Openings represent the weakest point in a wall, and constitute the permeability of the edge where trespass and intrusion are most likely. Doors and windows shape the building façade, presenting a rhythm of propriety to the outside world but also producing the natural light necessary to perform tasks on the inside of the wall. This dichotomy challenges architects to resolve the sometimes incompatible: organization and available light, security and transparency.
The simplest openings are just that, open, but mankind finds ways to screen the outside; the earliest closures used plant materials and animal hides. The first use of glass as a building material by the Romans in 300 BCE allowed visual connection with the outside without noise, dust, and thermal discomfort from the raw climate. Window glass remained uncommon until the 1600’s, and only important rooms had glazed openings – other openings had shutters. In 1696 the English placed a tax on windows, ensuring that common people avoided putting windows into unimportant spaces… including bedrooms, servant’s rooms, privies, and anywhere that didn’t require daylight.
The window tax didn’t end until 1851, when construction of the Crystal Palace in London demanded the resources of the nation’s glassmakers for a building made entirely of windows. Joseph Paxton designed the Crystal Palace for “The Great Exhibition of the Works of Industry of all Nations.” Celebrating industrial practice and culture, the exposition structure embodied the most advanced technology of its time – an enclosure of 990,000 square feet 1,851 feet long by 128 feet high, constructed with a frame of cast iron columns and trusses supporting 293,655 individual panes of glass. It was a marvel of engineering.
Glass can make entire walls disappear; the boundary between inside and out becomes potential and not permanent. The Crystal Palace changed the way people approached architecture, and challenged accepted modes of living. With glazing, the world outside might be threatening, but one could see its dangers and its beauty without participating in it. A small pane of glass could become a plane of glass, opening up new experiments in living – conservatories, sunrooms, and cupolas, sheltered but transparent, lifted out of the darkness of rooms lit by lanterns and meager framed windows. From the ganged windows of factories to the flight of the Farnsworth House, glass replaced walls and roofs, expanding interiors by borrowing from the outside. The view from the villa becomes a daring exploration of pure space, barely interrupted by the requirements of jamb and mullion.
Bill Bryson writes, “Today we are used to encountering glass in volume, but to someone living in 1851 the idea of strolling through cubic acres of airy light inside a building was dazzling…. It would have appeared as delicate and evanescent, as miraculously improbable, as a soap bubble.”
With new technologies, windows have realized greater strength than their nineteenth century predecessors. Windows stiffened with stainless steel splines, laminated with multiple layers of glass and interlayers of Lexan, can resist bullets and blasts, hurricane winds and debris impacts. These armoured plates are no longer the weakest link in the wall, but the one thing they cannot do is… open. Therefore, these may be the riskiest windows of all, demanding mechanical ventilation 100% of the time and eliminating all possibility of egress in an unthinkable scenario.
Modern technology provides defenses against other enemies – ultraviolet rays, solar heat gain, and glare. Glass coatings defy climatic foes, improve energy efficiency, and allow windows to expand to previously unrealized sizes. (The largest single window in the world was made for the Dubai Aquarium, measuring 21 feet wide by 18 feet high, comprised of 15 inch-thick acrylic polymer. Although it does not connect inside and outside, it does link people to a vibrant environment on the other side of the window.)
We have arrived at infinite possibilities for designing windows, from small penetrations in a solid mass to an entire building clothed in glass. From the Miesian drapery of transparent walls to the deformations of geometry by Frank Gehry, architects have choices. Yet the responsibility to design the thoughtful location of pane and plane, with proper respect given to the climate and orientation where it rests no longer allows a complete default to mechanical systems for light and ventilation to heat and cool the interiors. Mies designed the Lake Shore Towers in Chicago without air conditioning, abdicating the issue entirely but leaving occupants to swelter in Midwestern summers, reducing energy use in direct concordance with comfort.
Without openings we are blind, disconnected from weather, daylight, fresh air, street life, and human congress. The provision of windows is so critical that building codes regulate the minimum size of windows in living and sleeping areas. It’s a long way from the punitive taxes of earlier times.