Unoccupied hours temperature setpoints?

[John_187]

Hello,

I am wondering if there are any code requirements for unoccupied hours temperature setpoints for an office building for example? Anyone have any experience on this? Thanks for the help.

 

[GT-EGR]

Mechanical code usually has a small section in the upfront general chapter 3. NJ for example just says minimum for occupancy on design heating day is 68 deg.

You can infer and argue that comfort cooling and heating is geared towards the occupants - so when the building is unoccupied you can definitely let your setback temps rise. Typical commercial I would say is 80 cooling, 65 heating, sometimes pushing the boundary to 85 or 60 (but I'm sure you'll get a lot of different opinions). The main things you have to watch out for is you definitely have to make sure freezing conditions don't happen anywhere near any water rooms or pipes, and that your system could take an hour (or more, or less) if you don't have capacity built into your systems for warmup/cooldown by the time people get there - since in addition to fighting against very cold outside morning conditions, you also have the thermal capacity of an entire cold building fighting your heating system as well.

 

[IRstuff]

OSHA and ASHRAE typically only address occupied temperatures:

https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=interpretations&p_id=24602.

However, there are possibly things like mold and survivability of LCD displays that would impose lower limits on office buildings from getting too cold and/or damp.

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[LittleInch]

Code requirements - I doubt they exist.

Realistic customer expectations and issues,

I've seen anywhere from 5C, 10C or 16C depending on what's in the building and how long it sits there unoccupied.

Heat up times could be an issue like GT-EGR says and hence oversizing your heating equipment to cope.

Differential temperatures in different parts of a building are problematic for condensation and potential for mold etc.

so each location will be different.




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[ChasBean1]

John 187, if the government starts mandating what off-hours temperatures should be, please sign me up for a different government.

 

[John_187]

ChasBean1, yea I agree, but wasn't sure with all the bogus time wasting bullshit codes they already have.

Thanks everyone for the responses.

 

[chicopee]

In a case like the OP stated, a little common sense is better than codes. In an office building you may have different occupancies such as dining facilities, retail shops, security stations manned 24 hours a day, janitorial services,etc..., so the situation has to be thoroughly thought out.