The 1,000m² trap: How a tenant's mezzanine could trigger an EPC B requirement
The Government's recently published Interim Response to the consultation on Minimum Energy Efficiency Standards (MEES) has introduced a significant change in direction for non-domestic rented buildings.
Rather than requiring all commercial buildings to progress through EPC C before reaching EPC B, the Government now proposes a size-based approach. Under the proposals, privately rented non-domestic buildings with a Gross Internal Area (GIA) of less than 1,000m² would remain subject to the existing minimum standard of EPC E, while buildings with a GIA of 1,000m² or more would be expected to achieve EPC B by 2031, subject to the existing seven-year payback test and exemptions. There are, of course, still questions around how multi-let buildings are measured, or situations where tenants occupy more than obe adjacent unit, but we have to await the detail to properly advise on that.
Most commentary has focused on the new EPC B target. However, for many industrial landlords and asset managers, the more important question is much simpler:
How do you know whether your building is actually over 1,000m²?
For some buildings, the answer may depend not on the original construction, but on alterations made by the tenant.
When 970m² Becomes 1,030m²
Industrial occupiers regularly install mezzanine floors to increase storage capacity, create offices or improve operational efficiency. In many cases, these are installed several years into a lease and become part of the building for the purposes of an EPC assessment. Imagine a warehouse originally measured at 970m² GIA, a tenant subsequently installs a permanent 60m² mezzanine and the building is now assessed at 1,030m² GIA.
That seemingly modest alteration could have a significant regulatory consequence. Rather than remaining within the proposed regime that requires only an EPC E, the property may now fall within the scope of the proposed EPC B requirement from 2031. Of course, they may exempt tenant’s mezzanines, but the EPC has always used TUFA (total useful floor area) which equates to GIA on the day of inspection. In other words, a tenant alteration costing relatively little could fundamentally change the landlord's future compliance obligations. It doesn’t even need to be a mezzanine. If a tenant installs a fixed stair and creates storage space above partitioned office space this would also be included in GIA and add to the building area.
The financial implications could be considerable. The difference between achieving EPC E and EPC B is often substantial, particularly for older industrial stock. Meeting EPC B may require improvements such as replacement lighting systems, removal/decommissioning of all fossil fuel plant and replacement with electric alternatives, improved insulation or renewables.
For an asset manager planning future capital expenditure, discovering that a building has unintentionally crossed the 1,000m² threshold could materially affect investment forecasts.
Would You Even Know?
One of the challenges is that many landlords often don't monitor changes that affect EPC calculations.
Mezzanines are frequently installed with landlord's consent, but once the licence for alterations has been completed, the revised floor area is not usually recorded within the property management system. Years later, when an EPC is required, the assessor measures a building that bears little resemblance to the original records, so if the Government proceeds with the proposed size threshold, accurate floor area records will become considerably more important than they are today.
Asset managers should consider whether their existing processes capture tenant-installed mezzanines or any other permanent internal alterations affecting GIA and check the EPC rating that results before granting consent.
Can Your Lease Help?
Existing leases were drafted before anyone anticipated a distinction between buildings above and below 1,000m². Standard alterations provisions often require landlord's consent before structural works or the installation of mezzanine floors, but they rarely address the impact those works may have on future MEES obligations. Landlords reviewing new leases should consider whether additional provisions would be beneficial, for example requiring tenants to notify the landlord of alterations that may affect an EPC assessment, provide updated floor plans or measured surveys following alterations, and ensuring tenants supply full information about the works to allow the EPC model to be updated accurately. Whether a landlord can recover any additional compliance costs resulting from tenant alterations may depend on the drafting of the lease so should be considered as part of the legal advice.
Don't Assume the Existing EPC Tells the Whole Story
As portfolios move closer to EPC B, the quality of the assessment becomes increasingly important. Many EPCs are produced using limited information, requiring assessors to rely on default assumptions within the SBEM methodology. Where more comprehensive evidence is available, Level 5 modelling can often provide a more accurate representation of the building and this is particularly relevant where buildings have undergone alterations over many years. Accurate construction details, verified insulation levels, lighting designs, HVAC specifications and properly modelled building geometry can all influence the outcome of the assessment. This is about ensuring that the assessment reflects the building as it actually exists, rather than relying on poor default assumptions that may no longer be correct. For buildings sitting close to EPC B, that additional level of accuracy can make a significant difference to future investment decisions.
Another Proposal Worth Watching
Although the Interim MEES Response confirms the Government's preferred direction on minimum standards, another proposal remains under consideration that could prove equally significant for landlords. The EPC consultation sought views on requiring privately rented non-domestic buildings to hold a valid EPC throughout the duration of a tenancy, rather than only when an EPC is triggered by a letting, sale or construction event. If that proposal is ultimately introduced, EPCs would become an ongoing compliance obligation rather than a transactional document. For buildings where tenants regularly install mezzanines or undertake internal alterations, landlords would need robust processes to identify changes affecting the EPC and determine whether reassessment is required as a mid-tenancy EPC could cause serious compliance issues and require unplanned capital expenditure. Combined with the proposed 1,000m² threshold, that would place far greater emphasis on maintaining accurate building records throughout the life of an asset.
Why Dynamic Building Models Matter
At MEES Solutions, we retain the underlying models for every building we assess, allowing us to revisit them whenever circumstances change. If a tenant installs a mezzanine, changes the lighting, upgrades the heating system or undertakes other alterations, we can update the existing model rather than starting the assessment from the beginning. More importantly, we can model potential improvements before any money is spent. If you want to know whether replacing lighting alone would achieve EPC B, we can test it. If you want to understand whether roof insulation delivers a better return than photovoltaic panels? We can compare the options. If you need to establish whether a newly installed mezzanine changes the building's regulatory position? We can answer that too. By maintaining ‘live’ building models rather than simply issuing EPC certificates, we help our clients understand the consequences of changes before they become expensive compliance problems.
Looking Ahead
The Government's proposed 1,000m² threshold creates a new dividing line within the commercial property market. For many landlords, the critical question will not only be "What is my EPC?" but also "What is the true size of my building?". A tenant-installed mezzanine may seem like a straightforward operational improvement, but it could also move a property into an entirely different regulatory category, with significantly higher future energy efficiency expectations.
For asset managers, the answer is not to wait until the next EPC is commissioned. It is to maintain accurate records, understand how tenant alterations affect the building, and use robust energy modelling to plan ahead.
At MEES Solutions, that's exactly what we do. We don't just produce EPCs—we maintain detailed digital models of our clients' buildings, allowing us to assess the impact of alterations, model improvement scenarios and provide practical advice as regulations evolve. As the proposed MEES changes move towards implementation, that ability to make informed decisions from an up-to-date model will become increasingly valuable
Could your portfolio be affected?
If you have buildings close to 1,000m², tenant-installed mezzanines or EPCs that may no longer reflect the property, our complimentary EPC & MEES Review is a sensible place to start. We can look at one building, a site or your full property schedule to help identify where the risks sit and which assets should be prioritised for further assessment.
The initial review meeting is complimentary, with no obligation to commission any resulting EPC work.