Economics + Productivity

I. Indoor Air Quality

Over the past 20 years, building envelopes have become more airtight and energy efficient due to increasingly stringent building regulations (Allen 2016). While tighter envelopes reduce the number of air changes per hour due to infiltration of outside air, and therefore reduce energy consumption, low ventilation rates are associated with increased concentration of indoor pollutants that can be detrimental to productivity and wellness (Gerardi 2010).

Indoor air pollutants can be classified as gases, volatile organic compounds, particulate matter, infectious agents, and allergens and they come from building and occupant sources (Gerardi 2010). CO2 has been linked to decreased cognitive performance and increased rate of Sick Building Syndrome Symptoms (Allen 2016, Vehvilainen 2016, Apte 2000). CO2 is produced at a rate of 35,000 – 50,000 ppm per breath, which is 100 times higher than the concentration typical outdoor air (Prill 2013). Nitrogen dioxide is an indoor pollutant that is also produced by human activity and is typically generated by heating and cooking appliances. Nitrogen dioxide can cause serious damage to the respiratory tract and exacerbate asthma (Gerardi 2010). Volatile organic compounds (VOCs), are also known indoor irritants which often have unpleasant odors and have been linked to headaches, respiratory problems, and cancer (Fisk 2004). While VOCs are predominantly emitted by indoor furniture and building materials, use of cleaning products, perfumes, and even human metabolism can introduce VOCs inside buildings.

While higher ventilation rates improve health and productivity, increasing ventilation rates may impose energy costs and increase HVAC systems (Fisk 2017). This is particularly true if the HVAC system is a variable air volume system (Mumma 2003). Using a dedicated outdoor air system, however, can increase energy savings by 42% compared with a variable air volume system with an economizer (Mumma 2003). Natural ventilation and mix-mode ventilation provide direct access to outside air and can also be used to provide fresh air and thermal comfort at a low cost (Dean 2016).

Occupant Health
Bringing outdoor air into a building has the potential to significantly reduce the adverse effects of indoor air pollutants by reducing their concentration in indoor air (Gerardi 2010). While high ventilation rates above code minimums have been shown to improve air quality and health outcomes (Fisk 2017, Tarantini 2017), many buildings do not ventilate according to even ASHRAE standards (Mendell 2013, Allen 2016). Poor indoor air quality can lead to illness, causing medical expenses and absenteeism from work and school. The most common building related illnesses with a clear clinical diagnosis are respiratory infections and asthma (Gerardi 2010). Infections can stem from viral, bacterial, fungal, or animal protein sources. Sick Building Syndrome (SBS) is a common acute condition triggered by indoor pollutants with symptoms ranging from irritation of sinuses, dull headache, rash, and fatigue (Geardi 2010). SBS symptoms typically subside when exposure to indoor irritant ends. Increase in ventilation rates in office settings has shown to decrease SBS symptoms (Heerwagen 2000, Apte 2000, Shan 2016).

Asthma is an ailment associated with poor indoor air quality and disproportionally impacts low-income and racial minority children (Gauderman 2005). In a Center for Disease Control study, the economic burden of asthma was estimated to be more than $80 billion per year (Nurmagambetov 2018). A major factor in the development and exacerbation of asthma is exposure to indoor allergens and irritants, with as much at 40% of the excess asthma in minority children attributed to exposure to indoor allergens (Lanphear 2001). The Seattle Housing Authority, an entity that provides low income housing in Seattle, implemented the Breath Easy Program in 2003 in an effort to reduce asthma and other ailments associated with poor indoor air quality. Breathe Easy homes are new and renovated housing projects that improve indoor air quality through enhancing exterior envelope, replacing off-gassing indoor materials, and installing energy recovery ventilators with continuous fresh air supply (Takaro 2011). A study found that Breath Easy homes reduce asthma related clinical visits from 62% to 21% and nearly eliminated exposure to mold, rodents, and moisture (Takaro 2011).

Multiple studies have indicated that increasing ventilation rates with outdoor air reduces the spread of airborne infectious disease by diluting bacterial and viral load in indoor air (Sepannen 1999, Li 2006). Increasing classroom ventilation rates have also shown to decrease absenteeism in school and office settings. A study of 162 classrooms in California, increasing ventilation rates decreased illness related absence by 3.4% (Mendell 2013). These results echo other studies that increased ventilation rates greatly benefit occupant health and reduce sickness related absence in work and school settings (Mendell 2005, Wyon 2004, Wargocki 2000, Fisk 2017, Allen 2016). Another study found that doubling of ventilation rate in an office space from 25 to 50 cfm per person lead to a 35% decrease in short term absence (Milton 2000).

