The Energy Passport: Assessing the Energy Performance of Buildings

The energy passport, also known as the Energy Performance Certificate (EPC), is a requirement established by European Directive 2002/91/EC and the Grand Ducal Regulation of November 20, 2007, amended on July 1, 2012. This system aims to inform future owners or tenants about the energy status of a property and to encourage owners to invest in energy renovation works.

What is the energy passport?

The energy passport is a quality label that evaluates the energy performance of a residential building. It is divided into several classes and provides essential information on the dwelling's energy consumption, thermal insulation, CO2 emissions, and energy performance level. It allows consumers to quickly see whether the building is energy-efficient or not, even without technical knowledge.

When is an energy passport mandatory?

According to the requirements, issuing an energy passport is mandatory in several cases. It is required for any new construction, extension of more than 80 m², or significant modification or transformation of a residential building. Furthermore, it is necessary upon a change of owner or tenant if the building does not yet have this certificate.

Who issues energy passports?

Energy passports are issued by architects, consulting engineers, and other experts approved by the Minister of the Economy and Foreign Trade. These qualified professionals collect the necessary information, perform the required calculations, and issue the Energy Performance Certificate. It is important to ensure you use approved service providers to guarantee the reliability of the results.

What information is included in the energy passport?

The energy passport provides essential information about the building's energy performance. It assesses the dwelling's primary energy requirement, which includes energy consumption for heating and the preparation of domestic hot water. It also indicates CO2 emissions, which correspond to climate-damaging gases emitted during the combustion of fossil fuels.

The Energy Performance Certificate also classifies the building according to its overall energy performance, its thermal insulation class, and its energy performance class. These classifications make it possible to quickly identify the energy quality of the dwelling.

Why is it important to have an energy passport?

The energy passport offers many advantages. On the one hand, it informs future owners or tenants about the dwelling's energy characteristics, thereby allowing them to make an informed decision when buying or renting. On the other hand, it encourages owners to invest in energy renovation works based on the results of the Energy Performance Certificate, which contributes to reducing energy consumption and CO2 emissions.

The energy passport is a requirement established by European Directive 2002/91/EC and the Grand Ducal Regulation of November 20, 2007, the latter having been amended on July 1, 2012. This set of rules is specifically applicable to residential buildings, provided their commercial areas account for less than 10%.

These rules define a calculation method as well as requirements in terms of energy performance. The goal is twofold: on the one hand, they inform future owners or tenants of a property's energy status, and on the other hand, they encourage owners to invest in energy renovation works for their properties, based on the results of the energy passport.

The Energy Performance Certificate (EPC) is mandatory for any new construction, extension of more than 80 m², modification, or significant transformation. It is also mandatory upon a change of owner or tenant if the building does not yet have an EPC. The request for an EPC is the responsibility of the owner or their representative, and the document is issued by architects or consulting engineers.

Each owner receives an original copy of the energy passport, which is updated after 4 years to reflect actual energy consumption. It is valid for 10 years from the date of issue, and renewal is not mandatory except in the event of insulation works. The EPC applies to the residential building as a whole. In the case of terraced or semi-detached houses, an EPC is required for each building.

The energy passport serves as a quality label to evaluate the dwelling's energy consumption. It is divided into three classes:

The energy performance class, which depends on the primary energy requirement. This requirement takes into account the building's thermal envelope, its technical installations, and the environmental aspect of the energy source used.
The thermal insulation class, which is based on the heat requirement for heating. It evaluates the thermal quality of walls, roofs, slabs, and windows, as well as the type of construction, the quality of execution, and the building's orientation.
The energy performance level, which measures CO2 emissions. The rating ranges from A (best class) to I (worst class).

Depending on the EPC, the dwelling can be classified as a passive house (PH) for classes less than or equal to A, a low-energy house (NEH) for classes less than or equal to B, and an energy-saving house (ESH) for classes less than or equal to C.

