The difference using actual values vs default values makes to an EPC rating.
Case Study: The 25-Point EPC Gap
Case Study: The 25-Point EPC Gap
This case study demonstrates the impact of using default values rather than actual values in an EPC assessment. We modelled the same building twice:
Once using default values
Once using the actual values we observed during a detailed site inspection
The result:
A 25 point (entire EPC band) improvement by using actual values over default values.
The Building:
50,000 sq. ft. office building
2007 construction
Brick and metal curtain wall construction
Flat metal-clad roof
Original double-glazed curtain glazing
Nothing unusual, very typical of UK commercial stock built at this time.
Default Values Result:
Using default values, the building scored D78, a result that closely matched a previous EPC issued by another assessor.
Whilst that score was technically compliant, it didn't accurately or fairly reflect the actual efficiencies of the buildings systems, and therefore didn’t achieve a good result for the client. If the D78 rating was lodged, the client would have to undertake far greater building upgrades to reach an EPC B target for example.
Actual Values Result:
We then rebuilt the energy model using observed, verified data from our on-site inspection. We included:
Actual heating efficiency
Actual cooling efficiency
Actual lighting specifications and controls
Hot water efficiency
The EPC improved from D78 to C53: That’s a 25-point gain, an entire EPC band higher, without any physical upgrades to the building.
This change wasn’t achieved through capital works or retrofits. It was achieved using our professional, accurate, best-in-class approach. The same approach we use for every project.
Why It Matters:
An inaccurate EPC can lead to:
Unnecessary capex
Misguided upgrade strategies
Lower asset value and marketing appeal
Increased tenant disruption
At Hollen+, we take the time to find as much actual data as possible, rather than relying on defaults.
When time is taken to properly inspect a building and input real, verified data, the true performance is revealed, and that often means better outcomes for owners, investors, and occupiers alike.
If your building has an EPC that doesn’t reflect recent upgrades, or just feels lower than it should be, we would be happy discuss and provide an expert opinion.