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Air and dust samples were collected on two floors of an office building during a double-blind particle intervention study to examine spatial and temporal variability of airborne endotoxin over a period of weeks, and to characterize endotoxin activity and lipopolysaccharide (LPS) content in carpet and chair dust. Air samples were collected on multiple days within and across weeks. Dust samples were collected from carpets and chairs one day per week for three weeks. Endotoxin was measured using a Limulus assay. Dust samples were analyzed for LPS by determination of 3-hydroxy fatty acids (3-OHFAs) using gas chromatography-mass spectrometry. The geometric mean (geometric standard deviation) for 96 indoor air samples was 0.24 (1.6) EU/m3. Significant within-floor spatial variation of airborne endotoxin was found (P

In laboratory experiments, we investigated two task/ambient conditioning systems with air supplied from desk-mounted air outlets to efficiently ventilate the breathing zone of heated manikins seated at desks. In most experiments, the task conditioning systems provided outside air while a conventional ventilation system provided additional space cooling but no outside air. Air change effectiveness (i.e., exhaust air age divided by age of air at the manikin's face) was measured with a tracer gas step-up procedure. Other tracer gases simulated the release of pollutants from nearby occupants and from the floor covering, and the associated pollutant removal efficiencies (i.e., exhaust air concentrations divided by concentrations at manikin's face) were calculated. High values of air change effectiveness (approximately 1.3 to 1.9) and high values of pollutant removal efficiency (approximately 1.2 to 1.6) were measured when these task conditioning systems supplied 100% outdoor air at a flow rate of 7 to 9 L s-1 per occupant. Air change effectiveness was reasonably well correlated with the pollutant removal efficiency. Overall, the experimental data suggest that these task/ambient conditioning systems can be used to improve ventilation and air quality or to save energy while maintaining a typical level of IAQ at the breathing zone.

Occupants of office buildings are exposed to low concentrations of complex mixtures of volatile organic compounds (VOCs) that encompass a number of chemical classes and a broad range of irritancies. “Sick building syndrome” (SBS) is suspected to be related to these exposures. Using data from 22 office areas in 12 California buildings, seven VOC exposure metrics were developed and their ability to predict self-reported SBS irritant symptoms of office workers was tested. The VOC metrics were each evaluated in a multivariate logistic regression analysis model adjusted for other risk factors or confounders. Total VOCs and most of the other metrics were not statistically significant predictors of symptoms in crude or adjusted analyses. Two metrics were developed using principal components (PC) analysis on subsets of the 39 VOCs. The Irritancy/PC metric was the most statistically significant predictor of adjusted irritant symptoms. The irritant potencies of individual compounds, highly correlated nature of indoor VOC mixtures, and probable presence of potent, but unmeasured, VOCs were variously factored into this metric. These results, which for the first time show a link between low level VOC exposures from specific types of indoor sources to SBS symptoms, require confirmation using data sets from other buildings.

The existing literature contains strong evidence that characteristics of buildings and indoor environments significantly influence rates of respiratory disease, allergy and asthma symptoms, sick building symptoms, and worker performance. Theoretical considerations, and limited empirical data, suggest that existing technologies and procedures can improve indoor environments in a manner that significantly increases health and productivity. At present, we can develop only crude estimates of the magnitude of productivity gains that may be obtained by providing better indoor environments; however, the projected gains are very large. For the U.S., we estimate potential annual savings and productivity gains of $6 billion to $19 billion from reduced respiratory disease; $1 billion to $4 billion from reduced allergies and asthma, $10 billion to $20 billion from reduced sick building syndrome symptoms, and $12 billion to $125 billion from direct improvements in worker performance that are unrelated to health. Sample calculations indicate that the potential financial benefits of improving indoor environments exceed costs by a factor of 18 to 47. The policy implications of the findings are discussed and include a recommendation for additional research.

To study the effects of atmospheric pressure fluctuations on the entry of radon and soil-gas contaminants into houses, we have simultaneously measured the changes in atmospheric pressure and the gas flow rate between the interior of an experimental basement structure and the underlying soil. Atmospheric pressure fluctuations draw soil gas into the experimental basement without the indoor-outdoor pressure differences commonly associated with advective entry of soil-gas contaminants. The soil-gas flow rate induced by a change in atmospheric pressure depends on both the characteristic response time of the soil and the time-rate-of-change of the atmospheric pressure fluctuation. Spectral analysis indicates that relatively low-frequency fluctuations in atmospheric pressure are the most important for driving soil-gas into and out the of the experimental structure; more than 60% of the total power of the soil-gas flow spectrum occurs at frequencies less than 100 d −1 . A transient finite-element model based on Darcy's law correctly predicts both the dynamics and the magnitude of the observed gas flow. Atmospheric pressure fluctuations may increase the long-term radon entry rate into the experimental structure by as much as 0.2 Bq s −1 , which is more than twice the measured diffusive entry rate into the structure and comparable to the radon entry rate driven by a − 0.4 Pa, steady indoor-outdoor pressure difference.

The air change effectiveness (ACE), an indicator of the indoor airflow pattern, was measured in twenty-six laboratory experiments. Ventilation air was supplied through inductiontype diffusers located in the ceiling and removed through a ceiling-mounted return grille. The tracer gas stepup measurement procedure was employed. In five of the experiments, pollutant removal efficiencies were also measured for simulated pollutant emissions from the floor covering and for simulated emissions from occupants. In experiments with heated supply air, supply air flow rates typical of the minimum supply flow rates of VAV ventilation systems, and 100% outside air, the ACE ranged from 0.69 to 0.89. These results indicate that significant short circuiting of ventilation air between the supply air diffuser and return air grille does occur under these adverse conditions. Mechanical recirculation of air, such that the supply air contained approximately 50% outside air, increased the ACE by about 0.05. When the supply air was cooled, the ACE ranged from 0.99 to 1.15, adding to existing evidence that short circuiting is rarely a problem when the building is being cooled. The pollutant removal efficiency for simulated pollutant emissions from the floor covering (PREfloor)was strongly correlated with ACE (R 2 = 0.98) and the values of PREfloor were within approximately 0.1 of the values of ACE. The pollutant removal efficiency for simulated pollutant emissions by occupants varied between workstations and was not as well correlated with the ACE.

