Hi Markus,
Following our correspondence as of Jul/13/2017, we've modeled the garage ventilation claiming some energy savings.
We've provided explanation reflecting all details including all considerations related to CIR 10371.
The reviewer's reply however is stating (quoted):
"…parking garage spaces must include a minimum of 0.75 cfm/ft2 of ventilation/exhaust air flow… Provide documentation to verify that the minimum exhaust rates outlines in Table 6-4 are reflected for the parking garage spaces in the actual design"
CIR 10371 is stating that the Proposed case shall reflect the actual design….
Our impression is that the reviewer probably didn't allocate our explanation among the numerous attachments (the project is very big though).
Our explanation was like this (quoted):
"While modeling the Garage ventilation, the following considerations were taken, including those of CIR 10371.
1. Proposed case
1.1. Proposed case is reflecting the actual design, which is in accordance to the local norms
1.2. Proposed case is provided with control ventilation strategies, capable to automatically detect contamination levels of concern on parking garages - CO in this case. Below, an extract from the project documentation is illustrating these intentions.
1.3. The exact location of these CO sensors will be provided in the construction documentation and their proper functioning will be verified during the Commissioning procedure.
1.4. Proposed case is modeled such that a minimum air flow of 0.05 cfm/square foot is maintained.
1.5. Propose case is not claiming energy savings more than 75%.
2. Baseline case
2.1. The Baseline case fan volume is set to comply to the minimum required ASHRAE 62.1 parking ventilation rates of 0.75 cfm/square foot.
2.2. Baseline system fan power is calculated at 0.3 watts per cfm.
2.3. Baseline ventilation is arranged with DCV control and it operates upon schedule which is reflecting a typical behavior of such control.
3. Extracts from the project design concept related to Garage ventilation
……..
Car park ventilation systems
During the winter and transitional period within the daytime the system is working with heating coils, which is activated upon zone's temperature settings. During the summer time this coil is off.
The ventilation system is not functioning during the night, weekends and holidays.
Control of the degree of air pollution in the parking lot
In the compartments of the parking lot, the CO sensors monitor the degree of air pollution from the exhaust gases. When a pollution level of 20 mg / m3 is established in some compartment, any of the CO sensors in this compartment will send a signal to the BAS and the exhaust fan servicing the compartment (if it was turned off) is turned on. Disconnection of this exhaust fan is carried out with a decrease in CO concentration below 20 mg / m3.
………."
Could you please take a look and advice - is it something wrong there, should we do some rewording and to upload it within the reply.
Thanks a lot for your support.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
August 2, 2017 - 11:41 am
Is is very hard to say what the reviewer is looking for without seeing the whole comment. I don't know what was in Table 6-4, but that sentence alone indicates that they want to see additional documentation to confirm the minimum exhaust rates in the proposed design. I am not sure how that connects, or not, to the partial sentence before it.
What you submitted appears to be mostly correct. The one odd item is 2.3. I am not sure why you have DCV in the baseline?
Vassil Vassilev
ManagerTermoservice
13 thumbs up
August 3, 2017 - 4:11 am
Hi Marcus,
Thanks for your reply.
The whole comment of the reviewer (technical advice 2. to IEQp1) is:
"It is unclear if the parking garage spaces are ventilated in accordance with Table 6-4 of ASHRAE Standard 62.1-2007. Note that Table 6-4 requires that parking garage spaces must include a minimum of 0.75 cfm per square foot (3.8 L/s per square meter) of ventilation/exhaust airflow, unless two or more sides of the parking garage are comprised of walls that are 50% open to the outdoors. Provide documentation to verify that the minimum exhaust rates outlined in Table 6-4 are reflected for the parking garage spaces in the actual design."
In item 2.4 of our explanation a DCV was added because when filling-in the MEPCalculator, in the tab "Process Loads", in the section Garage Fan Power Calculation upon checking the condition "Credit is taken for garage fan power", in the Note 1. is written:
"The Baseline parking area must meet the requirements of ASHRAE 90.1-2010, Section 6.4.3.4.5 which establish mandatory Demand Controlled Ventilation (DCV)."
So, we've created a schedule most likely close to the Proposed ones, meaning that the system will not be activated during weekends and holidays (EFLH 1963).
Because of providing the needed data in this section, we didn't prepare an Exceptional Calculation Method, but just created all the explanation I've send you in the previous mail as an attachment named "Garage Fan Power" and in the section Special Circumstances of the EAp2 form we've noted about this issue and the associated with it attachment.
