Dark and reflective glasses

Graña y Montero is the most important building and engineering company in Peru. Its very conspicuous headquarters are located along the Via Expresa, a vital artery of Lima that endures intense traffic all day long. 

The main facade of Graña y Montero's new tower is oriented to the West. It is fully glazed.

The project's descriptive memory most likely justified the specification of a fully glazed facade pleading the generally undisputed economic argument that this solution will allow the building to take advantage of natural light.

A second goal of its designers is aesthetic and symbolic: such a conspicuous location provides the opportunity to position this building and engineering company as a company identified with global modernity, suggesting to potential customers that their own buildings will also have that character. "If you hire us, your building will look like any building in a more developed country, or like any building that is occupied by the most dynamic, succesul and powerful company in a not so developed country."

When it was just a project, one might have believed this choice was a wise bet. The company, however, has occuppied this location for many years before the tower got built, and its members have a long experience of the level of discomfort that is caused by solar radiation on facades with this orientation. In fact, they have tried to mitigate its effect installing all kinds of gadgets in the buildings that previously existed in the very same piece of real estate.

Disdaining other architectural options available, its designers decided on a very dark tinted glass to circumvent this challenge.

Probably convinced of the advantages of this kind of glass by gentle resellers, other architects have made the same choice in west facing facades.

An obvious inconvenient of this kind of glasses is that to reduce solar gain by 50% they admit only 20% of natural daylight; a transparent glass, on the other hand, admits more than 90% of natural daylight. This condition forces the occupants of the buildings that feature this kind of glass to turn on the artificial lighting in winter days. 

Though it is not necessarily always easily visible from the outside, dark and reflective glasses are not more successful in keeping the heat and preventing glare than transparent glass: in summer, curtains, stores and blinds get pulled down and windows cease to be a source of natural daylight.

The use of dark and reflective glasses is far from guaranteeing that windows will be a source of free light. 

Even when both in winter and summer there is plenty of natural daylight, the building cannot take advantage of its abundance. 

Ideally, in winter the glass should be completely transparent, absorbing as much daylight and even the weak heat that the sun might supply. In summer, windows that open to an orientation from where the sun isn't could also feature completely transparent glass, thus allowing as much daylight as possible. These windows can achieve this ideal condition and performance only if they could be totally protected from the sun rays by a proper shield.

If such a shield can be deployed to cast an exact eclipse on the glassed windows only when the sun would otherwise impact on them and totally removed when its presence is not required buildings could go back to completely transparent glass, which is the best way to take full advantage of daylight all year round, and also gain the weak heat that the sun might supply in winter.

Only this technology hasn't existed yet.

The kind of shields that were available to the designers of buildings such as the Graña y Montero's new tower are reviewed in the adjoining entries.