Car Parking Ventilation Fans

7 posts / 0 new
Last post

Up here in the True North the CaGBC established that CO sensors are standard practice hence no credit for CO sensors in parking garages regardless of the local building code.

Christopher Jones, P.Eng.
Tel: 416.644.4226 ? Toll Free: 1.888.425.7255 x 527

Chris Jones
crollinjones's picture
Joined: 2013-12-12
Reputation: 0

Dear Modellers;

I am modelling a residential building with underground car park, the car
parking will be mechanically ventilated via variable speed fans using
ducted ventilation system to provide an air-change rate comply with ASHRAE
62.1-2007. Pollutant sensors (PS) are connected to BMS to control fans
speed at parking floors to achieve ventilation recommended by ASHRAE 62.1.

Pollutant sensors locations and numbers have been determined to ensure that
no part of the car park is located more than 25 meters from a sampling
point, monitoring locations selected are considered worst-case within the
car park area. And that each area which is serviced by a separate
ventilation system has a separate monitoring point. In addition, one
sampling point is provided at each of the entrances and exits of the car
park. The monitoring will take place within the breathing zone between 1
and 1.8m above the floor and more than 0.1 m from walls or air conditioning

Based on the occupancy schedule of the project, it is assumed that the
number of vehicles moving in the parking area will be minimal between 8:00
pm to 8:00 am, this means that the CO levels in this period will be less
than 50 ppm -given the large parking areas and small number of cars using
the garage during these hours- and based on the sequence of operation for
this system, the fan speed will be reduced at least 50% for 12 hour.

The sequence of operation of this system will be as the following:

a) Less than 25ppm, fan speed will be 1.5 ACH

b) At 25ppm, fan speed will be 3 ACH

c) Between 25ppm to 50 ppm, Fan speed will be 3 ACH to 6 ACH

d) At 50ppm, fan speed will be 6 ACH

Feedback CO sensors will reduce the fan speed by at least 50% for 12 hours
a day and hence the energy consumption will be reduced by at least 45% a

My questions are:

1) a) Does the above sounds as an exceptional calculation (For me it
is not standard practice and therefore can be done as an exceptional

b) b)f the answer is YES, can I assume the saving is 45%

I will appreciate your feedback


*Sherif Farag*

*Sustainability Consultant*

P.O. Box: 127842

Abu Dhabi, UAE

M: +971 55 199 0022 | E: sherif.sabr at | Skype ID: sherif.farag9

Sherif Farag's picture
Joined: 2012-12-25
Reputation: 0

Whoops, I obviously missed in your first line that you stated the building IS residential, in which case it is probably true that there will be 24/7 garage access. So you might just want to apply the ESMFHR Sim Guidelines methodology.

Nathan Miller, PE, LEED AP BD+C ? Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100

Nathan Miller's picture
Joined: 2011-09-30
Reputation: 200

I think you?ve presented a reasonable approach to an exceptional calculation, if you can establish it as reasonable that the fans would operate full-bore 24/7 otherwise. Does the garage have 24/7 access? If not, the reviewer might decide that it would be standard practice to have a time clock shut-down the fans during off-hours, and only allow credit for turning down the fans during hours of normal operation.

As a point of reference, for multifamily high-rise projects with parking garages, the Energy Star Multifamily High-Rise Simulation Guidelines- (Hey look everybody, they?ve just released the Jan 2015 version!), state :

For example, reduced fan runtime from installing CO sensors in residential associated garages may be modeled using 8.4 hr/day fan runtime in Proposed Design,
compared to 24 hr/day runtime in the Baseline Building Design. If Demand Control Ventilation is modeled in the Proposed Design, the baseline ventilation CFM must be
based on the lesser of the design ventilation flow rates required by the applicable code and the actual specified flow rate.

So for that kind of parking garage application it is reasonable to claim ~65% fan reduction.

I?ve had this exceptional calculation rejected on LEED projects where the CO control is required by local code, because the reviewer stated that it is thus standard practice, and not worthy of an exceptional calculation. I always found that unreasonable, as it punishes a project that happens to have a more strict local code, where as a similar building located elsewhere could receive the credit for the same measure.

Nathan Miller, PE, LEED AP BD+C ? Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100

Nathan Miller's picture
Joined: 2011-09-30
Reputation: 200


I?ve received credit for this energy conservation measure from LEED reviewers as an exceptional calc, but the schedule you apply to the fan needs to be well thought out.

I?ve taken 50% credit through 95% fan power savings credit depending on the operating schedule. For example, a 24 hour hospital has 3 peak usage periods per day during shift changes.

LEED reviewers will push back on this measure, and have required me to show 3 similar projects nearby that don?t have the technology installed built in the last 5 years.

Good luck on this.


Fred Betz PhD., LEED AP ?BD+C
Senior Sustainable
Design Consultant

5802 Research Park Blvd. | Madison, WI 53719

P: 608.236.1175 | F: 608.238.2614
fbetz at |

Fred Betz's picture
Joined: 2011-09-30
Reputation: 0

That ruling seems crazy to me. In cold climates, there is a heated make-up air system. If you are allowed to claim 75% fan energy savings, then if follows that you would be allowed to claim 75% heating savings. That can be huge in a large parkade.

I can?t imagine any building not using CO control in parking areas these days. The baseline case should include CO control IMHO.

Christopher Jones, P.Eng.
Tel: 416.644.4226 ? Toll Free: 1.888.425.7255 x 527

Chris Jones
crollinjones's picture
Joined: 2013-12-12
Reputation: 0

The best recent relevant interpretation I could find on is dated April 2, 2014 and pasted below.

LEED Interpretation ID#10371 made on 04/02/2014

Prerequisite/Credit: EAp2 - Minimum energy performance
Rating System Family: Building design + construction
Rating System Version: v3 - LEED 2009

Clarification is requested regarding whether garage demand control ventilation may be modeled for credit. Garage Ventilation is not addressed by ASHRAE 90.1 ? 2007, Appendix G, therefore if savings is claimed it must be modeled as an Exceptional Calculation Measure (ECM). Garage demand control ventilation is increasingly becoming standard practice in newly constructed buildings. In order to take credit for this measure as an ECM, it must be demonstrated that the proposed design goes beyond standard practice.

ECMs must be approved by the Rating Authority. As the Rating Authority for LEED projects, the GBCI will accept an ECM for garage demand control ventilation under the following circumstances:
1) Baseline case shall meet the requirements of ASHRAE 90.1-2010, Section Enclosed Parking Garage Ventilation. Baseline fan volume shall be based on the minimum required ASHRAE 62.1 parking ventilation rates of 0.75 cfm / square foot. Baseline system fan power shall be calculated at 0.3 watts per CFM.
2) Proposed case shall reflect the actual design. Evidence shall be provided documenting that demand control ventilation strategies are sufficient to automatically detect contaminant levels of concern in parking garages (Carbon Monoxide, Particulates, VOCs, etc. and NO2) and modulate airflow such that contaminant levels are maintained below specified contaminant concentration as identified in ASHRAE 62.1-2010 Addendum d. Evidence shall also be provided that contaminant sensors are placed in space in an appropriate manner for detection of contaminant in question and that the sensors be calibrated yearly.
3) If other activities occur in the garage area, the ventilation for these uses shall be in addition to garage vehicle ventilation.
4) Proposed case shall be modeled such that a minimum air flow of 0.05 cfm/square foot is maintained.
5) A narrative shall 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 LEED Form.
6) No more than a 75% fan energy savings shall be claimed for this measure.


Paul Riemer, PE, LEED AP BD+C

Paul Riemer's picture
Joined: 2011-09-30
Reputation: 0