SAP Calculations for Extensions

SAP Calculations for Extensions (Heat Loss Calculations)

Our highly experienced SAP Assessors have delivered SAP calculations (heat loss calculations) for thousands of highly glazed residential extensions, handling projects with varying degrees of construction complexity and site constraints.

We have a proven 100% success rate in demonstrating compliance with Approved Document L of the Building Regulations for highly glazed extensions. With our expertise, you can be confident that your design will meet regulatory requirements without compromise when you instruct us to carry out SAP calculations for your extension project.

Do I need a SAP Calculation for my extension?

Approved Document L: Volume 1 of the Building Regulations limits the amount of glazing in extensions to 25% of the new floor area (plus any existing windows removed as part of the works). This restriction helps prevent excessive heat loss, as glazing typically has lower thermal performance compared to the insulation standards required for external walls and roofs.If a project stays within this glazing allowance, a SAP calculation is not mandatory for the extension.However, modern design trends often favour bright, open spaces, leading many extensions to exceed the 25% glazing limit.To accommodate this, Approved Document L: Volume 1 offers a ‘design flexibility’ option. This allows applicants to proceed with their proposed design, provided they can demonstrate that the overall energy efficiency of the dwelling remains at least as effective as it would have been with a conventionally glazed extension of the same size.One way to meet this requirement is by submitting a SAP calculation for the highly glazed extension to the Building Control Body (BCB).

Heat Loss Calculations for Highly Glazed Extensions – Expert Assessment & Advice to Guarantee Compliance

SAP Calculations are an effective way to demonstrate that highly glazed extensions, orangeries, and garden rooms comply with the overall requirements of Approved Document L: Volume 1 of the Building Regulations under the ‘Design Flexibility Criterion’.

Often referred to as heat loss calculations for over-glazed extensions, SAP assessments are increasingly being requested by Building Control Bodies. This is due to the growing trend of incorporating high levels of glazing in modern designs, including bi-fold doors, floor-to-ceiling windows, roof lights, and lanterns.

For more information about SAP Calculations or to discuss your specific requirements, please call us on 0208 908 5141 email us at info@quodox.co.uk