IAQ By Design
PROVIDE OUTSIDE AIR
to dilute space and occupant generated contaminants
SELECT A CONTROL STRATAGY
that is stable and reduces energy consumption
MAINTAIN PRESSURE TO REDUCE MIGRATION
of moisture and contaminants across the building envelope
COMPLY WITH REQUIREMENTS
of the IMC, ASHRAE, local codes and standards
A healthy indoor environment
High-quality air requires that harmful contaminants be maintained below threshold levels. Diluting supply air with outside air is often the only way to reduce harmful contaminants to acceptable levels.
ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality, the International Mechanical Code (IMC) and many local codes specify dilution (outside) airflow rates for acceptable IAQ.
The ventilation rates prescribed are required to dilute both human bioeffluents and space borne contaminants. Dilution airflow rates also play a significant role in building pressurization and have a significant effect on envelope moisture and mold growth.
Failure to provide proper dilution airflow rates to occupants places owners and engineers at significant and unnecessary risk. Occupants exposed to poor indoor air have shown both an increase in health problems and a reduction in productivity.
A properly designed and operated building can be healthy, sustainable and energy efficient.
Reduce Contaminants and Provide Outside Air
Whether your building uses small unitary ventilators or large built-up systems, failure to assure that adequate outside air is provided by each air handler will result in a poor indoor air environment. Simply setting the outside air intake flow rates manually by setting dampers or fans cannot assure adequate dilution air is provided at the breathing zone.
External variations in wind and stack pressures, on all air handling systems, will result in widely fluctuating outside air intake flow rates. Mixed air plenum pressure variations on VAV systems intensifies the problem when the supply airflow rate changes from initial setup conditions.
Strategies that do not directly measure airflow rates cannot assure ventilation compliance and generally result in poor occupant satisfaction and health. Failure to provide proper dilution air increases both owner and designer liability.
A pressure differential across the building envelope can transport a significant quantity of moisture into interstitial wall cavities and results in mold and fungal growth. Such growth is becoming an increasing concern and is evidenced by insurance companies’ “mold exclusion” clauses in both commercial and residential policies.
Systems must be designed to control building pressure and have adequate capacity to remove moisture from properly supplied outside air.
Everyone is concerned about rising energy costs. However, energy accounts for less than 2% of the total operating cost of a building while employee wages account for more than 80%. The key is to balance energy and productivity.
Implement a system that will provide proper rates of outside air (no more, no less) and select a control strategy that minimizes fan energy to get the benefit of improved IAQ while minimizing energy consumption.
Comply with Codes
The IMC specifies outside air ventilation rates for compliance. It is based on the ridged interpretation of the Ventilation Rate Procedure of ASHRAE Standard 62.
ASHRAE Standard 62 defines acceptable IAQ as air in which “a substantial majority (80%) of the people exposed do not express dissatisfaction.” Failure to provide active control of outdoor air at each intake will result in a significant percentage of the occupants being dissatisfied with the building’s indoor air quality.
Provide airflow measurement with controls to assure that harmful contaminants are removed by maintaining proper dilution airflow rates of outside air to the breathing zone. The heart of the solution is the use of EBTRON thermal dispersion airflow measuring devices to directly measure outside, supply, return and critical zone airflow rates.
When properly implemented, your facilities will meet the requirements of ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality, and comply with local building codes. Your HVAC system can assure that both human bioeffluents and space generated contaminants are maintained below threshold levels required for acceptable human productivity and health.
The measurement and control of dilution airflow rates can meet the requirements of the Ventilation Rate Procedure of ASHRAE Standard 62, with little uncertainty or risk. Methods that indirectly determine outdoor airflow rates, such as CO2 demand controlled ventilation strategies that can only detect human bioeffluents, can not assure that minimum ventilation rates of outdoor air are provided.
Provide Outside Air
Regardless of the size of the air handler, install an EBTRON airflow measuring device at each outside air intake on your building. Use your B.A.S. to maintain the airflow setpoint by modulating control dampers and/or fans. Contact your EBTRON representative regarding product selection, placement and control strategy options for your specific application.
