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CONTENT
3CYCLE SYSTEM
In response to the environmental challenges posed by the construction industry, the 3cycle building system emerges as a pragmatic solution, aiming to address the ecological impact of traditional construction practices.
At its core, the 3cycle building system adopts engineered timber as a primary structural element, significantly lowering the carbon footprint of the buildings it constructs.
Central to the 3cycle approach is the dedication to the design for disassembly principles. By prioritizing adaptability and flexibility in building design, and ensuring that each component or even material can be disassembled without damage, the 3cycle system extends the life expectancy of buildings and materials, thus it contributes to a substantial reduction in future emissions and waste.
The 3cycle system is designed to seamlessly integrate with existing methods of production. It is an open-source system, intended to be accessible to a broad spectrum of prefab timber house producers. This approach ensures that 3cycle buildings can be both affordably and efficiently produced.
The high degree of customization possibilities of the 3cycle system components allows architects and designers to find non-repetitive and tailored results for most building-typologies and building sites.
CIRCULARITY
3cycle buildings are circular in multiple levels. The largest circular unit in the system is the entire building, as it can be demounted, moved and reassembled on a different site, if the need occurs. Secondly, full room modules can be reassembled, removed or added to a building. The smallest reusable parts of the building systems are its components. They are designed for disassembly, allow for easy repair or upgrade and can be easily reused in differing combinations in the same or other buildings. All building components, designed based on the principles of the 3cycle system, should be recyclable and maximise the use of low-emission and bio-based materials.
The core of the building system is its design for disassembly, following the standard ISO 20887. Connections are easy to open and demounting does not result in damage or contamination of the buildings, modules or components materials. Preserving their value keeps the materials from being dumped on landfills or burned in incineration plants and makes them more attractive for future reuse. All the materials which continue to be reused and which are circulating in the building stock save on future extractions of resources and productions of materials, thus reducing the environmental impact on climate and ecosystems. This way, 3cycle buildings can contribute to the transition towards a sustainable building sector with responsible consumption and production.
To ensure the circularity of the 3cycle system any future adaptations should be in accordance with the described circularity levels and the standard ISO 20887.
BASE MODULE
The key part of a building in the 3cycle building system are the Base Modules. They are highly customizable components to which further elements of the building system can be attached.
Each Base Module is composed of a list of components.
• The End Frame is a structural frame located at two sides of each module. Its height determines the height of the Base Modules. The dimensioning, materiality and/or coating of the frame posts can be based on specific building projects and their required spatial properties, structural strength and/or fire safety.
• The Floor Component is attached mechanically to two End Frames. The components can be customized in regards of structural strength (type and amount of floor beams) and thermal or acoustic insulation. Typically, insulating material is filled in between the structural beams of the component.
• The Ceiling Component closes the Base Module to the top. For that purpose a CLT plate is laid onto two End Frames. The components function is, in contrast to the Floor Component, not structural. Its main purpose is to allow for a high degree of prefabrication off-site, including interior works. Additionally, the component is a fire barrier which protects the structural components above. Different coatings or claddings can be used to increase the fire safety. Building acoustics are improved, as floors and ceilings are not joined structurally.
• The Upper and Lower Side Beams are structural beams hanging between two End Frames. They are required at the envelope of a building to attach facade panels. In the interior of a building the use of Lower Side Beams is recommended beneath interior walls. Otherwise their use is not mandatory and Side Beams can be left out for efficient material usage, undisturbed room clearance and to run building services vertically in the building (see chapter Shafts).
• Side Posts are required between Lower and Upper Side Beams on exterior facades of 6 meters modules for better load distribution.
The Base Module can always be disassembled into its sub-components, as all connections are mechanical and reversible. This preserves their value and increases the chance of sub-components being reused in various building projects with different requirements.
The dimensions of the Base Modules are restricted by transport limitations. The standard width of a module is 3 meters and the standard lengths are 3, 4.5 and 6 meters. Different lengths, heights or non-rectangular shapes can be introduced, if required. However, the use of standard components has to have priority to ensure the circularity of the system.
MODULE ARRANGEMENT
• Generally, all Base Modules should be placed in a 3 by 3 meters design grid to enable the connection of multiple modules independent from their rotation.
• Multistorey buildings should aim for a similar arrangement of Base Modules in each floor to ensure that each frame post of the upper modules is connected to another one beneath.
• Balconies, fire escape stairs and other structures which might be added to the outside of the building have to be self-standing and can be only anchored to the Base Modules.
• The Base Modules are most stable and least deforming along their End Frames. Connecting a Base Module to a 90 degree rotated one increases the stiffness of the structure and reduces the need for shear walls.
• The standard Base Module is designed for up to four storey buildings. Taller buildings should use variants of the Base Module or other building systems with adequate structural capacity on their base.
BUILDING ENVELOPE
The building envelope consists of roof and facade elements which are fixed to the Base Modules.
The Exterior Facade Panels are hung with hook plate connectors to the End Frames or Upper Side Beams of the Base Modules. These panels are insulated and protect against wind and rain. Windows and exterior doors are placed in them. The type of construction, thermal performance, window ratio and design can be chosen based on the project. However, the weight and structure of the panels have to be according to the limitations and positions of the hook plate connectors.
