How we assessed a mixed-use commercial building and identified a clear pathway from a G rating to Band A through staged improvements.
Energy Performance Direct was commissioned to carry out a full non-domestic energy assessment of a commercial building located near Exeter in Devon. The property, totalling 793.5 square metres of useful floor area, comprises office accommodation and workshop space. The building is heated by an oil-fired boiler system with air conditioning serving the office areas.
The client required a commercial Energy Performance Certificate for regulatory compliance, along with a detailed Energy Advice Report setting out a practical improvement roadmap. With the building classified at NOS3 complexity level, our Quidos-accredited assessor conducted a thorough SBEM assessment covering the full building envelope, heating and cooling systems, lighting installations and hot water provision.
G
Baseline Rating
793.5
Floor Area (sq m)
70.84
kWh/m2/yr
19.4
kgCO2/m2/yr BER
Our SBEM assessment identified the proportional contribution of each building system to the overall carbon emissions. This breakdown is essential for targeting improvements where they will have the greatest impact.
The dominant source of carbon emissions. The building uses older fluorescent lighting (T12 and T8 tubes) throughout both the office and workshop areas. Upgrading to LED would deliver the single largest improvement.
The oil-fired system serving hot water contributes nearly a third of emissions. Replacing with electric point-of-use heaters eliminates the oil dependency and reduces both emissions and running costs.
The oil boiler heating the offices and workshop areas accounts for a fifth of carbon output. A split or multi-split air conditioning system with COP 3.5 or better would dramatically reduce this figure.
Cooling accounts for a small proportion of total emissions. Some spaces exceeded the solar gain limit defined in the National Calculation Methodology, suggesting consideration of solar shading measures.
The SBEM assessment and subsequent Energy Advice Report identified several factors contributing to the building's poor baseline energy performance:
The building relied on an oil boiler for space heating and hot water. Oil is one of the highest-carbon fuels for commercial heating, and its use significantly depressed the EPC rating. Removing the oil boiler was identified as the single most impactful improvement.
The building used 38mm (T12) and 26mm (T8) fluorescent tubes throughout. With lighting responsible for 48.5% of carbon emissions, this represented a major opportunity for improvement through LED replacement.
The building featured a combination of single-glazed and double-glazed windows. Solid walls lacked adequate insulation, cavity walls had uninsulated cavities, and some loft spaces were poorly insulated, contributing to significant heat loss.
The assessment identified spaces where solar gain exceeded the limits defined in the National Calculation Methodology, highlighting overheating risk without adequate solar control measures.
Our Energy Advice Report provided a phased improvement strategy, allowing the client to prioritise investment and achieve progressively better ratings. Each stage builds on the previous one, offering a practical pathway from the baseline G rating towards Band A.
Removing the oil boiler is identified as the single biggest improvement. This alone achieves MEES compliance by bringing the rating to Band C.
With lighting accounting for 48.5% of carbon emissions, this single measure delivers a substantial rating improvement and ongoing energy cost reduction.
This comprehensive fabric-first approach combined with renewable generation targets the highest achievable rating. The advice report also recommends consideration of Phase 3 electrical upgrades for future-proofing, including provisions for heat pumps, EV charging and battery storage.
Beyond the staged improvement roadmap, the EPC recommendations report identified further measures categorised by payback period:
Oil-fired heating is one of the biggest factors holding back commercial EPC ratings. Switching to electric heat pump or split AC systems can deliver a step-change improvement.
Lighting often accounts for the largest share of carbon emissions in commercial and industrial buildings. LED upgrades offer rapid payback and significant rating improvements.
A staged approach to improvement allows building owners to spread investment while achieving MEES compliance at Stage 1, before pursuing higher ratings.
Comprehensive fabric upgrades (windows, walls, roof) combined with renewable energy generation can bring even a G-rated building up to Band A over time.
Professional SBEM modelling allows each improvement to be quantified before committing expenditure, reducing risk and optimising investment decisions.
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