second skin facade
Second-skin façade of teflon-coated and open-weave fibreglass textile, specially developed for the renovation of the Westraven office block in Utrecht. The textile functions as a sunblind without simultaneously impeding the view of the outside world. Above all, it makes it possible to open the windows of the building, even at a great height, without being troubled by the wind. The light turbulence behind the textile neutralizes the force of the wind, so that the cavity between the textile and the thermal facade is relatively tranquil, although it does enjoy a constant supply of fresh air. As a consequence, the offices can be ventilated directly with fresh air from the outside.
The façade screen was inspired by textile applications in horticulture, and is extremely light in comparison to other second-skin solutions. A relatively light construction is therefore sufficient to support it. At Westraven, the textile is spanned to steel balusters by means of aluminium tubes, with use being made of the existing construction for the window-cleaning facilities.
The gauze has been comprehensively tested with respect to a large number of technical and functional criteria. It reduces the forces of wind and sun adequately, but it is also sufficiently transparent and translucent. The fabric is colourfast, is unaffected by water, grease and dirt, is resistant to the weather, fungus, rust and insects, and is easily cleaned if necessary. Moreover, it does not flap or vibrate, and the risks of icing up have been extensively tested.
The translucence and transparency from inside to outside are linked to a combination of factors. The difference between the light intensities inside and outside, the colour and degree of reflection of the textile, and the angle of the sun all play a role. In addition, the distance of the textile to the building and the mesh-size and the thread thickness of the fabric in relation to the resolution of the human eye are also factors to take into account. Because the gauze is thin, a good view remains possible across a very wide angle.
At Westraven, the screen alternates with strips of glass at head height. Because the textile façade has no sound-deadening properties, the building has a glass second-skin on the motorway side.