Improving EPC Ratings in Commercial Buildings: How Glazing Performance Impacts Energy Costs and Building Efficiency
Improving EPC Ratings in Commercial Buildings: How Glazing Performance Impacts Energy Costs and Building Efficiency
Energy performance is now a critical consideration for commercial buildings across the UK. Rising energy costs, tighter legislation and increasing pressure to improve efficiency are all driving building owners and developers to reassess how their buildings perform. One of the most influential elements within the building envelope is the glazing system.
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What Is an EPC Rating?
An Energy Performance Certificate (EPC) provides a measure of how energy efficient a building is. For commercial properties, EPC ratings are typically derived using the Simplified Building Energy Model (SBEM), which assesses performance based on heating and cooling systems, insulation, air tightness, lighting efficiency and glazing specification.
The result is a rating from A for most efficient to G for least efficient. EPC ratings are not just informative. They are commercially important, legally relevant and increasingly influential in how buildings are valued, marketed and occupied.
For landlords and developers, a poor EPC can restrict future letting options and highlight that the building envelope is underperforming. In many cases, glazing is one of the biggest opportunities for improvement.
Rising Energy Costs
Over the past 12 months, energy costs have remained a major concern for commercial building owners. In 2026, global instability, fuel market volatility and wider cost-of-living pressures have all continued to influence the cost of heating and cooling buildings.
For buildings with large glazed elevations, this has a direct effect on operating costs. In winter, poorly performing glazing allows heat to escape. In warmer months, solar gain can increase internal temperatures and place additional demand on air conditioning systems.
In both cases, HVAC systems have to work harder, increasing energy consumption and long-term running costs.
The Role of Glazing in Building Performance
Glass performs a dual role in modern buildings. It allows natural daylight into the internal space while also acting as part of the building envelope. The amount of solar energy transmitted through glass is often referred to as the G-value or solar factor.
At the same time, glazing affects how well a building retains heat or prevents heat from entering. Poorly specified glazing can result in excessive heat loss, high solar gain, uncomfortable internal temperatures and increased reliance on HVAC systems.
In buildings with extensive glazing, these effects are amplified.
What Is U-Value?
The U-value is a measure of how easily heat passes through a building element. It is expressed in watts per square metre per Kelvin (W/m²K). In simple terms, the lower the U-value, the better the insulation.
Older single glazing and standard double glazing with air-filled cavities often perform relatively poorly by modern standards. Modern insulated glass units using argon or krypton gas-filled cavities, low-emissivity coatings and triple glazing can significantly improve thermal performance.
This can have a major effect on a building’s ability to retain heat in winter and reduce unwanted heat gain in summer.
When Glass Becomes the Problem
In many existing commercial buildings, the glazing is one of the weakest elements of the envelope. This is especially true where buildings still rely on outdated double glazing, failed sealed units or older façade systems with poor thermal performance.
South-facing elevations can be particularly challenging because of increased solar exposure. If the glass is not correctly specified, buildings may suffer from overheating, excessive solar gain and inflated cooling costs during warmer periods.
In these situations, the most cost-effective solution may not be another short-term repair. It may be a more strategic upgrade of the existing glazing.
Why Upgrading Glazing Can Make Commercial Sense
While high-performance glazing upgrades can appear expensive at the outset, they often deliver strong long-term value. Improved insulation can reduce reliance on mechanical heating and cooling systems, lower ongoing energy bills and enhance a building’s overall EPC rating.
For buildings with large glazed areas, replacing outdated units with modern high-performance glass can deliver a meaningful improvement in energy performance, occupant comfort and building value.
In the right circumstances, the savings achieved through reduced energy demand can offset the initial investment faster than many building owners expect.
How Dortech Maintenance Can Help
Dortech Maintenance Ltd can assess the performance of existing glazing and help clients understand where the façade is underperforming. We can undertake calculations, review likely thermal performance, and make recommendations for upgrading the glass specification to improve efficiency and reduce energy demand.
We can also go much further than simply replacing individual panes of glass. Where required, Dortech Maintenance Ltd can replace glazing systems wholescale, including:
- Aluminium windows
- Entrance and exit doors
- Glass screens
- Curtain walling
From assessment and recommendation through to project management and installation, we can support the complete process of improving a building’s glazing performance.
The Long-Term Benefit
For commercial buildings with large glazed façades, improving the specification of the glass or the wider glazing system can have a significant impact on energy efficiency, occupant comfort and operating cost.
Better-performing glazing can improve EPC ratings, reduce energy waste and help future-proof the asset against rising energy costs and tighter performance expectations.
For building owners, developers and facilities teams, that makes glazing improvement not just a repair decision, but a strategic investment in the long-term performance of the property.