Monthly gas and electricity use data from a set of 13 study apartments and 20 control apartments from three apartment buildings (B1 B3) in California were analyzed. The study apartments were retrofit with simultaneous energy savings and indoor environmental quality (IEQ) improvements as the goal. The control apartments were not retrofit. Pre-retrofit modeling indicated annual energy savings of 21percent, 17percent, and 27percent for the study apartments in B1-B3, respectively. Based on a comparison of changes in energy use of study apartments to energy use changes of control apartments, total measured savings of gas energy plus site electrical energy were 28percent in B1, 5percent in B2, and 3percent in B3. Given the small number of study apartments and the substantial changes in energy use within control apartments, the project yielded no conclusive evidence of energy savings. Apartment energy use increased with number of occupants and with floor area; however, the association with occupancy was most evident. Climate differences did not appear to be the major driver for the variability in energy use among apartments. Changes in occupant behaviors affecting energy use may have overwhelmed and obscured the energy savings in this small number of buildings. Much larger prior studies employing similarmore » retrofits indicate that the retrofits usually do save energy.« less

Background: Limited evidence associates inadequate classroom ventilation rates (VRs) with increased illness-related absence (IRA) in students. Aims: The goal of this research was to characterize VR...

Evaluation of the Indoor Air Quality Procedure for Use in Retail Buildings Spencer M. Dutton, Wanyu R. Chan, Mark J. Mendell, Marcella Barrios, Srinandini Parthasarathy, Meera Sidheswaran, Douglas P. Sullivan, Katerina Eliseeva, William J. Fisk Environmental Energy Technologies Division Indoor Environment Group Lawrence Berkeley National Laboratory Berkeley, CA 94720 February 1, 2013 The research reported here was supported by the California Energy Commission Public Interest Energy Research Program, Energy-Related Environmental Research Program, award number 500-09-049.The study was additionally supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Building Technologies Program of the U.S. Department of Energy under contract DE-AC02-05CH11231.

Effect Of Ventilation On Chronic Health Risks In Schools And Offices Srinandini Parthasarathy 1 , William J. Fisk 1 , Thomas E. McKone 2 Indoor Environment Group Sustainable Energy Systems Group Environmental Energy Technologies Division Energy Analysis and Environmental Impact Department Lawrence Berkeley National Laboratory Berkeley, CA 94720 January 4, 2013 This work was supported by the California Energy Commission, Public Interest Energy Research Program, Energy Related Environmental Research Program, under contract 500‐09‐049. LBNL-6121E

In cleanrooms, very low particle concentrations are maintained by recirculation of air at a high rate (e.g., 600 room air volumes/hr) through highly efficient air filters. Results are reported in a Class M3.5 (Class 100) cleanroom with 28 m2 (300 ft2) floor area, where significant energy savings were realized by controlling the rate of air recirculation through the filters in response to real-time measurements of particle concentrations. An inexpensive, $2500, optical particle counter was used to measure particle concentrations. The effect of varying the recirculation airflow rate on particle concentrations was investigated. Changes in recirculation fan speeds of 10 percent or greater did not cause a noticeable particle release from filters or resuspension from indoor surfaces. With new automatic control systems in operation, there were occasional, usually fewer than 10/day, nonconsecutive l-min episodes in which the particle concentration exceeded Class M3.5 (Class 100) status. Depending upon the choice for baseline energy use, the energy consumption of the recirculating fans was reduced by 60 to 80 percent, and the estimated payback period for a 90 m2 (1,000 ft2) Class M3.5 (Class 100) cleanroom is from 1 to 4 yr.

Active sub-slab depressurization (SSD) systems are an effective means of reducing indoor radon concentrations in residential buildings. However, energy is required to operate the system fan and to heat or cool the resulting increased building ventilation. We present regional and national estimates of the energy requirements, operating expenses and CO 2 emissions associated with using SSD systems at saturation (i.e. in all US homes with radon concentrations above the EPA remediation guideline and either basement or slab-on-grade construction). The primary source of uncertainty in these estimates is the impact of the SSD system on house ventilation rate. Overall, individual SSD system operating expenses are highest in the Northeast and Midwest at about $99 y −1 , and lowest in the South and West at about $66 y −1 . The fan consumes, on average, about 40% of the end-use energy used to operate the SSD system and accounts for about 60% of the annual expense. At saturation, regional impacts are largest in the Midwest because this area has a large number of mitigable houses and a relatively high heating load. We estimate that operating SSD systems in US houses, where it is both appropriate and possible (about 2,6 million houses), will annually consume 1.7 × 10 4 (6.4 × 10 3 to 3.9 × 10 4 ) TJ of end-use energy, cost $230 (130 to 400) million (at current energy prices), and generate 2.0 × 10 9 (1.2 × 10 9 to 3.5 × 10 9 ) kg of CO 2 . Passive or energy efficient radon mitigation systems currently being developed offer opportunities to substantially reduce these impacts.

Healthy Zero Energy Buildings (HZEB) Program– Interim Report on Cross‐Sectional Study of Contaminant Levels, Source Strengths, and Ventilation Rates in Retail Stores Wanyu R. Chan, Meera Sidheswaran, Douglas Sullivan, Sebastian Cohn, William J. Fisk Environmental Energy Technologies Division Indoor Environment Group Lawrence Berkeley National Laboratory Berkeley, CA 94720 November 5, 2012 The research reported here was supported by the California Energy Commission Public Interest Energy Research Program, Energy‐Related Environmental Research Program, award number 500‐09‐049. The project was also supported by the U.S. Dept. of Energy Building Technologies Program, Office of Energy Efficiency and Renewable Energy under DOE Contract No. DE‐AC02‐05CH11231.

