Achieving a good EPC rating

Achieving a good EPC rating

Four months on from the introduction of Minimum Energy Efficiency Standards (‘MEES’, as set out in the Energy Efficiency Regulations 2015) few will have missed the news that it is now illegal to let a building which fails to meet the minimum required Energy Performance Certificates (EPC) rating of E.

Currently the MEES Regulations apply only to the granting of new leases and lease renewals, but from 2023, extend to all active leases.

So what advice is still left to give to those who must make the necessary changes (now or in advance of the 2023 deadline) or to anyone interested in making their building more sustainable and cost efficient to run?

Resistance to the new regulations – in the form of apathy or even defiance – is widespread, according to some sources. So can EPCs still be worth the bother?

We believe so. Far from being a pointless box-ticking exercise, EPCs are an extremely useful tool for informing a property owner or manager of their building’s estimated energy use, carbon dioxide emissions, fuel costs, energy performance and environmental impact.  An EPC assessment looks at four categories of data – HVAC (heating, ventilation, air conditioning), thermal elements, lighting, windows and building controls – and in doing so it provides the necessary information to improve a building’s performance.

Trident Building Consultancy has recently completed a flagship scheme which achieved high EPC and BREEAM ratings and as such provides several examples of best practice.

The Halo Building is Europe’s largest pathology laboratory and the administrative headquarters of Health Services Laboratories, a partnership between The Doctors Laboratory, Royal Free London NHS Foundation Trust and University College London Hospitals NHS Foundation Trust.  It is located in the heart of London’s MedCity and is a very comprehensive renovation of a 1970s office block.  Issues considered with the Halo Building include the following;

HVAC: Heating

Improving the energy performance of a heating system can be as simple as insulating a hot water cylinder or replacing an inefficient boiler.   Although the latter is more costly in the short term, the payback is immediate and long lasting. If the boiler cannot be replaced, the introduction of controls such as a room thermostat, individual Thermostatic Radiator Valves (TRVs) and boiler programmer will have a positive bearing on the EPC results.

We also recommended the use of smart storage heaters, which store and then release heat at pre-set times and temperatures, with a boost option to cater for unexpected heat demands. They are not only 27% cheaper to run than standard storage heaters, but also up to 47% more efficient than electric convector heaters.

Hot water is provided via high efficiency gas fired condensing boilers.

HVAC: air conditioning

For maximum efficiency, it is worth checking air supply and extract systems to ensure that the building is being operated in line with the specification and installation details. Bear in mind that the EPC assessment will benefit from specifications such as fan sizes and air flow details in place of standard software defaults.

At The Halo Building, two heat recovery units were included to allow for the transfer of thermal energy. High performance mechanical systems (including high efficiency chillers, boilers, and thermal heat recovery from the floors) were utilised to minimise carbon emissions.

Thermal elements:  wall insulation

Solid walls can have a detrimental effect on EPC ratings and so ideally should be insulated internally or externally. External wall insulation can benefit the property’s appearance and value, increase its longevity by protecting the existing substrate from the weather and reduce condensation.  And although it can be expensive, external wall insulation typically results in a reduction of up to 45% in heating loss, increasing the rating of the property by 10-20 points.

If a property has a cavity wall construction and is sheltered from driving rain or other penetrating damp, it is preferable that this is filled with insulation.  This is surprisingly simple and inexpensive to introduce and typically improves the energy rating by 5-10 points.

Both approaches were combined in the case of the Halo Building and the retention and renovation of the existing façade, together with additional insulation, increases the building’s energy efficiency by more than 60%.

It is worth noting that Building Regulations require that heat loss elements between a conditioned and unconditioned area are insulated to minimise heat transfer between the two areas – such as between an office present in a large warehouse.


The single biggest non-fabric influence on an EPC rating is lighting and this is true across all property types. Halogen or other forms of low energy lighting should be replaced with compact fluorescent light or light emitting diodes (LEDs).  Ideally a full lighting design should be commissioned prior to installation. Targets should be 3W/m2 for new build and 7W/m2 for fit-out and refurbishments. In retail properties, where display lighting is crucial, the use of tungsten bulbs should be avoided.

While LED bulbs are initially more expensive than incandescent or halogen bulbs, they use 90% less energy – thus creating substantial cost savings – and last up to 25 times longer.  Furthermore they do not contain any harmful substances like mercury, which is often found in compact fluorescent lamp (CFL) and halogen bulbs.

It goes without saying that natural light is cheap and environmentally friendly and has the greatest positive impact on wellbeing.  At the Halo Building natural light was increased with the addition of new windows and glazed curtain walling.  LED light fittings were used and their environmental impact was lessened further through the use of dimming lighting controls and a PIR system which allowed lighting levels to be adjusted according to external daylight.


Replacing single glazed windows with double or even triple glazing makes a considerable difference to an EPC.

The 1960s shell of the Halo Building featured inefficient singled glazed windows which were replaced with double glazed units, blinds and solar control glazing.

In reality, creating a truly sustainable building is much more than simply addressing the items on the EPC assessor’s checklist.  There are many other factors which can benefit a building and its occupants by reducing environmental damage and unnecessary expenditure, and creating an environment that is productive, pleasant and a source of pride.

Again, the Halo Building provides many examples. Sustainability was a major consideration in the supply chain:  all materials were specified to meet the highest sustainability standards and were responsibly sourced. Joinery and floor vinyl were rigorously tested and timber was FCA approved. Materials with little or no environmental impact were prioritised and local suppliers were selected to reduce transport emissions.

From solar thermal and PV panels, which generate hot water and electricity, through to bio-mass boilers and ground source heat pumps that replace conventional central heating systems, renewable energy can be infinitely more efficient.

Considerable savings can also be made in water usage.  At The Halo Building, all existing water systems were installed with low flush cisterns, water saving taps and proximity detection shut-off, saving approximately 5.45m3 water per person per year, and water meters were installed to control water usage.

Returning to the EPC assessment, perhaps the most important point to bear in mind is the need to have the relevant documentation at hand. Details such as u-values, model numbers, air tightness and extraction rates should be available wherever possible.

Finally it is worth noting that there can be a substantial gulf between a building’s sustainability strategy and design and its actual consumption. In many cases building managers do not have the necessary information to accurately monitor the performance of whole buildings.  But ongoing monitoring is vital to ensure that a building is, and remains, sustainable, and this can only be achieved through effective metering.  Landowners and building managers should be prepared to invest time in this, not only to meet the new strictures but to bring about an efficient, responsible building in which people are happy to work.



Achieving a good EPC rating