Finally, it is important to note that primary energy, which is a non-quantifiable and intangible measure, covers the heat requirements for heating and hot water preparation. It also includes the additional energy required for the exploitation process of the energy carrier used.

To determine the energy passport, reference is made to the Energy Reference Surface (SRE), which excludes unheated rooms. This area corresponds to the conditioned part of the net floor area within the thermal envelope. A conditioned space is a space that requires heating or cooling for standard use.

This information is specified in the Energy Performance Certificate (EPC), in the "Building Information" section. For example, a number like 475 represents the residential building's SRE (generally the heated area) in square meters.

The EPC also indicates CO2 emissions, which correspond to the climate-damaging gases emitted during the combustion of fossil fuels. These emissions are expressed in CO2 equivalents.

The final energy requirement (BEF) is another measure mentioned in the EPC. It indicates the annual amount of energy required (gas, heating oil, wood, etc.) for heating and domestic hot water in the respective units used for billing. It does not include energy consumed for cooking.

Of course, I will detail the calculation made in the previous example.

The objective is to determine a house's total energy consumption over a year, based on the Energy Reference Surface (SRE) and the Final Energy Requirement (BEF). In this example, the SRE is 475 m² and the BEF is 232 kWh/(m²/year).

Multiplying the BEF by the SRE: this gives the house's total energy consumption over a year in kWh. In the example, we have: 232 kWh/(m²/year) * 475 m² = 110,200 kWh/year.
Converting this energy into fuel units: the text gives the conversions of 10 kWh into liters of heating oil and cubic meters of gas. To obtain the consumption in liters of heating oil or cubic meters of gas, the total energy consumption is divided by 10. In the example, we have: 110,200 kWh/year / 10 = 11,020 liters of heating oil or m³ of gas per year.

This means that the house would consume 11,020 liters of heating oil or 11,020 m³ of gas per year for heating and domestic hot water, based on the calculated BEF and the building's SRE.

It is important to note that this calculation provides an estimate of energy consumption based on the calculated final energy requirement. Actual energy consumption may differ due to factors such as user behavior, the actual climate, and other unforeseen factors, as well as simplifications in the collection of building and installation data. This is why a verification is carried out after 4 years to compare the final energy requirement (calculated) with the final energy consumption (measured).

The calculation of the final energy requirement is based on average reference values for the climate and the internal temperature of the building. For this reason, the actual consumption can differ from the calculated value. For example, one could have a calculated final energy requirement (BEF (c)) of 232 kWh/(m²/year) and a measured final energy consumption (CEF (m)) of 206.6.

To determine the house's consumption based on the calculated final energy requirement, the SRE is multiplied by the BEF (c). This amount is then converted into liters of heating oil or cubic meters of gas using the following conversion: 10 kWh of heating oil is equivalent to 1 L of gas and 10 kWh of gas is equivalent to 1 m³ of gas.

Four years after the EPC is issued, a verification is performed to compare the final energy requirement (calculated) and the final energy consumption (measured) for heating and domestic hot water preparation. If there is a gas stove, its consumption is also taken into account. Any differences between the measured consumption and the calculated requirement can have several origins: actual use of the building differing from standard use, an actual climate differing from the reference climate, and other unpredictable factors, as well as simplifications when collecting building and installation data (areas, U-value, etc.).

The U-value is a measure of heat loss that is also taken into account in the evaluation of the building's energy performance.

To understand a dwelling's energy consumption, it is important to understand how the heat requirement and final energy consumed are calculated. Here is a detailed explanation of the different steps involved in this calculation:

Heat loss through elements: These losses are calculated by multiplying the surface area of the building elements (walls, roofs, floors) by their U-value. The U-value measures the heat loss of a material, i.e., its ability to let heat pass through. The higher the U-value, the greater the heat loss.
Heat loss through air leaks: These are heat losses due to air escaping the building through small holes, such as those around windows. These losses are often measured by an infiltrometry test, also called a Blower Door Test.
Heat loss through ventilation: These heat losses occur when warm indoor air is extracted by the controlled mechanical ventilation (CMV) system.
Solar gains through glazing: This is the heat gained through the building's glazing being exposed to the sun. It is a positive contribution because it helps to warm up the building.
Internal gains: These are heat gains from internal sources, such as people (100 watts per hour per person), household appliances, computers, etc.

