Phoenix Central Library
case study
10
Phoenix Central Library Public library
Central Avenue Phoenix, Arizona United States of America Bruder/DWL Architects Architect
Ove Arup & Partners, LA Energy Consultant 1990–1995 Dates
33.57°N Latitude
0°N Primary axis of orientation
Intelligent features
Building management system ■
Learning facility Weather data Responsive lights
Sun tracking facility ■
Occupant override
Self-generation – CHP/PV/wind Night cooling
Solar water heating
small light slot, which also accommodates the vertical circulation. The atrium, labelled as the ‘crystal canyon’ by the architect, has the main entrance lobby at its base. To the east and west of the rectangular floorplates are narrow service zones that have outer walls curved in plan and which project beyond the plane of the north wall to help shade its glass face. These ‘saddlebags’ contain fixed services such as stairs, toilets and mechanical and electrical equipment. To the south, a fully glazed wall is equipped with a sophisticated array of computer con-trolled louvres that adjust according to the position of the sun. The north wall is further protected by vertical sails of teflon-coated acrylic fabric whose profiles have been calculated to offer shading in spring and autumn without obscuring the views of the mountains beyond.
Energy strategy
Despite the tough environmental conditions, characterized by a desert climate, light and heat have been kept under control and utilized both to make the inte-rior layout more dramatic and to enhance the building from a functional and environmental point of view. A complex system of computer-controlled louvres intercept and reflect the rays of the sun to limit the harmful glare and heating effects of the sun.
Site and climate
The new library is located in the centre of the city, alongside the intersection of Central Avenue and the east-west transit freeway. It fronts a park created by a submerged freeway that lies beneath a landscaped slab. The environmental con-ditions are very tough, characteristic of the arid desert climate which gives it the name ‘Valley of the Sun’.
The Arizona winters are mild, with daytime temperatures in the range of 15–21°C. Night temperatures drop dramatically with the clear sky to just above freezing. Summer temperatures can reach as high as 48°C in the day, and night temperatures remain in the range of 26–32°C. Humidity is low, generally in the 20% range, except for the monsoon season which occurs in August and Sep-tember, with humidity levels in the upper 50% range. Annual rainfall averages 200–230mm. The air generally contains a lot of dust particles due to the vast amounts of exposed soil, and limited natural vegetation in the region.
Construction
The east and west walls are clad with a perforated copper. The structural frame is made from precast reinforced concrete columns and beams and floor units.
A steel structure supports the ‘saddlebags’ on the east and west walls. An inno-vative ‘tensegrity’ structure supports the roof of the reading room.
Glazing
The glazed façade to the north is protected by fixed teflon sails, and electron-ically operated external louvres protect the south-facing glazing. Glazed rooflights provide natural lighting to the reading room on the top floor.
Heating
When heating is required, batteries in the ventilation system warm the humidi-fied and filtered air to comfortable temperatures. The loadbearing concrete flank Intelligent skins
walls (300mm) on the east and west sides of the library can act as a thermal flywheel, absorbing heat during the day, and emitting it during the colder nights.
Cooling
Cooling seems inevitable in the Phoenix climate, but also for the preservation of books and other library materials. A cooling coil in the air conditioning sys-tem ensures cooled air is delivered to the space. Chilled water is provided by compressors, pumps, and cooling towers. The central atrium originates at its base with a black-bottomed pool of water, which acts as a natural cooling feature as the warm air passes over the water. Surrounding the pool of water, aluminium benches absorb the cooler temperatures. The high altitude sun is prevented from entering the space by the opaque flank walls and the sophis-ticated shading systems on the north and south façades.
Ventilation
The library utilizes eight air handling units per floor, and two air handlers per zone, to provide adequate ventilation which is heated and cooled according to need. Tempered air is supplied through circular vents in a raised floor in the reading room. On the lower four floors of the library, air is supplied through grilles in the ceiling. Along the east-west perimeter walls perforated alumini-um panels conceal huge supply and return air ducts and other services, all feed-ing from the ‘saddlebags’. Services are distributed laterally suspended beneath the floor slabs with aluminium panels to conceal the ducts and cables and enclose the space around light fittings.
Daylighting
A small central atrium known as the ‘Crystal Canyon’ measuring 8.5m by 14.5m provides some daylight in the depth of the floorplates. Light is reflected down the void by nine computer-driven mirrored louvres set in stainless steel rotun-das, which reflect sunlight down into the space below.
The great public reading room at the top of the building incorporates circular rooflights above the tensegrity roof structure. The 2m diameter lights that sit above each column on the upper level are glazed with blue laminated glass in the middle of which is a 400mm diameter hole that is clear to admit zenithal beams of sunlight. A slot of rooflights against the sidewall stresses the hover-ing of the lightweight roof, and washes the concrete flank walls with light.
