IAQ versus IEQ: What’s the difference?
Indoor air quality and indoor environmental quality are two terms that are easily confused because their acronyms are similar and concepts overlap
- Understand the concept of indoor air quality and indoor environmental quality through the ASHRAE standards.
- Know that how different ASHRAE standards overlap the IAQ and IEQ.
- Learn about the importance of IAQ and IEQ in other aspects of the green buildings and built environment.
Indoor air quality quantifies the minimum acceptable air quality that promotes the health and comfort of the human occupants. This includes the removal of harmful pollutants coming into the occupied space from outside or those being generated inside the space.
Indoor environmental quality, on the other hand, is a broader term that includes many factors such as air quality, lighting, acoustics and thermal conditions inside the building that affect the health and well-being of the occupants. A better IEQ rating increases the quality of life of the residents in the building.
Standards for IAQ and IEQ
More than 80% of people living in metropolitan areas are exposed to the air quality levels that exceed World Health Organization acceptable air quality limits. The so-called “sick building syndrome” of many traditional buildings reduces the productivity of the building occupants. Several studies and surveys draw a direct correlation between poor IEQ the number of the sick days taken by workers in the building.
Over time, ASHRAE has developed standards outlining various technical requirements to help designers create healthy and sustainable buildings. To fully appreciate IAQ and IEQ ratings, it is important to first understand ASHRAE 62.1: Ventilation for Acceptable Indoor Air Quality and ASHRAE 189.1: Standard for the Design of High-Performance Green Buildings.
- ASHRAE 62.1:This standard specifies ventilation rates, system design and operational instructions to maintain the acceptable air quality in a
- ASHRAE 189.1:This standard outlines the best practices to follow to provide the minimum requirements for planning, designing and constructing a building in which IEQ is enhanced.
Both of these standards apply to new construction and to the new systems within existing buildings. ASHRAE 189.1 is not a labelling guide such as a U.S. Green Building Council LEED designation, but acts as a design compliance measure for the International Green Construction Code and other model codes. These green codes provide the enforceable language to raise the baseline design requirements for a building project and establish the prerequisites for the green building rating systems such as LEED. IEQ is a very important category of credits in the LEED rating. Figure 1 captures the linkage of ASHRAE standards to one another and to the model codes.
Additionally, other ASHRAE standards such as ASHRAE 55: Thermal Environmental Conditions for Human Occupancy and ASHRAE 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings do converge with ASHRAE 62.1 to provide the acceptable IAQ and human thermal comfort while optimizing energy efficiency in the built environment.
ASHRAE 189.1: A closer look
ASHRAE 189.1 is not a code. Buildings consume lot of resources such as water and energy. As mentioned above, several labels and building rating systems are put in place to increase the resource use efficiency and reduce the adverse impact of the building on the environment. ASHRAE 189.1 is written in the mandatory code format so that it can be worked into several green building codes. Compliance with ASHRAE 189.1 is required to achieve energy labels and ratings.
Let us take a shallow dive into each section of ASHRAE 189.1 to get the broad understanding.
- Section 1 includes the goal and objective of the standard.
- Section 2 outlines the scope of the standard. This standard applies to the new building projects or to the new systems in the existing building. This standard does not apply to single-family houses or multifamily housing less than three stories. This section also affirms that this standard shall not be used to circumvent any health, safety or environmental requirements.
- Section 3 consists of the abbreviations, definitions and acronyms used throughout the standard. This section not only defines the keywords and common terms, but also provides the references to other technical literature.
- Section 4 covers the format of the standard. (Per this section, all buildings shall comply with sections 4 through 11.)
- Building projects shall comply with all mandatory provisions plus with the provisions in the prescriptive option to the performance option.
- Perspective option is concretely defined options with simple calculations.
- Performance options provide more design options to hit a performance target and may entail complex calculations and simulations.
Designers typically choose to meet the prescriptive options due to their simplicity and ease of achievability.
- Section 5 covers site Buildings often impact agricultural land, ecosystems and land erosion. Buildings can also contribute to the heat island effect and light pollution. Therefore, appropriate site selection is a key element.
- A building’s construction can only be allowed in existing building envelope, brownfield(land documented as contaminated) or grey field (land with high percentage of impervious surfaces)
- A building project may be allowed on a greenfield site if a long list of restrictions is met.
- It is mandatory to adopt provisions to reduce the heat island effect. If these provisions are not adopted, it decreases the building water and air quality and increases energy consumption.
