Space occupancy logging drives cost savings in historic building
The Flood Building, a local San Francisco landmark, is a 12-story historic commercial building that was built shortly after the turn of the century and survived both the 1906 and 1989 earthquakes.
So it may come as a surprise that, thanks to an energy retrofit by local engineering firm Carbon Lighthouse, the Flood Building's 290,000 square feet are carbon neutral and have energy efficiency and operating costs comparable to modern efficiency-oriented buildings.
As part of a comprehensive refurbishment of the 350-tenant building, Carbon Lighthouse deployed HOBO occupancy and light metering data loggers to determine if energy and money could be saved in the building's restrooms. These battery-powered devices can be easily installed on ceilings, light fixtures and stairwells - wherever data is needed. The loggers have two integrated sensors that together continuously collect time-stamped data at user-defined intervals. They also feature a large LCD display that visually confirms logger operation, a signal strength indicator that ensures correct logger placement, a large memory capacity that allows for longer deployments with fewer site visits, and a USB 2.0 computer interface for full-speed data offload.
The existing lighting in the bathrooms was connected to occupancy sensors that were several years old. Carbon Lighthouse wanted to first verify that the existing sensors were working properly and then determine if the runtime of the lighting would justify replacing them with more efficient devices.
In today's market of constant innovation and new energy-efficient products, replacing all restroom lighting with more energy-efficient fixtures seems like a no-brainer. But, as Matt Ganser, Director of Engineering at Carbon Lighthouse, explains, "In a new construction, it makes sense to use the most energy efficient systems. But when retrofitting an older building, you have to take a different approach."
"Commercial buildings like this often have systems running 24/7, and these systems are often selected for an upgrade. By looking at occupancy first, we can make realistic control changes that save time and energy."
According to Ganser, it took less than an hour to install the palm-sized, battery-powered occupancy/lighting loggers and take on-site measurements, including ballast, number of bulbs, type, etc. The loggers were then used to collect data for three weeks.
The data was downloaded from the loggers using HOBOware® Pro software and imported into Carbon Lighthouse's proprietary application.
"It's easy to do," said Ganser. "We can go from raw data to decisions in minutes. The data showed that occupancy was mostly between nine in the morning and six or seven in the afternoon, significantly less than half of a 24-hour period. Of the three representative data sets, the first two clearly show a well-functioning integration of occupancy and lighting, while the third shows a case where the lights were simply on all the time.
According to the data, the existing occupancy sensors for lighting control worked successfully, with the exception of the one men's restroom. There was no need to spend money on replacing the lighting sensors throughout the building. The next step was to calculate whether it would make sense to upgrade the lighting based on the lighting runtime. This was not the case.
"Manufacturers always want to sell new products, and the energy suppliers' programs offer incentives for new devices instead of promoting more efficient control of existing systems," says Ganser. "Just because a new appliance is more energy efficient than the existing system, the cost of replacement doesn't necessarily justify the purchase, especially when you can increase efficiency with retrofit controls. You can always replace appliances and reduce output, but this doesn't always result in sufficient cost savings. You can get better value for money elsewhere."
"With occupancy loggers like HOBO, engineers can quantify how spaces are actually being used. By removing the need for guesswork, engineers can tailor solutions to meet specific operational or cost-saving criteria."