Dear All,
Looking at the LEED submittal form for this credit I am really confused. Having assumed that this will be very easy with a constant volume system that works only with 100% outdoor air (no recirculation), I see now that the form requires entering Ev (system efficiency) values for each zone???
First of all, isn't this meaningless? 62.1 standard uses Ev values for systems that are multiple-zone and recirculating. What is the point in entering an Ev value for each zone?
Second, since I am forced to enter this value (otherwise the form does not calculate), what do you suggest I enter? My system is constant volume and rates that are 30% higher than 62.1 requirements are ducted to each zone without recirculation. Slightly less airflow rates are achieved for exhaust, again ducted from each zone and exhausted directly to the outisde without any recirculation.
Thanks for any replies,
Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
March 31, 2010 - 8:30 am
Omer,
With constant volume systems, Ev still needs to be determined from Table 6-3 in Standard 62.1. The value of Ev will be based on the highest Zp (breathing zone ventilation rate / design supply airflow) value of zones connected to the system. You are correct that with a 100% outside air system, Ev doesn't affect the final result.
Omer Moltay
Co-founderMimta EcoYapi
201 thumbs up
March 31, 2010 - 8:52 am
Yeah but when I follow the logic backwards, for Ev not to affect the final result it has to be equal to 1, meaning from Table 6.3 that max(Zp) has to be smaller than 0.15. How can this happen when I have a 100% outside air system?
Thanks,
Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
March 31, 2010 - 9:25 am
Omer, I understand the confusion here. Please refer to 6.2.4 (Equation 6-4) to calculate Vot (assume Ev = 1). You input your actual design OA in the LEED letter template and the template determines whether you're 30% over 62.1 requirements by comparing to the calculated Vot value. You may want to attach a brief narrative describing that you have 100% OA units. It looks like the template could use a check box for 100% OA conditions.
Omer Moltay
Co-founderMimta EcoYapi
201 thumbs up
April 2, 2010 - 6:51 am
Hi,
I think there's a catch here that I am seeing now. I did not tell you that my 100% outside air system works in parallel with fan coil units for zone conditioning. Looking at Appendix A, the calculations for Ev are necessary since there is secondary recirculation of outdoor air due to FCUs (not between zones but within zones). I did a quick calculation for one system and my Ev turned out to be 1.69.
Now I am trying to understand this. Does system ventilation efficiency really increase when there is secondary recirculation within zones?
Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
April 6, 2010 - 1:53 pm
Omer, for this type of system, Ev does not apply. The 100% outside air system simply needs to provide the appropriate breathing zone ventilation rate to each zone. Secondary recirculation applies more to fan-powered VAV box systems.
Omer Moltay
Co-founderMimta EcoYapi
201 thumbs up
April 6, 2010 - 2:23 pm
Thanks for the comment. But if Ev does not apply, what's the point in asking for this in LEED submittal? I mean even if you enter "1" for Ev, this has a meaning which could mislead.
Kate Randolph
Senior Sustainability ProfessionalKEMA
21 thumbs up
March 22, 2011 - 12:16 pm
Hello, we have an issue similar to Omer's and would like to hear Roger's advice.
For EQp1, we aren't sure what calculation methodology to use for our design approach. It is a multi-unit residential building, and the ventilation system is exhaust-only. Fans in the kitchens and bathrooms run continuously and exhaust directly to the outdoors, with no recirculation. These fans run in excess of the requirements per the Ventilation Rate Procedure. The review team has asked us to demonstrate specifically how sufficient outdoor air is provided to other living areas, such as the bedrooms and living rooms. Is there an established calculation methodology for this design approach under EQp1? We have reviewed ASHRAE 62.1, but haven't found an answer. Factors such as air distribution effectiveness don't seem to address exhaust-only systems. In summary: how should we calculate the air supplied to each living space (ie bedroom, living room) for an exhaust-only/ infiltration-only system? Thanks in advance.
Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
April 25, 2011 - 4:49 pm
Kate, this is a great question. You can use an exhaust-only system, but will need to adjust the ventilation effectiveness to account for "induced ventilation." Ez could be 0.8 if induced ventilation (under the main door to the unit, for example) is opposite from the exhaust point. It may be 0.5, if the induction point is near the exhaust point. You want to make sure that the corridors outside the units are provided with sufficient make-up air to maintain an appropriate air balance for the building as a whole. The user's manual provides additional guidance on multi-family residential applications.