A LEED Gold certified office refurbishment for 150 employees that improved indoor air quality through enhanced outdoor air ventilation, continuous monitoring of CO2, and avoiding VOC emitting materials saw an annual savings of $85,000 per year due to a 44% reduction in absenteeism (WGBC 2018). An internal survey of employees at the company revealed the reduction in absenteeism largely due to a 64% reduction in reported allergy problems and 68% reduction in respiratory problems (WGBC 2018).

Productivity
Reducing indoor air contaminants has been shown to increase mental cognition and productivity in office (Clements-Croome 2008, Wyon 2004) and school (Fisk 2017) settings in several academic studies. A study by Seppanen et al. found that work performance increased at a rate of 0.8% with every 10 cfm/person increase in ventilation between 14 to 30 cfm/person, but the benefit of increased ventilation was not as great over 30 cfm/person (Seppanen 2006).

Another study by Allen et al. comparing cognitive performance of office workers in variously ventilated spaces similarly found that increased ventilation and lower CO2 concentrations improves indoor air quality and significantly improves productivity (Allen 2016). The study used a validated, computer-based cognitive test to assess office worker performance. Ventilation rate, CO2, and VOC were all found to impact performance on the test. CO2 concentration had a major impact on cognitive function scores. Average cognitive scores for seven out of nine cognitive domains decreased as CO2 increased (Allen 2016). To contextualize this study, background outdoor CO2 concentrations are typically 350-400 ppm (NOAA Global Monitoring Laboratory 2020). ASHRAE Standard 62.1 suggests an airflow rate of 20 cfm/person, which corresponds to a CO2 concentration of 945 ppm, commonly stated as 1000 ppm (ASTM Compass 2020). This standard is commonly required by local building codes that use ASHRAE standards (Allen 2016). In Allen’s study, changes in CO2 concentrations from 550 ppm to 945 resulted in 15% reduction in cognitive test scores. Changes in concentrations from 550 to 1400 ppm, resulted in 50% decreases in cognitive scores. (Allen 2016). Overall, a 21% decrease in typical participant cognitive score across all nine cognitive function domains was seen with 400 ppm increases in CO2 concentrations. This is particularly concerning since many spaces far exceed the 1000 ppm standard. In one study, 45% of 435 classrooms in Washington and Idaho exceeded this threshold, and reported that elevated CO2 concentrations were associated with increases in student absences (Allen 2016). These findings suggest a benefit in cognitive performance from, at a minimum meeting the suggested 1000 ppm CO2 concentration standard, or even lowering CO2 concentrations below these ASHRAE standards.

The health and performance impacts of increased CO2 concentration is shown in the following table, and is based on information from multiple sources (Table 1).

II. Thermal Comfort

In a review of thermal comfort studies, seven out of nine studies revealed that users rated thermal comfort as the top priority to improving satisfaction in a building (Rupp 2015). Thermal comfort is the subjective assessment of one’s thermal satisfaction of the environment and is effected by environmental and personal factors. The four environmental factors that contribute to thermal comfort are air temperature, radiant temperature, air speed, and humidity (Lechner 2014). The personal factors are metabolic rate and clothing insulation (Lechner 2014). The most common physiological symptoms that cause a negative perception of thermal comfort are feeling too hot or too cold, but dryness of skin, nose, throat, nasal congestion, itchy skin, and headache. These factors have been found to directly correlate with temperature and relative humidity (Amin 2015, Ormandy 2012).

Acceptable temperature conditions are defined by ASHRAE as those comfortable to 80% of occupants (ASHRAE 55-2017), so 20% are inherently uncomfortable in these conditions. The following sections underscore the importance of improving thermal comfort beyond conventional standards.

