See all forum discussions about NC-2009 IEQp1
 Subscribe to new posts about NC-2009 IEQp1 Post a new question aboutNC-2009 IEQp1
See LEEDuser’s guidance on NC-2009 IEQp1»
FAQs about IEQp1 :

Is outdoor air quality testing required in a space using natural ventilation?

For a space designed to be naturally ventilated, can operable windows or vents be used to satisfy the 62.1-2007 requirements?

What options are available to projects outside the US to meet this prerequisite?

Can LEED 2009 projects elect to follow ASHRAE 62.1-2010 for this prerequisite?

Which units should be included in the calculations for this prerequisite?

View answers »

Forum discussion

NC-2009 IEQp1:Minimum IAQ Performance

IEQp1:Heating mode

Hi, Our project is located in Asia with a tropical climate. When we submitted our calculations for IEQp1: Minimum Indoor Air Quality Performance; the assessor came back with the following comment: It appears that the calculations may not have been performed for the worst-case conditions. Generally, worst-case conditions are during heating mode;Provide revised Ventilation Rate Procedure calculations for zone air distribution effectiveness, Ez, of 0.8 (for an overhead distribution system in heating mode) and when the VAV system is at minimum flow. My question is why we need to do calculations during heating mode as we do not use heating during any part of the year.

0
Post a reply

You rely on LEEDuser. Can we rely on you?

LEEDuser is supported by our premium members, not by advertisers.

Go premium for $15.95  »

Fri, 10/17/2014 - 10:46

If your building does not have heating, then you just need to write a response to the reviewer that says your building does not have heating. An Ez value of 1.0 is appropriate if your system is only cooling. However, if you have VAV boxes that vary the flow rate to the space, then you still need to make sure you evaluate the system at minimum expected flow rate.

Mon, 10/20/2014 - 01:03

Hi Ilona, Thanks for the info. Where do we input the minimum expected flow rate in the IAQ spreadsheet? is it Ep (Primary air fraction of supply air at conditioned analyzed) ?

Mon, 10/20/2014 - 16:52

If you have basic VAV boxes that modulate airflow from the air handling unit, then you would enter the percent airflow next to DS "Percent of total design airflow rate at condition analyzed." Ep is only applicable for alternate systems such as induction units, where the supply air is a mix of recirculated air and primary air.

Tue, 10/21/2014 - 01:27

Hi Ilona, Thanks. Yes we do have VAV boxes and we had entered the percent airflow next to DS as 100%,since we are using VAV boxes & operated only by cooling mode. so i am not sure of what the assessor means as "when the VAV system is at minimum flow"? do i need to need to change the percentage?where do i get that value from?

Tue, 10/21/2014 - 12:43

Stella, If you have VAV boxes, the supply air to your zone will only be 100% when you are at peak cooling on the hottest and sunniest day of the year when your space is fully occupied. During other times, say early in the morning or while the sun is blocked by clouds, your space won't need as much cooling. At that point, your VAV boxes will modulate to reduce the airflow to the space. Since the airflow to your space is reduced, the outdoor air to your space will also be reduced. That's why the reviewer wants you to evaluate the system at worst-case conditions. You need to determine the minimum setting on your VAV boxes and use that for the value of Ds.

Tue, 10/21/2014 - 12:48

Just to add to what Ilona said, the spaces that are not critical zones should be reduced as well. The 62MZCalc takes into account the unused OA that is recirculated from spaces that receive more OA than necessary. When those zones are reduced, the OA requirement is increased for the system.

Thu, 10/30/2014 - 02:18

Thanks Ilona & Andrew for your clarifications. The VAV will be at the minimum setting when the occupancy load is less, as it is controlled by the CO2 sensors. So if we require to do calculations when the VAV is set at the minimal supply, then do I need to alter my occupancy load too? Appreciate your help!

Thu, 10/30/2014 - 12:34

The VAV setting in the calculation should be altered based on the airflow to the room changing due to temperature. In almost all VAV applications, the aiflow changes based on a demand for more or less cooling. In the case of a cold day (no cooling load), and an occupied room, it is likely that you will be at minimum airflow and maximum occupancy. Your calculation needs to represent your actual building use. If the above is not a true case then you need to write a narrative as to why it is not. In the past, I have had conference rooms on a middle floor in the center of the building (no envelope load) and have not decreased the supply flow since the cooling load is based on the occupants only.

Fri, 10/31/2014 - 02:29

So in order to compute the worst case scenario i understand that i need to change the value for Ds to reflect the minimum setting on the VAV box. Are there any other parameters that i need adjust in the 62MZCalc ? As i believe if i am going to change the Ds to a lower % the fresh air requirement will be more.Do i need to adjust the total design air supply too? Forgive me for my ignorance. Thanks.

Add new comment

To post a comment, you need to register for a LEEDuser Basic membership (free) or login to your existing profile.