ventilation only & LEED

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The warehouse section of our facility in El Salvador is to be ventilated only. The textile section of the same building will be cooled and humidity will be controlled. Other areas such as offices and cafeteria will be cooled. There is no heating load in El Salvador. I reviewed inquiry 5088 (copy below) which would suggest the warehouse should be modeled with air conditioning in both the base case and the proposed case even though no cooling will be provided. Our building is a little different than the building in inquiry 5088 in that it has no heating load. Therefore by the 90.1 standard, the standard does not apply (section 2.2) and it is an unconditioned space. We feel the ventilated section of our building should be rated based on energy savings of standard ventilation equipment versus the proposed high efficiency fans and louvers that we are providing for ventilation. We would like to proceed with the ventilated enclosures being included in the model without heating or cooling. Please advise.

Inquiry Number:

EAc1: Optimize Energy Performance

Posting date:

It is not acceptable to allow spaces to exceed the unmet load hour requirements of the ASHRAE 90.1-2004 Appendix G methodology. This is a similar situation to naturally ventilated spaces, which are required to include cooling systems to meet space loads in the proposed case even if the actual building will contain no cooling. Building owners may always choose to turn off HVAC systems, or not have them installed at all to conserve energy, but the ASHRAE modeling protocol assumes that cooling systems will be installed and run with sufficient capacity to meet space loads. The applicant may use a set-point of 80 degrees Fahrenheit for the maintenance bays, but cooling system capacity must be increased until the requirements of ASHRAE 90.1-2004 section G3.1.2.2 are met. The project may still receive credit for using an efficient cooling system as compared to the ASHRAE baseline cooling system.

Inquiry []

Our project is located in Las Vegas and consists of a combination of office spaces and maintenance bays for earth-moving equipment. The owner is a large agency that sells, rents and repairs such equipment; these repairs are done both inside and outside the building envelope. The maintenance bays are occupied by mechanics and will be conditioned with evaporative coolers and gas furnace heat, the system supplies 100% outside air. This cooling system provides conditioning of the spaces but is not able to meet all peak loads for a climate such as Las Vegas even when these spaces are modeled with higher setpoint at 80 degrees. In reality, if the maintenance bays go above the temperature setpoints, the mechanics will continue work in the warmer conditions or take a break. This is not difficult for maintenance bays, where some of the work will also done outdoors with no conditioning at all. The owner does not want to fully condition the maintenance bays with the intention of achieving high levels of energy efficiency. We propose the following modeling approach for EA Credit 1. -Baseline model will have a mechanical system based on Table G3.1.1A of Appendix G with 80 degree temperature setpoint for the maintenance bays. -Proposed Design model will have the system as designed in the building that provides partial conditioning with the same 80 degree temperature setpoint. We will not model additional compressor cooling for hours where the system is not able to meet loads. This approach will result in exceeding the difference in the unmet load hours beyond 50 as required by Appendix G. However, this is a conscious decision by the owner who wants to maximize energy efficiency by providing limited conditioning through evaporative cooling for the maintenance bays, and allow the temperatures to float higher during peak conditions. We feel that this approach appropriately captures the intent of the design, and gives credit to the energy efficiency measures being taken. It also provides a way for demonstrating the value of an energy efficient approach to the community in Las Vegas where compressor cooling is increasingly used, often indiscriminately; this is a desert climate and a different approach to comfort and conditioning is possible. Is this approach acceptable? If not, can you advise us on an alternative approach that addresses the desire of the owner to demonstrate high levels of energy efficiency for using such a system?

Christian Stalberg2's picture
Joined: 2011-09-30
Reputation: 0

Hi Christian,

A LEED reviewer brought up this issue for a heated/ventilated-only
garage space recently. Owner did not want a cooling system beyond
ventilation, and one was not designed. Ultimately, our reviewer cited
TG3.1.1.b / G3.1.10 directly, and I conceded to model baseline-esque
cooling systems in both models.