Occupant Health

Current ASHRAE standards suggest a steady temperature within an allowed limit to control the indoor climate of a building and maintain thermal comfort. Studies show that a lack of thermal stimulation could have adverse effects on user health (Johnson 2011, van Marken Lichtenbelt 2018, Stoops 2004). One study found that the lack of exposure to variability of temperature could reduce the thermogenic capacity of the user and decrease amounts of brown adipose tissue (BAT). BAT is a thermogenic organ that releases energy as heat and is a large contributor to thermogenesis, the production of heat within the body (Johnson 2011). Variability in indoor temperatures can also contribute to our metabolic health where exposure to heat and cold more frequently could help create resilience to varying temperatures (van Marken Lichtenbelt). Studies also indicate benefits to mild exposure from heat and cold. Exposure to mild cold was found to influence the maintenance of weight and glucose metabolism. A small increase in mild heat exposure was linked with improved cardiovascular function (Stoops 2004), a decrease of blood pressure, cutaneous vasomotor function, and more efficient sweating (van Marken Lichtenbelt 2018). However, too much exposure to heat and cold could cause distress to the body including increased cardiovascular and respiratory issues (Uejio 2016), and sleep disturbance (Van Loenhout 2016).

Maintaining thermal comfort has also been found to reduce sick building syndrome (SBS) symptoms in building users (Amin 2015, Fang 2004). An increased temperature and relative humidity in a space can begin to generate increased levels of pollutants, leading to minor respiratory issues and other symptoms related to SBS (Heerwagen 2000). Several studies indicated that temperature was the most influential indoor air factor contributing to SBS symptoms and that persons not satisfied with the temperature experienced SBS symptoms such as dryness of skin, nose, throat, nasal congestion, itchy skin, and headache (Amin 2015, Ormandy 2012). One study predicted that absenteeism due to SBS symptoms could be up to 34% lower if employees had the means to control their immediate microclimate conditions (Heerwagen 2000).

Mental Health

The thermal environment of a space can have an impact on the psychological response of the user (Yoshida 2015, Tanabe 2007, Akimoto 2010). Studies have shown that thermal discomfort can lead to mental fatigue (Yoshida 2015, Tanabe 2007). One study by Yoshida at Osaka Prefecture University found that temperatures above the recommended thermal threshold correlated with mental fatigue (Yoshida 2015). In addition, when within a state of thermal comfort or thermal neutrality, the condition had a relaxing sensation in comparison with the uncomfortable thermal environment (Yoshida 2015). A different study by Tanabe at Waseda University confirms the claims made by Yoshiba that an increase in temperatures also increased mental fatigue in the test subjects (Tanabe 2007). An additional study conducted by Akimoto at Shibaura Institute of technology indicated that when in thermal discomfort, fatigue symptoms were exhibited for most of the working hours in the test subjects (Akimoto 2010). The study also indicated that worker vitality – referring to the desire to participate in activities after work hours—decreased in the thermally uncomfortable environment over the course of the day. There is a correlation between mental vitality and fatigue as the longer a subject was in thermal discomfort, the fatigue increased and the vitality level decreased (Akimoto 2010).

Personal control over the thermal environment of a space has also been correlated to positive psychological responses (Wagner 2006, Van Hoof 2010). A study conducted at a hospital by Wagner at North Georgia College and State University found that if the patient had control over their environment before a procedure, there could be a decrease in anxiety (Wagner 2006). The study also found that for patients about to undergo treatment, a warmer environment can decrease the patient’s anxiety and thermal comfort (Wagner 2006). Another study conducted by Fossum at the American Society of Peri Anesthesia Nurses looking at preoperative thermal comfort in a hospital associated warm air with positive feelings of comfort and decreased anxiety in preoperative patients (Fossum 2001).

Productivity

Investing in buildings that support and improve occupant productivity and performance over the lifespan of a building is important because more work can be produced in less time which can benefit the business both economically and in output efficiency (Zeiler 2009). Studies have found that temperature influences performance (Cui 2013, Seppanen 2006, Lee 2012, Fisk 2004). One study of a US office building found that cognitive function of employees decreased when exposed to consistently cold temperatures. The same reduction appeared when exposed to consistently warm temperatures (Cui 2013, Lee 2012). Several studies have found that perceived thermal comfort in classrooms showed improvements of productivity and performance (Zeiler 2009, Zomorodian 2016). The optimal temperature range for cognitive function was found to be between 22-26 degrees Celsius (Seppanen 2006). Optimal temperatures for performance can vary due to the type of task (Zeiler 2009, Heerwagen 2000, Tarantini 2017, Chang 2019, Schellen 2012). Furthermore, study subjects engaged in creativity-oriented tasks perform better in slightly warmer environment than average while those performing critical thinking tasks did better in spaces on the cooler end of the comfort spectrum (Heerwagen 2000, Chang 2019).