Artificial lighting
The library uses fluorescent lighting predominantly, while restricting incandes-cent illumination for special effects. Some areas of the lower floors need elec-tric light even in the summer.
Solar control
The glazed southern elevation is protected with automated solar tracking devices that minimize heat gain and glare. The computer-controlled louvres are intended to follow the angle of the sun, providing maximum solar protection and reducing the load on the mechanical cooling system. On the north wall, a system of 28 ‘shade sails’ cover the entire glazed surface, eliminating the harsh glare of the summer sun, while optimizing views out over the low rise city, and the mountains beyond.
The atrium skylights are protected by a second set of solid steel louvres, sus-Intelligent skins
Phoenix Central Library 101 Intelligent control
Daylight adjustment – reflection/protection ■ Glare control – blinds/louvres/fixed ■ ■ Responsive artificial lighting control
pended below the mirrored blades. These block the overhead midday sun from penetrating between the mirrored louvres.
Controls
The control system manages the control of the mirrored louvres above the
‘Crystal Canyon’ and the adjustable aluminium louvres on the southern elevation.
A row of six sensors mounted on the library’s roof measure sky conditions for brightness. Computers also track the sun’s position in the sky. These data are fed to computers that determine the optimum angle of the mirrored reflectors, and rotate the aluminium louvres during the course of the day to follow the path of the sunlight.
Performance
The library has received the maximum credit rebate offered by Arizona Public Service for energy efficiency in a commercial building, and an additional cred-it for use of sunlight for illumination.
Intelligent skins
102 Case studies
Credits
Architects: William P Bruder and DWL Architects & Planners (joint venture)
Acoustics, Structural and General Engineering: Ove Arup & Partners California
Building Systems: Bates/Valentino Associates Structural Engineer: Michael Ishler (tensegrity) Civil Engineering: Hook Engineering Landscape Architect: Martino & Tatasciore
Cost Consultants: Construction Consultants Southwest Project Manager: Carleton van Deman (DWL) General Contractor: Sundt Corp
Structural fabrics: FTL/Happold
Daylight regulation systems: Tait Solar Company
References
Archis, Architectur Stedebouw Beeldende Kunst (Architecture Urbanism and Visual Arts), 7.96 July, Netherlands Architecture Institute in association with Misset Publishers, Doetinchem Architectural Review, March 1996, Vol CXCIX, No 1189, pp 48 Architecture, April 1995, Vol 84, No 4
Architecture, August 1991, Vol 80, No 8 Architecture, October 1995, Vol 84, No 10 l’Architecture d’Aujourd Hui, 307, October 1996, p74
Architecture Interieure Cree, No 271, June/July 1996, pp 104–109 Blueprint, September 1995, No 120
GA Document, No 46, 1996
l’ARCA, The International Magazine of Architecture, Design and Visual Communication, April 1996, No 103
l’ARCA, The International Magazine of Architecture, Design and Visual Communication, September 1996, No 107
Progressive Architecture, February 1994, Vol 75, No 2
Web site: www.public.asu.edu/~bah24/c-index.htm – student case study of phoenix central library
Carleton van Deman, DWL Architects + Planners Inc Tim Christ/William P Bruder, William P Bruder Architect Ltd
Building data
Typical energy use for building type n/a
Annual CO2output n/a
Number of sensors n/a
Visited by authors ✗
Monitored by others ✗
Introduction
In 1992 Toftlund was declared a ‘Brundtland Town’ with the aim of realizing the recommendations made in the UN Commission’s Brundtland Report, Our Common Future. The town in southern Jutland is attempting to reduce ener-gy consumption by between 30% and 50%, thereby reducing environmental pollution caused by energy use. These were the levels of reductions that Brundt-land’s Report claimed would need to be applied across all industrialized countries in the next 30–50 years. The Brundtland Centre was designed as an exhibition, promotion and administrative centre for the Brundtland Town, and its strategies for energy reduction and care for the environment. It has become a centre for exhibition and educational activities in energy-related topics with dissemination papers, conferences and courses, and many forward-looking energy and environmental ideas and products. The building itself serves as a demonstration of energy-efficiency in buildings.
The intelligence factor
The daylight windows are fitted with reflective interpane blinds that are auto-matically tilted to maximize daylight penetration and reduce glare. The artificial lighting is automatically controlled in response to daylight levels. Ventilation fans in offices are activated only by movement sensors, which confirm occupation. The central atrium is used to pre-heat ventilation air, and can be naturally ventilated through openings in the roof. Photovoltaics on the atrium roof generate electricity.
Brief
The design was developed from the winning entry of an EC architectural ideas competition, ‘Working in the City’, won by KHR and Esbensen with ISLEF as