Sandro Fritschi

Research

The act of isolating buildings is a primordial and instinctive search for strategies to enhance our ability to endure thermal conditions that fall outside our ideal temperature range. This ranges from the use of clothing to the design and construction of buildings.

Around 1870 the first specifically manufactured isolation materials enter the market. Amongst them stone wool, a product that remains widely utilized to this day.

Stone wool has demonstrated its crucial role in enhancing energy efficiency and heat storage, especially following the oil and energy crisis of the 1970s, which spurred the widespread adoption of insulation. Since that pivotal period, the thickness of the insulation layer has risen significantly, growing from 4 to 30 centimeters up to the present day. Consequently, Switzerland annually utilizes around 400,000 tonnes of insulation materials, with stone wool representing 43% of the market.

There is in Switzerland a sole producer of Stone Wool, namely Flumroc. It manufactures this insulation product since 1950. Currently, Flumroc produces approximately 60,000 tonnes of stone wool each year for the market.

The resource for stone wool is a combination of three stones, Diabase, Dolomite, and Amphiboilite which are extracted the Grisons Mountains. At Flumroc, they undergo a process where they are fused at 1500 °C to create liquid stone. This molten stone is then spun into fibers and subsequently crafted into a fiber carpet. Through this method, one cubic meter of stone (with a density of 3000 kg/m3) is transformed into 100 cubic meters of stone wool, with a density ranging from 60 to 200 kg/m3.

Stone wool is used to a share of 69% for the insulation of new buildings, typically applied with a thickness ranging from 20 to 30 centimeters to meet required energy-saving standards. The remaining 31% is utilized for energy retrofitting purposes, either replacing existing insulation or adding a secondary layer.

Following 40 years of installation, the material requires replacement. The deconstructed stone wool insulation is subsequently either directly transported to a landfill or shredded, blended with other waste, and incinerated in a waste incineration plant. Ultimately, the burned waste also finds its way to the landfill as slag.

Only a very small percentage is recycled today even though stone wool possesses the potential for 100% recyclability as it can be remeleted together with the primary resources. Also, stone wool waste recovered from buildings without moisture damage shows properties corresponding to newly manufactured stone wool and could potentially be reused.

The reason for the common, non-circular disposal approach stems from low landfilling prices and the heightened transportation costs involved in returning the stone wool to the production facility, which exceed the expenses associated with direct landfill disposal. These factors contribute to a lack of economic viability for recycling the material.

However, the economic conditions must be structured to make material recycling financially viable. This entails ensuring that the deconstructed material can be easily transported to a collection point at a low cost and via a short transportation route.

The challenge lies in identifying suitable locations for collecting the materials. Ideally, these storage locations should be strategically situated in urban contexts, where most of the waste is generated. These logistical hubs should also align closely with the current transport routes to facilitate a seamless transition from the existing logistical routes.

In the case of Zurich, a promising site for this purpose could be the industrial zone along the Hardbrücke.

To ensure that a smaller amount of the still usable material ends up in landfill it is necessary to reevaluate the disposal practices and investigating how the material can be reused without remelting, considering economic viability and environmental sustainability.

Reclaiming Stone Wool

Reclaimed stone wool has the same physical properties as newly produced stone wool. This potential would make it possible to produce new insulation products from the harvested waste material and revaluing the material itself, by treating the waste as a resource.

In the reclamation process the stone wool undergoes sorting, cleaning and shredding before the resulting granulate can be converted into various new insulation products.

The reclamation infrastructure is located at Hardbrücke, where the largely demolished Güterbahnhof is being restored to its original logistical purpose. The existing structure of Güterbahnhof is connected with an extension on the east facade to accommodate the necessary spatial requirements to reprocess the stone wool.

The intervention activates the underutilized recycling potential of stone wool by implementing an infrastructure for recovering stone wool waste in the heart of Zurich, where the biggest quantity of waste is generated within Switzerland.

Furthermore, the Güterbahnhof provides a direct link to the railway network, enabling the interception of larger volumes of waste.

Within the facade of the adminstrative building, the insulation assumes a dual identity, functioning not just as a protective layer but as a deliberate ornament, a rediscovered design piece, carefully integrated into the appearance of the building, resembling the placement of a marble plate. This integration not only respects functionality but also positions stone wool as a material embedded within the urban environment.

Granulate Application

By reintroducing the material after it has been deconstructed, the stone wool can gain a new valuation, transitioning from a purely technical product to become a vital architectural element.

This potential is realised in the second intervention in a four story building conected to Hardbrücke. It contains music studios, rooms for the community of Hard and an event and exhibition space. These uses can harness the advantages of the presence of stone wool.

Within the music studios the stone wool creates soundproofing as well as good acoustic conditions. In the event space the ceiling insulation transforms into an acoustic ceiling.

The value of stone wool is no longer solely dependent on its technical performance but is rather determined by the time, knowledge, and care invested in the integration of the material in the design process.

The invisible thermal barrier might even transform into a visible architectural element on walls and ceilings, consciously avoiding its concealment beneath other materials.

The intervention functions as a prototype as the reclaimed stone wool has versatile applications for reuse in the construction industry. With 60% of stone wool employed in timber constructions in todays industry, this sector presents the most significant potential. The granulated material can be either blown into or inserted into the gaps within the timber framework. Establishing a viable and environmentally sustainable reintroduction into the construction cycle.