The energy passport: a tool for evaluating 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 20 November 2007, amended on 1 July 2012. The purpose of this system is to inform future owners or tenants about the energy status of a property and to encourage owners to invest in energy renovation work.

What is the Energy Performance Certificate?

The Energy Performance Certificate is a quality label that assesses the energy performance of a residential building. It is divided into several classes and provides essential information on the energy consumption of the house, the thermal insulation, the CO2 emissions and the level of energy efficiency. It allows consumers to quickly visualize whether the building is energy efficient or not, even without technical knowledge.

When is an Energy Performance Certificate mandatory?

Depending on the requirements, an Energy Performance Certificate is mandatory in several cases. It is required for any new construction, extension of more than 80m2, modification or significant transformation of a residential building. It is also required when there is a change of owner or tenant if the building does not already have one.

Who issues Energy Performance Certificates?

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

What information is included in the Energy Performance Certificate?

The Energy Performance Certificate provides essential information on the energy performance of the building. It assesses the primary energy demand of the home, which includes the energy used for heating and hot water. It also indicates the CO2 emissions, the greenhouse gases emitted when fossil fuels are burned.

The Energy Performance Certificate also classifies the building according to its overall energy performance, its thermal insulation class and its energy efficiency class. These classifications allow you to quickly identify the energy quality of your home.

Why is it important to have an Energy Performance Certificate?

The Energy Performance Certificate has many advantages. On the one hand, it informs future owners or tenants about the energy characteristics of the property, enabling them to make an informed decision when buying or renting. On the other hand, it encourages homeowners to invest in energy improvements based on the results of the EPC, thereby helping to reduce energy consumption and CO2 emissions.

The Energy Performance Certificate is a requirement established by the European Directive 2002/91/EC and the Grand Ducal Regulation of 20 November 2007, the latter amended on 1 July 2012. This set of rules is specifically applicable to residential buildings, provided that their commercial area is less than 10%.

These regulations define a calculation method as well as energy performance requirements. The purpose is twofold: to inform future owners or tenants of the energy status of a property and to encourage owners to invest in energy renovation work on their property based on the results of the Energy Performance Certificate.

An Energy Performance Certificate (EPC) is mandatory for any new construction, extension of more than 80m2, alteration or substantial alteration. It is also mandatory for any change of owner or tenant if the building does not already have an EPC. The application for an EPC is the responsibility of the owner or their representative and the document is prepared by architects or consulting engineers.

Each owner receives an original copy of the EPC, which is updated after 4 years to reflect actual energy consumption. It is valid for 10 years from the date of issue and does not need to be renewed, except in the case of insulation work. The EPC covers the whole building. In the case of semi-detached houses, an EPC is required for each building.

The Energy Performance Certificate acts as a quality label to assess the energy consumption of the home. It is divided into three categories:

The energy class, which depends on the primary energy demand. This requirement takes into account the thermal envelope of the building, 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 assesses the thermal quality of walls, roofs, ceilings and windows, as well as the type of construction, quality of workmanship and orientation of the building.
The energy performance level, which measures CO2 emissions. The rating is from A (best) to I (worst).

Depending on the EPC, the home can be classified as a Passive House (PH) for classes lower than or equal to A, a Low Energy House (NEH) for classes lower than or equal to B and an Energy Saving House (ESH) for classes lower than or equal to C.

Finally, it is important to note that primary energy, which is a non-quantifiable and non-palpable measure, includes the heat required for heating and hot water. It also includes the additional energy required to operate the energy source used.

To determine the energy pass, we refer to the Energy Reference Area (ERA), 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 normal use.

This information is given in the Energy Performance Certificate (EPC) in the Building Information section. For example, a number such as 475 represents the ERS of the house (usually the heated area) in square meters.

The EPC also indicates the CO2 emissions, the greenhouse gases emitted when fossil fuels are burned. These emissions are expressed as CO2 equivalents. Final energy demand is another measure mentioned in the EPC. It indicates the annual amount of energy (gas, oil, wood, etc.) required for heating and hot water in the units used for billing. It does not include energy used for cooking.

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

The aim is to determine the total energy consumption of a house over a year, based on the Energy Reference Area (ERA) and the Final Energy Requirement (FER). In this example, the ERA is 475 m2 and the FER is 232 kWh/(m2/year).

