Forum discussion
NC-2009 EAp2: Minimum Energy Performance
1) Assume the same scheduling is used in both design and baseline case, may I schedule lights to be off during occupied hours in a zone (both baseline and design models)?
2) Taking this a step further, can I model a control (in both baseline and designcase) that will mimick occupant behaviour to turn off lighting when a target lux level has been reached in the zone?
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
June 14, 2013 - 10:29 am
1) Schedule the lighting based on the expected occupancy pattern. If the lights in a certain area would normally be off then schedule it that way.
2) I assume you are talking about a control that responds to daylight. If so this is a viable control strategy and you can claim savings. So the "schedule" does not have to be identical if that is the only way you can model the savings (do an exceptional calculation). In many energy modeling software you can model such a control directly (keeping the schedules the same and avoiding the exceptional calculation).
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
June 14, 2013 - 1:33 pm
I am purposefully trying NOT to take "credit" for switching the lighting off, because I have no "automated" control. I would make use of the lighting level control functionality of energyplus to model user behaviour to switch the lights off when my near passive house zone is receiving many thousands of watts of direct solar radiation to avoid the useless extra light from the electric light and save some energy and avoid overheating this solar sensitive space.
Theoretically schedules are free to define as long as they are the same for the baseline, right? But is automated control used to model user behaviour (the same control in both baseline and design) allowed?
Take it a step further and apply the same logic to blinds that are user operated, or windows that are opened for natural ventilation.
I think you are getting my question...
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
June 14, 2013 - 3:17 pm
Always helpful to understand the motivation behind the questions!
Technically you are correct about the schedules and manual controls. Table G3.1 does indicate that the schedules must be typical and are subject to approval by the rating authority (GBCI). The reality is that schedules are typically not submitted or reviewed for LEED so no one would likely question it. Using automated control (a schedule) to simulate user behavior is technically not allowed but since you are keeping the schedules the same it would likely be acceptable.
One could certainly argue that you are modeling the building as accurately as you can. So if there is a conflict with the "rules" I tend to vote for the accuracy.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
June 14, 2013 - 3:30 pm
Thanks Marcus. I hate being an experimental rat, but in this particular case, I may need to.
A related question...if it turns out that my naturally ventilated building with radiant floor heating manages to get under 300 hours for the heating loads not met hours (assuming the cooling setpoint is set to some high setpoint so as to not turn on and I'm just concerned with heating load not met hours), it is more than likely that the unmet load hours from the baseline case is much less than that of my designcase model, simply because heating with air is much faster response time wise than radiant surface heating, i.e. the differential is very likely to exceed the required 50 hours.
May it be valid to decrease the heating sizing parameter of the baseline case to something less than 1.25, to increase the unmet load hours until they are within 50 of the designcase model?
I know this stuff is not exactly in the standard. Just like to hear your opinion.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
June 14, 2013 - 3:45 pm
You are allowed to do so based on G3.1.2.2. Make sure you have tried everything else first before reducing baseline capacities as this should be your last resort to get the unmet load hours in alignment. I reviewed a project recently where the capacities were reduced well under 100% and it calls into question the accuracy of the proposed design.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
June 14, 2013 - 4:08 pm
Awesome! Downward adjustment...who would have thought. Of course, your worries are the same as mine. Thanks for sharing your experience, Marcus. This means so much to the community of struggling young engineers.