Extensions · Fabric trade-offs
Area-weighted U-value calculations for extensions
A project-specific assessment where glazing and element performance need to be considered together.
Send a project
Overview
For some extensions and alterations, an area-weighted calculation can demonstrate that the proposed fabric arrangement performs no worse than the applicable reference approach. It can be useful where the design includes more glazing, but it is not an automatic workaround and suitability depends on the project and regulatory route.
Project requirements vary by building type, location and timing. Send us the project information and we will confirm the right assessment route before providing a quotation.
Particularly useful for
- Domestic extensions with significant glazing
- Projects comparing improved fabric specifications
- Designs where a simple elemental check is insufficient
- Building Regulations submissions needing a clear evidence trail
Our approach
- 01
Confirm that the method is appropriate for the particular work
- 02
Measure relevant element and opening areas from the drawings
- 03
Compare the proposed and reference heat-loss performance
- 04
Advise on the most effective specification changes and issue the calculation
What is included
A comparison of the proposed and reference fabric heat-loss performance for the agreed extension assessment. The report records the relevant element areas, U-values and assumptions, with focused specification advice where the proposed arrangement needs improvement.
Information to send
Provide existing and proposed plans, elevations and sections, plus the wall, roof and floor build-ups. Include window, door and rooflight sizes and performance data, and show existing openings affected by the extension. Send any specific request already received from Building Control.
Scope, fees and timing
This can be useful for an extension with significant glazing, but it does not guarantee that any glazing arrangement can be accepted. Suitability depends on the applicable guidance and the project. If the comparison is insufficient, a different assessment route or design changes may be needed; this is confirmed before additional work is agreed.
Based in Lincolnshire, we support architects, builders, developers and homeowners across the county and throughout England. Most calculation-led work can be reviewed from suitable digital drawings. Send the project location, stage and required date so we can confirm the scope, fee and programme before you instruct us.
Useful guidance
Start a conversation
Send us the project
Upload the drawings and a few project details. We will review what is needed and confirm the scope before work begins.
Get a quote