Seppanen and Fisk et al performed a statistical analysis of 24 studies and derived an equation that relates room temperature and employee performance (Seppanen & Fisk 2006). Researchers at the Indoor Environment Group of the Lawrence Berkeley National Laboratory used these findings to illustrate the impact of temperature changes on performance of employees (Table 2).

III. Daylighting

Occupant Health

Regulation of the circadian system is one of the largest ways light impacts the physiological health. Circadian rhythms “are the daily rhythms that repeat approximately every 24 hours and are driven by an endogenous clock. Nearly all behavioral and physiological parameters exhibit circadian rhythms and thus circadian clock synchronization is paramount to the body’s efficient and appropriate functioning. The neurobehavioral (e.g. sleep/wake cycle) and neuroendocrine (e.g. hormone production) axes are influenced by optical radiation both directly (acute effects) and indirectly, via circadian clocks that drive and coordinate the rhythmicity in these systems” (Figueiro 2008). Lucas notes that circadian rhythms are “a feature of nearly every physiological, metabolic, and behavioral system” (Lucas 2014). However, one of the most visible manifestations of the circadian system is the sleep-wake cycle through the ability of light to impact the secretion of melatonin from the pineal gland (Bedrosian 2016). “The timing of the periods of light (or darkness) and their duration plays an essential role” in biological functions and physiology (van Bommel 2006). Daylight is critical to maintaining proper circadian alignment because the “human body clock is usually slightly longer than 24 hours and thus needs a daily morning light signal to reset the clock to entrain with the Earth’s 24-hour rotation rhythm and the changing photoperiod” (Aries 2015). Though the maintenance of circadian rhythm is critical to physical health, it is important to note that “the impact of optical radiation on the neurobehavioral and neuroendocrine responses is not exclusively via the circadian system” (Figueiro 2008).

The strongest connection between the circadian system and disease has been found linking circadian disruption to increased cancer risk. This has been supported by extensive studies in epidemiological, clinical, and basic research (Bedrosian 2016). Though the primary concern is nighttime light exposure, “there is concern that the incidence and rate of development of breast and other forms of cancer are increased when melatonin suppression occurs night after night for a prolonged period,” (Boyce 2010) particularly when paired with studies showing melatonin-depleted blood increasing the growth rate of breast cancer tumors (Boyce 2010).

Productivity

Increases in performance and productivity due to improved lighting conditions have been observed in various companies, including Lockheed Martin, Verifone, and the Reno Post Office (Edwards 2002). By moving to an open office with integrated daylight, Lockheed Martin was able to increase contract productivity by 15% and believed the increased productivity helped them win a $1.5 billion defense contract (Edwards 2002). At Verifone, daylight helped their distribution center increase productivity by 5% and total product output by 25%-28%, “making the new building more cost effective than first predicted” (Edwards 2002). For the Reno Post Office, when combined with better electric lighting, indirect daylight increased the productivity of mail sorters by 6%-8% while decreasing errors to .1% (Edwards 2002). Lastly, Story County Human Services, in Iowa, was able to increase the amount of people served and seen. One group tripled the number of people served while another doubled the number of people served (Edwards 2002). Increases in performance are an important payback of investments in daylight because “the energy and operating costs of a building are small when compared to the cost of employees and initial construction. In terms of the financial returns from increased performance, the Reno Post Office saw productivity gains of $400,000 to $500,000 per year, paying for the renovations in less than a year while Lockheed Martin saw financial gains from increased productivity while also saving approximately $500,000 in energy expenses and decreasing absenteeism. (Edwards 2002).

Improved Financial Performance

Numerous studies have shown that daylit stores have higher sales numbers than non- daylit stores (Edwards 2002, Boyce 2003). Daylight “has aesthetic benefits that encourage customers to enter the store” (Edwards 2002) likely contributing to the fact that the Heschong Mahone Group found adding skylights increased store sales by 31%-41%” (Heschong 2002). The presence of skylights was found to be statistically significant to increased retail sales, ranking third in influence behind operating hours and years since the last store retrofit (Boyce 2003). In addition to encouraging sales, daylight improves color rendering and color discrimination, allowing employees to more quickly located stock from the storeroom and to make signage easier to read, preserving the value invested in the graphic design of the signage (Edwards 2002).