The performance of sub-slab-ventilation (SSV) systems has been parametrically studied with a numerical model that was earlier compared successfully with experiment (Bonnefous et al., 1992). The model distinguishes between the sub-slab gravel and the underlying soil. It is used w examine system performance for the following system parameters: the permeability of the soil and of the sub-slab gravel, the magnitude of pressurization (or depressurization) applied by the SSV system, and the mode of SSV application (i.e. pressurization (SSP) or depressurization (SSD)). The mechanisms contributing to the successful performance of SSP and SSD systems are identified. For SSD systems, the mechanisms are (1) the inversion of the pressure gradient across the basement slab, and (2) the reduction of the radon concentration in the soil. For SSP systems, the mechanisms are (1) the elimination of convective flow of soil-gas from the soil into the sub-slab gravel by pressurization of the sub-slab region, (2) the reduction of the radon concentration in the soil, and (3) the suppression of diffusion of soil-gas from the soil into the sub-slab gravel by advective flow of air from the gravel bed into the subgravel soil. Numerical modeling demonstrates that placement of a sub-slab gravel layer substantially improves the SSV system performance. Except in the case of highly permeable soils, SSD systems are predicted to perform better than SSP systems. This prediction is consistent with reported field experience. The numerical model is used to elucidate the reasons for this difference in performance.

Radon is the largest source of risk to human health caused by an indoor pollutant in the industrial countries. Subslab ventilation (SSV) is one of the most effective and common methods of reducing indoor radon concentrations in houses with a basement. In this paper, the impact of SSV on the air exchange rate is quantified, through numerical modeling of a prototype house with basement for a range of permeabilities of soil and subslab aggregate and various sizes of the cracks in the basement floor. We show that a SSV system can increase the air exchange rate by as much as a factor of 4.5. Then the energy and capital costs of a subslab depressurization (SSD) system are compared with those of direct ventilation of the basement which is required to lower the indoor radon concentration to an acceptable level for a Chicago climate. We show that (1) an exhaust ventilation cannot significantly reduce the indoor radon concentration and may even increase it, and (2) a balanced ventilation with heat recovery is only effective for low premitigation radon concentrations. However, both SSV and balanced ventilation systems are probably too expensive to be recommended in houses with low premitigation radon concentrations. A SSD system is the most cost-effective technique for reduction of high radon concentrations.

The research carried out in this project focuses on developing novel volatile organic compounds (VOCs) air cleaning technologies needed to enable energy-saving reductions in ventilation rates. we targeted a VOC air cleaning system that could enable a 50% reduction in ventilation rates. In a typical commercial HVAC system that provides a mixture of recirculated and outdoor air, a VOC air cleaner in the supply airstream must have a 15% to 20% VOC removal efficiency to counteract a 50% reduction in outdoor air supply.

The growing investment by governments and electric utilities in energy efficiency programs highlights the need for simple tools to help assess and explain the size of the potential resource. One technique that is commonly used in that effort is to characterize electricity savings in terms of avoided power plants, because it is easier for people to visualize a power plant than it is to understand an abstraction like billions of kilowatt‐hours. Unfortunately, there is no standardization around the characteristics of such power plants.In this article we define parameters for a standard avoided power plant that have physical meaning and intuitive plausibility, for use in back‐of‐the‐envelope calculations. For the prototypical plant this article settles on a 500‐megawatt existing coal plant operating at a 70% capacity factor with 7% T&D losses. Displacing such a plant for one year would save 3 billion kWh/year at the meter and reduce emissions by 3 million metric tons of CO2 per year.The proposed name for this...

Twelve public office buildings were selected for a study of relationships between worker's health symptoms and a number of building, workspace, job, and personal factors. Three buildings were naturally ventilated, three were mechanically ventilated, and six were air conditioned. Information on the prevalences of work-related symptoms, demographics, and job and personal factors were determined via a questionnaire completed by 880 occupants. Several indoor environmental parameters were measured. Logistic regression models were used to evaluate associations between symptom prevalences and features of the buildings, indoor environments, jobs, and personal factors. A substantial fraction of the occupants in these typical office buildings reported frequent work-related symptoms. The occupants of the mechanically ventilated and air conditioned buildings had sipifcantly more symptoms than occupants of the naturally ventilated buildings after adjustment for confounding factors. Increased prevalences of some symptoms were associated with several job and workspace factors including: presence of carpet, increased use of carbonless copy paper and photocopiers, space sharing, and distance from a window

Previous studies have reported a large and persistent discrepancy between field measurements and model predictions of pressure-driven entry of soil gas into houses, the phenomenon that causes high concentrations of radon indoors. The discrepancy is often attributed to poor understanding of inherently complex field sites. This paper compares measurements of soil-gas entry made at a full-scale test basement located in natural solid with predictions of a three-dimensional finite difference model. The results corroborate the earlier findings, with the model underpredicting the soil-gas entry rate by a factor of 7. The effect of seasonal changes in soil conditions on soil-gas entry is also examined. Despite large seasonal changes in near-surface soil moisture content and air permeability, there is no observable effect on soil-gas entry, apparently because critical soil conditions near the soil-gas entry location in the structure floor remain relatively constant. 24 refs., 5 figs., 1 tab.

