor checks
• SAP and SBEM compatible outputs
• BR 497 compliant calculations
• practical junction improvement advice
• fast turnaround

Calculations are undertaken in accordance with BRE BR 497.

Why choose Barlings KWA Ltd?

• Experienced in Building Regulations compliance
• Reliable and professional service
• Clear reports suitable for Building Control
• Practical advice to help projects meet Part L requirements
• Local Lincolnshire based service

We understand the requirements of construction projects and aim to provide a reliable and efficient service throughout the process.

More client feedback

“Always happy to answer any queries we have; the service and information they provide is excellent.”

— Kirsty Uttley

“A fantastic, professional company to work with. Great communication and turnaround time.”

— Chris Henderson

Get a Quote for Thermal Bridging Details

Need thermal bridging calculations for your project?

Please contact us to discuss your project or request a quote.

Email: [email protected] or [email protected]