Indoor Environmental Quality
By Rengie Chan and William Fisk
Indoor environmental quality (IEQ) can affect occupant comfort, health, and productivity, often with significant financial implications because the costs of salaries and health benefits far exceed the costs of energy, maintenance, and annualized construction costs or rent (Fisk et al., 2011; Figure 1). The key components of IEQ are indoor air quality (IAQ), thermal comfort, lighting, and acoustics. Some of the key strategies describe below that can improve IEQ also have the potential to save energy and support sustainability.
Figure 1. Estimates of the annual benefits and costs of selected strategies to improve IEQ in U.S. offices (Fisk et al., 2011). The combined net benefits from improved work performance, reduced sick building syndrome (SBS) symptoms, and avoided illness absence from a set of non-overlapping scenarios is approximately $20 billion annually.
Applications
Indoor Air Quality
Contaminant source control, such as use of low-emitting building materials, can substantially reduce indoor air contaminant concentrations without increasing energy or equipment costs. Source control is implemented by many large organizations and is an element of green building rating and certification systems. Working with various existing building material labeling systems, this movement is compelling material manufacturers and suppliers to make information more accessible (Figure 2). But source control goes beyond just building materials, furniture, and office equipment, equally important are the pollutant sources that are brought into buildings by occupants and their activities (e.g., use of green cleaning products by Adobe). Proper capture and venting of cooking fumes is also important in spaces with cooking.
Figure 2. Examples of some recent efforts to develop a common tool to share data on green materials and products.
Particle filtration, using more efficient filters than commonly employed, can be highly effective at reducing occupants' exposures to particles from outdoor air and emitted from indoor sources (Fisk, 2013). Using high efficiency air filters that have low pressure drop (e.g., filters with deep pleating; Figure 3) is an effective strategy that adds little additional cost relative to the projected value of health benefits. A study from Europe estimated that the annual operating cost of filtration using high efficiency air filters (MERV 13) is $2.6 per person (Beko et al., 2008). Efficient particle filtration is especially important where the outdoor air has a high concentration of particles due to regionally poor air quality (e.g., large cities in China) or local particle sources such as wood smoke (e.g. Pacific Northwest in winter time).
Figure 3. Calculated filter pressure drop of 90 filters with different efficiency ratings at a given flow rate (Zaatari et al., 2014). This data shows a wide variety of pressure drops owning to differences in filter design.
Ventilation control systems that deliver adequate ventilation to building occupants are important both to IAQ and energy use. Outdoor air economizers and nighttime pre-cooling with outdoor air, both are simple strategies to implement, will reduce indoor concentrations of contaminants emitted from indoor sources and also save energy. Higher ventilation rates above ASHRAE Standards 62.1 (2013) are associated with reductions in acute SBS (sick building syndrome) health symptoms and improvements in aspects of work performance (Fisk et al., 2011). On the other hand, a dedicated outdoor air system (DOAS) that is often used with radiant systems may result in lower ventilation by eliminating the outdoor air economizer. DOAS may also result in poorer IAQ because the particle filtration of recirculated indoor air is eliminated.
Dampness and mold problems that can result from water leaks and poor relative humidity control can have a large impacts of occupants' health. Some building designs or mechanical systems that increase ventilation rates (e.g., evaporative cooling systems) will require careful attention to dampness and mold control, because such systems can also be sources of microbial contaminants and increase indoor air humidity.
Lighting
People associate daylight in offices with better comfort and health (Galasiu and Veitch, 2006). The strong preference for daylight, in addition to the energy saving potential, is driving designs that increase daylight. But in daylit offices, sun glare, direct sun and heat gain, are concerns that need to be addressed. Advanced lighting controls must be responsive to the different lighting level preferences of people, and their different responses to glare. Design strategies to incorporate daylight need also to consider that the preference for daylight may be strongly tied to a preference for a view to the outdoors. See integrated building envelope, daylighting, and lighting for more throughout discussions of technologies and economics.
Thermal Comfort
Avoiding over-cooling in summer, which is very common, and overheating in winter can improve occupant thermal comfort and cut energy costs. At the same time, work performance will often be improved (Seppanen and Fisk, 2006). Avoiding elevated temperatures can also improve satisfaction with air quality and reduce sick building symptoms. Large thermal zones controlled by a single thermostat are one common source of poor thermal control. Ceiling fans can enhance thermal comfort in warm environments (de Dear et al., 2013) at low energy cost (Figure 4). There is potential for radiant systems to improve thermal comfort by allowing finer zonal control, where the local gains and losses (e.g., hot or cold interior surfaces because of glazing) can be more easily balanced by surface temperature control.