I agree that the Proposed garage air flow rate is much smaller than in the Baseline and this is the only reason why the Outdoor air flows are not equal between the Proposed and Baseline (which is another remark we have to address), but the Proposed is made in accordance to the local codes, besides there are separate Smoke exhaust ventilation specifically to the garage areas, which airflow rate is 5.6 L/s.m2.
We didn't simulated the whole smoke exhaust ventilations (it is a separate schedule) as these are an emergency only activated systems.
So, how should we approach by replying to the reviewer? Should we upload again our explanation integrated as a Reply to reviewer's comment (if some rewording needed, please advice) or should we insist the client for a complete redesign of the whole garage systems.
As I've mentioned before, probably the reviewer didn't noticed our explanation, because the project is a huge one (about 70 HVAC systems in the Proposed) with lots of attachments (which are required though) and the reviewer's reply came after 10 working days after the design review application.
Your advice will be highly appreciated.
Thanks.
Vassil Vassilev
ManagerTermoservice
13 thumbs up
August 8, 2017 - 4:48 am
Hi Markus,
Probably you didn't have a time to read the long reply I've send you (with the idea of providing you the needed info), but what actually I'd like to understand is:
For parking garage ventilation (Proposed), should we apply the requirement of a minimum air flow rate of 0.75 cfm/ft2 as a mandatory condition?
When we create the Baseline model - yes, but CIR 10371 states that Proposed case is reflecting the actual design, meaning that these air flows (Propose and Baseline) will very seldom be equal, which is facing another remark - the one for an equal OA flows, because all parking garages are 100% OA.
Your opinion is highly appreciated.
Thanks.
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
August 9, 2017 - 11:42 am
It sounds like you are dealing with comments in both IEQp1 and EAp2.
For IEQp1, the reviewer is asking you to verify that the requirement of 0.75 cfm/ft2 can be met by the design exhaust system (at peak capacity). DCV in parking garages is a very common strategy in LEED projects and is certainly acceptable for IEQp1. In responding to the IEQp1 comment you could demonstrate that the project complies with the 2009 International Mechanical Code Section 404, which requires that the exhaust system be capable of 0.75 cfm/ft2 but may operate as low as 0.05 cfm/ft2.
For EAp2 it sounds like the reviewer might be questioning a difference in OA flows reported in the Air-Side HVAC tab of the MEPC. Parking garage exhaust is not typically reported here but instead should be reported in the Process Loads tab to avoid confusion, then the OA flows in the Air-Side HVAC tab would be identical.
Vassil Vassilev
ManagerTermoservice
13 thumbs up
August 10, 2017 - 1:39 am
Thanks for the reply Tyler,
It clears a lot. The only reason that the garage ventilation was included in the MEPC was because it has some kind of heating - heating coils activated only when the space temperature falls below 5 deg C (41 F), so if reported as Process loads how the heating load should be reported.
One final question:
Since it is required that Baseline should have also DCV, should the DCV operating schedules be identical.
Thanks
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
August 10, 2017 - 2:27 pm
I would keep the exhaust fan inputs in the Process loads tab and report the heating system only (without the exhaust airflow) in the air-side HVAC tab.
The requirement for DCV indicated in the MEPC is only applicable to 90.1-2010, so that would not apply if this is a v3 project unless you are choosing to use 90.1-2010 with the adjusted point thresholds.
Vassil Vassilev
ManagerTermoservice
13 thumbs up
August 10, 2017 - 3:10 pm
Hi Tyler,
Thanks for your reply.
In case however of v3 project (which actually our case is) what could be the Baseline operating schedule – is it going to be like 100% Available when DCV is not mandatory for this version? It could make the airflow rate difference even bigger and how it could be accepted by reviewers?
Thanks
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
August 11, 2017 - 9:17 am
It looks like I was mistaken on my last reply. Since you are applying LI 10371, the Baseline is required to meet ASHRAE 90.1-2010 Section 6.4.3.4.5 which requires DCV even for v3 projects. However, this only requires the exhaust rates to be reduced by 50%, so the operating schedules may be different than the Proposed case (assuming the design DCV reduces the exhaust rates by more than 50%).
Vassil Vassilev
ManagerTermoservice
13 thumbs up
August 11, 2017 - 9:43 am
Thanks a lot.
Now everything is perfectly clear.
Appreciated very much.