EBTRON technology is ideal for the measurement of low airflow rates associated with outdoor air intakes. Other technologies lack sensitivity at low airflow rates and require reduced intake free area (greater pressure drop, energy consumption and system modification) for proper application.
EBTRON has been successfully installing airflow measuring devices in outside air intakes since the late 1980’s. We are the leader in outside air measurement technology!
Building pressure is the result of a difference between the outside air and exhaust air mechanically forced into and out of a building. The objective is to maintain a building NET positive during periods of dehumidification (cooling) and NET neutral during periods of humidification (heating).
In some areas of the country, a 1,000 cfm negative pressurization flow can transport up to 1,000 gallons of water across the building envelope each year.
When the outdoor dew point is high, a positive pressurization flow will dry the building envelope and prevent air carried water transport, thus reducing mold.
The pressurization flow is most effectively controlled by maintaining airflow differentials within a pressure zone.
Unlike static pressure control, airflow control is stable; unaffected by changes in adjacent pressure zones or wind.
A proper control strategy is essential to optimize energy. When it comes to IAQ, control strategies using airflow measurement devices can result in significant savings.
Airflow measurement allows the sequencing of dampers and fans, thereby reducing pressure losses and fan energy. Dynamic reset of outside air intake setpoints can also be accomplished.
Comply with Codes
Existing code language does not dictate how a system must perform during operation.
By installing permanently mounted airflow measurement devices with active control, you can assure that the building meets ventilation requirements during operation and over time – something that codes don’t require, but you need, to assure a quality indoor environment.
“You wouldn’t attempt to you try to control temperature without permanently mounted thermostats, so, why would you try to control ventilation rates without permanently mounted airflow measuring devices?”
By monitoring and controlling airflow rates, you will have diluted many harmful contaminants from numerous sources that create an unhealthy indoor environment. The building envelope will be dryer and your mold growth potential will be reduced. Your IAQ risk will be minimized and your building can conform to local codes and/or comply with ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality.
As for the ultimate benefit, the occupants of your building will most likely show a decrease in health problems and an increase in productivity.
Installing airflow measurement devices directly at the outdoor air intake of each air handler can assure that the ventilation rates required to dilute contaminants are maintained every hour of every day.
In a joint 2000 report, Lawrence Berkley National Laboratory and the U.S. Department of Energy estimated that improving indoor air quality could yield up to $208 billion annually through decreased health care costs and improved productivity.
Since the annual cost per square foot for employees is typically 150-250 times the cost for indoor ventilation, even large percentage increases in annual ventilation costs are quite small compared to the employee benefits.
The occupant benefit alone is worth the investment on systems and equipment for improved IAQ!
LESS MOLD EXPOSURE
Mold and fungal growth will be minimized by controlling envelope and space moisture. Assuring proper building pressurization and providing sufficient equipment capacity to remove the moisture of the dilution air passing through the air handling systems are prerequisites to moisture management.
Liquid flow is by far the most dangerous source of moisture, about 100 times more potent than airflow, and 1000 times greater than diffusion. Gravity is a strong driving force for liquid water and air pressure differential can augment or retard water flow. Besides the physical augmentation of liquid water flow, the moisture contained in moving air as water can be properly managed through pressurization.
By providing the proper pressurization flow, the HVAC system essentially dries the building envelope in the summer and minimizes moisture accumulation in the winter.
LOWER ENERGY USE
Control of key airflow rates using airflow measurement devices permits the use of sequential control strategies that reduce pressure drops across control dampers, hence, reducing energy costs.
In addition, accurate measurement and control of flow rates result in conditioning only the amount of outside air actually required for occupant well-being and building pressure.
There is no better way to reduce your IAQ risk than to assure that your building meets ventilation codes and standards during operation.
By providing accurate airflow measurement devices and controls to maintain key airflow rates, you have the ability to document compliance and limit your liability. The bottom line benefit is “peace of mind”.