Polypropylene, Polyester and Polyethylene are the main raw materials that make up the under-tile and under-tile sheets

In the in the field of sustainability of the materials that are used on construction sites for waterproofing roofs, in the past we have dealt with the recycling systems of bitumen cardboard sheets, which are used for the installation of bent tiles and tiles, making the roof waterproof and in the same ventilated weather and bituminous sheaths, which are positioned above the pitch of the brick or wooden roof, to protect it from water infiltrations.

If in the past, during the demolition phases, the waste material of the construction site was sent without any prior selection to the landfill, today it is right and necessary to select the products waste for their recovery.

The attic and under-tile sheets are relatively recent products that are used to avoid water percolation inside the house, to reflect heat towards the outside, to promote the breathability of the roof package, to reduce the formation of humidity caused by internal and external factors and for other purposes.

How are the attic sheets composed?

The most popular are made of polypropylene or polyester or polyethylene, through the calendering of raw materials in thin and very resistant layers.

They are usually made in layered packages of two, three or four sheets each with a specific task that we can summarize:

• Finishing layers

• Carrier layer

• Reflective layer

• Armature

To realize the constitution of a square meter of waterproof sheet we can say that the weights can vary from 100 to 400 grams, they can have some layers coupled together or provide for a mesh reinforcement which increases its tensile strength.

What functions do the attic sheets have?

In the past, the waterproofing of the roof, whether it consisted of a pitch, the brick or a wooden planking, relied on bituminous compounds, liquid sheaths or sheaths in rolls, the task of waterproofing the roof.

With the large-scale use of wooden roofs, it was noticed that the laying of bituminous compounds had a contraindication, as the humidity that migrated from the the house was blocked by the impermeable layer, with the consequence of causing the wooden planking to rot over time.

For this type of construction, recycled cardboard sheets soaked in bitumen were adopted, which allowed, through their conformation, both the ventilation of the roof that the ease of laying the brick roof.

The subsequent adoption of attic sheets had a more rapid use in northern Europe, as the use of wood for roofs was more widespread than in the south, furthermore, the final covering was often represented by the tiles and these were easy to lay on a double wooden battens rather than on the bituminous slabs.

Thus was born a wide range of products for the most diverse needs:

• Waterproofness

• Breathability

• Reflection

• Protection

• Isolation

• anti-condensation

How to recycle attic sheets?

The great diffusion of these protection systems has, in the last thirty years, increased exponentially the production creating, after a natural period of time, the first returns as waste to be recycled.

Normally, since the products consist of primary polymers, such as polypropylene, polyester and polyethylene, their recovery follows the path of post-consumer plastic waste, with the transfer to the recycling platforms that will provide for their selection, grinding, washing, densification, ready to be extruded in new recycled raw material.

A more problematic path exists for those sheets that are composed of different plastics, such as the combination with polyurethanes, polyesters, aluminum films or various coatings.

In these cases, the transfer of these composite sheets to the mechanical recycling plants creates a rather high percentage of non-recyclable waste, as separation by type becomes difficult of polymers of the various layers and, therefore, their recycling as a new matria prima.

Certainly some combinations of polymers, such as PE + PET, could be used as recycled raw materials, but the other types are still difficult to recycle.

Automatic translation. We apologize for any inaccuracies. Original article in Italian.