Approximately ten percent of the energy consumed in U.S. commercial buildings is used by HVAC systems to condition outdoor ventilation air. Reducing ventilation rates would be a simple and broadly-applicable energy retrofit option, if practical counter measures were available that maintained acceptable concentrations of indoor-generated air pollutants. The two general categories of countermeasures are: 1) indoor pollutant source control, and 2) air cleaning. Although pollutant source control should be used to the degree possible, source control is complicated by the large number and changing nature of indoor pollutant sources. Particle air cleaning is already routinely applied in commercial buildings. Previous calculations indicate that particle filtration consumes only 10percent to 25percent of the energy that would otherwise be required to achieve an equivalent amount of particle removal with ventilation. If cost-effective air cleaning technologies for volatile organic compounds (VOCs) were also available, outdoor air ventilation rates could be reduced substantially and broadly in the commercial building stock to save energy. The research carried out in this project focuses on developing novel VOC air cleaning technologies needed to enable energy-saving reductions in ventilation rates. The minimum required VOC removal efficiency to counteract a 50percent reduction in ventilation rate for air cleaning systems installed in the HVAC supply airstream is modest (generally 20percent or less).

Recommended Changes to Specifications for Demand Controlled Ventilation in California’s Title 24 Building Energy Efficiency Standards W.J. Fisk, D.P. Sullivan, D. Faulkner Environmental Energy Techologies Division Indoor Environment Department Lawrence Berkeley National Laboratory Berkeley, CA 94720 April 8, 2010 The research reported here was supported by the California Energy Commission Public Interest Energy Research program award number 600303000 and by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of the Building Technologies Program, U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

CO 2 MONITORING FOR DEMAND CONTROLLED VENTILATION IN COMMERCIAL BUILDINGS W.J. Fisk, D.P. Sullivan, D. Faulkner, E.Eliseeva Environmental Energy Technologies Division Indoor Environment Department Lawrence Berkeley National Laboratory Berkeley, CA 94720 March 17, 2010 The research reported here was supported by the California Energy Commission Public Interest Energy Research program award number 600303000 and by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of the Building Technologies Program, U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Author(s): Destaillats, Hugo | Abstract: Chemical reactions involving ozone of outdoor origin and indoor materials are known to be significant sources of formaldehyde and other irritant gas-phase oxidation products in the indoor environment. HVAC filters are exposed to particularly high ozone concentrations--close to outdoor levels. In this study, we investigated chemical processes taking place on the surface of filters that included fiberglass, polyester, cotton/polyester blend and synthetic (e.g., polyolefin) filter media. Ozone reactions were studied on unused filter media, and on filters that were deployed for 3 months in two different locations: at the Lawrence Berkeley National Laboratory and at the Port of Oakland. Specimens from each filter were exposed to ozone under controlled conditions in a laboratory flow tube at a constant flow of dry or humidified air (50percent relative humidity). Ozone was generated with a UV source upstream of the flow tube, and monitored using a photometric detector. Ozone breakthrough curves were recorded for each sample exposed to ~;;150 ppbv O3 for periods of ~;;1000 min, from which we estimated their uptake rate. Most experiments were performed at 1.3 L/min (corresponding to a face velocity of 0.013 m/s), except for a few tests performed at a higher airflow rate, to obtain a face velocity of 0.093 m/s, slightly closer to HVAC operation conditions. Formaldehyde and acetaldehyde, two oxidation byproducts, were collected downstream of the filter and quantified. Emissions of these volatile aldehydes were consistently higher under humidified air than under dry conditions, at which levels were near the limit of detection. Our results confirm that there are significant reactions of ozone as air containing ozone flows through HVAC filters, particularly when the filters are loaded with particles and the air is humidified. The amount of ozone reacted was not clearly related to the types of filter media, e.g., fiberglass versus synthetic. Specific fiberglass filters that were coated with an impaction oil showed significantly higher formaldehyde emissions than most other samples. Those emissions were magnified in the presence of particles (i.e., in used filters), and were observed even in the absence of ozone, which suggests that hydrolysis of filter binder or tackifier additives may be the reason for those high emissions. Mass balance calculations indicate that the emission rates of formaldehyde and acetaldehyde from the filters are generally not large enough to substantially increase indoor formaldehyde or acetaldehyde concentrations.

LBL-31942 UC-402 Preprint ITlI Lawrence Berkeley Laboratory If l1l;:I UNIVERSITY OF CALIFORNIA ENERGY & ENVIRONMENT DIVISION Submitted to Environmental Science and Technology Field Study and Numerical Simulation of SubSlab Ventilation Systems Y.c. Bonnefous, A.J. Gadgil, W.J. Fisk, R.J. Prill, and A.R. Nematollahi May 1992 ol-Lr H,(J ~~z o OJ ;t>- ENERGY & ENVIRONMENT DIVISION i-' n ::r;-wo- l-:> t

Where indoor concentrations are high, radon entry into houses with basements is usually due primarily to the convective transport of soil gas through openings in the subsurface part of the building shell. The factors determining the rate of entry may conveniently be divided into those associated with the undisturbed soil and those associated with the structure and its surroundings. This paper uses a numerical model to determine the influence of the latter factors on the soil gas and radon entry rates. The most important of these is the presence or absence of a gravel layer below the slab; the presence of the gravel can increase the radon entry rate through the perimeter gap betureen the foundation footer, slab, and wall (slab-footer gap) by as much as a factor of 5 over that for homogazeous soil. The permeability of the gravel becomes important when the soil permeability is unusually high, i.e., greater than 10−10 m2. Of lesser importance are the thickness of the gravel layer and the radium content of the gravel. The sizes and numbers of openings in the slab are relatively unimportant so long as the total opening area is vey small compared to the slab area. If cracks in the basement walls are major radon entry paths, as in concrete-block construction, the permeability of the soil restored to the region adjacent to the walls after completion of construction (backfill) is the determining factor in convective radon entry through these openings; if the soil is packed loosely, so that there is a gap between wall and soil, radon entry through a wall crack may be further increased by as much as a factor of 7.5. Radon entry rates through the slab-footer gap and through openings in the slab are only weakly influenced by the permeability of the backfill. The resistance of the perimeter gap to soil gas entry becomes significant when the gap width falls below 0.001 m, assuming a soil permeability of 10−11 m2.

