Part L
Thermal bridging and psi-values
Junction calculations that replace default values in SAP and can improve the result.
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Energy & performance calculations
U-value calculations
A qualified energy assessor calculates the U-value of each wall, floor and roof build-up to the BRE conventions Approved Document L refers to, so you can check the specification against Part L before you build.
When you need it
Part L sets limiting U-values for new and replacement walls, floors, roofs, windows and doors, and the SAP or SBEM calculation needs the U-value of every element. Approved Document L says U-values should be assessed using the methods and conventions in BRE BR 443. Building control may ask for calculations for extensions and conversions as part of the application.
A calculation based on the actual products and thicknesses is more reliable than a generic table. It also shows quickly whether a thinner build-up or a different insulation will still work.
What is included
Included
- Review of each proposed build-up and the products specified
- U-value calculation to BR 443 conventions for each element
- Comparison with the Approved Document L limiting values that apply
- Advice on adjustments where an element falls short
Priced separately
- Condensation risk analysis
- Thermal bridging and psi-value calculations
- SAP or SBEM calculations
- Recalculation after product or specification changes
Your written quotation confirms the exact scope, what is included and any limits for your building.
What you receive
A U-value calculation sheet for each element, showing the layers, thicknesses and result against the target, ready for building control or your energy assessor.
Sent as a PDF. We can send it to your building control body or agent on request.
Our reports and testing support the compliance process. Approval and completion decisions remain with your building control body: the local authority, a registered building control approver, or the Building Safety Regulator for higher-risk buildings.
How to prepare
- Section drawings showing each build-up
- Insulation and board products, with thicknesses
- Structure type: timber, masonry or steel, with stud or joist spacing
- For floors, the floor perimeter and area
- Whether the work is a new build, extension, conversion or renovation
Send what you have. Missing details will not stop an enquiry; we will tell you anything still needed.
How it works
Tell usChoose the service or describe the job.
Written quotationScope, deliverables and price, confirmed in writing.
We manage the workArranged and coordinated by RegulaBuild. Technical work is carried out by appropriately qualified professionals.
Your reportThe output named in your quotation, with any follow-up.
Questions
What is a good U-value?
Lower is better. The target depends on the element and the type of work, so we compare each result with the limit that applies to your project.
Can I use the manufacturer’s calculation?
Often, if it matches your exact build-up. If the structure, thickness or finishes differ, a project-specific calculation is safer.
Often booked with
Combine them in one quote request
Part L
Overglazed extension calculations
Calculations showing an extension with generous glazing still meets the energy standard.
Energy calculationsView service
Part L
Energy and SAP calculations
Design-stage and as-built SAP calculations for new and converted homes, with the EPC lodged at completion.
Energy calculationsView service
Where we work
U-value calculations across England
Request a quote
Discuss u-value calculations
Start with this service and add anything else you need. If you are unsure, say so and we will advise.