In cooperation with researchers, a Swiss manufacturer has developed a dimensionally stable and therefore fire-resistant blown-in fiber insulation material made from recycled paper. The product could give new impetus to waste paper insulation. Because cellulose fibers are considered to be particularly sustainable.
The use of cellulose for building insulation became widespread in western industrialized nations in the 1970s, when the need for inexpensive thermal insulation materials increased, particularly in the USA due to the rise in the price of heating oil. It has been used to insulate in Switzerland since the 1980s. However, the natural insulating material was a niche product for a long time.
That has changed in recent years. Sales have increased significantly. According to a market analysis by the consulting firm Interconnection Consulting, the Swiss thermal insulation market grew by 4.2 percent in 2019 and generated a sales volume of CHF 330 million. In terms of value, mineral wool (42.3 percent share) and rigid polyurethane foam (15.4 percent) are currently growing the most. At 7.8 percent, the market share of cellulose and other natural fibers (excluding wood fibers) is comparatively modest. But compared to other markets like Germany, where the share is only 1.8 percent, alternative insulation materials are quite popular in Switzerland.
The most important growth driver is the timber construction industry, which is benefiting from changes in fire protection. Because insulating materials made from paper fibers are primarily used in this sector, sales have increased after new regulations have come into force: in 2005, for example, the construction of multi-storey wooden buildings was made possible; and with the 2015 revision, the legislature allowed wood for all building categories.
Most sustainable insulation material
The scope of cellulose fluff includes roof, wall and ceiling cavities. The insulating material is made from sorted newsprint, which is pre-shredded into flakes in mechanical processes, mixed with flame retardants, ground, impregnated and finally loosened and compacted. The recycled paper content of the finished product ranges from 75 to 90 percent, depending on the supplier.
Pulp fibers have low thermal conductivity and offer very good thermal insulation in summer. In addition, the pulp is inexpensive. According to a list by the consulting portal Energieheld Schweiz, cellulose has one of the lowest prices per square meter after wood fibers and is similarly cheap to expanded polystyrene.
But the material scores most in terms of the ecological balance: no other insulating material has a larger recycled content and a lower primary energy content, which makes it the most sustainable of all insulating materials in the building sector. Since the fraying process is very simple and paper does not develop much resistance, little energy is required for production, explains Michel Alder, Managing Director of the manufacturer Isofloc AG. According to the KBOB database for public construction, the company from Bütschwil, founded in 1980, is the supplier of the most sustainable insulation product in Germany. Paper-based insulation is one of its main products, accounting for 60 to 70 percent of sales.
problem of setting
Company boss Alder confirms the increasing demand for cellulose in the market. In order to be able to continue to serve them, Isofloc has teamed up with the Federal Materials Testing and Research Institute (Empa) as part of a two-year Innosuisse industrial project. The aim was to develop a dimensionally stable and fireproof blow-in insulation material made from waste paper for prefabricated wooden element construction.
To do this, a binding agent had to be found that met two basic conditions: it had to be demonstrably non-toxic, cheap and available in large quantities. A binding process also had to be developed because the tufts should flow well when blown in, but should stick firmly in the cavity.
Polymer chemist Thomas Geiger from Empa's Laboratory for Cellulose and Wood Materials explains why bonding is so important: "The waste paper flakes are filled into prefabricated wooden compartments, which are then closed by screwing on a wooden counter plate, which compresses the material slightly and gives it a certain inherent stability . However, vibrations are exerted on these complete walls during the erection, loading and transport process. And then it can happen that the flake filling builds up slightly, i.e. it sinks a little and this creates new cavities in the wooden building element.»
Dimensional stability through bonding
The process of compacting the filling material is called settlement. Preventing this was the focus of the project. The background was the achievement of better fire classes. “The compartments are filled with the insulating material. However, if settlement occurs as a result of production, then you have a chimney effect in the event of a fire, which means that more oxygen can enter and fan the fire," says Geiger. "But if you strengthen the structure with binding agents in such a way that the filling remains stable and without the formation of cavities in the compartment until the final assembly of the element, there are no cavities in the event of a fire and therefore no longer a chimney effect and thus, to a certain extent, fire protection."
It was Geiger's task and that of his laboratory colleagues to find a suitable substance. In a series of tests, around 40 different additives were tested. A substance from the food industry finally showed the desired property in adhesive tests at Empa and in pilot tests in the Bütschwil production hall, namely a reliable connection of the cellulose structure even in the event of fire.
Finally, the flakes were blown into test wooden frames and exposed to a flame of up to 1000 degrees in the fire laboratory for one hour, with the result that the new insulation withstood the fire test. Exactly which substance is involved remains a trade secret for the time being.
Tinkering with the injection process
Isofloc Managing Director Alder is extremely satisfied with the result: "The binding agent ensures that the fiber cube remains within the compartment and results in secure adhesion. The insulating material thus remains in the construction as a whole cube and provides active fire protection.»
Now the product has to be further developed in terms of application and machine technology so that it is suitable for mass production, which requires technical tests. Machine technicians are in the process of building a new generation of blowing machines. The dosing of the binder is important here: "While the standard cellulose product is being introduced, the binder must be injected at the inlet of the injection nozzle at the same time, so that a bond is created between the wooden structure and the cellulose," explains Alder.
The designers are currently working on fine-tuning. The main challenge is that the nozzles always spray the same amount of adhesive onto the loose insulation material.
Boost thanks to wooden housing construction
Michel Alder hopes that the new development will be 10 to 15 percent more economical, especially in the fast-growing multi-storey residential building sector. He is certain that the new product will be a milestone and generate additional double-digit growth.
Isofloc already cooperates with large timber construction companies. Isofloc filled the roof and wall elements with cellulose insulation for the "Sue & Til" development in Winterthur, which was completed in 2018 and is currently the largest wooden housing estate in Switzerland. And the company will also insulate a residential building with waste paper as part of the “Lokstadt” construction project in the same city.
The trend towards sustainable building is fueled by the current climate debate. Thomas Geiger is convinced that it will ultimately lead to a rethink. "Natural substances and sustainable materials that come out of certain cycles and are CO 2 -neutral are becoming more and more important."
And you are on the right track there. Because the paper flakes are a real alternative to petroleum-based insulation products, says the specialist from Empa, and adds: "If you look at the entire process from tree management to cellulose production and paper use to recycling, you have a cycle that is really sustainable. And as insulating material, waste paper remains in the building in question for a very long time, possibly over 50 years, until the building is demolished, converted or renovated.”
Antonio Suarez / September 14, 2020