This pilot scale study evaluated the counting accuracy of two people counting systems that could be used in demand controlled ventilation systems to provide control signals for modulating outdoor air ventilation rates. The evaluations included controlled challenges of the people counting systems using pre-planned movements of occupants through doorways and evaluations of counting accuracies when naive occupants (i.e., occupants unaware of the counting systems) passed through the entrance doors of the building or room. The two people counting systems had high counting accuracy accuracies, with errors typically less than 10percent, for typical non-demanding counting events. However, counting errors were high in some highly challenging situations, such as multiple people passing simultaneously through a door. Counting errors, for at least one system, can be very high if people stand in the field of view of the sensor. Both counting system have limitations and would need to be used only at appropriate sites and where the demanding situations that led to counting errors were rare.

Data from published studies were combined and analyzed to develop best-fit equations and curves quantifying the change in sick building syndrome (SBS) symptom prevalence with ventilation rate. For each study, slopes were calculated, representing the fractional change in SBS symptom prevalence per unit change in ventilation rate per person. Values of ventilation rate, associated with each value of slope, were also calculated. Linear regression equations were fit to the resulting data points, after weighting by study size. Integration of the slope-ventilation rate equations yielded curves of relative SBS symptom prevalence versus ventilation rate. Based on these analyses, relative SBS symptom prevalence increases approximately 23percent (12percent to 32percent) as the ventilation rate drops from 10 to 5 L/s-person and relative prevalence decreases approximately 29percent (15percent to 42percent) as ventilation rate increases from 10 to 25 L/s-person.

We developed and pilot-tested an overall protocol for intervention studies to evaluate the effects of indoor environmental changes in office buildings on the health symptoms and comfort of occupants. The protocol includes a web-based survey to assess the occupant's responses, as well as specific features of study design and analysis. The pilot study, carried out on two similar floors in a single building, compared two types of ventilation system filter media. With support from the building's Facilities staff, the implementation of the filter change intervention went well. While the web-based survey tool worked well also, low overall response rates (21-34percent among the three work groups included) limited our ability to evaluate the filter intervention., The total number of questionnaires returned was low even though we extended the study from eight to ten weeks. Because another simultaneous study we conducted elsewhere using the same survey had a high response rate (>70percent), we conclude that the low response here resulted from issues specific to this pilot, including unexpected restrictions by some employing agencies on communication with occupants.

We model radon entry into basements using a previously developed three-dimensional steady-state finite difference model that has been modified in the following ways: first, cylindrical coordinates are used to take advantage of the symmetry of the problem in the horizontal plane, thereby increasing resolution and computing eficiency without signifiant loss of generality; second, the configuration of the basement has been made m e realistic by incorporating the concrete fmtm which sup ports the basement walls and floor; third, a quadratic relationship between the pressure and flow in the L-shaped gap between slab, footer, and wall has been employed; and fourth, the natural convection of the soil gas which follows from the heating of the basement in winter has been taken into account. The temperature field in the soil is determined fiom the equation of energy consmation, using the basement, surface, and deep-soil temperatures as boundary conditions. The pressure field is determined from Darcy's law and the equation of mass conservation (continuity), assuming that there is nofIow across any boundary except the soil surface (atmospheric pressure) and the opening in the basement shell (fixed pressure), Since the energy conservation equation includes both heat advection and conduction, the temperature and pressure equations must be coupled. After the pressure and temperature fields have been obtained, the velocity field is found fiom Darcy's h. Finally, the radon concentration field is found from the equation of mass-transport, assuming that diffusive entry through openings may be neglected. The convective radon entry rate through the opening or openings is then calculated. In this paper we describe the modified model, compare the predicted radon entry rates with and without the consideration of thermal convection, and compare the predicted rates with rates determined from data from seven houses in the Spokane River valley of Washington and Idaho. Although the predicted rate is much lower than the mean of the rates determined from measurements, er-TOTS in the measurement of soil permeability and variations in the permeability of the area immediately under the basement slab, which has a signifiant influence on the pressure field, can account for the range of entry rates inferredfiom the data.

Radon control systems were installed and evaluated in fourteen homes in the Spokane River Valley/Rathdrum Prairie and in one home in Vancouver, Washington. Because of local soil conditions, subsurface ventilation (SSV) by pressurization was always more effective in these houses than SSV by depressurization in reducing indoor radon levels to below guidelines. Basement overpressurization was successfully applied in five houses with airtight basements where practical-sized fans could develop an overpressure of 1 to 3 Pascals. Crawlspace ventilation was more effective than crawlspace isolation in reducing radon entry from the crawlspace, but had to be used in conjunction with other mitigation techniques, from the crawlspace, but had to be used in conjunction with other mitigation techniques, since the houses also had basements. Indoor radon concentrations in two houses with air-to-air heat exchangers (AAHX) were reduced to levels inversely dependent on the new total ventilation rates and were lowered even further in one house where the air distribution system was modified. Sealing penetrations in the below-grade surfaces of substructures was relatively ineffective in controlling radon. Operation of the radon control systems (except for the AAHX's) made no measurable change in ventilation rates or indoor concentrations of other measured pollutants. Installation costs rangedmore » from approximately {dollar sign}4/m{sup 2} for sealing to {dollar sign}28/m{sup 2} for the AAHXs. Annual operating costs for the active systems were estimated to be approximately {dollar sign}60 to {dollar sign}170.« less

