Stairwell Lighting zone

I'd imagine this means that the stairwell on each floor (or group of floors) will be controlled separately. So for a 10 story building, if someone is going from the 7th to the 8th floor, only those ones get turned on, and not the entire 10 floor stairwell when the occupancy sensor is triggered. That's how I'd interpret it. If you only have a 2-story building, then you likely only have 1 zone anyway. 

Note that 30 min is the max, many set that number to anything between 5 and 15 min to conserve energy.

Words and phrases with definitions in 90.1 are in italics. It does not appear that this phrase is explicitly defined. I would interpret the control zone as the lighting circuit being controlled. So I think you could have the entire stairwell as one control zone.

I agree with Waleed in that it makes sense to separately control portions of the stairwell in a way that allows only the part of the stairwell in use to be illuminated. I don't see this as any sort of safety issue since anytime someone enters the stairwell the lights would go on.

@Agata, perhaps you should explain to the client that this is a “bi-level” control where lighting is never really off. Its “off” position is at 50% lighting output for safety reasons, and when triggered by an occupant it’s raised to 100% output. I’m not sure I see how controlling the entire stairwell will improve safety. 

Back to the other question, seems like there’s no clarity on the issue of controlled zone. I checked the 90.1 User Manual and they explained all the previous items in the section except this one. 
 

I would like to install this kind of lighting, where can I find more details about it?

@Richard, a simple web search should return many options. This short study explains what to expect from implementing them https://www.lrc.rpi.edu/programs/DELTA/pdf/DELTAMultiFamilyCorridors.pdf

I've been trapped in the current news cycle. ...Did I miss some awesome party? Did Nadav turn this into a chat room?

Boy, it sure would be nice if could get together and have a rockin' party around now, wouldn't it?

But that post that you're referring it is actually spam that slipped through our filters. I'm deleting it now--sorry for the inconvenience!

Bonjour à tous, Bonjour Waleed,

Pourriez-vous me dire si cette exigence de l’ASHRAE s’applique également aux cages d’escalier de sortie / cages d’escalier d’urgence? les cages d’escalier d’urgence doivent rester allumées tout le temps ON à 50 % de leur capacité d’éclairage?

Merci beaucoup

Hello everyone, Hello Waleed,

Could you tell me if this ASHRAE requirement also applies to egress stairwells/ emergency stairwells? emergency stairwells must stay on all the time ON at 50 % of them lighting capacity?

Thanks a lot

Yes it applies to all stairwells.

It says that the lighting must be reduced by at least 50% so that does not mean they must stay on all the time. You can turn them off when unoccupied as well according to this provision. 

Thank you very much Marcus, So if I put a presence detector/occupant sensor, is that enough? no need then to put a dimmable DALI lighting which in order to reduce the power to 50%? For our project of 45 floors, it seems to us that the dimmable lighting in the stairwells costs us a fortune, that's why we are looking for the most economical and easy way.

I will appreciate your return, 

Yes occupancy sensors for at least 50% of the light fixutres would be acceptable.