Hi
We are modelling an office building in Switzerland with LEED v4 Core and Shell and have a question regarding the required ventilation rate for parking garages. According to ASHRAE 62.1 Table 6.4, a minimum exhaust rate of 3.7 l/sm² is required. This would more than double the rate as required by our national standard SWKI VA 103-01. We would like to keep the rate prescribed by our national code, but maintain the credit for EQ Minimum Indoor Air Quality Performance and EA Minimum Energy Performance.
We would like to apply LI 10371 and LI 10247 and model garage demand controlled ventilation. This gives us the next points to consider:
- we should prove that our approach suffices with an Exceptional Calculation Measure (ECM)
- the proposed building is modeled as designed, taking into account requirements for sensors as in LI 10371
- Focus can be limited to contaminant CO
- a minimum of 0.05 cfm/sq ft (= 0.258 l/sm²) must be guaranteed
- LI 10371: CO must be limited according to values in ASHRAE 62.1 addendum d, but LI 10247 states: "all concentration limits must be based on local code or some other cognizant authority. If the contaminant is CO, a concentration limit of 35 ppm time-weighted average (8 hours) and levels not the exceed 50 ppm at any time is recommended."
We have some questions about the correct procedure, to assure compliance with LEED, and realize a sufficient air quality in the parking garage with energy-efficient systems.
Our national code maintains a limit for CO of 100 ppm, which is proven through a stationary CFD simulation. The number of cars, usage of the building, driving distance, start/stops etc are taken into account when determining the minimal ventilation rate. The exposure time is not mentioned and can also not be considered in our stationary simulation. As it is a parking garage, people will not linger here. In ASHRAE 62.1 Table B-2 gives the maximum exposure (WHO/Europe) of 90 ppm for 15 minutes. As mentioned before, in LI 10247, a much lower threshold is recommended (but not required?).
Would it suffice for EAp2, as ECM, if we can prove with a CFD simulation that our parking garage ventilation concept maintains a maximum CO level of 90 ppm? A narrative can explain how the sensors are placed, on which thresholds they will act, and what is taken into account in our national standard to determine flow rates?
For IEQp1, would it suffice that we can theoretically realize the 3.7 l/sm² with the smoke extraction fans? However, they are only activated in case of an emergency.
Thank you for your feedback!
Sarah
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
March 18, 2019 - 3:38 pm
EAp2 - the proposed simulation must be based on the 9 ppm value in ASHRAE 62.1-2010 addendum d
EQp1 - LI 10247 allows the use of the local code so this can be used. The ASHRAE value of 3.7 does not apply. In general you can't use smoke extraction fans since they are only used in an emergency.
Sarah Leenknegt
Dr.Lemon Consult AG
4 thumbs up
March 25, 2019 - 9:07 am
Hi Marcus
Thanks for your feedback.
EQp1 - following LI 10247, we maintain the required ventilation levels as prescribed in the local code (which ensures max. 100 ppm), and this suffices for the EQp1 credit: correct?
EAp1 - if we don't take credit for demand controlled ventilation in the parking garage, LI 10371 doesn't apply. We then model the parking garage ventilation identical in proposed and baseline building, with 3.7 l/sm² and an identical schedule: correct?
To me, the requirement of 9 ppm (over 8 hours) in a parking garage seems rather extreme, as there is no reason why anyone would be remain in the garage that long. If we would have to prove with a ECM, that we can ensure this low level, we would end up much higher than 3.7 l/sm², whereas the baseline model only has to adhere to ASHRAE 62.1-2010 Tabel 6.4 and would suffice with 3.7.
Best regards
Sarah
EAp2 - the 9 ppm value in
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
March 25, 2019 - 3:12 pm
EQp1 - correct
EAp1 - if you treat this identically it is just another process load. So the baseline is modeled identically to the proposed design.
Norbert Szircsak
Colliers International11 thumbs up
August 4, 2020 - 10:55 am
Sarah, Marcus,
Maybe I should post it at the IEQ credit but this is where I found this conversation.
I bumped into this issue too during the review at IEQp1.
I wonder if this demand controlled exception based on local code is acceptable for Option 1 too if everything else is according to ASHRAE?
Or in order to use this Interpretation you have to go for Option 2 and the CEN standard.
Thank oyu in advance.
Norbert
Tyler Thumma
7GroupLEEDuser Expert
60 thumbs up
August 21, 2020 - 11:38 am
The interpretation specifically says "this approach is acceptable for projects pursuing Option 2 (EN 15251 and EN 13779) of EQ Prerequisite Minimum Indoor Air Quality Performance" so I think you can only use Option 2.