Multiply the FEB by the FER: this gives the total energy consumption of the house over a year in kWh. In the example we have 232 kWh/(m2/year) * 475 m2 = 110,200 kWh/year.
Conversion of this energy into fuel units: the text gives the conversion of 10 kWh into liters of fuel oil and cubic meters of gas. To obtain the consumption in liters of oil or cubic meters of gas, divide the total energy consumption by 10. In the example we have: 110,200 kWh/year / 10 = 11,020 liters of fuel oil or m3 of gas per year.

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

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

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

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

Four years after the EPC is set up, an audit is carried out to compare the final energy demand (calculated) and the final energy consumption (measured) for heating and hot water. If a gas oven is present, its consumption is also taken into account. Possible differences between the measured consumption and the calculated requirement can have several causes: an actual use of the building that differs from the standard use, an actual climate that differs from the reference climate and other unpredictable factors, as well as simplifications in the collection of building and installation data (surfaces, U-values, etc.).

The U-value is a measure of heat loss that is also taken into account when assessing the energy performance of a building.

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

Wall losses: These losses are calculated by multiplying the surface area of the walls (walls, roofs, floors) by their U-value. The U-value measures the heat loss of a material, i.e. its ability to transmit heat. The higher the U-value, the greater the heat loss.
Air leakage losses: These are heat losses due to air escaping from the building through small holes, such as those around windows. These losses are often measured using a blower door test.
Ventilation losses: These heat losses occur when warm indoor air is exhausted through the controlled mechanical ventilation (CMV) system.
Solar gain through glazing: This is the heat gained when the building's glazing is exposed to the sun. It is a positive contribution as it helps to heat the building.
Internal gains: These are heat gains from internal sources such as people (100 watts per hour per person), appliances, computers, etc.Taking all these factors into account, we can determine the heat demand of the dwelling, which is the net heat required to maintain a comfortable indoor temperature.
Heat demand of the dwelling: To this net demand we add the losses of the heating system, the heat demand for the production of domestic hot water (DHW) and the losses of the system, the energy consumption of the auxiliaries and the energy consumption for cooling. The solar thermal input for DHW and/or heating is then subtracted. The total is the final energy consumed.
Annual primary energy consumption of the dwelling: To obtain this total, we subtract the autoproduction of electricity (if any) from the final energy consumed and add transformation losses. Primary energy is the energy taken directly from the earth, before any transformation.

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

Here are some multiple-choice questions about the Energy Performance Certificate:

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

a) Water consumption of the building
b) Potential energy savings
c) Greenhouse gas emissions
d) Moisture content of the building

Answer: c) Greenhouse gas emissions

Question 2: What is the Energy Reference Area (ERA) in the energy certificate?

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

Answer: b) The heated surface of the building

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

a) To encourage owners to invest in insulation
b) Set rental prices for properties
c) To determine the market value of properties
d) To provide information on the size of dwellings

Answer: a) Encourage homeowners to invest in insulation

Question 4: What is the common unit of measurement for energy consumption in the Energy Performance Certificate?

a) Kilowatt hour (kWh)
b) Joule (J)
c) calorie (cal)
d) watt (W)

Answer: a) kilowatt-hour (kWh)

Question 5: What does the acronym EPC mean in the context of the energy pass?

a) Energy performance calculation
b) Energy Performance Certificate
c) Energy Performance Rating
d) Energy Performance Consumption

Answer: b) Energy Performance Certificate

Question 6: What information is provided by the final energy demand in the energy performance certificate?

a) Total energy consumption of the building
b) The target temperature of the building
c) The number of electrical appliances in the building
d) The cost of the energy used

Answer: a) Total energy consumption of the building

Question 7: What does European Directive 2002/91/EC recommend for residential buildings?

a) Ban the construction of new residential buildings
b) Reduce the energy consumption of existing buildings
c) Increase energy costs for residential buildings
d) reduce the size of residential buildings

Answer: b) Reducing the energy consumption of existing buildings

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

a) The energy savings achieved by the insulation
b) The materials used to insulate the walls
c) The recommended indoor temperatures
d) The efficiency of the heating system

Answer: b) Materials used for wall insulation

Question 9: What does the acronym ERS mean in the context of the Energy Performance Certificate?

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 certificate?

a) Annual energy costs
b) The efficiency of the heating system
c) The level of thermal insulation of the building
d) The estimated lifetime of the building

Answer: c) The level of thermal insulation of the building