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The Differences Between SAP Calculations for New Build Properties vs SAP Calculations for Extensions- Made Simple 

What Are SAP Calculations?

Before diving into the differences, let's briefly explain what the key fundemantal differences of what a SAP Calculations is.

In a nutshell, SAP Calculations are the UK government's method for assessing and comparing the energy and environmental performance of residential properties. These calculations are essential for obtaining a Building Regulations compliance certificate, which is required before a new property or extension can be signed off by building control.

SAP Calculations for New Build Properties

For new build properties, SAP Calculations are a fundamental part of the design and construction process and, in most buildings, a legal requirement. Here’s 4 main reasons why:​

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1/ Building Regulations Compliance:

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For New Build projects, SAP Calculations are required to demonstrate compliance with Part L of the Building Regulations, which focuses on the conservation of fuel and power (ADL1, 2022). These calculations ensure that the new property meets stringent energy efficiency standards, covering aspects such as insulation, heating systems, and renewable energy sources. Generally most planning departments and building Control Bodies will require both an ‘As Designed SAP Calculation’ to be carried out pre-construction and an ‘As Built’ Sap Calculation post construction.​

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2/ Detailed Assessment:

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The process involves a thorough evaluation of the building’s design, including the materials used, thermal insulation, air tightness, and the efficiency of heating and hot water systems. The calculations also take into account the orientation of the building and local climate conditions. This means we will need as much information as possible at the design stage: Plans, Specifications, Proposed renewable technology, proposed insulations etc.​

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3/ Energy Performance Certificate (EPC):

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Upon completion of the SAP Calculations for a new build, generally an Energy Performance Certificate (EPC) is issued. This can only come from a SAP assement. A Domestic Energy Assessor cannot produce an 'On Contruction EPC' on your newbuild property. This certificate is crucial for selling or renting the property, as it provides potential buyers or tenants with an overview of the building’s energy efficiency.​

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4/ Design Flexibility:

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For new builds, there is greater flexibility in design choices, as the entire structure is being built from scratch. This allows developers to incorporate the latest energy-efficient technologies and construction methods to meet SAP requirements. We often work with architects who experiment with a few SAP models before we issue the final ‘As Designed’ SAP Calculations.

SAP Calculations for Extensions

When it comes to extensions, the approach to SAP Calculations is somewhat different, reflecting the unique challenges of modifying an existing structure and the needs of the Building Control Body. These are often triggered as a result of ‘Excessive Glazing’, ie more glazing than is permitted in the Building regualtions. When this occurs, it doesn’t mean you will have to scrap your plans and start again, but rather the deemed impact of the extra glazing is ‘offset’ against other elements of either the extension itself or the main property its attached to.

 

This can be demonstrated through an "area weighted U Value calcualtion", however in most cases compliance is demonstrated through a SAP Calculation.

 

Here are the 4 main differences applied to a SAP Calculation for an Extension project vs a SAP calculation for a new build project:​

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  • Specific Building Regulation Requirements:

​While new build projects must comply with certan sections and tables of ADL1 (download here) of the Building Regulations, different sections of the same document apply to extensions. These sections of the regulations focus on alterations to existing buildings, ensuring that any new addition does not negatively impact the overall energy efficiency of the property and has different methodology to a new build project.​ For example, there will be no 'Target Building' for the existing building with an extension to be compared against (measured as the TER), whereas in a new build project that measure will be present. 

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  • Targeted Assessment:

​​SAP Calculations for extensions usually involve a few steps:

Step 1: assessing the thermal performance of the new structure individually as a first instance, testing to see that the U Values comply. This will include evaluating the extension’s insulation, windows, and the integration with the existing heating system.​ If that doesn't meet the requirements (usually due to excessive glazing), we then move to step 2.

Step 2: Building the extension and the existing building model into a SAP calculation.

Step 3: Demonstrate thorugh contrasting SAP reports that the existing building plus the proposed extension is more energy efficeint than the existing building plus an extension built to meet the tabled values in Part L. 

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  • Consideration of Existing Structures:

​​If the extension is not meeting the regulations, (for example the glazing as mentioned above), using the above approach allows the Energy Assessor to consider the existing building's energy performance, and with the guuidance of the homeowner or architect make improvements in these areas. The SAP Calculations accounts for how the extension affects the overall energy efficiency of the property, and whether any upgrades to the existing building are required as compensation to meet the standards (Simple wins to the existing properties we have used in the past have included improvements in: loft insulations, heating controls, cavity wall insulations and window upgrades).​

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  • Proportional Requirements:

​​For extensions, generally the requirements can be more flexible compared to new builds, especially if the extension is modest in size. However, it’s still crucial that the extension adheres to energy efficiency standards to avoid penalties or delays in obtaining Building Regulations approval. Sometime this means a readjust on the ammount of glazing in the extension if improvements to the main house are not practical. 

 

Why Choose us for Your SAP Calculations?

Whether you’re constructing a new property or extending an existing one, understanding the nuances of SAP Calculations is essential for a successful project. Here is why many people trust SAP2SBEM.co.uk for their project:​

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  • We always strive to deliver accurate and reliable SAP Calculations tailored to your specific project needs.

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  • We works closely with architects, builders, and homeowners up and down the country to assist with compliance with all relevant regulations, helping you avoid costly delays and ensuring a smooth approval process. This bank of knowledge will only help your project. 

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  • We regularly review our pricing structure and aim to keep our prices competitive and always look for cost saving compliance routes for your build. There is a lot of work involved in a project, so please beware of cheap SAP quotes. Sadly every year we pick up on poorly assessed projects where compliance has not been achieved due to substitutions or poor assessment. We are regularly audited independently, and openly share the results of these audits. 

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  • We are qualified and registered with Elmhurst Energy Systems for both new build Domestic and Non Domestic compliance projects and often work on mixed development projects. 

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  • We also cover many other New Build Compliance Services and Calculations, please go to our services page for more options.

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