SBEM Calculations for Modular Buildings

SBEM Calculations for Modular Buildings

Trends in Modular Buildings 

Over the past 8 years, there have been numerous new additions to the Building Regulations to cover the use of modular buildings. These cover buildings that are prefabricated and designed for delivery to site as sub-assemblies, connected together and completed on site.

Traditionally modular buildings have been used for temporary offices and classrooms, but there is a growing trend, being led by Europe, to use this process for different types of building, including new homes. With the rise in property prices and a greater consideration for sustainable buildings, this trend will grow.

The benefits of modular construction are numerous: the speed at which buildings can go up reduces from years to weeks with a modular approach; there are large cost efficiencies from the mass-construction and highly-accurate factory processes; and there is far less impact on the area surrounding the development with most of the construction happening offsite.

Compliance & Regulations for Modular Buildings 

When a modular building, whether it is a new construction or a refurbished one, is proposed for a new development, the design and installation of the unit must be assessed under the Government’s approved methodology for calculating the energy performance of buildings (for commercial buildings this would be SBEM: Simplified Building Energy Model), to guarantee that it is compliant with Approved Document L of the Building Regulations.

These assessments must be carried out at design stage and the end result will produce a BRUKL (Building Regulation UK Part L) report which is to be provided to the Building Control Body (BCB). Results are expressed in terms of carbon dioxide emissions, which will determine a pass or fail.

Modular Building Exemptions 

There are certain types of non-domestic modular building that are exempt from Approved Document Part L2, meaning that SBEM calculations are not required, and they are:

  • Standalone buildings under 50m2.

  • Buildings with a low energy demand – for example buildings that do not require heating or air conditioning.

  • Buildings to be used as a place of worship.

  • Temporary buildings: defined as a building that is used on a single site for a period less than two years and then destroyed. 

Special Considerations for Modular Buildings 

For modular and portable buildings which do not fall within one of the exemptions above, a SBEM calculation will be required.

The Building Regulations do however provide the following special considerations for non-exempt modular and portable buildings:

  1. Recycled buildings

To pass a SBEM calculation buildings must be shown to have a Building CO2 Emission Rate (BER) less than a given Target CO2 Emission Rate (TER). For modular and portable buildings, if more than 70% of the external walls, floors and roofs were originally manufactured prior to the date the current Building Regulations came into force (for example, prior to 6th April 2014 for the 2013 regulations) an allowance is applied to the TER. The older the original manufacture, the greater the allowance.

  1. Short term hire 

Modular and portable buildings with a planned service life of more than two years, but with an intended time on each given site of less than two years must still pass a SBEM calculation. However, as these buildings must often be on-site and operational in a matter of days there is no requirement to undertake a new SBEM calculation each time the building is moved. Instead a SBEM calculation must be produced when the portable building is first constructed. This SBEM calculation will be based on a generic configuration and gas boiler heating system. 

Gaining Professional Guidance 

At Energytest we work on SBEM calculations for all types of developments every day and by involving one of our trained consultants at an early stage, we can help you develop your project successfully to meet the correct Building Regulations and avoid any unwanted and costly delays.