Each Exterior Facade Panel is a bit lower and shorter than the Base Module it is attached to. The resulting gaps between different Exterior Facade Panels in horizontal and vertical direction are required to join the vapor barrier after assembly on-site. This way, Exterior Facade Panels can be installed already in the factory and only lightweight Facade Joints have to be added on-site.
Different kinds of insulated roof constructions can be added on top of the Base Modules. However, in order to preserve the building's adaptability over time it is recommended to use Roof Modules which are based on the same 3 by 3 meters design grid as the building system. If Roof modules are used which do not extend above the Exterior Facade Panels the latter can be demounted or mounted independently during a building's life. In this case insulated Roof Joints are placed above Exterior Facade Panels to avoid cold bridges.
FOUNDATION
The foundation has to support the four bottom faces of the Frame Posts of each Base Module. The gaps between the structural beams of the Floor Component are filled with insulation. Ventilated foundation types, such as stripe foundations with base floor or any types of pile foundations are preferably used as they reduce the risk of moisture damage from condensation in the Floor Components. The use of screwpile foundations can improve the adaptability and circularity of the building as they can be easily added, removed and reused or recycled.
BUILDING SERVICES
Centralized or decentralized Ventilation systems with heat recovery can be used to provide fresh air. Decentralized systems consist of individual units placed through the exterior walls and do not require venting air via pipes to a centralized core.
Multiple Heating systems can be used with the 3cycle building system. Easiest to implement are traditional radiators and floor, wall or ceiling-mounted radiant electric heaters. They do not hinder the adaptability of the building system and allow easy removal or adding of modules from or to a building. Water-based in-floor radiant heating systems are generally cheaper to operate than the previous systems and can be joined with sustainable systems such as heat pumps or solar collectors. However, they require more work on-site as the heating pipes and the final floor layer have to be finished in situ. Expansion or downsizing of a building is in this case more work intensive, too. Therefore, the fitting heating system has to be chosen based on the expected amount of the building's transformation during its lifetime.
Water and sewage can be distributed vertically in shafts. In the best case a wetroom is planned in a single module with an adjacent vertical shaft to reduce pipe lengths and avoid the crossing of pipes through multiple modules. Pipes can be distributed in Floor Components, however penetration of the Ceiling Component, which is visible to the interior, has to be avoided. In best case, furniture with sewage connection, such as toilets and showers, should be placed as close as possible to vertical shafts.
The distribution of Electricity is project specific and can be done in floor or ceiling height and exposed or covered. Preinstalled cable channels can be used to wire the building on-site after finishing the installation of all modules. Otherwise, the tolerance gap between the Base Modules is wide enough to distribute electricity vertically without damaging Floor or Ceiling Components.
SHAFTS
Three categories of shafts can be implemented in the 3cycle building system.
Type A shafts are not causing irreversible changes to the Base Modules and allow to run electric cables and pipes with under 8.5 centimeter diameter. Pipes or cables with more than 2.0 centimeter diameter can only be implemented if no Upper Side Beam is installed, thus if it is not on an exterior facing wall. These also require drilling through the Ceiling Component. However, the holes are small enough to be closed in future with minimal visual impact.
Type B shafts require a cut-out in the Ceiling Component and no Upper and Lower Side Beams can be installed. Therefore, Type B shafts cannot be placed along exterior facades, as well.
Type C shafts use typically a 3 meters long Base Module with modified Floor and Ceiling Components. The shaft spans between both End Frames and can be adjusted in its width. The largest shaft of this kind has no Floor or Ceiling Component installed. Type C shafts require Upper and Lower Side Beams for structural integrity during transport and lifting. Therefore, they can be placed along exterior facades.
Placing Type B and C shafts in a Base Module is resulting in a configuration that cannot be reversed on-site without swapping components. Therefore, it is recommended to place as few as possible modified modules with shafts in a 3cycle building to ensure high reusability of the modules. It is better to use fewer large shafts than many smaller ones.
CIRCULATION
Horizontal circulation spaces such as corridors follow in optimal case the 3 by 3 meters design grid and are placed in standard Base Modules. Alternatively, a self-standing deck access can be placed, similar to balconies, in front of the facade of a building.
Vertical circulation is ensured firstly by stairs. Based on the building type, module height and length different stair types can be used. For public staircases a U-turn stair in a 6 meters module can be used. In lower modules with non-public functions can be used straight stairs or spiral stairs. Exterior stairs and exterior fire safety stairs have to be self-standing and can only be anchored to the Base Modules. Elevators are not part of the modular system due to the high amount of regionally available products as well as country and project specific requirements. Small elevator systems might be placed into modified Base Modules, while larger ones are built as self-standing structures in between Base Modules or anchored to the exterior of the building. Elevator shafts can function as shear walls if designed accordingly.
LICENCE
3cycle building system is developed at the Timber Architecture Research Centre PAKK at the Estonian Academy of Arts and licensed under CC BY 4.0.
Guide / 3cycle building system - sustainable construction system for modular and circular buildings
Made by NOMAD architects for Timber Architecture Research Centre PAKK.
December 2023