MarketPavement light
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Pavement light

Pavement lights (UK), vault lights (US), floor lights, or sidewalk prisms are flat-topped walk-on skylights, usually set into pavement (sidewalks) or floors to let sunlight into the space below. They often use anidolic lighting prisms to throw the light sideways under the building. They were developed in the 19th century, but declined in popularity with the advent of cheap electric lighting in the early 20th. Older cities and smaller centers around the world have, or once had, pavement lights. In the early 21st century, such lights are over a century old, although lights are being installed in some new construction.

Uses
Sidewalk prisms are a method of daylighting basements, and are able to serve as a sole source of illumination during the day. At night, lighting in the basements beneath produces a glowing sidewalk. Vault lights may be used to make subterranean space useful. They are more common in city centers, dense, high-rent areas where space is valuable. Historically, landlords took an interest in improving not only the floor area ratio, but the amount of space that was naturally lit, on the grounds that this was profitable. Occupiers valued daylight not only as a way of saving on artificial lighting costs, which were higher historically, but also as a way to let premises remain cooler in summer, and a way to save on ventilation costs, if using gas lighting rather than arc lamps or early incandescent lights. Pavement lights and related products were historically marketed as a way of saving on artificial lighting costs and making space more usable and pleasant. Modern studies of similar daylighting technology provide evidence for those claims. Vault lights also are used in floors under glass roofs, for example in Budapest's historic and New York's mostly-demolished old Pennsylvania Station . Vault lights also could be set into the basement floor, underneath other vault lights, creating a double-deck arrangement, which would light the subbasement. Manhole covers and coalhole covers with lighting elements were also made. Some steps have vault lights set into the vertical stair risers. == History ==
History
A basement that extends below a sidewalk or pavement is called an areaway, -reinforced concrete. Cutaway view.|Armoured glass in concrete Wrought iron, Peel-and-stick prism films recently have come on the market, with acrylic micro-prisms that internally reflect light somewhat like glass pendant prisms. Structure File:Lucidux daylighting.gif|alt=Diagram of prisms in a pavement bending light to hit a wall of glass prims lying directly under and in line with the basement wall, which bend the light further to the horizontal|Two-stage refraction system for basement lighting; prism wall below center, shop above left. Note I-beam and masonry wall. File:Prism salesroom.gif|alt=A brightly-lit room with the inside edge lined with carrell desks. The ceiling is made of pendant prisms, supported by a very unobtrusive frame (which is in turn supported at wide intervals by slender diagonal braces from the walls). The wall over the desks is made of prism tiles.|The same system used to light a salesroom inside a hollow sidewalk; prism wall is on the right File:Daylit basement 112 state st.jpg|alt=A black-and-white photo of an unfurnished basement, horizontally lit with diffuse light. It has a pale coffered ceiling, with thickish round pillars supporting the intersections of the beams. The lower half of both pillars and walls is covered with dark wood panelling. The bare floor is pale grey.|A basement daylit by sidewalk prisms (prisms out-of-shot to the left) In some cases, a second vertical curtain of prisms was installed under the building sill. These were analogous to the prism transoms used over above-ground windows and doors. The light could be bent in two stages and used to daylight the whole basement. The areaway under a sidewalk light usually has a masonry wall separating it from the soil under the street, although it may extend partly under the street. Support for the vault light frames varies. Steel cross-beams supported by columns are common in older buildings; metal decks are common in newer ones. == Current state and trends ==
Current state and trends
Manufacture, maintenance, and repair Some modern pavement lights are quite different from historic ones, While some cities have preservation measures for vault lights, others actively remove them and fill areaways. Damp areaways may corrode the steel load-bearing elements supporting the pavement roof. Moisture may come from leakage from above or from groundwater from below. • Astoria, Oregon, has a community program for restoring vault lights, funded by the Astoria Downtown Historic District Association. A volunteer plan to replace broken glass with squares of Lexan, topped with resin embedded with glass teardrops, was prevented by legislation. • Chicago, Illinois, has extremely extensive sidewalk vaults, but many of them do not have vault lights. There is no inventory of them. The city is filling in all vaults, as some are structurally unsound. • Dunedin, New Zealand has well-preserved Luxfer and Hayward Brothers vault lights. • London, England has many vault lights, many made by the Hayward Brothers. Historic preservation legislation encourages a market in new pavement lights. • New York City has large numbers of vault lights, mostly in the SoHo district. More than half of the subway stations originally had vault lights, but these had mostly been blocked off. Installing and restoring vault lights has become part of modern construction practices. It has no preservation project for its prisms, however, and fills those that break with concrete. See also Portland Underground. • Pretoria, South Africa has Hayward vault