Hidden solution controls a glaring problem
Any long-term renovation project comes with issues, and the recent conversion of the West Block courtyard in Ottawa to the new home of the House of Commons for the next 10 years, is no exception. In this case, a hidden solution was found to one of the most glaring problems.
By Terry Coffey
To convert the exterior courtyard to an indoor space, architects AFGM designed a multilayer roof structure comprising a supporting steel structure, outer glazing, an access catwalk, and an inner laylight. This plan would create an impressive space, full of light.
Impressive but problematic.
As the proceedings of the House of Commons are televised, control of light through the roof structure is critical to prevent glare. Draper, a U.S.-based manufacturer of custom solar control solutions, was tasked to provide a way to maximize the diffuse daylight in the space without permitting direct sunlight to strike any part of the debating chamber at any time during the day.
Given the complex geometry of the roof and the need to block direct sunlight, it wasn’t possible to use an “off the shelf” solution. As a result, Draper worked closely with facade engineers, Front Inc.; climate engineers, Transsolar Inc; and skylight contractor, Seele; to develop a custom motorized louver system.
There were three big challenges to address:
• Motorized louvers rarely rotate more than 90°, but this project required a drive mechanism that could rotate the louvers through 180°, allowing them to track the sun continuously throughout the day.
• The louver system needed to cope with the irregular shaped skylight elements.
• The system needed to allow adjustment to run on a number of different slopes.
The final design comprises a drive bar with sections of rack mounted at each louver location. These racks engage toothed wheels mounted on the louver shafts. Consequently, as the actuator drives forward and back, the louvers are rotated.
The louvers slowly rotate 180° every day during daylight hours, then retract to their original position overnight. Adjusting the actuator stroke allows the amount of louver rotation to be increased or decreased as required.
Using 3-D printers, prototypes of components were produced to check their integration with the structure.
Due to the precision required, two mock-up systems were built and reviewed by the design team and modifications made to address issues that were highlighted. Noise measurements resulted in the original actuator being replaced by one which achieved significantly quieter operation.
The mock-up also allowed consideration of maintenance issues, including louver or actuator replacement and, in an emergency, the ability to close a bank of louvers if an actuator failed.
In addition to the prototyping and approval process, each segment of the louver system was completely built and tested in the factory before shipment to Ottawa.
In the end, the custom louver system, while critical to the successful operation of the debating chamber, is almost invisible both from the interior and the exterior because of its position in the middle of the multi-layer roof structure.
Terry Coffey, ISF is with Draper, Inc.; www.draperinc.com. Drawings and photos supplied by Draper, Inc., unless otherwise noted.