Medical buildings can also reap financial benefits from utilizing daylight. Healthcare facilities benefit from reduced operating costs and energy bills because “patients recover faster in daylit recovery centers” (Edwards 2002). Patients in sunny rooms had “marginally less pain, took 22% less analgesic medication per hour, and had 21% less pain medication costs,” helping reduce overall facility operating costs (Joseph 2006). Additionally, myocardial infarction patients experienced shorter stays when assigned to sunny rooms compared to rooms in shade, particularly for women patients. Mortality rates were lower in the sunnier rooms as well (Ulrich 2008). Overall, daylit post-surgical facilities improve the mental well-being of patients, and by “improving the mental well-being of patients improves their recovery rates” (Edwards 2002). By decreasing the amount of pain medicine used and the length of recovery time, healthcare facilities are able to treat more patients within the same time frame, increasing their efficiency.

Improved Academic + Cognitive Performance

Daylight has been shown to contribute to higher cognitive performance and increased test scores for children. Studies have shown that “students in daylit schools had higher reading and math achievement scores” (Edwards 2002) and that “children in classrooms with the best daylighting…showed higher end-of-year test scores than children in classrooms with no daylight” (Boyce 2003). In one study of schools in North Carolina, two schools in the same district had increased test scores of 7% and 18% compared to a 5% increase in a newly built schools that didn’t incorporate daylight and a 5% average increase across the district (Edwards 2002). Additionally, “students have shown better behavior in properly [day]lit libraries than traditional fluorescent-lit schools” (Edwards 2002). While there is difficulty in saying precisely why daylight has positive impacts on students, possible causes include “better distribution of light, improved visibility from improved light, better color rendering, and the absence of flickering from electrical lighting” (Edwards 2002). It is worth noting that while the “positive effect of daylighting was distinct from all other attributes from windows,” (Edwards 2002), “it is not [just] daylight per se that enhances education, but the way that it is delivered,” due to potential for visual and thermal discomfort (Boyce 2003).

IV. References

Review Articles

• Aries, Mbc, Mpj Aarts, and J. Van Hoof. “Daylight and Health: A Review of the Evidence and Consequences for the Built Environment.” Lighting Research & Technology 47, no. 1 (2015): 6-27.
• Attema, Jeremy, Fowell, S.J., Macko, M.J., & Neilson, W.C. “The Financial Case for High Performance Buildings.” San Francisco: Stok LLC. (2018).
• Bedrosian, Tracy A. “Endocrine effects of circadian disruption.” Annual review of physiology 78 (2016): 109-131.
• Boyce, Peter. “The benefits of daylight through windows.” Troy, New York: Rensselaer Polytechnic Institute (2003).
• Clements-Croome, Derek J. “Work performance, productivity and indoor air.” Scandinavian Journal of Work Environment & Health Supplement (2008): 69-78.
• Dean, Edward. Zero Net Energy Case Study Buildings. Volume 2. 2016. Pacific Gas and Electric Company
• Edwards, L., and P. Torcellini. Literature review of the effects of natural light on building occupants. National Renewable Energy Lab., Golden, CO.(US), 2002.
• Figueiro, M. G., G. C. Brainard, S. W. Lockley, V. L. Revell, and R. White. “Light and human health: An overview of the impact of optical Radiation on visual, circadian, neuroendocrine, and neurobehavioral responses.” IES TM-18-08. (2008).
• Fisk, William J., Olli Seppanen, and David Faulkner. “Control of temperature for health and productivity in offices.” (2004).
• Fisk, William J. “The ventilation problem in schools: literature review.” Indoor Air 27, no. 6 (2017): 1039-1051.
• Gerardi, Daniel A. “Building-related illness.” Clinical Pulmonary Medicine 17, no. 6 (2010): 276-281.
• Heerwagen, Judith. “Green buildings, organizational success and occupant productivity.” Building Research & Information 28, no. 5-6 (2000): 353-367.
• Johnson, F., A. Mavrogianni, M. Ucci, A. Vidal Puig, and J. Wardle. “Could increased time spent in a thermal comfort zone contribute to population increases in obesity?.” Obesity reviews 12, no. 7 (2011): 543-551.
• Joseph, Anjali. The impact of light on outcomes in healthcare settings. Center for Health Design, 2006.
• Li, Yiping. “Role of ventilation in airborne transmission of infectious agents in the built environment-a multidisciplinary systematic review.” Indoor air 17, no. 1 (2007): 2-18.
• Ormandy, David, and Véronique Ezratty. “Health and thermal comfort: From WHO guidance to housing strategies.” Energy Policy 49 (2012): 116-121.
• Prill, R. “Measuring Carbon Dioxide Inside Buildings–Why is it Important.” Energy Proram, WSU, Washington, USA (2013).
• Rupp, Ricardo Forgiarini, Natalia Giraldo Vásquez, and Roberto Lamberts. “A review of human thermal comfort in the built environment.” Energy and Buildings 105 (2015): 178-205.
• Seppanen, O, Fisk, W.J., Lei, Q.H. “Room temperature and productivity in office work” Lawrence Berkeley National Laboratory 2006
• Seppänen, O. A., W. J. Fisk, and M. J. Mendell. “Association of ventilation rates and CO2 concentrations with health andother responses in commercial and institutional buildings.” Indoor air 9, no. 4 (1999): 226-252.
• Stoops, John L. “A possible connection between thermal comfort and health.” (2004).
• Tarantini, Mariantonietta. “A co-citation analysis on thermal comfort and productivity aspects in production and office buildings.” Buildings 7, no. 2 (2017): 36.
• Van Bommel. “Non-visual biological effect of lighting and the practical meaning for lighting for work.” Applied ergonomics 37, no. 4 (2006): 461-466.
• Van Hoof. “Thermal comfort: research and practice.” Frontiers in Bioscience 15, no. 2 (2010): 765-788.
• Van Marken Lichtenbelt, W. D, Pallubinsky, H, & Te Kulve, M. Modulation of thermogenesis and metabolic health: A built environment perspective. Obesity Reviews, 19 (2018): 94-101.
• WGBC (World Green Building Council). The Business Case for Health and Wellbeing in Green Building. 2018.
• Zomorodian, Zahra. “Thermal comfort in educational buildings: A review article.” Renewable and sustainable energy reviews 59 (2016): 895-906.

