Use of ventilated envelopes in building retrofitting.

The application of a continuous thermal insulation on the external face of building walls ameliorates the thermal performance of external walls and alleviates problems related to thermal bridges. However a further improvement of this insulation system may be achieved by using ventilated walls, which consist of an open ended cavity placed between an insulating board {directly applied on the external side of outer walls) and an external cladding. The convective natural flow which occurs in the cavity, permits to cool the surface of the insulating board in summer and to control condensation problems in winter. The use of ventilated envelopes does not reduce the living space and presents also interesting economic aspects. The present paper compares the thermal behavior of an existing building, before and after the application of a ventilated envelope, with some references to the economic aspects of this approach.