SBEM Calculations for Extensions

SBEM Calculations for extensions offer greater flexibility with building design and are required for larger commercial extensions. A large extension is essentially treated as a new complex building and will therefore need to adhere to the standards and regulations set out for new commercial buildings.  

Feel free to give Elmhurst Energy Consultancy a call if you are unsure whether or not your extension requires an SBEM Calculation. Either way, we can help you with information or calculations. 

Whole Building Calculation Method 

U-Value Calculations can be undertaken to determine that the new thermal elements introduced as part of the extension meet the required standards established in Building Regulations/Standards. However, limits on the amount of glazing and thermal elements may make the building design tricky. A Whole building calculation method uses SBEM to provide greater design flexibility and demonstrate reasonable provision towards compliance. 

An SBEM Calculation will demonstrate that the CO₂ emissions for the building and proposed extension, do not exceed that of the building and a notional extension, which already complies with the standards.

When are SBEM Calculations Required for Extensions?

Not all extensions for non-dwellings require an SBEM Calculation, however, large extensions will need an SBEM Calculation if:

• The floor area is greater than 100m²

AND 

• the total useful floor area of the extension is more than 25% of the existing building floor area 

According to regulations if your building meets the above criteria then it will be treated as a new building and will have to comply with the more stringent Building Regulations/Standards which applies to new buildings.