The full spectrum of building types that have achieved EnerPHit can be seen on the International Passivhaus Database. The Passivhaus Institute maintains a database of several thousand qualified Passivhaus designers and consultants, and any client wishing to target Passivhaus or EnerPHit compliance should ensure that their designers are suitably qualified. Any project targeting EnerPHit must deliver excellent levels of airtightness. The ground floor is the most challenging aspect of any deep retrofit. Where this represents only a small proportion of the building envelope it may not be necessary to insulate this element to achieve EnerPHit. Passivhaus and EnerPHit-certified buildings require mechanical ventilation with heat recovery. By understanding what will be required to achieve EnerPHit certification, the designer can prepare the client and the design team to deliver necessary information. EnerPHit is a standard with a very clear methodology that offers reliable outputs but requires active engagement by the client and design team as early as possible in the design process.