Primary Research

• Akimoto, Takashi, Shin-ichi Tanabe, “Thermal comfort and productivity-Evaluation of workplace environment in a task conditioned office.” Building and environment 45, no. 1 (2010): 45-50.
• Allen, Joseph G., Piers MacNaughton, Usha Satish. “Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound exposures in office workers: a controlled exposure study of green and conventional office environments.” Environmental health perspectives 124, no. 6 (2016): 805-812.
• Amin, Nor. “Architectural evaluation of thermal comfort: sick building syndrome symptoms in engineering education laboratories.” Procedia-Social and Behavioral Sciences 204 (2015): 19-28.
• Apte, Michael G. “Associations between indoor CO2 concentrations and sick building syndrome symptoms in US office buildings: an analysis of the 1994-1996 BASE study data.” Indoor air 10, no. 4 (2000).
• Chang, Tom Y. “Battle for the thermostat: Gender and the effect of temperature on cognitive performance.” PloS one 14, no. 5 (2019).
• Cui, Weilin, Guoguang Cao, Jung Ho Park, Qin Ouyang, and Yingxin Zhu. “Influence of indoor air temperature on human thermal comfort, motivation and performance.” Building and environment 68 (2013): 114-122
• Fang, L, Wyon, D. P, Clausen, G, & Fanger, P. O. Impact of indoor air temperature and humidity in an offce on perceived air quality, SBS symptoms and performance. Indoor Air, 14(S7) (2004): 74-81.
• Fossum, Susan, Hays, Judy, & Henson, Mary Margaret. (2001). A comparison study on the effects of prewarming patients in the outpatient surgery setting. Journal of Perianesthesia Nursing, 16(3), 187-194.
• Gauderman, W. James. “Childhood asthma and exposure to traffic and nitrogen dioxide.” Epidemiology (2005): 737-743.
• Heschong, Lisa, Roger L. Wright, and Stacia Okura. “Daylighting impacts on retail sales performance.” Journal of the Illuminating Engineering Society 31, no. 2 (2002): 21-25.
• Lanphear, Bruce P., C. Andrew Aligne, Peggy Auinger, Michael Weitzman, and Robert S. Byrd. “Residential exposures associated with asthma in US children.” Pediatrics 107, no. 3 (2001): 505-511.
• Lee, M. C., K. W. Mui, L. T. Wong, W. Y. Chan, E. W. M. Lee, and C. T. Cheung. “Student learning performance and indoor environmental quality (IEQ) in air-conditioned university teaching rooms.” Building and Environment 49 (2012): 238-244.
• Mendell, Mark J., Ekaterina A. Eliseeva, Molly M. Davies, Michael Spears, Agnes Lobscheid, William J. Fisk, and Michael G. Apte. “Association of classroom ventilation with reduced illness absence: a prospective study in California elementary schools.” Indoor air 23, no. 6 (2013): 515-528.
• Mendell, Mark J., Quanhong Lei, M. G. Apte, and William J. Fisk. “Outdoor air ventilation and work-related symptoms in US office buildings-results from the BASE study.” (2005).
• Milton, Donald. “Risk of sick leave associated with outdoor air supply rate, humidification, and occupant complaints.” Indoor air 10 (2000): 212-221.
