Rear-ventilated cladding for exterior walls

The ventilated cladding of exterior walls, including thermal insulation and connections, ensures that the basic building physics requirements for meeting the energy certificate, including summer and winter heat and moisture protection, are met. Due to the pronounced system and functional separation and the generally small construction mass, the construction method is characterized by high C02-eq and circularity efficiency. The method is suitable as a sustainable construction method for both renovations and new buildings.

The following applies to the rear-ventilated cladding of external walls (vertically mounted and rear-ventilated boundary of the building envelope): externally positioned and rear-ventilated cladding of external walls, including thermal insulation and interfaces with connecting components such as glazing, roof edges, flooring surfaces or supporting structure elements.

The main layers consist of supporting structure elements such as columns, joists, walls (shell construction, or mounting base for facade anchoring), substructure, insulation layer and exterior cladding. Each of the layers fulfills defined functions such as weather protection, thermal insulation, airtightness, load transfer, etc. and must be coordinated holistically. The minimum performance requirements are the fulfillment of the energy certificate including summer and winter heat and moisture protection. The performance requirements can be supplemented on a project-specific basis, for example with fire protection requirements, etc.

The multi-layer structure should be assigned information for the project planning and as a basis for the tendering as a complete component “rear-ventilated cladding of external walls”. This information usually includes the phase-specific technical specifications and the geometric information with a low level of detail (LOG 200-300) for generating the quantity takeoffs (cost estimate / cost projection).

The use case defines a collaboration between architecture and facade planning (ARCH synergy model) that focuses on synergies. The facade planning is assigned to the architecture with regard to the BIM processing. The facade engineering services are assigned to the architectural facade BIM model by means of specifications or attributes. Thus, the use case primarily defines the collaboration and the requirements for the ARCH model and explicitly the requirements for the statements to be generated from the model.

Minimal specifications or typical attributes are:

• Definition of component groups and construction types (basis for the BIM-generated bill of materials for cost estimate / cost projection and bill of quantities)
• Specifications of U-values, line allowances, etc. (basis for energy certificates and assessment of thermal comfort)

Geometrically, the ARCH model, with a targeted low LOG, is based on the architectural planning and the technical details or layer plans developed by the facade engineering.

• Consistent information management
• Increased efficiency in processing and collaboration
• Increased cost accuracy due to BIM-generated mass statements
• Conceptual description of the interface between architecture and facade planning (handling of different LOG requirements)
• Representation of the facade in the ARCH model
• Minimal geometric modeling (low LOG level) that allows coordination with the structural design
• Adequate information of the ARCH model (medium level of information need) for content coordination and the respective project-specific parameters, e.g. burglary class, CO2 footprint, etc., between architecture, building physics, structural engineering, fire protection and facade planning.

• Preliminary project: Generate bill of quantities for cost estimate (CO) in m2 and running meters Interfaces, for running meters, define where measurements are taken (inside, axis, outside)
• Construction project: Generate bill of quantities for cost estimate (CO) in m2, running meters Interfaces and quantities
• Define exterior-facing and back-ventilated cladding of exterior walls incl. thermal insulation
• Interfaces to connecting components such as glazing, roof edges, flooring surfaces or supporting structure elements.
• Modeling of sealing, landscaping, opening elements (accessibility, windows, sun/glare protection, fire protection concept, heating, ventilation, air conditioning and sanitation), etc.
• Determining the fastening technology
• Modeling guidelines for correct execution in the construction project

• The use case focuses on the project planning phases, including the basics for the submission. In explicit deviation from the building envelope use case, the current use case avoids double modeling of architecture (ARCH) and facade models. Accordingly, with regard to facade planning, we speak of an ARCH synergy model.
• The use case only includes the presentation of the digital input and its implementation as a level of information need, i.e. who does what, who when, what and how (level of detail) when applying the BIM method.
• All topics related to the scope of services and thus to contractual and fee-related issues are explicitly excluded.
• All services described by all parties must be specifically agreed as of today.
• The implementation phases are not part of the use case
• Lightning protection, electrical and HVAC planning only take place in the implementation phase
• Photovoltaics (PV) are treated in the same way as a facade element
• The substrate is always a load-bearing element (concrete, wood, etc.)
• Cantilevered facade elements are not considered, but the architectural design of the facade cladding (design) must be taken into account.
• Contractual and fee-related services must be agreed in writing in advance between the parties.

• AM Suisse - Dachverband für die Fachverbände Agrotec Suisse und Metaltec Suisse
• ARCH model – architecture model
• GWP - Global Warming Potential
• LCA - Life-Cycle-Assessment
• LOG - Level of Geometrie
• LOI - Level of Information
• SIA - swiss socity of engineers and architects / DE: Schweizerische Ingenieur- und Architektenverein
• SFHF - Schweizerischer Fachverband für hinterlüftete Fassaden
• SZFF - Schweizerische Zentrale Fenster und Fassaden

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The documents reflect the current best practice and do not claim to be complete. They should not to be understood in the sense of a generally valid recommendation or guideline from a legal point of view. The documents are intended to support appointing and appointed parties in the application of the BIM method. The documents must be adapted to the specific project requirements in each case. The examples listed do not claim to be complete. Its information is based on findings from practical experience and is accordingly to be understood as best practice and not universally applicable. Since we are in a phase in which definitions are only emerging, the publisher cannot guarantee the correctness of individual contents.