I'm not sure section 2.2 is a great defense as it states the standard
doesn't apply to *envelopes* without a heating/cooling system... not
ventilation systems (2.2.b.). A better defense is if your warehouse is
by 90.1 glossary terms an unconditioned space, by virtue of not meeting
any of the three conditioned space definitions. In that case, I think
you could flatly reject TG3.1.1.b as "not applicable" if it were brought
up. In our garage space above, this wasn't an option as it was
definitely a heated space (see glossary for underlined terms).

I'd agree modeling both models with ventilation only is the intuitive
thing to do in the context of a validation (LEED) model. The intent of
this language however, if I'm not mistaken, is to discourage/punish
design decisions to omit heating and/or cooling systems entirely to save
energy. Never mind that's actually a very effective strategy, under the
right circumstances and in moderation... I've got some contrarian
opinions in this department, so I'll keep my mouth shut =).


Nick-Caton's picture
Joined: 2011-09-30
Reputation: 605


For good or bad, I have ended up modeling many Warehouse Distribution
Centers, which in essence have a very small front office and a very large
warehouse that is only ventilated (by code). I have had to argue with LEED
reviewers this point, fortunately successfully. The warehouse area is by
definition "unconditioned space", just like Nick states. Though you still
have to model an HVAC system per ASHRAE, but spreading the setpoints
basically to outside air design conditions. The reviews I have had have
made it through this way. By doing this with the setpoints, you will not
have any unmet hours. But you are still providing the right amount of
ventilation air per 62.1 and the right power for all the fans. The office
is a totally different story, which you pretty much know the answer to.

I have had the comments go both way on the following. Since the Warehouse
is not conditioned I had one reviewer tell me to change the Baseline HVAC
system to packaged units due to the fact that the only conditioned space was
a tiny 10,000 sq.ft. space. Other reveiwers have left me keep my standard
ASHRAE System 8 baseline with the modifications mentioned above for the
warehouse area. (I usually utilize two air handlers: one for warehouse and
one for offices).

Jorge E. Torres Coto

Jorge Torres-Coto2's picture
Joined: 2011-10-02
Reputation: 0

Please note that 90.1-2010 has new baseline HVAC system
types for heated only storage which are heating and
ventilation units. It also contains an allowance for fan
power related to non-mechanical cooling fans.


Jason Glazer's picture
Joined: 2011-09-30
Reputation: 0

After almost seven weeks wait, we finally received a response from USGBC. I
post it below for the benefit of all:

Thank you for your technical customer service inquiry regarding LEED-NCv2.2.
Thank you for your technical customer service inquiry regarding LEED-NCv2.2.
Yes, as unconditioned space, these enclosures may be modeled without heating
or cooling. The inquiry further explains that energy savings are being
taken for these ventilated only areas based on the proposed high efficiency
fans and louvers provided. Note that in the unconditioned space, the
ventilation fans should be modeled identically in the Baseline and the
Proposed case, as process energy use. In the Baseline case, the fans may be
modeled with the minimum motor efficiency as required by ASHRAE 90.1-2004,
Table 10.8, and they should be modeled in the Proposed case with the motor
efficiency as designed. Also, note that the fan schedules should be modeled
identically in the Baseline and Proposed case. If the fans as designed are
controlled by air temperature; the Baseline fans should be modeled to
operate in the same manner.

If any further savings are anticipated by additional energy efficiency
measures for the ventilation fans, these should be modeled using the
Exceptional Calculation Methodology. A narrative should describe all
Baseline and Proposed case assumptions included for this measure, and the
calculation methodology used to determine the projected savings. The
narrative and energy savings should be reported separately from the other
efficiency measures in the template, Section 1.7. The Baseline case
description should verify that the efficiency measure is not standard
practice for a similar newly constructed facility by referencing a recently
published document, utility incentive program that incentivises the
equipment installed, or by documenting systems used to perform the same
function in other newly constructed facilities. Savings associated with the
Proposed case measure should also be justified with published or monitored

Christian Stalberg2's picture
Joined: 2011-09-30
Reputation: 0