Figure 4. Project by Center for the Built Environment (CBE) to develop efficient prototypes of an integrated ceiling system that has ceiling fans, induction units, and nozzles. This work is conducted in collaboration with Armstrong World Industries (Arens and Brager, 2012).
Acoustics
A survey of 101 California buildings (including offices, public buildings, educational buildings, hospital, etc.) found the lowest satisfaction ratings for noise level (37% dissatisfied) and sound privacy (60% dissatisfied) (Moezzi et al., 2014), indicating that acoustic conditions are very important for occupant satisfaction. There are many complex relationships affecting privacy and acoustic quality (e.g., organizational culture, nature of work, management structure, and worker psychology) that should be considered when designing the office layout. For example, a study of fifteen LEED-certified office buildings found that among the three open-plan office types, occupants in bullpen configurations were more satisfied with acoustic quality than those in cubicles (Lee, 2010). This suggests that better understanding of occupant psychology (e.g., bullpen type offices allow workers to adjust work etiquettes in response to their neighboring coworkers) may be more important than having partitions.
Emerging technologies and strategies
Below are several examples of new technologies that have the potential to improve IEQ in innovative ways.
Sensor technologies: While lighting and occupancy sensors are already common in buildings, as well as thermostat and CO2 sensors used for HVAC (heating, ventilating, and air-conditioning) control, new technologies are emerging that take into account multiple indoor environmental attributes to enable more advanced control. Sensor technologies may become available that can manage multiple aspects of IEQ in 5 to 10 years. For example, personalized preferences can be better satisfied by integrating people-counting and recognition technologies into control systems. Smartphones allow more ways for users to control lighting levels and room temperature. Low cost indoor air quality sensors being developed have the potential to detect specific air pollutants of health concern and send signals to control systems (e.g., particles and specific volatile organic compounds). Ventilation control can also make use of outdoor air quality data in its control algorithm, and outdoor air intake velocity sensor to improve system performance.
Building materials as passive air cleaners: Building materials that can remove air pollutants are potential alternatives to conventional air cleaners that can be energy costly to operate. Studies in a laboratory setting show that activated carbon mat and and perlite-based ceiling tile can remove ozone in buildings without generating undesirable by-products (Cros et al., 2012). New wallboard and coating systems are being introduced that claim to remove formaldehyde from indoor air. Formaldehyde increases the risks of cancer and may increase allergy and asthma health outcomes. Long term performance data are needed. Commercial products with data to show their efficiencies may take 10 or more years to become available on the market.
Indoor microbial environments on health and productivity: Very little is known about the airborne microbial communities in built environments. Some of the factors that can affect their presences may include human occupancy, outdoor air, ventilation strategies, humidity, space cleaning, and other aspects of building design. Allergens and airborne infectious agents have clear and important health consequences to building occupants. Ventilation and filtration strategies that can reduce allergies, asthma symptoms, and disease transmission will have substantial health and productivity benefits. There are existing HVAC technologies that aim to provide antimicrobial protection (e.g., UV lights, antimicrobial coatings), but more research that focus on asthma and disease transmission reduction is needed.
Photobiology: The link between lighting and health and well-being goes beyond visibility. Insufficient or inappropriate light exposure can disrupt standard human rhythms, which may result in adverse consequences for performance, safety, and health (Bellia et al., 2011). Lighting designs that consider both the visual and non-visual effects on human physiology and behavior (e.g. circadian rhythms and metabolic activities that can in turn affect disease prevalence) may bring great benefits to building occupants. A shift from lumens to circadian efficiency as LED technologies become more common is likely to change future designs of lighting intensity, spectrum, and timing of exposure.
Thermal comfort controlled by occupants: Occupant's ability to control their environment is a strong determinant for occupant satisfaction. Technologies such as personal environmental control systems (PECS; Figure 5) has the potential of achieving high satisfaction at low energy costs. In mixed-mode buildings, buildings can perform well when the system is designed with high degrees of direct user control, such as operable windows (de Dear et al., 2013). The ways occupants interact with the building introduce new opportunities and challenges in maintaining comfort in thermal non-uniform and non-steady state environments. More reliance on personal environmental control and natural ventilation may be the trend in the next 5 to 10 years in effort to reduce HVAC energy use.
Figure 5. Personal environmental control systems (PECS) can provide comfort in naturally ventilated or radiantly cooled buildings, where the air temperature is less-controlled and likely to be slowly-responding relative to conventional HVAC systems (Arens and Brager, 2012).
