The energy class is the indicator that shows how energy-efficient a home is. If you have an older home in Attica, it is almost certain to be in one of the lower classes. And that means high energy bills, cold rooms in winter and possible problems with damp and mould.
The good news: with the right insulation measures, the energy class rises significantly and energy savings can reach up to 60%.
The energy class is a building's rating on a scale from A+ (the most efficient) to H (the most energy-hungry), based on its annual primary energy consumption per square metre. It is issued by a certified energy inspector through the Energy Performance Certificate (EPC), which is mandatory for every sale or rental of a property in Greece.
Important: the energy class does not only measure how much energy you consume, but how efficiently the building performs as a whole. Two homes of the same floor area can have completely different classes if one has thermal insulation and the other does not.
The Energy Performance Certificate (EPC) is the official document that certifies a property's energy class. It is issued by a certified energy inspector after an on-site inspection of the property and is entered in the Register of Energy Performance Certificates of the Ministry of Environment.
It contains:
When it is mandatory: for every sale or rental of a property, for joining subsidy programmes, and for a major renovation of more than 25% of the building envelope.
Validity: 10 years from issue, provided no major work is carried out that changes the building's energy characteristics.
Near-zero consumption
The highest class. New high-specification buildings with excellent thermal insulation, triple-glazed windows, a heat pump and renewable energy sources. Rare in older homes.
Excellent energy performance
Buildings with an exceptional building envelope and modern mechanical and electrical systems. Also mainly new builds.
Good energy performance
Usually buildings from after 2012 built under KENAK (the Greek Energy Performance of Buildings Regulation), with good thermal insulation and modern heating systems. The target for older homes undergoing a major renovation.
Satisfactory performance
The minimum target for the energy upgrade of an older home. It requires a solar water heater, a natural gas boiler and double-glazed windows.
Average performance
Usually buildings from after 1979, built under the thermal insulation regulation of the time. Older houses that have had a substantial renovation.
Low performance
Buildings with limited or ageing thermal insulation measures. Each step down can mean 40% more consumption than the one before.
Very low performance
The majority of buildings built before 1980. No thermal insulation, single-glazed windows, old heating systems. Tens of thousands of homes in Attica fall into this category.
The energy class does not depend on a single factor. It is the result of a combination of:
Upgrading the energy class does not necessarily require a major renovation. There are measures that deliver results immediately, with a clear financial payback:
The single most important measure for the energy upgrade of a building. With external thermal insulation, energy savings can reach up to 60% and the class rises by 2-3 steps. It pays for itself in 3-5 years.
It is worth noting that a low energy class is often linked to damp and mould problems inside, as cold walls without thermal insulation encourage the condensation of water vapour.
Read more about external wall insulation
Heat losses through an uninsulated roof can reach up to 25% of the total. Roof insulation is one of the most cost-effective measures, with a low application cost and a significant improvement in the class.
Find out more about Roof Thermal Insulation
When external wall insulation is not feasible, interior thermal insulation with Knauf mineral wool is an effective alternative. It can be applied in any season without any external works.
Modern thermally broken frames with double glazing significantly reduce heat losses.
Replacing an old boiler with a modern high-efficiency one or a heat pump.
A basic requirement for class B. Low application cost and immediate savings on domestic hot water.
For an older home in a low class (Z or H), combining external wall insulation with roof insulation is the most efficient way to move up classes quickly at a reasonable cost.
| Measure | Estimated class improvement | Energy savings |
|---|---|---|
| External wall insulation | 2-3 steps | Up to 60% |
| Roof insulation | 2-3 steps | Up to 60% |
| Replacing windows and doors | 1-2 steps | 10-15% |
| Heating upgrade | 1-2 steps | 20-30% |
| Solar water heater | 1 step | 10-20% |
Note: the estimates refer to a typical home in class Z or H. The exact improvement depends on the characteristics of each building and the climate zone.
Before deciding which measures to carry out, a thermographic inspection is the most reliable tool for finding exactly where your building is losing energy. A special thermal camera captures thermal bridges, cold spots and hidden heat leaks that cannot be seen with the naked eye.
The EPC is mandatory:
It is issued by a certified energy inspector after an on-site inspection and is valid for 10 years.
The energy class directly affects the market value of a property. In European markets that have already fully integrated energy performance into property valuation, low-class buildings sell at a significant discount compared with high-class ones. This trend is also growing stronger in Greece, as buyers become increasingly aware of energy costs.
In addition, the European Energy Performance of Buildings Directive (EPBD) sets specific targets for the coming years, with low-class buildings facing increased regulatory requirements.
If you want to improve your home's energy class, the first step is an on-site assessment. With 25+ years of experience in building thermal insulation in Attica, Goumas Insulation helps you identify the weak points of your building and choose the measures that deliver the most.
From the Energy Performance Certificate (EPC) issued by a certified energy inspector. If you do not have an EPC, you can have one issued at any time.
The cost depends on the floor area of the property. It usually ranges from €150-300 for a typical home.
The Energy Performance Certificate is valid for 10 years from issue. If major work is carried out during that period that changes the building's energy characteristics (e.g. external wall insulation, replacing windows and doors), it is advisable to have a new EPC issued to record the new, improved energy class.
In practice, no. Classes A and A+ are achievable mainly in new buildings. However, an old house can reach class B or B+ with a major renovation that includes external wall insulation, roof insulation, replacement of windows and doors and an upgrade of the heating system.
For most homes in Attica, external wall insulation combined with roof insulation is the measure with the greatest return per euro invested. It drastically reduces heat losses through the building envelope and pays for itself in 3-5 years.
Yes. Properties with a high energy class have a higher market value, lower energy costs and are easier to rent out. This trend is intensifying with the new European directives.
Yes, significantly. An uninsulated roof accounts for up to 25% of a building's heat losses. Roof thermal insulation improves the class by 1-2 steps, depending on the condition of the building.
Yes, although less effectively than external insulation, because it does not completely eliminate thermal bridges. It is the right solution when external wall insulation is not feasible. Read about interior thermal insulation.
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