Daylight redirecting film (DRF) is a thin, flexible plastic film which can be applied to a window to refract or reflect incoming light upwards so that the deeper parts of the room are lit more evenly. It can be used as a substitute for opaque blinds.[2] It is a form of prism lighting.
Optimal daylighting of a room using prism lighting. The prism tile canopies mounted outside over the windows send light skimming across the ceiling, so that workers deeper in the room also have natural light coming over their left shoulders. Multiple prescriptions of prism tiles are used, so some light is also sent horizontally and slightly downwards.[1]
The reflection-based daylight redirecting film, stuck to the inside of top part of the windows, is reflecting light sharply up onto the ceiling. This is a suboptimal use of prism lighting. While the ceiling does diffuse the reflected light, it still mostly lights the area nearest the window, where it is superfluous. However, glare is reduced without reducing the amount of daylight in a room.
The same film in a similar room, but at another sun angle. The light is reflected at a shallower angle, lighting the room more evenly.
The same light, redistributed by prism tiles in the window.
The human eye's response to light is non-linear: halving the light level does not halve the perceived brightness of a space, it makes it look only slightly dimmer.[3][4] If light is redistributed from the brightest parts of a room to the dimmest, the room therefore appears brighter overall, and more space can be given a useful and comfortable level of illumination (see before and after images from an 1899 article, left). This can reduce the need for artificial lighting.
Refraction and total internal reflection inside optical prisms can bend beams of light. This bending of the light allows it to be redistributed. The prism structure only bends light appropriately at certain angles; if the angle of incoming light changes, a variety of prisms or a movable prism awning may be needed.
While the films do save energy from lighting, the savings vary substantially by climate, aspect, electricity costs, and existing lighting type. At 2014 costs, including labour, payback time may be measured in decades.[5]
Window films are also used for cooling and heating energy saving, and to block UV.
Manufactureedit
Daylight redirecting film is made of acrylic[5] on a flexible polyester backing, one side coated with a pressure-sensitive adhesive (to make it peel-and-stick).[2]
There are two types of film. Some film is moulded with tiny triangular prisms, making a flexible peel-and-stick miniature prismatic panel. The prisms are joined at the edges into a sheet. A prism sheet is somewhat like a linear Fresnel lens, but each ridge may be identical. Unlike a Fresnel lens, the light is not intended to be focused but used for anidolic lighting.
Another film is moulded with thin near-horizontal voids protruding into or through the acrylic; the slits reflect light hitting their top surfaces upwards.[6][2] Refraction is minimized, to avoid colouring the light.[2]
The slit-based films are more transparent (both are translucent), but when the sun is high, they tend to send the light up at the ceiling, not deeper into the room. Prism-based films are translucent rather than transparent, but offer finer control over the direction of the outgoing light beam; the film can be made in a variety of prism shapes to refract light by a variety of angles. Prism-based films are a lighter modern version of glass prism tiles.
Daylight redirecting window film was initially made of one redirecting film and one glare-reducing diffusing film, often located on different interior surfaces of a double-glazed window,[2] but integrated single films are now available.[7]
^ Henry Crew, Ph.D.; Olin H. Basquin, A.M., eds. (1898), "Pocket Hand-book of Electro-glazed Luxfer Prisms containing useful information and tables relating to their use For Architects, Engineers and Builders.", Glassian
^ abcdePadiyath, Raghunath; 3M company, St Paul, Minnesota (2013), Daylight Redirecting Window Films, U.S.A. Department of Defense ESTCP Project number EW-201014, retrieved 2017-10-09{{citation}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
^ V. B. Bhatia (2001). Astronomy and astrophysics with elements of cosmology. CRC Press. p. 20. ISBN978-0-8493-1013-3.
^ abDaylight Redirecting Window Film, Energy Efficiency Emerging Technologies. E3tnw.org
^"SerraGlaze : Q&A" (PDF). Sweets.construction.com. Retrieved 13 February 2019.
