Part L SAP Calculations
For Over Glazed Extensions

When building a residential extension, if the area of glazing exceeds 25% of the new floor area you will be required to show compliance with Part L1B of the Building Regulations

When do you need a SAP Calculation for your extension

If your proposed extension has more glazing (windows, doors or rooflights) than 25% of the new floor area, you will need a SAP Calculation to comply with Part L Building Regulations. Due to increased heat loss through glazing as opposed to insulated walls or roofs there are restrictions in the building regulations to the area of glazing permissible within an extension. to prevent excessive heat loss and energy inefficiency.

To meet the regulations, you must show that your extension will not increase CO₂ emissions of the dwelling more than a Building Regulations compliant extension.

Our SAP Calculations demonstrate that, by making energy-saving improvements elsewhere in your home, your proposed extension will perform as well as — or better than — a standard, compliant extension.

The Process

A SAP assessment involves several steps to evaluate the energy performance of your property:

Data Collection: This includes gathering architectural drawings, and details about construction materials and insulation, also specification of heating, hot water and ventilation systems.
Energy Modelling: Using Elmhurst Design SAP10 software, we calculate the building's predicted energy consumption, carbon emissions, and overall efficiency.
Compliance Checks: We ensure that the property meets all relevant standards under Part L of the Building Regulations.
Recommendations: If the building does not meet the required standards, we provide practical solutions to improve its energy performance.
Certification: Once compliance is achieved, an As-Built SAP calculation report and an Energy Performance Certificate (EPC) are issued, reflecting how the building has been constructed.

Why Choose E & S Bristol

At E & S Bristol we have extensive knowedge, providing calculations for building control approval on a wide variety of residential extensions including basement excavations, pool houses, orangeries and conservatories open to the dwelling.

Irrespective of the amount of glazing, E & S Bristol will you propose a workable solution in line with your design
As part of our service we will provide U-Value calculations for all new thermal elements

We will make recommendations to reduce the CO2 emissions associated with the extension and, if required the existing dwelling
We will provide notional and proposed SAP calculations along with a summary letter for building control explaining how requirements have been met

Whether you’re constructing a new home, converting an existing property, or planning an extension, E & S Bristol is your trusted partner for SAP calculations. Contact us today to discuss your project requirements and find out how we can help you achieve compliance effortlessly.