Hacker News Reader

Comment by mixmastamyk | Hacker News Reader

Indeed, also at every tech office I've worked at, late at night I'd see all the lights in the entire building on until 11pm on the chance the cleaning crew might still be emptying a wastebasket.

Not to mention the nightly vacuuming of entire floors. A waste of energy and time, that also made it really hard to get work done without noise cancelling equipment.

View on HN

Most of the Microsoft buildings I’ve worked in have lights automatically turn off at 8pm, with motion sensors to turn on again if needed.

In MN, “daylight harvesting” must be provided for fixtures within 15’ of a window, this can be automatically done by a photocell connected to a dimming relay, or manually with a dimmer switch. Offices with windows must also have controls, either photocell or manual-on/auto-off (vacancy sensor). Interior enclosed spaces are allowed to have standard single-pole switches, but these days we’re putting in occupancy sensor switches, the tenants prefer them.

Many or most of the installs have occupancy sensors for general lighting, or a time clock that shuts them off during non-business hours.

A 32w LED 2x4 is roughly equivalent to a 96w 3-lamp CFL 2x4, or 3x as efficient. You can power roughly 135-140 32w fixtures on a 277v 20A circuit [(277x20x.8)/32] which will illuminate ~11k sq ft. With 2 20A circuits, you can light up an entire office tower floor (floorplates are generally 18-23k sq ft). Assuming a ~10,000 watt load, and $0.08/kWH, it costs $0.80/hr to illuminate 20,000 square feet. It’s not as big of an energy waste these days, but it’s still a waste.

LED lights are incredibly efficient though. Large buildings are creepy if you turn off most of the lights.

The worst is just empty buildings waiting for a tenant that blaze lights 24/7

salt on the wound is when you see a new mixed use apartment with the vacant retail on the ground floor being a pit of coarse gravel before a tenant (and their custom floor) are found, but lit up like a target all the same.

Reply on news.ycombinator.com