All about energy in Brussels. A Sibelga initiative
en menu
Logo energuide

What are the legal obligations with regard to thermal insulation?

In Brussels, the BEP (Building Energy Performance) regulations require owners to comply with a certain level of thermal insulation for buildings where work is being carried out.

It is crucial to take these requirements into account: significant fines are prescribed if you do not comply with these standards! It is also in the owners' interest to comply, since a well-insulated home consumes less energy and has a higher market value

To whom do these thermal insulation obligations apply?

These regulations apply to any heated and/or air-conditioned building where construction, reconstruction or transformation work requiring an urban planning permit is carried out.

This is, of course, provided that this work covers the building shell and influences its energy performance.

Some exceptions exist - please consult the Brussels Environment website for more information on the conditions that apply in each case.

What are the requirements of the BEP regulations regarding insulation?

The main principles are as follows... the precise thresholds of the BEP requirements depend on the nature of the work and the use of the property. These are available on the Brussels Environment website

1. Limiting thermal bridges to construction junction points

A thermal bridge is a weak link in the external structure of the house (on an outside wall, the roof or the ground). This phenomenon occurs when there are interruptions in the thermal insulation or gaps between floor slabs.

In other words, it is a matter of avoiding heat loss at the junction points of the building walls.

2. Insulating the walls of the shell covered by the work

Specific values for each component are provided for in the BEP regulations:

  • The Umax value indicates the maximum level of heat loss not to be exceeded. This corresponds to the amount of heat that the building element or wall allows to pass through per second and per square metre with a difference of 1 °C between the two sides of the wall.
    -> The lower the Umax value, the better the insulation.
  • The Rmin value indicates the minimum thermal resistance to be met. This measures the level of heat resistance provided by, for example, insulation, double glazing, floors, roofs and walls.
    -> The higher the Rmin value, the less heat loss there is and therefore the better it is.

For roofs and exterior walls, for example, these values correspond approximately (depending on the composition of the wall) to 15 cm of glass wool or about 12 cm of synthetic foam. There is no obligation on the type or thickness of insulation material used, as long as the required performance is achieved. However, the energy premiums awarded are increased for natural insulating materials.

Read our advice for insulating an existing wall.

3. Limiting energy needs/consumption and ventilation

The BEP regulations prescribe further measures which have a direct influence on insulation, technology choice and the use of renewable energy: 

  • limit the 'net energy requirement for heating' (NRH) if it is a dwelling;
  • limit 'primary energy consumption' (PEC) for heating, domestic hot water, cooling and auxiliary equipment;
  • ventilate the premises by complying with flow rates to ensure a healthy indoor climate and intensive ventilation in the event of overheating or occasional heavy pollution;
  • limit the risk of overheating.

What happens if I do not take account of these obligations?

Fines of up to several thousand euros are prescribed for owners of buildings that do not meet these standards.

On the other hand, it is in your interest to comply with the requirements of the BEP regulations, or even to do better! Indeed, most energy premiums impose stricter conditions than the 'legal minimum'. In addition, a well-insulated dwelling will obtain a BEP certificate that is much more attractive if you rent it out or sell it on.

Do not hesitate to insulate beyond the requirements. Not only will you be rewarded financially, but you will also pre-empt more demanding legislation in the future. More information on the website of Brussels Environment.

Don't miss our new tips

Subscribe to our newsletter and stay informed about energyfacts.

We promise we will only use your data to send you our newsletter as stated in our privacy policy.

More about this topic in these dossiers

Did you find this article useful?
How could this article be improved?

We promise we will only use your data to send you our newsletter as stated in our privacy policy.

Tips on how to save energy!

We promise we will only use your data to send you our newsletter as stated in our privacy policy.