• Mumma, Stanley, Jeong, Jae-Weon, and William P. Bahnfleth. “Energy conservation benefits of a dedicated outdoor air system with parallel sensible cooling by ceiling radiant panels.” ASHRAE Transactions 109 (2003): 627.
• Nurmagambetov, Tursynbek, Robin Kuwahara, and Paul Garbe. “The economic burden of asthma in the United States, 2008–2013.” Annals of the American Thoracic Society 15, no. 3 (2018): 348-356.
• Shan, Xin. “Comparing mixing and displacement ventilation in tutorial rooms: Students’ thermal comfort, sick building syndromes, and short-term performance.” Building and Environment 102 (2016): 128-137.
• Schellen, Lisje, Marcel GLC Loomans, Martin H. de Wit, Bjarne Wilkens Olesen, and W. D. van Marken Lichtenbelt. “The infuence of local effects on thermal sensation under non-uniform environmental conditions—Gender differences in thermophysiology, thermal comfort and productivity during convective and radiant cooling.” Physiology & behavior 107, no. 2 (2012): 252-261.
• Takaro, Tim K. “The Breathe-Easy Home: the impact of asthma-friendly home construction on clinical outcomes and trigger exposure.” American Journal of Public Health 101, no. 1 (2011): 55-62.
• Tanabe, Shin-ichi. “Workplace productivity and individual thermal satisfaction.” Building and environment 91 (2015): 42-50.
• Uejio, C. K. “Summer indoor heat exposure and respiratory and cardiovascular distress calls in New York City, NY, US.” Indoor air 26, no. 4 (2016): 594-604.
• Van Loenhout. “The effect of high indoor temperatures on self-perceived health of elderly persons.” Environmental research 146 (2016): 27-34.
• Vehviläinen, Tommi. “High indoor CO2 concentrations in an office environment increases the transcutaneous CO2 level and sleepiness during cognitive work.” Journal of occupational and environmental hygiene 13, no. 1 (2016): 19-29.
• Wagner, Doreen, Byrne, Michelle, & Kolcaba, Katharine. Effects of Comfort Warming on Preoperative Patients. AORN Journal, 84(3) (2006): 427-448.
• Wallingford, K. M. “NIOSH Indoor Air Quality Investigations in Non-industrial Workplaces: An Update.” 1986.
• Wargocki, Pawel, David P. Wyon, and P. Ole Fanger. “Productivity is affected by the air quality in offices.” In Proceedings of Healthy Buildings, vol. 1, no. 1, pp. 635-40. 2000.
• Wyon, David P. “The effects of indoor air quality on performance and productivity.” Indoor air 14, no. 1 (2004): 92-101.
• Yoshida, Atsumasa, Hisabayashi, Takezo, Kashihara, Kenta, Kinoshita, Shinichi, & Hashida, Shoko. (2015). Evaluation of effect of tree canopy on thermal environment, thermal sensation, and mental state. Urban Climate, 14, 240-250.
• Zeiler, Wim. “Effects of thermal activated building systems in schools on thermal comfort in winter.” Building and Environment 44, no. 11 (2009): 2308-2317.

Print Media

• Lechner, Norbert. Heating, cooling, lighting: Sustainable design methods for architects. John Wiley & Sons, 2014.