foster + partners tops out calgary's skyline with a bow

‘the bow’ by foster + partners, calgary, canadaimage © nigel young/ foster + partners

calgary has just welcomed the tallest addition to its skyline, ‘the bow’ office building by internationally-renowned practice foster + partners. the 237-meter high tower implements several design strategies to reduce the structure’s energy use and provide maximum comfort while integrating into the city’s existing infrastructure. the ground floor is connected to the public realm through an exterior plaza and the covered walkways that stretch throughout the urban grid. shops, restaurants and cafes offer a social public atmosphere for the community, with office spaces above serving various companies. the general form follows that of an arc segment in footprint which affords several structural advantages. the concave side faces south to accept natural sunlight and frames undisturbed views of the rocky mountains. the curtain wall has been offset from the floor planes opening up a series of atria and three six-storey sky gardens located at the 24th, 42nd, and 54th floors that create a thermal buffer as well as promote interdisciplinary collaboration, being the only access points to each office unit. the convex side stands to break through the prevailing winds, greatly reducing the amount of steel needed in the structure as the geometry itself helps to withstand the lateral force. an exposed triangulated mesh spans 6-storey bays and helps to visually break down the towering structure to a more sensible human scale.

in contextimage © nigel young/ foster + partners

nigel dancey, senior partner of  foster + partners states:

‘the tower’s form was shaped by the unique calgary climate – facing south, the building curves to define a series of spectacular light-filled six-storey atria, with mature sky gardens, cafes and meeting areas, which bring a vital social dimension to the office floors. this principle extends to the base of the tower, which is highly permeable, with a +15 enclosed bridge connection to downtown, an atrium of shops and cafes and a fantastic new plaza. every aspect, from the raised floors to the diagrid structure, is designed to be highly efficient. the bow is a bold new symbol for calgary, and is testament to the strength of our team and excellent local relationships.’

image © nigel young/ foster + partners

exposed triangular structural sections bring a new aesthetic to the cityimage © nigel young/ foster + partners

image © nigel young/ foster + partners

image © nigel young/ foster + partners

image © nigel young/ foster + partners

image © nigel young/ foster + partners

concave side faces the mountains and collects natural sunlightimage © nigel young/ foster + partners

facade detailimage © nigel young/ foster + partners

 (left) view up the reticulated structure(right) interior atriumimage © nigel young/ foster + partners

atrium roofimage © nigel young/ foster + partners

sectionimage © foster + partners

project info:

client: h+r real estate investment trustappointment: 2005construction start: 2007completion: 2013site area: 17,500m² / 188,300ft²area (gross external): 199,781m² / 2,149,644ft²typical floor area (net): 3,584m² / 38,564ft²height: 236m / 774.3ftnumber of floors: 58structure: steel-braced moment frame with a diagridcapacity: 4000facilities: offices, public plaza, retail facilities,parking facilities: 1360 car spacesmaterials: 39,000 tonnes of steel was used, 900,000ft² of glass was usedsustainability: the building’s form deflects the prevailing winds, allowing for a lighter structure. the solar heat collected in the atrium is redistributed throughout the year by means of extraction during winter and heat exchange during summer, reducing the load on the mechanical systems. 3 x 6 storey-high “sky gardens” with natural vegetation at levels 24, 42 and 54.  large glazed areas reduce the need for artificial lighting. heat redistribution system. displacement ventilation via a raised floor.tenant: encana and cenovusdeveloper: matthews southwest developmentsarchitect: foster + partnersfoster + partners design team: norman foster, david nelson, spencer de grey, nigel dancey, james barnes,  julia vidal alvarez, laura alvey,tim bauerfeind, jakob beer, karin bergmann, mattias bertelmann, stephen best, federico bixio, marie christoffersen, vasco correia,kirsten davis, ulrich hamman, michelle johnson, arjun kaicker, sabine kellerhoff, chiu-ming benny lee, mathieu le sueur, shirley shee ying leung,alissa macinnes, carsten mundle, florian oelschlager, cristina perez, susanne reiher, diana schaffrannek, anja schuppan, carolin senfleben,robert smith, eva tzivankicollaborating architect: zeidler partnershipstructural engineer: yollescivil engineer: kellam bergmechanical engineers: cosentinimain contractor: ledcor constructionfire consultant: leber rubesvertical transport consultant: kjaacoustic consultant: ceramicost consultant: altus helierlighting consultant: claude engle lighting designlandscape consultant: carson mccullochplanning consultant: sturgess architectureenvironmental consultant: transolarwind engineer: rwditransportation engineer: da wattsignage consultant: cygnuscode consultants: leber-rubesart consultant: via partnershipartist: jaume plensacladding: brook van dalen