Minimum IAQ performance monitoring requirement

We also use the same system for many projects. The LEED reviewers approve CO2 sensor inside the space, it must install at the breathing zone.

Dang, do you mean that with evaporative cooling you don't need to install any air flow monitor, only CO2 monitor to meet the monitoring requirement? Is this an exception as there is no mention of CO2 monitor for the mechanically ventilated spaces in terms of monitoring.

Yup, DEC system use exhaust fan to to supply fresh air, so based on LEED guideline, exhaust fan is defined natural ventilation and CO2 sensor combined with alarm devices is accepted.

Besides that, DEC system is also accepted as cooling system if your system demonstrate they can monitor and control to mantain system at temperature/humidity setpoints. 

Dang, for your DEC system do you also require MERV filtration for IAQ prequisite? 

Apologize for my mistake, because DEC system have two category: positive pressure (using supply fan) and negative pressure (using exhaust fan).
- In positive pressure, your supply fan must be install the monitor outdoor air intake flow.
- In negative pressure, exhaust fan is consider as natural ventilated, so you can install CO2 sensor at breath level.
MERV 11 or higher filtration is rerequisite in case your project locate in a non-attainment area for PM2.5 (in USA)
Beside that, to persure IEQ Enhaced Indoor air quality strategies - option 1 in DEC system is a big issue. 
You can only install filter at positve pressure case, Supply/Exhaust air flowrate is very big, the cost to maintain and replace is consider. 

I see, thanks a lot for the clarification.

Our system is negative pressure system (cooling pad/curtain) in Cambodia. Actually we don't try to achieve the enhanced credit, but just the prerequisite. According to ASHRAE 62.1 we need to have MERV6 filtration, is it even for negative pressure system also?

Your project is outside USA so you don't need install MERV 6 filtration.

Your system are using exhaust fans, so will you install MERV 6 on the water curtain? 

Hi Dang, oh really? Where can I find the requirement about outside the US?

Yes our fans are exhaust type. Seems we need to install up stream the cooling pad, unless as you mentioned it is not needed outside USA

In ASHRAE 62.1-2010, Section 4. And in online form, you must install MERV when your project is non--attainment.

4.1 Regional Air Quality. The status of compliance with national ambient air quality standards shall be determined for the geographic area of the building site. 

4.1.1 In  the  United  States,  compliance  status  shall  be either in “attainment” or “non-attainment” with the National Ambient  Air  Quality  Standards  (NAAQS). In  the  United States, areas with no EPA compliance status designation shall be considered “attainment” areas.
Note:    The  National  Ambient  Air  Quality  Standards (NAAQS) are shown in Informative Appendix I, Table I-1.