Practical and accurate technologies are needed for continuously measuring and controlling outdoor air (OA) intake rates in commercial building heating, ventilating, and air conditioning (HVAC) systems. This project evaluated two new measurement approaches. Laboratory experiments determined that OA flow rates were measurable with errors generally less than 10percent using electronic air velocity probes installed between OA intake louver blades or at the outlet face of louvers. High accuracy was maintained with OA flow rates as low as 15percent of the maximum for the louvers. Thus, with this measurement approach HVAC systems do not need separate OA intakes for minimum OA supply. System calibration parameters are required for each unique combination of louver type and velocity sensor location but calibrations are not necessary for each system installation. The research also determined that the accuracy of measuring OA flow rates with velocity probes located in the duct downstream of the intake louver was not improved by installing honeycomb airflow straighteners upstream of the probes. Errors varied with type of upstream louver, were as high as 100percent, and were often greater than 25percent. In conclusion, use of electronic air velocity probes between the blades of OA intake louvers or at the outlet face of louvers is a highly promising means of accurately measuring rates of OA flow into HVAC systems. The use of electronic velocity probes downstream of airflow straighteners is less promising, at least with the relatively small OA HVAC inlet systems employed in this research.

Heating, ventilating, and cooling classrooms in California consume substantial electrical energy. Indoor air quality (IAQ) in classrooms affects student health and performance. In addition to airborne pollutants that are emitted directly by indoor sources and those generated outdoors, secondary pollutants can be formed indoors by chemical reaction of ozone with other chemicals and materials. Filters are used in nearly all classroom heating, ventilation and air-conditioning (HVAC) systems to maintain energy-efficient HVAC performance and improve indoor air quality; however, recent evidence indicates that ozone reactions with filters may, in fact, be a source of secondary pollutants. This project quantitatively evaluated ozone deposition in HVAC filters and byproduct formation, and provided a preliminary assessment of the extent to which filter systems are degrading indoor air quality. The preliminary information obtained will contribute to the design of subsequent research efforts and the identification of energy efficient solutions that improve indoor air quality in classrooms and the health and performance of students.

Heating, ventilating, and cooling classrooms in California consume substantial electrical energy. Indoor air quality (IAQ) in classrooms affects studenthealth and performance. In addition to airborne pollutants that are emitted directly by indoor sources and those generated outdoors, secondary pollutants can be formed indoors by chemical reaction of ozone with other chemicals and materials. Filters are used in nearly all classroom heating, ventilation and air?conditioning (HVAC) systems to maintain energy-efficient HVAC performance and improve indoor air quality; however, recent evidence indicates that ozone reactions with filters may, in fact, be a source of secondary pollutants. This project quantitatively evaluated ozone deposition in HVAC filters and byproduct formation, and provided a preliminary assessment of the extent towhich filter systems are degrading indoor air quality. The preliminary information obtained will contribute to the design of subsequent research efforts and the identification of energy efficient solutions that improve indoor air quality in classrooms and the health and performance of students.

Seit es Raumlufttechnische Anlagen gibt, wurde uber ihre Wirtschaftlichkeit nachgedacht, am haufigsten, um verschiedene Anlagenkonzepte miteinander zu vergleichen. Ein Zusammenhang von Raumklima und Produktivitat wurde fruher auch schon untersucht. Ein Uberblick uber einige sehr fruhe und ausfuhrliche Arbeiten wird in [O-36, 37] gegeben, bei denen vor allem der Einfluss zu niedriger und zu hoher Temperaturen und zu starken Larms auf die Arbeitsproduktivitat untersucht wurde. Jetzt gibt es eine viel umfassendere Untersuchung [O-25], die hier in etwas gekurzter Fassung wiedergegeben werden soll. Diese Untersuchung ist die Basis eines REHVA Guide Books [O-38]. Hier wird der Einfluss des Raumklimas, also auch der Einfluss der Luftqualitat, des Ausenluftwechsels auf die Leistungsfahigkeit, aber auch auf Fehlzeiten durch Infektionskrankheiten ausgedehnt. Die Schwierigkeit der Materie und die Unsicherheit der Aussagen werden nicht bestritten, aber das Argument, dass unsichere Annahmen zu besseren Ergebnissen fuhren konnen als gar keine, uberzeugt und gibt den Mut sie [O-25] hier wiederzugeben.

The Institute of Medicine (IOM) of the National Academy of Sciences recently completed a critical review of the scientific literature pertaining to the association of indoor dampness and mold contamination with adverse health effects. In this paper, we report the results of quantitative meta-analysis of the studies reviewed in the IOM report. We developed point estimates and confidence intervals (CIs) to summarize the association of several respiratory and asthma-related health outcomes with the presence of dampness and mold in homes. The odds ratios and confidence intervals from the original studies were transformed to the log scale and random effect models were applied to the log odds ratios and their variance. Models were constructed both accounting for the correlation between multiple results within the studies analyzed and ignoring such potential correlation. Central estimates of ORs for the health outcomes ranged from 1.32 to 2.10, with most central estimates between 1.3 and 1.8. Confidence intervals (95%) excluded unity except in two of 28 instances, and in most cases the lower bound of the CI exceeded 1.2. In general, the two meta-analysis methods produced similar estimates for ORs and CIs. Based on the results of the meta-analyses, building dampness and mold are associated with approximately 30% to 80% increases in a variety of respiratory and asthma-related health outcomes. The results of these meta-analyses reinforce the IOM's recommendation that actions be taken to prevent and reduce building dampness problems.

