What are SBEM calculations?

SBEM calculations do a lot of heavy lifting in how we measure and improve energy use in commercial buildings. If you’re planning a new build or converting a commercial space, you’re going to run into SBEM at some point. SBEM stands for Simplified Building Energy Model. It’s a method used to calculate how much energy a non-domestic building will use, and how much CO2 it will produce. These calculations are needed to demonstrate compliance with Part L2A of the Building Regulations, and you need them to get a valid EPC (Energy Performance Certificate). All new non-domestic buildings in the UK need SBEM calculations. That includes everything from small office blocks to large warehouses, schools, leisure centres and retail fitouts. These buildings also contribute a significant chunk of our emissions, about 14% of the UK’s direct CO2, comes mostly from heating. Add in electricity use, and buildings overall (residential and non-domestic) account for around a quarter of national emissions. So SBEM is a key part of a bigger shift in how we think about construction and environmental responsibility.

Overview of what SBEM calculations cover

An SBEM assessment takes a wide-angle view of a building’s performance. It looks at the building fabric first (walls, floors, and roof) and checks how well they retain heat. Then it moves on to systems like heating, cooling, ventilation, hot water, lighting. If there are renewables like solar panels or heat pumps, those are factored in too. Essentially, the assessment compares two figures: the Target Emission Rate (TER), which is the maximum allowable CO2 emissions for a building of that type, and the Building Emission Rate (BER), which is what your actual design will emit. If the BER is lower than the TER, you pass. If not, there is still some work to do.

Why do you need SBEM calculations?

The simple answer is that it’s a legal requirement, but it’s not just about compliance. Getting an SBEM done early can help define better design decisions. An adjustment or spec change now could save a retrofit costs at a later stage. It’s also about clarity. With a proper SBEM calculation, there is no assumption about what might work, you’re working from real performance data. If you’re aiming for BREEAM certification or thinking long-term about energy costs and operational efficiency, SBEM is a foundation for all of that.

When do you need SBEM calculations to be carried out?

As with many of enevo’s services, the earlier we get involved, the sooner we can make a difference, so ideally at the design stage. This is when there is still flexibility to tweak the spec, upgrade insulation, or rethink the heating strategy. Waiting until after the build adds more risk and potentially more expense. That said, you also need an SBEM at the as-built stage to confirm final compliance and issue the EPC. So, it’s a two-step process: design, then as built. Extensions and conversions can also trigger new SBEM calculation requirements, depending on the extent of work and what systems are being installed.

How are SBEM calculations worked out?

The calculations are done using government-approved software. At enevo, our specialists use IES VE, a detailed thermal modelling tool. It lets us input all necessary building data – floorplans, U-values, system specifications, lighting layouts, renewables – and simulate how it performs over time. The assessor will break the building into zones based on usage, (for example, a contact centre sales floor is not the same as a storage room). Every space, every system, every light fitting plays a part. It’s a lot of variables, but it builds a precise picture. Depending on the building’s design and the systems being proposed, different assessment levels are needed. Most standard projects will fall under a Level 4 SBEM assessment, but more complex buildings may require Level 5. Level 5 is required for advanced features such as:

• Atriums
• Ventilation with enhanced thermal coupling to structure
• Automated blind control systems

Meanwhile, HVAC configurations that typically trigger a Level 4 requirement include:

• Variable air volume (VAV) systems
• Dual duct or packaged VAV units
• Fan coil systems (2, 3 or 4 pipe)
• Constant volume (CAV) systems
• Chilled beams (active or passive) and displacement ventilation
• Water loop heat pump systems

If your SBEM is being completed for Building Regulations compliance, which it usually is for new commercial builds, then Level 4 is the minimum requirement.

What happens if SBEM calculations don’t meet Building Regulations?

It happens. Sometimes, despite best efforts, designs don’t quite meet the requirements. That’s where enevo’s assessor recommendations are key. It could be as simple as upping insulation in one area. Or maybe a more fundamental rethink of heating strategy or lighting types. At enevo, we work with you to get the building to a pass. The bigger headache is when clients are already at the as-built stage, and nothing can be changed easily at that point.

How long does an SBEM calculation take?

It varies, but for most standard projects, we can turn around the design-stage assessment in three to five working days. If you’re in a pinch, we can offer a 24-hour fast-track service too. The key is having your documents ready. Clear drawings, specs, and details mean we can get going quickly.

How much do SBEM calculations cost?

Every project is unique and the answer to this depends on the size and complexity of the project. A relatively straightforward single-unit retail shell might be around £300 to £500. Larger or more complex projects with lots of zones, specialist systems or renewables could be £1,000+. We can provide a clear quote and breakdown once we understand your plans.

How can enevo help you with SBEM calcs?

We have a long history of delivering compliance assessments for clients large and small across the UK. We’ve completed thousands of SBEM calculations across numerous sectors, from business parks to mixed-use retail and everything in between. Our team includes Level 4 and Level 5 qualified assessors, which means we can handle more complex systems like chilled beams or atria. We offer a clear five-step process:

• Plan review
• Design stage calc
• Improvement advice (if needed)
• As-built calc, and
• EPC delivery

We’ll talk you through options, flag anything that could become a problem later, and we’ll always aim to help you avoid unnecessary costs. If you’re not sure what level of SBEM you need or you’re looking at floorplans wondering what triggers what, just get in touch. We’re happy to help and talk through things. If you’re starting to work on your next project, let’s make sure SBEM isn’t a roadblock. Get in touch with the enevo Building Compliance team and we’ll walk you through what you need, what it might cost, and how we can help you get it over the line.