Prototipos desarrollados en centros de investigación

Occidental Chemical Center

case study

22

Occidental Chemical Center Corporate office building 360 Rainbow Boulevard Niagara Falls, New York USA

Cannon Design Architect

Professors John Yellott and Richard S Levine, Burt Hill Kosar Rittelman Associates Energy Consultant Hooker Chemicals and Plastic Corporation Client 1978–1981 Dates

43.00°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

ing provides up to 161,150ft²(14,971m²) of column-free office space around a central core for 500 Occidental employees. An additional 41,300ft²(3836m²) of commercial and office rental space was provided for sub-letting. A second skin was wrapped around the inner glazing, creating a perimeter cavity of 1500mm the full height of the building. This is broken only at the entrance point, where it draws people through the thick glazed skin into a double-height foyer space. The new office building provided a consolidated base for the company’s local administrative operations, accommodating approximately 500 staff.

Energy strategy

The double skin performs as an unconditioned thermal zone that changes the energy performance characteristics of the building from heating-load dominated to cooling-load dominated. It virtually eliminates infiltration and reduces the impact of extreme external temperatures. The cavity acts as a thermal buffer in winter (heat demand condition), allowing for lateral re-distribution of solar heated air. It can also be automatically opened in summer (cooling demand con-dition) to vent away convective warm air. Louvres within the void are adjustable for solar control, and can be closed at night to increase insulation. They pro-vide an effective balance between daylighting, solar shielding and thermal con-ditioning demands. It was estimated that the building would consume less than one-third of the energy required for a conventionally designed office building.

After the building footprint was established, three alternative design solutions were developed, each representing an incremental response to energy conservation objectives.

Site and climate

The 2.3-acre site overlooks the Niagara River Gorge and Falls. It is located in a cold and cloudy area, experiencing many of the secondary climatic effects from the colder northern areas of Canada.

Construction

The main structure is a steel frame encased in concrete on a 4586mm grid (15ft). Composite concrete floors are cast onto metal decking.

Glazing

The outer skin is a white aluminium curtain walling system with blue-green tint-ed insulating glass. It transmits up to 80% of visible light. The inner skin con-sists of clear single glazing. Louvres in the cavity void were selected

‘off-the-shelf’ (normally used as HVAC dampers for high velocity applications).

A mock-up that was made at Arizona State University determined the U-value of the double skin as 0.27Btu/°F ft²h, which equates to about 1.54W/m²K.

Heating

The building was originally designed to be heated by a 2 million Btu gas-fired boiler. A change of use whereby one floor was dedicated to a 24-hour central computer facility for the whole corporation led to a much higher cooling load than was originally anticipated. This led to the chillers being run all year round, and the waste heat being used during the heating season. Domestic hot water is preheated through a ‘shell and tube’ heat exchanger by heat rejected from the chiller condenser.

Double skin 1.54W/m²K

Slab 1.14W/m²K

21 December 24° 70° 21 June

The double skin serves to reduce the impact of severe outside temperatures by limiting the effect of infiltration on the conditioned interior to an insignificant level. In the winter, a degree of solar collection offsets subfreezing external con-ditions by acting as a thermal buffer to the internal conditioned environment.

Some convection will occur around the building, with warm air flowing from sun-nier sides to cooler, more shaded exposures. Under extreme conditions (sunny, very cold, windy), it has been shown that the temperature in the buffer space varies 5.5°C from bottom to top. Convection currents around the building hold the temperature differential between north and south to 8.3°C. At night when the building is unoccupied, it was intended that the cavity louvres would be closed up completely to retain conditioned air from daytime operation. In prac-tice the louvres are often not closed except during rare weekends when the computers are shut down and when the weather is very cold.

A heat wheel on the exhaust air extract achieves between 10% and 15% heat recovery for preconditioning ventilation air.

Cooling

Two electrically driven centrifugal chillers meet the predominant cooling load with heat recovery, which provides chilled water to the air handling units. These are supported by three cooling towers, with one dedicated to heat rejection from the computer space. When the building is in a net heat gain, heat is rejected through the closed circuit cooling towers. The system therefore acts as a

‘hydronic heat pump’.

The double skin reduces the impact of outside temperatures and in summer, the cavity can be vented at top and bottom to increase airflow, and reduce solar build-up.

Ventilation

The heating, ventilating and air conditioning needs are met by two low-pressure variable air volume (VAV) air handling units. Minimum ventilation air is pre-heated/precooled through an air-to-air heat exchanger from toilet room exhaust Intelligent skins

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air. The inner zone is served by VAV only, whereas the outer zone has fan-assist-ed VAV with heating coils.

Electricity generation

The building is located in an area that is well served by huge hydroelectric gen-erating plant on the adjacent Niagara River.

Daylighting

The design was driven by a desire for maximum transparency to preserve out-ward views of the Niagara Falls and to maximize internal daylighting. The white aerofoil louvres in the double skin cavity reflect daylight deep into the internal spaces. Even with the louvres in their fully shaded position, sufficient light will be refracted by the white louvre surfaces. More than 50% of the usable floor area benefits from daylighting.