A new residential building - built in hybrid modular structure

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A new residential building - built in hybrid modular structure

Sophie Xiying Liu

Business Development Manager | 16.07.2019

In Lenzburg, a new timber residential building has been erected in the fastest speed ever in Switzerland.

The staircase and lift core were attached to the building in front.
The staircase and lift core were attached to the building in front.

An innovative and eco-friendly residential building has been realised in just five months in Lenzburg, built based on a collaboration among Renggli AG, the property owner AXA and Bern University of Applied Sciences BFH. 

This high-performance construction system adopts a brand new hybrid modular structure, and follows a surprisingly simple principle: all the apartment modules are fully prefabricated by Renggli, the timber construction expert, and equipped with the bathrooms, kitchens, doors, windows and coverings, as well as the full services of building technologies during the manufacturing process in the factory.

Higher buildings thanks to the steel structure

While the modules were being manufactured in the factory, the foundation and the steel structure were built on site in Lenzburg. The ground slab is the same as it is under the conventional multi-storey residential buildings. Different from previous modular constructions, this project uses steel framework as the supporting structure, through which the loads can be efficiently transferred to the foundation. As the modules below no longer needs to support the load above, using this system can build up to eight storeys. Furthermore, the noise is significantly reduced by a sophisticated acoustic solution between the timber modules and the steel structure, thus can meet the soundproof requirements for multi-storey residential buildings. 

“This new building system is a step towards Manufacturing 4.0 in the construction industry,” says Roman Hausammann from the Institute for Timber Construction, Structures and Architecture IHTA at BFH, “The complexity was eased by the development of the hybrid construction system and validated by the inspections. Each building element is prefabricated as one complete system component.” So the kitchens are built-in as one piece, all the bathrooms are identical, and the staircases are installed as standard elements. 

The prefabricated modules were delivered by low loader trailers from the factory to the site, and then were assembled within a few hours. As the interior work of the modules has been completed, all needs to be done was to insert the modules into the steel framework and connect them with each other, as well as to connect the building services. The staircase and lift core were attached to the building in front.

Prefabrication of the timber modules in the Renggli factory in Schötz, Switzerland

Renewing and preserving the affordable living spaces

This hybrid construction system was developed as a part of an Innosuisse (Swiss Innovation Agency) project. Comparing to the conventional construction approaches, Hello Lenzburg project saves about 9 months of construction time. Thus, it can reduce the vacancy duration and ease the housing shortages. “The high level of prefabrication in the factory and the computer-aided manufacturing can ensure better quality and shorter construction time”, explains Max Renggli, CEO of Renggli AG, “The average cost of residential apartments in the future can be reduced considerably, by the prefabrication technology, the standardization of apartments and the resulting scaling-up of projects. It is much easier to estimate costs with the modern construction method than with the conventional construction methods, it even allows us to estimate costs at different stages.” 

Eventually the cost saving will be reflected in the rent. “In particular, this construction method allows the long-term thinking investors to replace the outdated rental apartments that are not worth renovating, with the modern affordable apartments. Ideally, the short construction time can also help retain the current tenants”, says Simon Haus, Head of Asset Management at AXA, who worked on this project. 

The buildings at Hello Lenzburg is built aligning with the Minergie-A and ecological standards. The photovoltaic system generate electricity for the Zusammenschluss zum Eigenverbrauch (ZEV, Association for the Purpose of Own Consumption in English). The building is heated by the renewable energy generated from the downhole heat exchanger.

Entrance with kitchen
Bath room and sleeping room

Lower price, but without compromising living standard

Hello Lenzburg adopted the new modular construction approach for the first time. It demolished an old property owned by AXA, and replaced it with a new building that offers three types of apartments: from one-bedroom to two-bedroom, all with modern floor plans. These apartments also ensures the accessibility for people with disabilities. The rents are set in the affordable ranges. For example, a two-bedroom apartment costs about CHF 1,600 per month. “As an institutional investor, we also want to maintain the stock of our affordable apartments”, Mr. Haus continues, “The hybrid modular building gives us the opportunity to renew our portfolio. Therefore, the pension fund from the second pillar and the third pillar can be invested sustainably.” 

The lessons and experience learned from this pioneering project will be further developed and continuously improved for the future projects. The Hello Lenzburg project team conducted a workshop and surveys among the tenants who live in four other similar properties. During the visit of a pre-constructed prototype, the tenants were able to get a clear understanding of the apartments and to give their feedback, which was incorporated into the final design of these apartment modules. 

“The cooperation between the Berne University of Applied Sciences BFH, Swiss KMU (Swiss Association of Small- and Medium-sized Enterprises in English) and AXA within the framework of an Innosuisse project has demonstrated the innovation strengths of Switzerland and enhanced our work place,” summarizes Roman Hausmmann. 

Other partners who also contribute in this interdisciplinary collaboration include H. Wetter AG (steel construction), Schindler (elevators), Geberit (sanitary technology) and Amstein and Walthert AG (building technology).

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