Hello,
I am currently modeling a building which is aiming to achieve EQ credit for increased ventilation. How should I model baseline minimum fresh air rates in this case? As in proposed (62.1-2010 + 30%), or the minimum OA rates by 62.1?
By reading G3.1.2.6 exception c: "If the minimum outdoor air intake flow in the proposed design is provided in excess of the amount required by the rating authority or building official, then the baseline building design shall be modeled to reflect the greater of that required by the rating authority or building official and will be less than the proposed design.”, it seems that the proposed is 62.1+30% and the baseline with the minimum required by code.
Does this exception applies when we are attempting EQ credit Enhanced IAQ strategies – increased ventilation? I ask this because by having different OA intake flows in proposed/baseline (according to exception c) in order to attempt the increased ventilation credit, the proposed design is being penalized at the whole-building energy simulation level, which in my opinion is contradictory.
Thank you all in advance.
Francesco Passerini
engineer90 thumbs up
November 5, 2018 - 12:59 pm
In my opinion it is not contradictory.
The OA increase can be seen from two points of view: it's positive for indoor air quality but it is negative as for the energy need.
Best Regards
David Eldridge
Energy Efficiency NinjaGrumman/Butkus Associates
68 thumbs up
November 5, 2018 - 2:13 pm
Agree with Francesco. 90.1 Appendix G although made for use in building rating systems doesn't assume that a project is pursuing LEED or any other rating system or any specific credits from that rating system, and I expect that the particular clause you cited was added after many industry members had discussion about this exact scenario, where some buildings would actually show INCREASED percentage savings over the baseline by having higher outside air quantity compared to the required values, more than required by code or jurisdiction.
So that said, USGBC / GBCI in this case as the rating system authority could provide guidance to manipulate Appendix G and not follow that clause - I don't believe they have done that in this case as the clause seems to be included specifically for the situation you describe and based on a lot of feedback provided under earlier versions of LEED and 90.1 that buildings were taking an unfair advantage of the energy code in the rating system by using higher airflow rates in the baseline.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5915 thumbs up
November 5, 2018 - 3:25 pm
You have it right in your modeling question and yes that exception applies.
Greenlab
Green Lab6 thumbs up
November 6, 2018 - 7:34 am
Yes, after reading more information, as well as your comments, I also have to agree with Francesco. Now it is just a question of weighting the impact of having 30%+ OA on the building rating, and discussing with design teams in order to take the decision of whether to attempt increased ventilation or not.
Thank you all for the replies.
Regards