HVAC Systems Affecting Perception

While attending the Philadelphia AIA Design on the Delaware conference, I stood in the meeting room pre-function space, a balcony overlooking the lobby. The first thing catching my attention was movement - not people, nor banners, but pendant light fixtures. It was disconcerting seeing fixtures acting as perpetual pendulums. Notice the position of the light fixture in comparison to the stair balustrade. The arc the fixture traveled was about three feet and the period was about 5 seconds.

Upon investigation, the HVAC system relied on side wall outlets to condition the lobby space. When standing on the stair adjacent to the fixture, the air movement was easily detectable on my skin. This suggests that the supply air velocity was 5 mph (440 fpm) or greater at a distance of about 15 feet from the air outlet.

Be careful selecting pendant light fixtures and coordinating the HVAC design. The surface area presented by the fixtures provides ample opportunity for supply air to set the fixtures in motion.