ASHRAE 189.1 mandates designers to follow ASHRAE 90.1 for the reduction of the light pollution and comply with allowable backlight and glare ratings. For the further sustainability, ASHRAE 90.1 offers other prescriptive and performance-based options as well.
- Sections 6 and 7 talk about the water use efficiency and energy use efficiency, All the provisions given in the context of the water and energy management decreases the adverse effect of the building on the environment.
- Section 8 covers the IEQ in great detail. For the purpose of this article, this section is most important one. All the provisions in this section enable the occupants of the building to be more productive and healthier as compared to traditional buildings. This is why all the green building codes, standards and rating systems address IEQ.
- Mandatory IEQ requirements cover the acoustics, IAQ, daylighting, thermal comfort and soil gas intrusion.
- Prescriptive options include additional provisions for the daylighting and material use/selection.
- Performance options includes the acceptable levels for daylighting and material selection.
- Sections 9 sets the provisions for reduction of a building’s impact on the atmosphere and resources. Following these guidelines helps to increase the recycling of the waste produced by the building and reducing the impact on the earth and ozone layer (i.e., by selecting environmentally friendly refrigerants, performing the life cycle assessment of the building,).
To improve IAQ, designers must meet all requirements of section 4 through section 7 of ASHRAE 62.1. The International Mechanical Code only requires the minimum ventilation rates from section 6 of the ASHRAE 62.1. However, LEED and Energy Star ratings require full compliance with all sections of ASHRAE 62.1.
ASHRAE standard 189.1 goes above and beyond some areas of standard ASHRAE 62.1 such as requirements to monitor intake flow of the outside air for variable air volume systems, using MERV 8 filters upstream of the VAV coils and additional requirements for outside air cleaning.
Other environmental factors
Requirements for the ozone cleaning in nonattainment geographical locations is very important. According to the Environmental Protection Agency, if the air quality in a geographic area meets or is cleaner than the national standard, it is called an attainment area (designated “attainment/unclassifiable”); areas that don’t meet the national standard are called nonattainment areas. In some cases, EPA is not able to determine an area’s status after evaluating the available information and those areas are designated “unclassifiable.”
ASHRAE 62.1 only requires the ozone cleaning in certain geographical locations where ozone levels can be very high. ASHRAE 189.1 essentially increased the requirements for ozone cleaning in all major metropolitan areas. This can be considered a significant add-on from the equipment perspective as carbon filters to clean ozone tend to increase the footprint and cost of the heating, ventilation and air conditioning equipment (such as dedicated OA units and roof top air conditioning units).
To improve IEQ, smoking is not allowed inside buildings and walk-off mats should be used at every entrance to reduce the amount of moisture entering the building.
Thermal comfort is another essential element of the IEQ. ASHRAE 189.1 mandates buildings comply with ASHRAE 55. Over-cooling and -heating are two factors that directly cause thermal discomfort and increase the energy use of the space. Good comfort criteria depend upon the design conditions that at a minimum include temperature, air speed and relative humidity conditions.
For acoustics control, sound transmission should be reduced from both external and internal sources. Mechanical ventilation units can also limit incoming noise by fitting silencers into the ductwork.
Practices for daylighting and reduction of soil pollutants (i.e., radon gas) using the gas retarding systems also helps to achieve the optimal levels of the IEQ. Certain adhesives and sealants produce harmful emissions and should be removed from the dwelling spaces inside the building. Per the ASHRAE 189.1, acceptable emission levels of the materials shall be determined by CA/DHS/EHLB/R-174 and shall comply with the limit requirements for either office or classroom spaces regardless of the space type.
Volatile organic compounds content shall comply with and shall be determined according to SCAQMD Rule 1168 and Green Seal Standard GS-36. Figure 4 illustrates the various aspects of the IEQ as described in section 8 of ASHRAE 189.1.
Bringing it all together
All the above sections describe how an environmentally friendly building can be designed. In the terms of practicality, design, construction and operation go hand in hand for the best results.
The process for constructing the building and then operating it is elaborated in last section of ASHRAE 189.1 (section 10).
- Mandatory construction practices include soil erosion control, commissioning and IEQ management during construction.
- Mandatory operational requirements include the plans for operations and maintenance throughout the service life of the building.
- Buildings must be built as design. To ensure this outcome:
- Building acceptance testing should be done.
- Proper installation and startup must be completed.
- A master plan of operation for all design aspects such as power and water usage/metering should be developed.
Other steps and considerations during the construction process include:
- Development and implementation of the testing and balance plans are vital for maintaining the IAQ throughout the life cycle of the building.
