In Belgium, the EU Energy Performance of Buildings Directives have been fully implemented on a regional level by various pieces of legislation, most notably the Flemish Energy Decree of 8 May 2009, the Brussels Ordonnance of 2 May 2013, the Walloon Decree of 28 November 2013 and the Walloon Government Decision of 15 May 2014.

In all three regions, newly constructed buildings or substantial renovations generally require a building energy performance study, as well as a broader study of all energy efficiency and interior climate conditions. This mechanism is not only informative but also allows the competent authorities to enforce certain efficiency standards for new buildings. Selling or letting existing buildings also requires an energy performance certificate (EPC), although this is only intended for informing the possible buyer or tenant. In principle, all EPCs are valid for a maximum period of 10 years.

EPC requirements differ in each region depending on the type of building, its surface area, and whether it is constructed, renovated, sold or let. In addition, different efficiency measurements are used, with the full set of measurements and related thresholds mostly only applying to new construction projects. Finally, the required minimum efficiency thresholds also differ between regions and are periodically increased to achieve overall long-term EU energy efficiency goals.

In Flanders

In the Flemish Region, for newly constructed, expanded or renovated residential or nonresidential buildings for which the building permit request was submitted after 1 January 2018, the maximum allowed E-rate decreases every year. Buildings with a higher E-rate will be fined, while buildings with a substantially lower E-rate may be rewarded with subsidies offered by the grid operator. Separate EPC systems exist for residential, nonresidential and public buildings. For public buildings, a floor surface of more than 250 square meters requires that a Display Energy Certificate be displayed in a publicly visible place. For selling or leasing existing buildings, an EPC has to be part of all publicity and annexed to the actual contract.

Moreover, a new renovation obligation for nonresidential buildings has been adopted in Flanders as of 1 January 2022. This obligation applies to every new owner, tenant under a lease that includes construction works, and long leaseholder (emphytéote/erfpachter) of offices or retail buildings. Basically, they have to comply with the following new energy regulations within a five-year period:

• Installation of roof insulation
• Installation of high-efficiency glazing
• Replacement of heating systems that are more than 15 years old which do not meet the minimum installation requirements for renovations
• Replacement of refrigeration units that are more than 15 years old and installation of systems that do not require ozone-depleting or noxious refrigerants

The following is also required within the same five-year period:

• The new owner of a nonresidential building of less than 500 square meters has to obtain a level C (or above) EPC.
• For buildings of more than 500 square meters, they have to use a minimum of 5% of renewable energy.

In Brussels

In the Brussels-Capital Region, an energy performance of buildings (EPB) certificate is required instead of an EPC. An EPB is compulsory when selling or renting a home larger than 18 square meters or an office larger than 500 square meters. As of 2025, all homes will have to have an EPB certificate. There are three different models of the EPB:

• EPB “New construction”: for new constructions (houses, schools, offices, etc.) for which the first planning permission was submitted after 1 July 2008
• EPB “Residential unit”: for older (possibly renovated) dwellings (planning permission submitted before 1 July 2008)
• EPB “Tertiary unit”: for older offices larger than 500 square meters (planning permission submitted before 1 July 2008)

As a general rule in the Brussels-Capital Region, the maximum allowed primary energy consumption rate for new buildings, substantial renovations and renovations that have an impact on the E-rate is 45 kilowatt-hours per square meter for houses and 90-2.5x ratio of protected volume over heat loss surface kilowatt-hours per square meter . Likewise, in the Flemish Region, each real estate transaction of an existing building requires an EPC to be obtained before and published together with each market consultation or contract negotiation.

In Wallonia

Similar standards apply in the Walloon Region, where the most important current maximum standard for new or substantially renovated or rebuilt residences, offices, service buildings and schools is an E-rate of 80 kilowatt-hours per square meter. For new or substantially renovated buildings, however, there is currently only an EPC obligation for single-family houses and apartments. For other residential buildings, offices, service buildings and schools, the implementing regulation is still lacking. Similar to the other regions, selling or letting existing buildings in the Walloon Region requires a completed EPC to be part of all publicity and contractual documents.

Q-ZEN is the new standard for new buildings: From 1 January 2021, all new buildings must be “quasi” or nearly zero-energy. A quasi zero-energy building is one that meets the following criteria:

• The envelope is well insulated and airtight (insulation requirement for each wall Umax, overall insulation requirement K ≤ 35 and overheating index < 6500 Kh).
• The systems are efficient.
• The small amount of energy required for heating and hot water production is mostly produced from renewable energy sources.

This translates into an overall energy performance requirement of Ew ≤ 45 and Espec ≤ 85 kWh/m² year corresponding to the A label.