UNLABELLED: Ultraviolet photocatalytic oxidation (UVPCO) systems for removal of volatile organic compounds (VOCs) from air are being considered for use in office buildings. Here, we report an experimental evaluation of a UVPCO device with tungsten oxide modified titanium dioxide (TiO2) as the photocatalyst. The device was challenged with complex VOC mixtures. One mixture contained 27 VOCs characteristic of office buildings and another comprised 10 VOCs emitted by cleaning products, in both cases at realistic concentrations (low ppb range). VOC conversion efficiencies varied widely, usually exceeded 20%, and were as high as approximately 80% at about 0.03 s residence time. Conversion efficiency generally diminished with increased airflow rate, and followed the order: alcohols and glycol ethers > aldehydes, ketones, and terpene hydrocarbons > aromatic and alkane hydrocarbons > halogenated aliphatic hydrocarbons. Conversion efficiencies correlated with the Henry's law constant more closely than with other physicochemical parameters. An empirical model based on the Henry's law constant and the gas-phase reaction rate with hydroxyl radical provided reasonable estimates of pseudo-first order photocatalytic reaction rates. Formaldehyde, acetaldehyde, acetone, formic acid and acetic acid were produced by the device due to incomplete mineralization of common VOCs. Formaldehyde outlet/inlet concentration ratios were in the range 1.9-7.2. PRACTICAL IMPLICATIONS: Implementation of air cleaning technologies for both VOCs and particles in office buildings may improve indoor air quality, or enable indoor air quality levels to be maintained with reduced outdoor air supply and concomitant energy savings. One promising air cleaning technology is ultraviolet photocatalytic oxidation (UVPCO) air cleaning. For the prototype device evaluated here with realistic mixtures of VOCs, conversion efficiencies typically exceeded the minimum required to counteract predicted VOC concentration increases from a 50% reduction in ventilation. However, the device resulted in the net generation of formaldehyde and acetaldehyde from the partial oxidation of ubiquitous VOCs. Further development of the technology is needed to eliminate these hazardous air pollutants before such a UVPCO device can be deployed in buildings.

LBNL-62202 Evaluation of a Combined Ultraviolet Photocatalytic Oxidation (UVPCO) / Chemisorbent Air Cleaner for Indoor Air Applications Alfred T. Hodgson, Hugo Destaillats, Toshifumi Hotchi, and William J. Fisk Environmental Energy Technologies Division Indoor Environment Department E.O. Lawrence Berkeley National Laboratory Berkeley, CA, USA January 27, 2007 This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Building Technologies Program of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Carbon dioxide (CO{sub 2}) sensors are often deployed in commercial buildings to obtain CO{sub 2} data that are used to automatically modulate rates of outdoor air supply. The goal is to keep ventilation rates at or above code requirements, but to also to save energy by avoiding over ventilation relative to code requirements. However, there have been many anecdotal reports of poor CO{sub 2} sensor performance in actual commercial building applications. This study evaluated the accuracy of 44 CO{sub 2} sensors located in nine commercial buildings to determine if CO{sub 2} sensor performance, in practice, is generally acceptable or problematic. CO{sub 2} measurement errors varied widely and were sometimes hundreds of parts per million. Despite its small size, this study provides a strong indication that the accuracy of CO{sub 2} sensors used in commercial buildings is frequently less than is needed to measure peak indoor-outdoor CO{sub 2} concentration differences with less than a 20% error. Thus, we conclude that there is a need for more accurate CO{sub 2} sensors and/or better sensor maintenance or calibration procedures.

This paper provides a review of current knowledge about the suitability of sorbent-based air cleaning for removing volatile organic compounds (VOCs) from the air in commercial buildings as needed to enable reductions in ventilation rates and associated energy savings. The fundamental principles of sorbent air cleaning are introduced, criteria are suggested for sorbent systems that can counteract indoor VOC concentration increases from reduced ventilation, major findings from research on sorbent performance for this application are summarized, novel sorbent technologies are described, and related priority research needs are identified. Major conclusions include: sorbent systems can remove a broad range of VOCs with moderate to high efficiency, sorbent technologies perform effectively when challenged with VOCs at the low concentrations present indoors, and there is a large uncertainty about the lifetime and associated costs of sorbent air cleaning systems when used in commercial buildings for indoor VOC control. Suggested priority research includes: experiments to determine sorbent system VOC removal efficiencies and lifetimes considering the broad range and low concentration of VOCs indoors; evaluations of in-situ regeneration of sorbents; and an updated analysis of the cost of sorbent air cleaning relative to the cost of ventilation.

Outdoor air ventilation rates vary considerably between and within buildings, and may be too low in some spaces. The purpose of this study was to evaluate the potential work performance benefits of increased ventilation. We analyzed the literature relating work performance with ventilation rate and employed statistical analyses with weighting factors to combine the results of different studies. The studies included in the review assessed performance of various tasks in laboratory experiments and measured performance at work in real buildings. Almost all studies found increases in performance with higher ventilation rates. The studies indicated typically a 1-3% improvement in average performance per 10 l/s-person increase in outdoor air ventilation rate. The performance increase per unit increase in ventilation was bigger with ventilation rates below 20 l/s-person and almost negligible with ventilation rates over 45 l/s-person. The performance increase was statistically significant with increased ventilation rates up to 15 l/s-person with 95% CI and up to 17 l/s-person with 90% CI. Practical Implications We have demonstrated a quantitative relationship between work performance and ventilation within a wide range of ventilation rates. The model shows a continuous increase in performance per unit increase in ventilation rate from 6.5 l/s-person to 65 l/s-person. The increase is statistically significant up to 15 l/s-person. This relationship has a high level of uncertainty; however, use of this relationship in ventilation design and feasibility studies may be preferable to the current practice, which ignores the relationship between ventilation and productivity.