^Object of the Moment: 3M Daylight Redirecting Film by 3M, by Selin Ashaboglu, March 02, 2017
November 28, 2023
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Daylight redirecting film DRF is a thin flexible plastic film which can be applied to a window to refract or reflect incoming light upwards so that the deeper parts of the room are lit more evenly It can be used as a substitute for opaque blinds 2 It is a form of prism lighting Optimal daylighting of a room using prism lighting The prism tile canopies mounted outside over the windows send light skimming across the ceiling so that workers deeper in the room also have natural light coming over their left shoulders Multiple prescriptions of prism tiles are used so some light is also sent horizontally and slightly downwards 1 The reflection based daylight redirecting film stuck to the inside of top part of the windows is reflecting light sharply up onto the ceiling This is a suboptimal use of prism lighting While the ceiling does diffuse the reflected light it still mostly lights the area nearest the window where it is superfluous However glare is reduced without reducing the amount of daylight in a room The same film in a similar room but at another sun angle The light is reflected at a shallower angle lighting the room more evenly Contents 1 Function 2 Manufacture 3 See also 4 ReferencesFunction edit nbsp Uneven light from a window nbsp The same light redistributed by prism tiles in the window The human eye s response to light is non linear halving the light level does not halve the perceived brightness of a space it makes it look only slightly dimmer 3 4 If light is redistributed from the brightest parts of a room to the dimmest the room therefore appears brighter overall and more space can be given a useful and comfortable level of illumination see before and after images from an 1899 article left This can reduce the need for artificial lighting Refraction and total internal reflection inside optical prisms can bend beams of light This bending of the light allows it to be redistributed The prism structure only bends light appropriately at certain angles if the angle of incoming light changes a variety of prisms or a movable prism awning may be needed While the films do save energy from lighting the savings vary substantially by climate aspect electricity costs and existing lighting type At 2014 costs including labour payback time may be measured in decades 5 Window films are also used for cooling and heating energy saving and to block UV Manufacture editDaylight redirecting film is made of acrylic 5 on a flexible polyester backing one side coated with a pressure sensitive adhesive to make it peel and stick 2 There are two types of film Some film is moulded with tiny triangular prisms making a flexible peel and stick miniature prismatic panel The prisms are joined at the edges into a sheet A prism sheet is somewhat like a linear Fresnel lens but each ridge may be identical Unlike a Fresnel lens the light is not intended to be focused but used for anidolic lighting Another film is moulded with thin near horizontal voids protruding into or through the acrylic the slits reflect light hitting their top surfaces upwards 6 2 Refraction is minimized to avoid colouring the light 2 The slit based films are more transparent both are translucent but when the sun is high they tend to send the light up at the ceiling not deeper into the room Prism based films are translucent rather than transparent but offer finer control over the direction of the outgoing light beam the film can be made in a variety of prism shapes to refract light by a variety of angles Prism based films are a lighter modern version of glass prism tiles Daylight redirecting window film was initially made of one redirecting film and one glare reducing diffusing film often located on different interior surfaces of a double glazed window 2 but integrated single films are now available 7 See also editPrism lighting Window filmReferences edit Henry Crew Ph D Olin H Basquin A M eds 1898 Pocket Hand book of Electro glazed Luxfer Prisms containing useful information and tables relating to their use For Architects Engineers and Builders Glassian a b c d e Padiyath Raghunath 3M company St Paul Minnesota 2013 Daylight Redirecting Window Films U S A Department of Defense ESTCP Project number EW 201014 retrieved 2017 10 09 a href Template Citation html title Template Citation citation a CS1 maint multiple names authors list link CS1 maint numeric names authors list link V B Bhatia 2001 Astronomy and astrophysics with elements of cosmology CRC Press p 20 ISBN 978 0 8493 1013 3 Jianhong Jackie Shen Yoon Mo Jung 2006 Weberized Mumford Shah model with Bose Einstein photon noise Appl Math Optim 53 3 331 358 CiteSeerX 10 1 1 129 1834 doi 10 1007 s00245 005 0850 1 S2CID 18794171 a b Daylight Redirecting Window Film Energy Efficiency Emerging Technologies E3tnw org SerraGlaze Q amp A PDF Sweets construction com Retrieved 13 February 2019 Object of the Moment 3M Daylight Redirecting Film by 3M by Selin Ashaboglu March 02 2017 Retrieved from https en wikipedia org w index php title Daylight redirecting film amp oldid 1178760013, wikipedia, wiki, book, books, library,
