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Minimum Energy Efficiency Standards

MEES Regulation

The Minimum Energy Efficiency Standards Regulations (MEES) came into force in April 2019.

The first and most significant change was that property for let was required to have an EPC rating of 'E' or better. 'F' or 'G' rated property was required to be upgraded to 'E' or an exemption obtained under specific and limited conditions

Secondly, requirements to present EPC were extended to lease renewals and extensions to an ongoing tenant. 

Finally, 'historic' status no longer gives exemption to EPC regulation, but can be used in mitigation of requirement to upgrade an 'F' or 'G' rated listed building.

Sale transactions are not affected, and property rated 'F' or 'G; can be sold.

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What can be done to improve poor ratings ?

The scope of cost-effective 'improvements' includes the following:-

  • Lighting. First and most obvious is implementation of LED lighting. Most effective when replacing  poor efficiency types such as GLS and T12 / T8 tubes.

  • Removal of heating in warehouse and industrial zones. The model assumes there is none.

  • Implement de-stratification fans in tall heated zones.

  • Insulate partitioned offices built into 'shell'  industrial units, especially the ceiling.

  • Move from electric to gas or LPG-fired heating.

  • Place insulation on top of suspended ceilings. Add spray-on insulation to un-insulated cladding roofs and walls.+

  • Partition-off heated areas from areas where no heating is required. 

MEES Process

Property with a historic 'F' or 'G' rating will require re-assessment.

It is quite reasonable to expect that changes since the original assessment may have introduced some of the required improvements. A better general quality of assessment and changes in the modeling  software may also help.

If an 'F' or 'G' rating persists, then the software model can be tested with 'what-if' analysis to determine what changes might give the required improvement in rating. 

Familiarity with the modelling is necessary, since the scope of effective 'improvements' is wider than might be imagined.


Enercert provides Air-conditioning Energy Inspections of premises as required by regulation.  This regulation and inspection process is also known as ‘TM44’, after the CIBSE ‘Technical Manual’ which is used as the specification for the methodology and content of the inspection.

Enercert offers:

  • Expertise and experience to ‘Level 4’, 

  • Independence from air-conditioning contractors when auditing maintenance and technical matters.

  • Fully holistic assessment arising from experience with EPC, DEC and Commercial Green Deal assessment.


For further information, please refer to the following ‘Briefing Notes’, the FAQ and the Method Statement provided. The Method Statement is a document required by the TM44 standard, which must be provided to the building occupant where an inspection is to take place. It gives a summary of the process and requirements from the occupant’s point of view.

Summary of the ACEI Regulation:

The purpose of this regulation is the comprehensive examination of these energy intensive systems with a view to providing a wide range of relevant cost-saving suggestions.  ACEI is effectively a compulsory energy audit, and often results in identification of savings worth many times its cost.


Premises with more that 12kW of cooling are required to have an AC energy inspection every 5 years. The inspection is a holistic survey of the equipment  (installation, maintenance and use) the building (insulation, heat gain from windows, heat gain from machinery) and the operation (settings, dead-bands, sensors etc...)  of the systems.  ACEI is much more that an additional maintenance visit due to the wide scope of the CIBSE  TM44 standard by which it is alternatively known.


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