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Measuring IAQ Comfortability

Comfort Issues and Productivity

Comfortability of indoor air can directly affect concentration and productivity which impacts the cost of doing business. Comfort is a phenomenon that is both physical and psychological, and it varies greatly from person to person.

Common measurable characteristics of comfort includes the following:

  • Temperature
  • Humidity
  • Air velocity
  • Air Ventilation
  • Air Volume

 

  • How can the above characteristics affect our indoor comfort?
  • Why do we need to perform such measurements?
  • Are there any recommended ranges for indoor air to adhere to?

The following discussion address the above questions.

Temperature


Why Measure?  
Temperature is one of the basic IAQ measurements that has a direct impact on perceived comfort and, in turn, concentration and productivity.

What Standards? 
According to ASHRAE Standard 55, the recommended temperature ranges perceived as “comfortable” are 22.8 to 26.1°C in summer and 20 to 23.6°C in the winter.

How to Measure? 
Measurements should be taken periodically at many areas of the building to be sure that air is distributed evenly and temperatures are consistent.

Measuring Instruments: Q-Trak, IAQ-Calc, VelociCalc
 

Humidity


Why Measure?
Too little humidity in a space may create static build-up and people will sense that their skin feels dry. Too much humidity and people will think it feels “Sticky”. Apart from comfort level, humidity also impacts on the growth of biological contaminants such as growing of fungal which has an impact to our health.

What Standards?
According to ASHRAE Standard 55, indoor humidity levels should be maintained between 30% and 65% for optimum comfort.

How to Measure?
Humidity can be measured in several ways. Typically, references such as relative humidity, wet bulb, dry bulb, humidity ratio and absolute humidity are used. ASHRAE Standard 55 links temperature and humidity together to provide a measure of thermal comfort. The objective should set appropriate temperature and humidity levels so as to maximize occupant comfort while controlling energy consumption. The “comfort zone” shown on the graph is based on the subjective response people tested under a variety of conditions and their perception of what was or was not comfortable.

Measuring Instruments: Q-Trak, IAQ-Calc, VelociCalc
 

Velocity

Why Measure?
Air comfort also involves making sure that sufficient air is moving in a space. Too much air movement may be perceived as “chilly” and too little may create a sense of stuffiness.

What Standards?
According to ISO 7730, a suitable air movement is recommended to be 0.25m/s.

How to Measure?
Checking the velocity of air around supply diffuser, indoor space and occupant areas is a good indicator that air is being appropriately distributed or balance throughout the building and reaching all the space intended. Air velocity meters may be used to measure air velocity.

Measuring Instruments: VelociCalc
 

Volume
 


Why Measure?
It is important to calculate the amount of outdoor air being supplied into indoor environment. The exchange of air can have a large impact on indoor air quality as it may increase the amount of outdoor pollutants being introduced, or conversely, dilute and help remove contaminants generated indoor.

What Standards?
ASHRAE Standard 62 lists recommended outdoor air requirements expressed in terms of cubic feet per minute 9cfm) per person depending on the type of space and activity.

How to Measure?
Fresh air is usually transported into inbuilding’s via air ducts. In a nutshell, we need to obtained the average measured air velocity of the air in the air ducts via usage of Air Velocity Meters, and multiply it by the cross-sectional area of the duct to determine the volumetric flow rate. For details on measuring flows in air ducts, ASHRAE Standard 111 may be referred to for additional information.

Alternatively, an air capture hood such as the AccuBalance are capable of providing fast and accurate means of measuring volumetric airflow.

Measuring Instruments: VelociCalc, AccuBalance
 

Ventilation


Why Measure?
The introduction of outdoor air helps dilute unwanted pollutants and gets them out of the building faster.

What Standards?
ASHRAE Standard 62 presents recommendations pertaining to ventilation. It recommends a minimum volume per person over time, depending on the type of space and activity performed, expressed in cubic feet per minute per person. It recommends an indoor level not to exceed about 700 ppm above outdoor ambient air which is typically about 300 to 400 ppm.

How to Measure?
A good indicator of proper ventilation is the level of Carbon Dioxide present in a space. Carbon dioxide is a normal by-product of respiration. Elevated levels of carbon dioxide may indicate additional ventilation is required. Indoor Air Quality Monitors may be used to perform measurements of Carbon Dioxide.

Measuring Instruments: Q-Trak, IAQ Calc