Extension SAP Calculations
Extension SAP Calculations & Part L Compliance
Crowther Solutions provides Extension SAP Calculations for extensions, conversions and highly glazed residential projects across the UK. Where a proposed extension exceeds the normal glazing allowances under Part L, SAP modelling can be used to assess the proposed design against a compliant notional alternative.
With experience dating back to 2005, we provide clear technical guidance on the assessment results and the effect that proposed changes to the specification may have on compliance.
The "Notional vs. Proposed" Approach
Under current Part L requirements, the total area of windows, roof windows, rooflights and doors in an extension is normally limited to 25% of the extension floor area, plus the area of any existing openings that are no longer exposed because of the extension. Where the proposed design exceeds this allowance, a SAP-based assessment can be used as an alternative method of demonstrating compliance.
Notional Extension: A compliant reference model of the same size and shape as the proposed extension, using the permitted glazing allowance and the relevant minimum standards.
Proposed Extension: The actual proposed design, including the intended glazing areas and project specification.
The assessment compares the performance of the existing dwelling plus the proposed extension against the existing dwelling plus the notional extension. This allows highly glazed designs to be assessed properly rather than simply relying on the standard glazing allowance.
What Our Service Includes:
Proposed & Notional SAP Modelling: Comparative assessment of the proposed extension against the compliant notional alternative.
U-Value Calculations: Thermal calculations for walls, floors, roofs, glazing and other relevant building elements.
Compliance Guidance: Where the initial proposal does not meet the required target, we can model alternative specification options provided by the project team and advise on how those changes affect the assessment result.
Clear Written Summary: A straightforward summary of the assessment outcome for submission to Building Control.
A Practical Approach to Extension Compliance
With experience dating back to 2005, Crowther Solutions understands the practical challenges involved in extension compliance. We focus on clear, proportionate assessment and straightforward technical guidance, helping clients understand what is affecting the result and where changes to the proposed specification may improve compliance.
Get a Quote for Your Extension.
Send us your drawings and project information and Crowther Solutions will review the assessment requirements and provide a project-specific quotation. We work with homeowners, architects, developers and builders across the UK on extension SAP calculations and Part L compliance.
