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NC-2009 EAp2:Minimum Energy Performance

reference systems for a warehouse building

We are working on a warehouse project with small attached administration building. I have a question regarding reference systems for this project. The warehouse building has floor heating and exhaust fans (outdoor air is supplied naturally via loading gates; there's no cooling system). Administration building (which is smaller than 1900sqm) has a separate HVAC system (AHUs and VRF system). 1. According to table G3.1.1A the reference system for the warehouse (predominant condition) should be system 7. However there are no supply fans in the proposed case so I'm not sure if we should include them in the reference model? 2. Since the administration office is smaller than 1900sqm exception a) of section G3.1.1 doesn't apply. In that case since there are different occupancy and loads schedules than in the warehouse we assumed that exception b) should be implemented and system 4 should be modeled (electric heating in the administartion building), is that correct?

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Tue, 09/09/2014 - 14:09

To avoid some of the "rules" around heating only systems I would apply Addendum dn and model the warehouse as a system 9 or 10. Then apply exception b to the office.

Thu, 09/11/2014 - 10:43

Thank you Marcus. I checked Addendum dn and as you mentioned system 11 would be most appropriate for the warehouse. If I understood it well, this system should be modeled as packaged rooftop with warm air furnance? And I have one more question regarding fans in this reference system: 1. In the proposed case there are only exhaust fans (outdoor air is supplied naturally via loading gates). Should the fans in the reference be simulated identically as in the proposed case or should the energy usage of the reference fans be calculated based on ASHRAE guidelines (power of fans calculated based on pressure drop only for exhaust airflow control devices)?
Profile picture for user sheffer
Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Thu, 09/11/2014 - 14:52

The addendum mislabels the system numbers. If you look in 90.1-2010 they are labeled system 9 and 10. ASHRAE 90.1-2010 defines System Type 9 as a constant volume warm air furnace, gas fired, with no cooling. System Type 10 is defined as a constant volume warm air furnace, electric resistance. The Baseline efficiencies for these systems should be determined based on ASHRAE 90.1-2007 Table 6.8.1E. Baseline system air flow rates for System Types 9 and 10 shall be determined based on the temperature differential between 105 degrees F and the design space heating temperature setpoint, the minimum outdoor air flow rate, or the air flow rate required to meet applicable code or accreditation standards, whichever is greater. The fan power for System Type 9 or 10 should be 0.3 Watts per cfm of Baseline heating supply airflow. Should the system include a fan to provide non-mechanical cooling (i.e. increased fan air flow rates set to operate once indoor or outdoor temperature exceed a certain temperature, or direct or indirect evaporative cooling), the Baseline model should also include a separate fan to provide non-mechanical cooling, sized and controlled the same as the Proposed design. For non-mechanical cooling fans, the Baseline fan power should be modeled as 0.054 Watts per cfm of non-mechanical cooling airflow.

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