Stewards of the iconic buildings and grounds of Capitol Hill since 1793.


TPainting depicting ceremony in which Pocahontas was baptized and given the name Rebecca
This painting depicts the ceremony in which Pocahontas, daughter of the...


A virtual Map of Capitol Hill from above
View a map of the U.S. Capitol and other buildings and grounds cared for by the...


Photo of Stephen T. Ayers, FAIA, LEED AP, Architect of the Capitol in front of the Capitol Building
On February 24, 2010, President Barack Obama nominated Mr. Ayers to serve as...


The Capitol Crypt, which now houses statuary and exhibitions, was once used as an informal storage space where bicycles were parked, seen here circa 1900.
The term “crypt” has long referred to a space beneath the main floor of a...

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Windows of Capitol Hill

The AOC is responsible for nearly 600,000 square feet of windows

Architect of the Capitol Stephen T. Ayers, FAIA, LEED AP, reflects on the almost 600,000 square feet of windows – of all different shapes, size and age – cared for by the AOC.

"Even at the United Nations, where legend has it that the building was designed so that there could be no corner offices, the expanse of glass in individual offices is said to be a dead giveaway as to rank. Five windows are excellent, one window not so great."
Enid Nemy

Recently I was honored to speak at the National Institute of Building Sciences (NIBS) Conference held here in Washington, D.C. On the day I made my presentation, they were hosting a symposium with the theme, “Fenestration: A World of Change.”

For those of you who are not architects or engineers (which I am sure is many of you), fenestration is the design and placement of the windows in a building. With more than 30 buildings in our care, the AOC is responsible for almost 600,000 square feet of windows.

Circular windows on the Senate side of the Capitol are hinged to let fresh air in.
Circular windows on the Senate side of the Capitol are hinged to let fresh air in.
Windows at the Library of Congress Thomas Jefferson Building
Busts are framed by round windows at the Thomas Jefferson Building.
National Statuary Hall contains a lantern to allow natural light to fill the room.
National Statuary Hall contains a lantern to allow natural light to fill the room.
Skylight at the Capitol Visitor Center
Skylights in the Capitol Visitor Center allow visitors a view of the Capitol Dome.

This includes skylights, floor-to-ceiling windows, and windows that are over 100 years old. We take great care of all of these windows for preservation reasons, as well as for sustainability reasons.

The Cannon House Office Building, completed in 1908, still has its original yellow pine windows, made from old-growth forests. This type of wood contains a high amount of resin, which resists rot and weathers better. When the building undergoes a top-to-bottom renewal in the future, the plan is to preserve as much as possible of the original windows, instead of replacing them.

Revitalizing older materials for continued use, such as with the Cannon Building windows, is also a sustainable practice. Instead of throwing out original materials that are still useful, we understand that energy (sometimes called embodied energy) was expended to create the windows and that we would actually use less energy to restore them than it would to completely replace the windows. And once the windows are replaced, they will probably have to be replaced every 25 to 30 years. It just makes sense then, to preserve the original windows.

We have many unique windows on Capitol Hill. For example, take this circular window (top right) from the Senate side of the Capitol Building, which is hinged in the middle to allow the staff in this office to get fresh air during the day.

At the Library of Congress Thomas Jefferson Building, the round windows on the building’s west front feature busts of nine famous men, including my favorite, Benjamin Franklin. They look incredible, especially at night when the windows are lit from inside the building.

My favorite room in the Capitol, however, is National Statuary Hall. Originally the chamber for the House of Representatives from 1807-1857, it contains a lantern that allows natural light into the space. It’s a brilliant example of how we can use natural light to improve the quality of our buildings.

Another great example of using natural light in buildings can be found at the Capitol Visitor Center, the ninth increment of growth in the Capitol’s 217-year history. Its design included two 30 by 70-foot skylights, located in the main visitor gathering area called Emancipation Hall, and four smaller skylights. All six skylights provide not only light, but also a sense of orientation and destination for visitors who come to see the Capitol.

The employees of the Architect of the Capitol take great pride in preserving the thousands of windows in our care. So the next time you are visiting Capitol Hill, I encourage you to pay special attention to our windows. You may see something unique that you haven’t seen anywhere else before.

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