By taking all these factors into account, we can determine the dwelling's heat requirement, which is the net heat needed to maintain a comfortable indoor temperature.

Dwelling's heat requirement: To this net requirement, we add the heating installation's losses, the heat required to produce domestic hot water (DHW) and the installation's losses, the energy consumption of auxiliary equipment, and the energy consumption for cooling. We then subtract the solar thermal gains for DHW and/or heating. The total gives the final energy consumed.
Dwelling's annual primary energy consumption: To obtain this total, self-generated electricity (if any) is subtracted from the final energy consumed, and transformation losses are added. Primary energy is energy drawn directly from the planet, before any transformation.

According to the Grand Ducal Regulation amended on July 1, 2012, a residential building is a building in which at least 90% of the SRE is intended for residential purposes. And since January 1, 2011, the Energy Performance Certificate (EPC) has been mandatory for all new buildings. Functional buildings, on the other hand, are reference buildings for calculating energy performance.

Here are multiple-choice questions on the topic of the energy passport:

Question 1: What information is provided by the energy performance level in the energy passport?

a) The building's water consumption
b) Potential energy savings
c) Greenhouse gas emissions
d) The building's humidity level

Answer: c) Greenhouse gas emissions

Question 2: What does the Energy Reference Surface (SRE) represent in the energy passport?

a) The building's total area
b) The building's heated area
c) The building's non-habitable area
d) The surface area of the building's exterior walls

Answer: b) The building's heated area

Question 3: What is the main objective of the energy passport for residential buildings?

a) To encourage owners to invest in insulation works
b) To set rental prices for properties
c) To determine the market value of properties
d) To provide information on dwelling sizes

Answer: a) To encourage owners to invest in insulation works

Question 4: What unit of measurement is commonly used for energy consumption in the energy passport?

a) Kilowatt-hour (kWh)
b) Joule (J)
c) Calorie (cal)
d) Watt (W)

Answer: a) Kilowatt-hour (kWh)

Question 5: What is the meaning of the acronym EPC in the context of the energy passport?

a) Energy Performance Calculation
b) Energy Performance Certificate
c) Energy Performance Classification
d) Energy Performance Consumption

Answer: b) Energy Performance Certificate

Question 6: What information is provided by the final energy requirement in the energy passport?

a) The building's total energy consumption
b) The building's setpoint temperature
c) The number of electrical appliances in the building
d) The costs of the energy used

Answer: a) The building's total energy consumption

Question 7: What does European Directive 2002/91/EC advocate regarding residential buildings?

a) A ban on building new residential buildings
b) Reducing the energy consumption of existing buildings
c) Increasing energy costs for residential buildings
d) Decreasing the living space of residential buildings

Answer: b) Reducing the energy consumption of existing buildings

Question 8: What information is provided by the thermal insulation class in the energy passport?

a) The energy savings achieved through insulation
b) The materials used for wall insulation
c) The recommended indoor temperatures
d) The efficiency of heating installations

Answer: b) The materials used for wall insulation

Question 9: What is the meaning of the acronym SRE in the context of the energy passport?

a) Ecological Reference Surface
b) Energy Repair Surface
c) Energy Reflection Surface
d) Energy Reference Surface

Answer: d) Energy Reference Surface

Question 10: What information is provided by the energy performance class in the energy passport?

a) The annual cost of energy
b) The efficiency of heating equipment
c) The building's thermal insulation level
d) The building's estimated lifespan

Answer: c) The building's thermal insulation level