The standards applicable to the insulation of new buildings are changing rapidly. Today, in Brussels, new homes have to reach a level of insulation – known as the K level – lower than 40. From 2015 onwards, all new buildings will have to be ‘passive’. By 2021, ‘zero energy’ will be expected.

The various terms that can be applied to a home to define its energy performance correspond to precise standards:

• A home is considered to be low energy when its level of insulation is lower than 30.
• When the level is below 15, we talk about a passive home, i.e. one that is very, very well insulated and needs only back-up heating.
• The term zero energy refers to a house where the K level is again below 15, but which also generates its own energy (using solar panels, a heat pump, etc.).