Case Study – Commercial Office Unit in Northampton

Office Energy Performance Certificate Northampton


A commercial epc was required in the town of Northampton. Northampton is one of the largest towns in the UK with a population of 245,899 according to the  the 2021 census. It has an unemployment rate of 3.2% at June 2023 which is below the average UK figure of 4.2% according to the Office of National Statistics. This means it has a healthy commercial environment and explains why it is one of the main areas we carry out commercial EPCs.

Project Overview

The building needing the EPC was a small modern office block built in the mid 2000’s. The EPC was required by the customer as part of the owners pension fund provision. These properties are usually managed by a pension fund and the purpose of the EPC is two fold. Firstly, to ensure the building has a valid EPC on the epc register and secondly, that the building meets the Minimum Energy Efficiency Standard and therefore can be leased.

EPC Process


The building had a previous expired EPC on the register, so it was straightforward to provide the customer with a fixed price. The building was 188m2 over 2 floors and fell within the most common type of commercial epcs in Northampton we do, which has between 10 and 20 zones. Therefore, a price of £250 was quoted which the customer accepted.

The Site Visit

Customers are always asked if they have a floor plan of the building, as this speeds up the time spent on site and reduces the disturbance to people working in the building. On this occasion no plan was available, so one had to be created whilst on site.

The main purpose of the site visit is to obtain information and photographic evidence about the:

  • Building fabric construction type
  • HVAC system
  • Glazing type and dimensions
  • The activity of the zones within the building
  • The type of lighting
  • The provision for hot water

As with many modern office buildings in Northampton, many features of the building are uniform, which speeds up the data entry once off site.

A total time of 45 minutes was spent on site and overall the project could be classed as straightforward and on the easier side of assessments.

Off site data entry

Once off site, the data obtained has to be entered into the SBEM software.

The 1st step involves zoning the floor plans.

Zones are areas of a specific activity within a commercial building. If adjoining rooms have the same activity type, HVAC system, building fabric construction type, and lighting type, then they can be zoned together which reduces the time taken to enter the data into the software.

Here is the floor plan of the project

Floor Plan Office at Bassett Court Northampton

Here is the subsequent project zoning plan.

zoned floor plan

Because of the varying HVAC systems and different lighting in each zone there was little opportunity to combine the zones.

Summary of elements in the building

Total Zones for the project
Building fabric construction type
HVAC system
Glazing type and dimensions
The type of lighting
The provision for hot water
All elements built to 2002 building regulation - insulation assumed.
Mostly air con multi-splits systems, storage heaters in some zones
Double glazed PVC to 2002 building regulations
Lighting comprising 50% CFL and 50% LED
Instantaneous hot water at the point of use

Results and Achievements

After double checking all the data entry, the software performed the calculations and produced the following EPC rating.

EPC Rating – Office Unit Northampton

EPC Rating Office unit Northampton

The second part of the EPC rating shows what the building would rate if it were new and how it compares to other typical properties of that age and size and activity, this is shown below.

epc rating comparisions

Project Summary

Overall, the property rated better than typical of the existing housing stock, this was due to the exact efficiencies of the air con system being identified during the survey.

air con efficiencies labelOn many surveys the air con efficiencies of the units can’t be determined because very often they are not accessible and the client has no paperwork, in which case the software will then default to fairly low rating of the units which impacts the EPC rating.

Air con system in a commercial building will help the EPC to rate well. This with all the fabric elements (walls, roof, floors) being assumed to be insulated and produced a good rating and no surprises on what would be expected for a building in Northampton of that age.

There was still some scope for improvement shown on the recommendation report, by changing all lights to LED and installing solar pv panels.

A straightforward commercial EPC project like this would be completed in a day.


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Rickie Dickson
Written by Rickie Dickson

Rickie Dickson is an experienced and qualified domestic and non domestic energy assessor. He helps homeowners and businesses in all matters relating to energy efficiency, from meeting building regulations compliance to improving a property’s energy rating score.