BORROWING AN OLD IDEA: LIGHT

In Victorian era homes, a "borrowed light"—
basically, a  normal window placed in an
interior wall—brought natural light
into landlocked rooms.

In the nineteenth century, before the coming of the gasolier and the incandescent lamp, natural light was a valuable commodity indeed. Victorian architects used great ingenuity to ensure that windowless interior spaces such as halls and service areas would be at least habitably lit. 

There were a number of ways to obtain natural light beside windows. Skylights and roof windows were used in many types of buildings, although they weren’t common in homes because of their expense and proclivity to leak.

Transoms were used to light hallways
and provide cross ventilation.

In Victorian factories, where good visibility was critical, ranks of north-facing clearstories were set in sawtooth roofs, or else monitors (narrow, glass-walled penthouses running along the roof ridges) were provided to admit light and air to work areas below. And in multistoried Victorian apartment and hotel buildings, central air shafts were used for both light and ventilation.  

In homes, however, the interior window or “borrowed light” was the most popular device for lighting deep interior areas. Some borrowed lights were simply standard windows installed in interior walls to transmit or “borrow” light from a bright room to one in which there were no windows—for example, between a kitchen and an interior pantry.  

Transom hardware
allowed the sash to be
opened without reaching.

Another form of borrowed light was the transom, an openable window installed above a doorway. Before the advent of electric light and mechanical ventilation, the transom served both to light and ventilate windowless interior spaces. Transoms were frequently installed above bedroom doors, where they could conveniently light an otherwise dark central hall while simultaneously providing cross ventilation in bedrooms. They were generally preferred over skylights, since they were less expensive and couldn’t leak.

Edison and the
incandescent lamp.

An even simpler and cheaper way to borrow light was to use French doors with opaque glass in bedrooms and baths. They allowed plenty of light into halls without compromising privacy.

In the late nineteenth century, multistory office buildings took the transom to its most extreme form: Many office partitions were built entirely of glass to allow light to penetrate into “landlocked’ interior spaces. Edison’s invention of the incandescent lamp in 1878 eventually reduced the need for  borrowed light. Nevertheless, natural light from openable windows remained more desirable—and less expensive—than artificial light.      

LED lighting: Efficient—but not
more efficient than natural light.

During the 1940s, however, the widespread introduction of the fluorescent lamp, which was three times more efficient Edison's incandescent bulb, made artificial light remarkably cheap. At the same time, the arrival of air conditioning eliminated the need for openable windows. This one-two punch made artificial lighting king for many decades. And although fluorescents had the greatest impact on commercial buildings, by the Sixties even home kitchens were awash in the glare of “luminous ceilings”.  
  

Borrowed lights: The idea is simple,
and the light is free.

Today's LED lighting technology is about twice as energy-efficient as the fluorescent lamps that preceded it, and about six times more efficient than incandescent bulbs—a phenomenal improvement, for sure. Yet it's important to recognize that, no matter how efficient artificial lighting becomes, it’s still cheaper, healthier, and better for the environment to use natural light whenever possible.  

All of the natural lighting devices that worked for the Victorians—skylights, roof windows, clearstories, monitors, and especially borrowed lights—are still excellent ways of bringing sunlight deep into interiors spaces. Try one of them at your house.  The idea is simple, and the light is free.