Diagonal stripes
LD+A The Magazine of the Illuminating Engineering Society of North America

Lamps & Fixtures in the Field  

Stairway to Savings



A t the Minneapolis Public Housing Authority’s redesigned senior high-rise apartment in Minneapolis, energy savings were achieved one step at a time. Davis & Associates, Eden Prairie, MN, outfitted all public spaces in the 210,000-sq ft building with LED luminaires from Lithonia Lighting. But perhaps the most unusual energy-saving measure was the addition of occupancy sensors to the egress lighting in the 25-story building’s stairwell.

Davis & Associates was tasked with the complete relighting of the public spaces after ceiling construction opened up the opportunity for extensive renovations. MPHA had additional funding for the lighting, so it decided to use the building as a test bed for LED technology. Davis & Associates replaced the 847 existing T8 fluorescent luminaires with 570 LED luminaires in 3,500K—58-W 2-ft by 2-ft LED fixtures and 41-W LED downlights—that reduced lighting loads by 38 percent.

The new luminaires also increased illuminance levels throughout the facility: light levels rose from 3 footcandles average in corridors to 8.6 fc avg. and from 62 fc avg. in the community room to 64 fc avg. “Light levels were our number one concern,” because of the senior population, says Shawn Meyer from Davis & Associates. “We held forums with the tenants, and initially there was some concern about the new lighting. But once the building was completed we put in a comment box and we had no additional feedback other than ‘We love it.’”

To get the tenants on board, Davis & Associates educated them about the lighting controls (Sensor Switch). Throughout the facility, occupancy sensors turn off lights in unoccupied areas that had previously been illuminated 24/7. Custom 5-W LED sconces were added to the corridors to increase the perception of brightness and ease tenants’ fears that corridors would be dark.

Convincing city officials that the occupancy sensors didn’t deter safety was another challenge. “Minneapolis building code did not allow occupancy sensors in emergency egress areas, and stairwell lighting needed to be seven times brighter to meet the new building codes,” explains John Plifka, MPHA manager of facilities and development.

Davis & Associates built redundancy into the control system, so that “each fixture is individually controlled,” notes Meyer. After mocking up the new egress lighting and petitioning the city, the team received a code variance to allow occupancy sensors in stairwell risers, which are now only on about 8 percent of the day. The sensors are estimated to reduce actual lighting energy use by 77 percent compared to the previous system.

November 2011

bottom shadow