New facades enhance energy efficiency of buildings

Recently, two researchers from School of Building Engineering at UPM have developed a ventilated façade with a double chamber and flow control device that significantly saves energy in buildings. This sustainable and efficient solution can be applied in both rehabilitation works and new buildings due to its simplicity of implementation.

The facade is the main constructive element of a building that allows us to meet the requirements of energy efficiency and interior comfort established in the national and international rules and directives of the construction sector. The type of system, the design and the right execution of the façade itself are critical aspects that determine the final energy consumption of the building.

Today, the air flow expenses are of 40% -- 65% of the total expenses of a building. Buildings in a Mediterranean-continental climate like in Spain suffer in winter energy losses through their north and east facades due to low temperatures. Likewise, these buildings in summer obtain energy gains through their south and west facades due to solar radiation. In both cases, the air flow is needed in the building in order to maintain suitable inner conditions for their inhabitants, counteracting the energy gains-losses trough the building envelope.

In order to improve the energy efficiency of facades, two researchers from the group of Tecnología Edificatoria y Medio Ambiente (TEMA) at UPM have developed a new system of ventilated façade. Today, the conventional ventilated facades are composed of an inner sheet, thermal insulation, ventilation chamber and exterior finish.

The new facade designed adds a second air chamber between the existing one and the facade insulation, both chambers are interconnected by the bottom of the façade. Another feature is a new element at the top to regulate the air flow in the chambers, depending on the gradient of the existing temperature between inside and outside the building.

Ventilated façade with a double chamber presents two improvements over the conventional system. Firstly, energy gains-losses are reduced through the facades reducing, consequently, the energy consumption due to air flow. Secondly, the design of the system helps to reduce the vertical temperature gradient along the envelope, homogenizing the air temperature in the chambers throughout the year.

By minimizing the vertical thermal gradients, global consumption due to energy gains-losses through the façade depends less on the height of the building, preventing the upper houses to present higher or lower indoor comfort and degree of energy efficiency than the lower houses. Besides, this system is a sustainable and efficient solution that can be applied in both rehabilitation works and new buildings due to its simplicity of implementation.

The initial over cost can be short-term amortized if we consider the remarkable energy savings of this design.

The authors of this work say, "this research work highlights the potential energy efficiency of buildings through the redesign of conventional construction systems."

This work has been recently published in the Energy and Buildings journal and also been patented.