[Bldg-sim] GBCI approval of carbon monoxide control of garage fans?

[Paul Riemer]

Continuous low level exhaust can ensure your occupied space is positive and the garage is negative, especially under apartments that are not directly mechanically ventilated.

Can anyone show me a section of an ASHRAE or other code that prohibits the continuous ventilation of a garage?

I respect USGBC/GBCI's authority to make determinations for their ratings systems; such as method(s) of determining savings for CO control of garage fans.
However, they need to take ownership of those determinations and apply them consistently and transparently.

Paul Riemer



From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Erik Dyrr
Sent: Friday, November 13, 2009 5:05 PM
To: Nathan Miller
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] GBCI approval of carbon monoxide control of garage fans?

I don't know what section of 90.1 requires garage ventilation control either.  Nathen's assumption that CO controlled garage ventilation fans rarely run is correct.  We did a fair amount of M&V for a utility that rebated CO control retrofits.  Significant savings were achieved.  Most systems ran 24/7 and CO systems rarely operated.

I think if you clearly make the case for the baseline and take a conservative estimate of the proposed, it will get accepted.  I was preparing to submit a project in this manner when it went bankrupt and came to a halt!
On Thu, Nov 12, 2009 at 9:13 AM, Nathan Miller <nathanm at rushingco.com<mailto:nathanm at rushingco.com>> wrote:
I know this is a contentious issue on bldg-sim regarding whether this should be a allowable measure or not.

I can tell you that on a recent office building project (LEED-NC v2.2) we submitted for energy savings from garage CO sensors. The only comment we got from the reviewer was that "ASHRAE mandates some sort of timed control or CO control as part of the mandatory measures," so we couldn't compare against a 24/7 constant volume system. I wish they had quoted a specific section of 90.1 for clarity.

We switched the baseline system to be off for ~6 hours during the night (not in agreement with the IMC requirement for continuous air movement), and they accepted our energy savings.

Our proposed case simply had the fans on a VFD and we created a custom schedule, which we presented to the reviewer, to reflect that the fans typically were at their lowest setting, and only ramped up for peak commuting hours (small peaks for morning and lunch, big peak at end of the day when all the cold engines start up and really put out the CO).

It is unclear to me if you are modeling a residential garage, where there may genuinely be 24/7 use, if you get to compare to a 24/7 constant volume system.

Nathan Miller
Senior Energy Engineer/Mechanical Engineer
direct: 206.788.4577
fax: 206.285.7111

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>] On Behalf Of James Hansen
Sent: Thursday, November 12, 2009 8:09 AM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] GBCI approval of carbon monoxide control of garage fans?

Does anyone know if the GBCI reviewers are currently accepting ECMs based off of garage carbon monoxide sensors to index garage fans?  Or if this can actually be included in the model with appropriate explanation?

IMC requires constant ventilation for enclosed garages, but allows CO-based systems to activate the fans.  This equates to a substantial energy savings since most systems like this only operate a few hours in the morning, evening, and at lunch (other than the minimum 0.05 cfm / sq ft continuous ventilation required by the IMC).

If we explain the system, and explain our assumptions for the use schedules that dictate the proposed building fan schedules for the garage, is this acceptable?

Do they require any backup support/studies for exactly how often the CO levels will rise above acceptable limits, or is it sufficient to make a conservative assumption that the garage fans will operate from 7-9am, 11-1pm, and 4-6pm at full load?  In my engineering experience, CO-based systems rarely run, and the circulation fans throughout the garage (which approximate the continuous 0.05 cfm / sq ft requirements of the IMC CO-based systems) are what really prevent isolated CO buildup.

Thanks in advance,

GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA  22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com<http://www.ghtltd.com/>
________________________________
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