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Ventilated rain screen facades - how they work in terms of building physics
The weather-protection and thermal insulation functions of ventilated
rain screen facades are structurally separate from each other. This
type of construction is regarded as reliable and long-lasting. Additional
protection functions characterize this facade system.
Ventilated rain screen facades can be used for all building heights and
applications as well as for all the required thicknesses of insulating
materials. Their components are the subconstruction, the insulation, the
ventilation space and the cladding.
Advantages
- Due to the structural separation of facade cladding and thermal insulation, ventilated rain screen facades provide lasting protection against condensation water and rain.
- In terms of building physics, the ventilated rain screen facades are a tried-and-tested type of construction for ensuring a pleasing indoor climate.
- Ventilated rain screen facades result in a considerable reduction in energy costs for heating and air-conditioning.
- Ventilated rain screen facade constructions are extremely robust.
- Ventilated rain screen facades have a long useful life, require no maintenance and, in economic terms, are an extremely advantageous solution for increasing the value of a building.
Type of construction of ventilated rain screen facades
A structural precondition is a loadbearing outer wall to which the
subconstruction can be anchored. The subconstruction – usually
made of aluminium – consists of wall brackets and carrier sections.
Depending on the required type of fastening for the cladding elements,
additional horizontal or vertical carrier sections can be used. The
wall brackets are normally thermally isolated from the outer wall so that
thermal-bridge losses due to the nature of the structure in question
can be calculated and reduced to a minimum.
A central functional characteristic of the subconstruction is the use of
fixed and sliding points. Fixed points carry the load of the construction
and bear the proportional forces exerted in the form of wind suction
and pressure. Sliding points absorb wind suction and wind pressure
forces.
The subconstruction can be adjusted in three dimensions. It can therefore
be positioned stress-free on the outer wall vertically, horizontally. Any
unevenness, dimensional tolerance deviations as well as thermal or
hygroscopic stress are thus reliably compensated.
The depth (cavity) of the subconstruction depends on the necessary
ventilation space and the thickness selected for the insulating material.
The facade cladding is fastened in place on the subconstruction.
Depending on the architectural requirements, the fastenings are visible
or hidden. The manufacturer‘s approvals and standards relating to
the materials are used to determine the actual dimensions of the facade
panelling in each case.
The benefits of ventilated rain screeen facades
One of the main tasks of buildingenclosing components in terms
of building physics is to provide protection against condensation
water. Ventilated rain screen facades are an especially effective way of
guaranteeing the required protection against condensation water. The
purpose of the ventilation is to keep the construction dry by enabling
a continuous flow of air between the ventilation area and the outside
air. Water vapour (moisture exuded by new buildings, moisture resulting
from use) is dissipated into the outside air without the formation of
condensation.
Open joints of the facade cladding provide an additional link to the
outside air. Another benefit in terms of building physics apart from thermal
protection during winter is the thermal protection provided during
summer. If the ventilation area is correctly designed, up to two thirds
of the heat load can be kept away from the inside of the building.
This makes it clear that outer walls with ventilated rain screen facades
also have a significant positive impact on the indoor climate of a
building.
In addition to protection against condensation, protection against
the effects of moisture is especially important. Ventilated rain screen
facades as a type of construction are assigned to stress group III (severe
stress of driving rain; annual precipitation > 800 mm).
Ventilated rain screen facades minimize building-related thermal
bridges and provide complete building protection under all climatic
conditions.
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