lights. • Sacramento, California has "hollow sidewalks", which originated when the city raised its street level to combat floods; some of these spaces are lit by vault lights. There are many stories told about these areas. Most of the lights have been removed. • Saskatoon, Saskatchewan has had sidewalk prisms. They have been used in music videos, and a Facebook group fought to save them. They were scheduled to be infilled in 2015. • Seattle, Washington raised its street level, by up to 22 feet in some places, in the aftermath of the Great Seattle Fire of 1889. Previously, the Pioneer Square area had flooded tidally. Seattle replaced some of its sidewalk vault lights in Pioneer Square with new pre-purpled ones in 2002. Seattle runs tourist trips through its underground. • Tijuana, Mexico has armoured unsolarized vault lights in the 1919 Casa de la Cultura. • Toronto, Ontario once had many vault lights, but the last known remaining example were in front of the shops at 2869 Dundas Street West (near Keele) until 2011. • Vancouver, British Columbia has an unofficial policy of requiring any applicants for development permits to fill in areaways, although some have been paved over or made sufficiently load-bearing to support a fire engine. Some of the remaining areaways have restaurants built into them. A walking map of the sidewalk prisms has been produced. There are ~130 remaining areaways, the records of which are not digitised, and no measures exist to promote their preservation. • Victoria, British Columbia has more than eleven thousand sidewalk prisms in seven locations (as of 2006), including an underground gallery running around an entire block outside the Yarrow Building. More than 670 of the prisms are missing or filled with concrete. Sidewalk prisms have been heritage-registered since 1990. Originally, there were hundreds of thousands of prisms. The city has some panels in storage for restoration, but is having difficulty finding a glass supplier. There are city plans to light the galleries below at night, creating glowing purple sidewalks in the downtown core. While they are protected, there is no funding for the preservation of sidewalk prisms. == Gallery ==
Gallery
File:Budapešť, Belváros, Váci út, Parisi udvar.JPG|alt=A rather Gothick 18th-century indoor mall, with high round-arched ceilings and ornate pendants from the roof.|The in Budapest, with pavement lights let into its polychrome tile floor to allow light from the glass dome skylights into the basement level (details) File:Toronto BCE Place at night.jpg|alt=A towering metal gridwork catenary arch forms a gallery over a shiny concrete concourse inset with glowing grids of glass. Beyond the arch, city lights of tall buildings are visible. A four-story historic stone building stands to the left; a plain modern building rises out of sight to the right.|The Brookfield Place in Toronto, Canada, at night File:Luik Gare Liège-Guillemins.jpg|alt=A close-up of a similar grid of glass squares, slightly blueish glass with a wavy lower surface, in full sunlight.|A similar floor by day at the Liège-Guillemins railway station in Belgium File:Michigan State Capitol Glass Bock Floor.jpg|alt=A cylindrical room with a glass floor surrounded by two higher stories of circular balconies with ornate bulbous balusters. The room is lit by incandescent lights.|The floor of the rotunda of the Michigan State Capitol has a wrought-iron frame shaped to give the illusion of a bowl shape from above (from below) File:Linares - Museo Arqueológico 7.jpg|In a glass-covered courtyard in the Museo Arqueológico de Linares File:GFRP Translucent deck panels.jpg|alt=Bridge at night with multicoloured LED lights lighting the bridge from below; each successive panel is lit in a different colour.|Translucent fiberglass deck of a bridge in Lleida, Spain, lit from below File:GLOBALGRID_translucent_decking01.jpg|alt=Pine decking with a panel of fiberglass showing a fine grid set in a mitered pine frame. The fiberglass is slightly blue-green, and sits squarely in front of the glass doors to the house.|Translucent fiberglass pavement light built into a balcony, allowing sunlight into the area under the deck File:Luxfer sidewalk.gif|alt=A bright grid of glass with deep cross beams and shallow along-sidewalk beams.|An area under a sidewalk, 1915, showing clear glass File:Multi-Prism_vault_lights_from_below.jpg|alt=View from below of small circular panes of translucent lavender glass, deeply set in a coffered grid. Each circle has three parallel pendant-prism ridges.|Purple-solarized vault lights from ca. 1880, Etna, California File:Chamberlin Hotel-5.jpg|Purpled and patched vault lights outside the historic Chamberlin Hotel in Portland, Oregon. Grouting has been used to re-seal cracked glass jewels. File:Pavement in Worcester Street, Wolverhampton - geograph.org.uk - 1670792.jpg|A pavement light set into the pavement outside a store (close-up) File:BurlingtonHousePavementWindow.jpg|A pavement light outside Burlington House in London, England File:Armored panels.jpg|Armoured vault lights installed in the sidewalk outside a store File:1886 diagram varied lenses.gif|Cross-section of a pavement light panel, showing alternating lenses and prisms File:Glass sidewalk pavement light, Geneva NY.jpg|alt=Square clear-glass pendant prisms.|Pavement lights in Geneva, New York (flash version). Large pendant right-angle prisms as in previous image. File:GLOBALGRID translucent decking10.jpg|Translucent fiberglass pavement light panel, close-up File:Sidewalk, R. Estudos - University of Coimbra - Coimbra, Portugal - DSC09050.jpg|In Portuguese pavement File:Ping Shan Tin Shui Wai Glass floor Terrace 2016.jpg|On a terrace File:Book Shelves (8712833696).jpg|In a library, glass above and below (close-up) == See also ==
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