Edition 2/2011 

  • Innovation
  • Aesthetics
  • Cost-effectiveness

The first self- and air-cleaning aluminium cladding panel

It’s not mere science fiction – but the result of some pretty intensive research: with its Reynobond®|Reynolux® with EcoClean™, Alcoa Architectural Products is launching a cladding panel that cleans both itself and the air around it.

Reynobond®|Reynolux® with EcoClean™ means that for the first time there is a cladding material involving aluminium (aluminium sheet or aluminium composite panel) that is both economic and environmentally friendly. With the aid of the sun and moisture, dirt and smog particles are rendered harmless. As a result, EcoClean™ helps the cladding both clean itself and keep the environment clean.

The result of four years’ research

For four years researchers at the Alcoa American parent company had been working on the method for transferring the titanium dioxide-based HYDROTECT™ technology of the Japanese firm TOTO® to a Reynobond® composite panel and Reynolux® aluminium sheeting.

Titanium oxide has been known for decades to have two unique properties. On being exposed to sunlight, titanium oxide acts as a catalyst in breaking down organic substances. At the same time, it forms a superhydrophilic (water-attracting) surface. It is a widely occurring chemical compound used in many different products, such as quick-setting concrete, pointing mortars and even suntan lotion.

Air-cleaning power of 80 trees

Up until now, the material could only be applied to surfaces such as concrete, glass, plastic and ceramic. However, because titanium dioxide attacks all organic matter, including also finishing coatings, it had so far proved impossible to apply it to coated aluminium sheet. Now the method developed by Alcoa, for which a patent is pending, prevents destruction of the finish coat.

To its powers of self-cleaning must be added that of air-cleaning. 1,000 m2 of Reynobond®|Reynolux® with EcoClean™ disperse as much smog as approximately 80 trees. This is equivalent to the daily emissions of four cars. Reynobond®|Reynolux® with EcoClean™ is therefore sustainability at its proactive best – testimony to Alcoa’s strong commitment to protecting the environment.

EcoClean™ leaves your façades shining longer

Building owners and architects want façades that will remain attractive and clean over the long term. But both of them have a common enemy working against them – time.

Time leaves its visible mark on a building. For years and decades the latter is exposed not only to the natural elements, but also to man-made pollutants. Smog attacks façades and destroys them. This is why building owners spend a considerable sum each year on cleaning and maintaining the façade of their building. But this only stops the damage – it does not eliminate it.

Reynobond®|Reynolux® with EcoClean™ helps building owners and architects regain the upper hand in this struggle. As a photocatalyst, EcoClean™ interacts with sunlight to break down organic substances on and around the panel surface. Because the cladding keeps ridding itself of dirt like this, it always remains clean, helping keep the building looking attractive.

Active breakdown of dirt

The cleansing properties of EcoClean™ start with the reaction of titanium dioxide under the influence of sunlight and minimal air humidity. When sunlight strikes a titanium dioxide particle, electrons within the latter are excited and promoted to a higher energy state.

The electrons charged in this way transfer their energy to moisture in the air, forming two free radicals, OH∙ (hydroxyl radicals) and O2- (superoxide anions). These free radicals are powerful oxidising agents that attack any organic material, both on the panel surface and in its vicinity. This material includes bird lime, moss, diesel fumes and smog.

Dirt residues are continually washed off

Once the titanium dioxide has done its job and the nitrogen oxide and other organic substances on the panel have been broken down and rendered harmless, its second main benefit comes into play – the creation of a hydrophilic (water-attracting) surface. In the presence of water, the Reynobond® panel is rendered super smooth on account of the EcoClean™ coating. So when it rains, the water does not remain on the surface, but collapses in on itself, running off the building at all points. As it does this, it takes with it most of the nitrates and organic substances that have been broken down.

Even the smallest amount of rain or humidity in the air, such as morning dew, will activate EcoClean™. Each time this happens, the water washes the dispersed pollutants from the building, leaving the façade cleaner than before. This is how façades remain clean and attractive for many years, only requiring infrequent cleaning.

Why EcoClean™ pays

Cleaning buildings costs money. Not only in terms of the labour, but also the cleaning agents used. The latter often consist of aggressive chemicals, and these also pollute the environment.

Because aluminium cladding panels that are coated with EcoClean™ have this self-cleaning capability, the cleaning and maintenance costs over the lifetime of the building are significantly reduced. By constantly ridding itself of dirt, the cladding always remains clean, helping keep the building looking attractive.

Building maintenance costs significantly reduced

The fact that its photocatalytic and superhydrophilic properties allow organic substances to be constantly broken down and washed away means that Reynobond®|Reynolux® with EcoClean™ can significantly reduce maintenance costs. Façades retain their completely clean appearance over a long period of time.

“This self-cleaning capability means that cleaning costs are reduced over a building’s lifetime,” explains Guy Scheidecker, Marketing and Distribution Manager for Alcoa Architectural Products. On the other hand, manufacture is slightly more involved, but this has only a minimal impact on the overall price of the cladding.

Depending on the type of cladding system, Alcoa assesses the increase in price as between 1.5 and 5 percent. There is no increase in effort or time for processing and installation specialists, however. Reynobond®|Reynolux® with EcoClean™ is just as easy to process and fit as traditional cladding products. And when the overall costs over a building lifetime are taken into consideration, a façade made up of Reynobond® or Reynolux® cladding coated with EcoClean™ is even more economic.

Studies so far have shown that on commercial buildings whose glass façades had been coated with TOTO’s Hydrotect™ technology (the basis for EcoClean™), a reduction in cleaning costs of up to 75 percent was possible!

Clean water is all that is needed when it comes to occasional cleaning of the cladding. It is only where there is heavy dirt in areas which are never exposed to sunlight that a mild detergent may in certain cases be needed.