Other Considerations
Beside good designs, IEQ also depends on good maintenance practices and the way occupants interact with the indoor spaces. The commissioning process can include IEQ to identify opportunities to make improvements. For campus-scale adoption, it is important to recognize good IEQ as part of the concept of "healthy buildings", that can also include issues affecting the well-being of employees and the larger community such as walkability, linkage between work and home environment, and environmental justice, are some extensions to the "healthy buildings" concept. Finally, the resilience of our built environment is becoming an increasing concern as we face climate change. Building designs may include features that can maintain IEQ during heat waves, power outages, and nearby wildfires, and can reduce risks of dampness and mold problems after severe storms and floods.
Institutional Requirements & Capacity
There are many aspects of IEQ that require a wide range of expertise from the design team, who needed to be educated on issues related to indoor air quality, lighting, thermal comfort, and acoustics. The design team will need inputs from the users (may include facilities, building managers, employees, and other stakeholders) so that their needs for IEQ are met. While simple IEQ checklists (e.g. LEED) are helpful, they are likely inadequate to ensure comfort, health, or productivity on their own. The Center for Built Environment (CBE) has an Occupant IEQ Satisfaction Survey that can be used to gather information for post-occupancy or post-retrofit evaluation (Figure 6). The effects of IEQ on health and productivity will require more specific tools to assess. Even though it is not the common practice, maintaining good IEQ will require long-term environmental monitoring as well as periodic evaluations from occupants. Thermal and visual comfort have been rigorously brought together in a Genentech case study building.
Figure 6. Example results of CBE's Occupant IEQ Satisfaction Survey (top) and performance evaluation tool to assess the effects of CO2 on decision making (bottom, Satish et al., 2012).
References
Arens, E. and G. Brager (2012) Improving Indoor Comfort While Using Less Energy. Center for the Built Environment, University of California Berkeley. http://uccs.ucdavis.edu/assets/event-assets/event-presentations/arens-brager-presentation
ASHRAE (2013) ANSI/ASHRAE Standard 62.1-2013 Ventilation for Acceptable Indoor Air Quality. American Society of Heating, Refrigerating, and Air Conditioning Engineers, Inc., Atlanta, GA.
Bellia, L., F. Bisegna, and G. Spada (2011) Lighting in indoor environments: visual and non-visual effects of light sources with different spectral power distributions. Building and Environment 46(10), 1984-1992.
Center for Built Environment, Occupant Indoor Environmental Quality (IEQ) Survey. http://www.cbe.berkeley.edu/research/survey.htm.
Cros, C.J., G.C. Morrison, J.A. Siegel, and R.L. Corsi (2012). Long-term performance of passive materials for removal of ozone from indoor air. Indoor Air 22(1), 43-53.
de Dear, R.J., T. Akimoto, E.A. Arens, G. Brager, C. Candido, K.W.D. Cheong, B. Li, N. Nishihara, S.C. Sekhar, S. Tanabe, J. Tanabe, J. Tofum, H. Zhang, and Y. Zhu (2013). Progress in thermal comfort research over the last twenty years. Indoor Air 23(6), 442-451.
Fisk, W.J. (2013) Health benefits of particle filtration. Indoor Air 23(5):357-368.
Fisk, W.J., D. Black, and G. Brunner (2011). Benefits and costs of improved IEQ in US offices. Indoor Air 21(5): 357-367.
Galasiu, A.D. and J.A. Veitch (2006). Occupant preferences and satisfaction with the luminous environment and control systems in daylit offices: a literature review. Energy and Buildings 38(7)728-742.
Lee, Y.S. (2010) Office layout affecting privacy, interaction, and acoustic quality in LEED-certified buildings. Building and Environment 45(7):1594-1600.
Moezzi, M., C. Hammer, J. Goins, and A. Meier (2014). Behavior strategies to reduce the gap between potential and actual savings in commercial buildings. Contract Number:09-327. Sacramento, California Air Resources Board.
Satish, U., M.J. Mendell, K. Shekhar, T. Hotchi, D. Sullivan, S. Streufert, and W.J. Fisk (2012). Is CO2 an indoor pollutant? Direct effects of low-to-moderate CO2 concentrations on human decision making performance. Environmental Health Perspectives 120(12):1671-1677.
Seppanen, O.A. and W.J. Fisk (2006) Some quantitative relations between indoor environmental quality and work performance or health. HVAC&R Research 12(4):957-973.
Zaatari, M., A. Novoselac, and J. Siegel (2014) The relationship between filter pressure drop, indoor air quality, and energy consumption in rooftop HVAC units. Building and Environment 73, 151-161.