The Amsterdam Arena with the retractable roof opened and closed

A retractable roof is a kinetic architectural element used in many sports venues, in which a roof made of a suitable material can readily be mechanically deployed from some "retracted" or "open" position into a "closed" or "extended" position that completely covers the field of play and spectator areas. They are generally used in locales where inclement weather, extreme heat, or extreme cold are prevalent during the respective sports seasons, in order to allow for playing of traditionally outdoor sports in more favorable conditions, as well as the comfort of spectators watching games played in such weather. Unlike their predecessors, the domes built primarily during the 1960s and 1970s, retractable roofs also allow for playing of the same traditionally outdoor sports in outdoor conditions when the weather is more favorable.

Another purpose of retractable roofs is to allow for growth of natural grass playing fields in environments where extreme hot and/or cold temperatures would otherwise make installation and maintenance of such a field cost prohibitive. Not limited to stadiums, retractable roofs are also used in residences, commercial buildings, swim centers, and other places with overhead enclosures. Installations throughout the world employ a variety of different configurations and styles.

[edit] History

Olympic Stadium in Montreal, Quebec was slated to be the first retractable roof stadium at its debut for the 1976 Summer Olympic Games. However, plagued by construction problems, the roof was not installed until 1987, and was not retractable until 1988. Even then, movement of the roof was impossible in high wind conditions, and technical problems plagued the facility. A permanent roof was installed in 1988. By contrast, the Rogers Centre (formerly known as SkyDome) in Toronto, Ontario had a fully functional retractable roof at its debut in 1989.

[edit] Types of retractable roofs

Architecturally speaking, retractable roofs vary greatly from stadium to stadium in shape, material and movement. For example, Miller Park has a fan style roof, while Toyota Stadium in Japan has an accordion-like roof. Most retractable roofs are made of metal, while some, such as the roof of University of Phoenix Stadium, are made of water-resistant fabric. Although each retractable roof differs in these aspects, Safeco Field's roof is unique in that it is the only one in North America that does not form a climate-controlled enclosure when in the extended position; rather, it acts as an "umbrella" to cover the playing field and spectator areas during inclement weather.^{[citation needed]}

[edit] Gameplay with retractable roofs

In North American major sports leagues, specific rules exist governing the movement of retractable roofs before and during gameplay. These rules vary between the NFL and MLB, as well as from stadium to stadium. In general, if a game begins with the roof open and weather conditions become less favorable during gameplay, the home team may, with the approval of the field officials and visiting team, request the roof be closed. Depending on the stadium, weather or gameplay conditions, and the judgment of the officials, play may or may not continue until the roof is fully closed. If the game begins with the roof closed (or it is closed after the game begins), it must remain closed for the duration of the game.

[edit] External links

• CBC archives The architect explains the roof system for SkyDome (now Rogers Centre) in Toronto.
• CBC Archives A clip from 1975 where the stadium architect talks about his design for the Montreal Olympic Stadium.
• CBC Archives A look back on the history of the Montreal Olympic Stadium (1999).
• Guidelines for movement of a retractable roof (Toronto Blue Jays)