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Forum discussion

NC-2009 EAp2:Minimum Energy Performance

Unmet Load Hours

Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

June 19, 2013

HVAC plans show the room setpoint. This should be the OPERATIVE temperature. However, most thermostats are sampling AIR TEMPERATURE, and that goes to say most conditioning equipment controls are based on AIR TEMPERATURE. I have a naturally ventilated facility where a user may open a window. The air temperature may fall below the thermostat setpoint of 20 degrees to say 18 deg, however the OPERATIVE temperature remains at around 22 because of my floor heating (floor is at about 25-30 deg C). Of course, no floor heating is going to heat the air up so fast. It's like I'm controlling operative temperature using air temperature and reporting unmet load hours per air temperature...perhaps I should report unmet load hours per OPERATIVE temperature. Your thoughts?

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Santiago Rodriguez

Revitaliza Consultores

LEEDuser Basic Member

47 thumbs up

Wed, 06/26/2013 - 16:35

I think that you would have to consider both temperatures, and make an average. Temperature differences inside the room can crate discomfort in the user, like in the case you mention.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Fri, 06/28/2013 - 17:35

You can set the temperature set points in the models at whatever you feel is most appropriate (within reason). The unmet load hours will adjust accordingly. The average Santiago suggests makes sense to us.

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