COOL-Coverings focused on the so-called building envelope – the outer part of the building that protects it from wind and weather and houses the interior environment and the construction components that shape it. More specifically, the partners took a closer look at the coatings and materials that affect the envelope’s ability to reflect, rather than absorb, sunshine. They were particularly keen to boost reflectance in the near-infrared range (NIR), a non-visible part of the spectrum, where the sun emits more than 40 % of its radiation.

By improving the reflectance of the materials, the partners were able to extend the range of colours available for cool construction. Traditionally, cool construction favours light colours – ideally white – over options such as brown or black, as darker shades take in far more solar radiation.

How not to soak up the rays

With COOL-Coverings, this limitation is about to become a thing of the past. Innovative materials are enabling architects and homeowners to keep a cool head when selecting darker shades. Working from a wider palette can be a matter of personal preference, but it can also be a requirement under restrictive building regulations.

The project involved 14 partner organisations from industry and academia. “We had three main objectives,” says Luis Guaita, head of research at Keraben Grupo, the lead partner. In addition to cutting energy consumption and increasing indoor comfort, the team also aimed to mitigate the appearance of urban heat islands. This phenomenon, which is created when heat accumulates in materials composing the built environment, adds to the difficulty of cooling down sun-kissed cities.

To meet their objectives, the partners incorporated nanoparticles and micro- or nano-sized pigments into coatings and surface layers.

“We implemented this technology for three types of material: ceramic tiles, acrylic paints and roof membranes,” Guaita explains, adding that the project managed to double the reflectance for darker colours.

Yes we cool

The new, NIR-reflective materials were exposed to real-life conditions in a demo park near Madrid, where they were used on the boiling roofs and façades of one-room units equipped to simulate the thermal behaviour of larger buildings. This rigorous testing confirmed the outstanding performance of COOL-Coverings’ tiles, paints and membranes.

How much energy can they help save? That depends on a lot of factors. Demo park data indicate that savings ranging from 4 to 7.5 % could be achieved by re-roofing, re-tiling or re-painting sun-baked buildings using COOL-Coverings materials that replicate the original colour. This conclusion takes account of the fact that cool analogues translate into higher heating bills, and was confirmed by simulations carried out for three different types of building considering typical weather in Madrid.

The new products will soon be available in shops around Europe, says Guaita, in a variety of bracing colours including an arctic black and a boreal brown. He is enthusiastic about their potential to increase energy efficiency simply and affordably, just by applying a layer of innovation to the building’s outer shell. No changes to the actual construction are required.

Refreshing ideas

Guaita is convinced that academia and industry complement each other in such endeavours, as they approach challenges from different angles.

“We need each other,” he notes, and generally underlines the importance of bringing in a wide range of expertise when it comes to meeting complex technical challenges.

The project ended in May 2013, but the partners remain committed to collaborative research. New ideas for nanotech-inspired energy-efficient products and processes are being generated in the context of the European Construction Technology Platform and the Nano-E2B-Cluster, which also backed COOL-Coverings. Sweltering summer days may soon be much easier to face.

Related artcile: Energy saving begins at home