- Plans to stop the moisture intrusion during the construction (i.e., protecting the materials) should be developed as moisture damage ruins IEQ.
- Plans for operation should include the requirements of the ASHRAE 62.1 (i.e., outdoor airflow verification procedures) and outdoor airflow measurement.
- A maintenance plan in accordance to ASHRAE Standard 180: Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems should be developed for mechanical, electrical and plumbing systems.
- A service life plan for different aspects of the building such as hardscape, structure and envelope must be prepared.
- Transportation (an often-neglected topic) should be documented via a plan that aims at the management of all the transportation activities (such as loading dock operation, carpool parking, etc.).
While section 8 of ASHRAE 189.1 directly addresses IEQ, the descriptions for other sections outlined above show an indirect link to this measurement. The relationship is visualized in Figure 4.
ASHRAE 62.1: A closer look
The ASHRAE 62.1 standard is not a code, but it is written in the mandatory language so that it can be adopted by different codes. Figure 5 breaks down ASHRAE 62.1 into different sections and references each to various model building codes such as the IMC and the Uniform Mechanical Code. These model codes in turn are accepted by various authorities having jurisdiction for implementation on mechanical systems.
- Sections 1, 2 and 3 cover the purpose, scope and definitions of the standard. Contaminants that adversely influence the IAQ should be considered while designing the building.
- Section 4 addresses the review and documentation of the outdoor air quality based on the regional and local air quality observations. Regional air quality varies by the geographical region of the building. National Ambient Air Quality Standards provides the long- and short-term exposure limits to the harmful pollutants. Acceptance criteria for the outdoor air conditions/quality should be met to ensure the good IAQ.
- Section 5 contains the general guidelines for the construction of the mechanical systems to ensure satisfactory IAQ can be achieved. Under these guidelines, systems and equipment ventilating the space can be constructed to limit the infiltration of the outdoor pollutants, growth of the contaminants inside the building and facilitate the elimination of unacceptable air out of the building. (Implementation of sections 4 and 5 provides the solid ground for finding the minimum ventilation rate for the space.)
- Section 6 of the ASHRAE 62.1 is most important section for a designer as it outlines the two procedures for establishing the minimum ventilation rate, which in turn ensures that adequate IAQ is maintained in the space. These procedures are ventilation rate procedure or IAQ procedure.
- The ventilation rate procedure is widely used primarily because it simplifies the calculations and the IMC adopts this method. By the help of the prescribed rates for each space type, a set of equations is used to determine the amount of the OA rates required for adequate ventilation.
- The IAQ procedure, on the other hand, is very complicated and uses a targeted approach for each containment type and concentration. ASHRAE 189.1 and LEED do not allow the ventilation rate calculation through this method and refers only to the ventilation rate procedure.
- Section 7 focuses on the construction, commissioning and startup of new buildings to ensure optimal For example, constructing ducts per Sheet Metal and Air Conditioning Contractors’ National Association standards and protecting the future occupied zones from gaseous contaminants during construction, balancing the ventilation systems in accordance with ASHRAE Standard 111: Testing, Adjusting and Balancing of Building HVAC Systems.
- Section 8 and 9 consists of the operations and maintenance practices that ensure satisfactory IAQ levels in the building and references, respectively.
The spirit of the sections 7 and 8 of ASHRAE 62.1 is same of the section 10 of ASHRAE 189.1 but ASHRAE 189.1 section 10 is overarching and much more inclusive.
Cueing into IAQ and IEQ
After reviewing both ASHRAE 189.1 and ASHRAE 62.1, we can better appreciate the complexity of green building design from an environmentally friendly practice point of view. We can also see how many different standards contribute to making the building design more efficient (see Figure 5).
IEQ plays a key role in the design of the high-performance green buildings. IAQ is a subset of IEQ but plays a huge part in promoting the quality indoor environment and building experience. The difference between IEQ and IAQ can be subtle, but understanding the overlap of both concepts is important to creating healthier and safer indoor environments.
The use of ASHRAE standards 62.1 and 189.1 can be enforced if the AHJ adopts them into the local codes. Even for the projects where the use of these standards is not mandatory through the AHJ, designing the building with compliance to these standards would ensure the acceptable level of IAQ and IEQ is always achieved. A well-designed building that is focused on enhancement of IAQ and IEQ is not only healthy for the planet, but is are also better for business. It increases the productivity and wellness of the occupants. Green building safeguards the human and environmental health and our collective future.