Openly clay hollow box ceiling
When planning and constructing our Openly Widnau apartment building, we were forced to take innovative paths and drive forward our own product developments. Without this intensive development work, we would not have been able to realize the building in a climate-positive way.
Construction of MFH Valley Widnau, Nov. 2023: A hollow box element with clay filling can be produced in three hours
Innovative construction method for a climate-positive apartment building - Valley Widnau
When planning and constructing our Openly Widnau apartment building, we deliberately opted for an innovative approach: in order to achieve our goal of a climate-positive building, it was necessary to drive forward our own product developments and create new solutions. We are particularly proud of our specially developed hollow clay box ceiling with a thickness of 380 mm, which combines numerous advantages.
Our box girder ceiling in detail:
Three-ply spruce board (42 mm)
Hollow box (280 mm high), filled with loose clay fill (140 mm)
Three-layer board (60 mm)
Costs 350 CHF/m2
This construction not only offers a high load-bearing capacity and enables large spans with minimal use of materials, but also impresses with its optimal building physics properties. The clay used ensures excellent heat storage (phase shift) and outstanding sound insulation thanks to its high mass. In addition, the clay regulates the humidity in the room and thus contributes to a pleasant and healthy living climate.
Modular construction for maximum flexibility
The entire building has a modular design and can be assembled using simple plug-in and screw connections. The timber box ceilings consist of prefabricated elements, which makes for a particularly economical and efficient construction method.
OPENLY construction system box girder floor with reuse steel girders
Clay - the sustainable building material of the future
Clay not only impresses with its very good thermal insulation, but is also open to diffusion, buffers humidity, absorbs odors and makes a significant contribution to a positive indoor climate. With a sound insulation index of 46 to 50 dB, clay also provides effective sound insulation. Its durability is impressive: clay lasts for over 200 years without losing any of its quality - that's real sustainability! Unlike many other building materials, clay does not have to be produced using energy- and CO₂-intensive firing processes. As a latent heat store, it absorbs heat and releases it again when required. In addition, clay filters environmental toxins and thus actively contributes to a healthy living environment.
Clay: sustainable building material with 200 years of durability and one of the 9 central building materials of the openly building system
Openly is a transparent and open system: we are happy to share our extensive expertise so that together we can make the greatest possible contribution to climate protection.
Our one-day training courses in the OPENLY.lab give more insight into the how and why and provide access to all OPENLY data.
The next training day is on 25.9.2025 in Widnau, SG.