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Ventilated facades

A ventilated façade comprises a ventilated envelope construction system consisting of an inner sheet, an insulating layer and an outer sheet unsealed. This type of facade finishes usually lets durable, high quality, and good thermal performance, but has a high price. It is a common solution used in institutional buildings.

To reduce the amount of energy consumed in the artificial climate of the building and increase thermal comfort inside the building, it is necessary to study and optimize the design of the ventilated facade, using the newest tools of numerical analysis.

There is already software available on the market that calculates the flows of energy exchange in the ventilated facade, taking into account both the heat flux vertical and horizontal.

construction

The facade of the building (inner leaf) is anchored by a substructure intended to support the outer leaf finish and an insulating layer by plastic pins or adhesive mortar. Once the insulating layer is positioned, the sheet is then mounted over. The substructure leaves an air gap of a few inches between the insulation and the plates that make up the second skin. The joints between these plates are open, allowing air flow.

 

The outer plates can be of different materials: stone, wood, sandwich panels, etc.. The outer skin or finishing must have slots on both the bottom and the top, to allow air exchange. In the singular points (ridge line, perimeter screens) must be disposed gutter or other protection elements to impede the entry of water into the inner chamber, would reduce the effectiveness of thermal insulation.

operation

The existence of joints between the pieces of the facade avoids typical problems of labor, so they are facades that present a good appearance for a long time. Also the outer sheet temperature changes in both the thermal insulator as in the waterproofing, prolonging its life. Finally, the existence of the outer sheet helps reduce thermal losses of the building: in the summer months the outer skin is heated creating a convective effect that circulates the air inside the chamber.

This "chimney effect" displaces the warm air and renews it with cooler air. In the winter months the air in the chamber is heated, but not enough to create the same effect and the heat is better preserved.

 

The facade glass or cladding is extended in order to form a chamber ventilated facade, to renew the look of a building without giving up the vision of its original appearance or incorporate the effect of Trombe as bioclimatic building improvement. But this type of facade also presents certain counterparties.

The lightweight ventilated façade system consists of:

Two curtain walls or

A curtain wall on the outside and other inside enclosure.

Advantages of the ventilated facade

Major ventilated façades provide weather protection and optimizes thermal comfort inside the chamber by ventilating air between the two walls.

To vent air from said chamber reduces the amount of thermal energy that reaches the interior of the building.

This system is very versatile since it allows for different types of ventilation, and use various types of materials in the interior façade, always keeping the outside with a separate issue.

Convection cooling

The ventilation of this type of facades is effected by natural or forced convection. Natural convection is caused by the "chimney effect" because of the air heating chamber, evacuating, and part of the energy absorbed by the outer glass sheet.

The forced ventilation acts on the speed of air convection inside the chamber, while controlling the flow of air that enters and exits the chamber. They are often installed inside the air-ventilated shade or other sun protection element, which may be varied considerably solar factor, light transmission, the surface temperature and heat transfer coefficient at will without having to change the glass outside.

The inside of the ventilated façade must consist of thermally insulating material and acoustically absorbent material. In the case of double glazed ventilated facades, shelterbelts should also placed inside the chamber to reduce the maximum possible amount of incident solar energy in the second facade. It is common in this type of glass facades to use semi-reflectants, colour- or screen-printed to the outer skin, which can play with different tones, so as to provide optimum light transmission and reflection of a good image. For the inner skin is preferred double glazing into the building providing a good acoustic and thermal insulation.