LBNL-59074 Parametric Evaluation of an Innovative Ultra-Violet Photocatalytic Oxidation (UVPCO) Air Cleaning Technology for Indoor Applications Alfred T. Hodgson, Douglas P. Sullivan, and William J. Fisk Indoor Environment Division, Environmental Energy Technologies Division, E.O. Lawrence Berkeley National Laboratory, Berkeley, CA, USA October 31, 2005 Abstract An innovative Ultra-Violet Photocatalytic Oxidation (UVPCO) air cleaning technology employing a semitransparent catalyst coated on a semitransparent polymer substrate was evaluated to determine its effectiveness for treating mixtures of volatile organic compounds (VOCs) representative of indoor environments at low, indoor-relevant concentration levels. The experimental UVPCO contained four 30 by 30-cm honeycomb monoliths irradiated with nine UVA lamps arranged in three banks. A parametric evaluation of the effects of monolith thickness, air flow rate through the device, UV power, and reactant concentrations in inlet air was conducted for the purpose of suggesting design improvements. The UVPCO was challenged with three mixtures of VOCs. A synthetic office mixture contained 27 VOCs commonly measured in office buildings. A building product mixture was created by combining sources including painted wallboard, composite wood products, carpet systems, and vinyl flooring. The third mixture contained formaldehyde and acetaldehyde. Steady state concentrations were produced in a classroom laboratory or a 20-m 3 chamber. Air was drawn through the UVPCO, and single-pass conversion efficiencies were measured from replicate samples collected upstream and downstream of the reactor. Thirteen experiments were conducted in total. In this UVPCO employing a semitransparent monolith design, an increase in monolith thickness is expected to result in general increases in both reaction efficiencies and absolute reaction rates for VOCs oxidized by photocatalysis. The thickness of individual monolith panels

LBNL-58936 Evaluation of Ultra-Violet Photocatalytic Oxidation (UVPCO) for Indoor Air Applications: Conversion of Volatile Organic Compounds at Low Part-per-Billion Concentrations Alfred T. Hodgson, Douglas P. Sullivan, and William J. Fisk Indoor Environment Department, Environmental Energy Technologies Division, E.O. Lawrence Berkeley National Laboratory, Berkeley, CA, USA September 30, 2005 Abstract Efficient removal of indoor generated airborne particles and volatile organic compounds (VOCs) in office buildings and other large buildings may allow for a reduction in outdoor air supply rates with concomitant energy savings while still maintaining acceptable indoor air quality in these buildings. Ultra-Violet Photocatalytic Oxidation (UVPCO) air cleaners have the potential to achieve the necessary reductions in indoor VOC concentrations at relatively low cost. In this study, laboratory experiments were conducted with a scaled, prototype UVPCO device designed for use in a duct system. The experimental UVPCO contained two 30 by 30-cm honeycomb monoliths coated with titanium dioxide and 3% by weight tungsten oxide. The monoliths were irradiated with 12 UVC lamps arranged in four banks. The UVPCO was challenged with four mixtures of VOCs typical of mixtures encountered in indoor air. A synthetic office mixture contained 27 VOCs commonly measured in office buildings. A cleaning product mixture contained three cleaning products with high market shares. A building product mixture was created by combining sources including painted wallboard, composite wood products, carpet systems, and vinyl flooring. A fourth mixture contained formaldehyde and acetaldehyde. Steady-state concentrations were produced in a classroom laboratory or a 20-m 3 environmental chamber. Air was drawn through the UVPCO, and single pass conversion efficiencies were measured from replicate air samples collected upstream and downstream of the reactor section. Concentrations of the mixtures were manipulated, with concentrations of individual VOCs mostly maintained below 10 ppb. Device

Technologies for real-time continuous measurement of the flow rates of outdoor air (OA) into HVAC systems are now available commercially. Our prior papers reported on laboratory-based evaluations of these measurement technologies and this document describes the methods and results of a field study of the accuracy of three of these technologies. From the field study data, we determined that neither wind speed nor wind direction have an important adverse impact on measurement accuracy. The field study confirmed that these three measurement technologies can provide reasonably accurate measurements of outdoor air intake rates in field settings, if the pressure signals are measured with high accuracy. Some of the pressure transducers marketed for use with commercial HVAC systems were determined to be sufficiently accurate for this application. Given the significant impact of OA flow rates on both energy use and occupant health, more widespread use of technologies that provide for real time measurements of OA flow rates seems warranted.

The primary goals of this research effort were to develop, evaluate, and demonstrate a practical HVAC system for classrooms that consistently provides classrooms with the quantity of ventilation in current minimum standards, while saving energy, and reducing HVAC-related noise levels. This research was motivated by several factors, including the public benefits of energy efficiency, evidence that many classrooms are under-ventilated, and public concerns about indoor environmental quality in classrooms. This project involved the installation and verification of the performance of an Improved Heat Pump Air Conditioning (IHPAC) system, and its comparison, a standard HVAC system having an efficiency of 10 SEER. The project included the verification of the physical characteristics suitable for direct replacement of existing 10 SEER systems, quantitative demonstration of improved energy efficiency, reduced acoustic noise levels, quantitative demonstration of improved ventilation control, and verification that the system would meet temperature control demands necessary for the thermal comfort of the occupants. Results showed that the IHPAC met these goals. The IHPAC was found to be a direct bolt-on replacement for the 10 SEER system. Calculated energy efficiency improvements based on many days of classroom cooling or heating showed that the IHPAC system is about 44% more efficient duringmore » cooling and 38% more efficient during heating than the 10 SEER system. Noise reduction was dramatic, with measured A-weighed sound level for fan only operation conditions of 34.3 dB(A), a reduction of 19 dB(A) compared to the 10 SEER system. Similarly, the IHPAC stage-1 and stage-2 compressor plus fan sound levels were 40.8 dB(A) and 42.7 dB(A), reductions of 14 and 13 dB(A), respectively. Thus, the IHPAC is 20 to 35 times quieter than the 10 SEER systems depending upon the operation mode. The IHPAC system met the ventilation requirements and was able to provide consistent outside air supply throughout the study. Indoor CO2 levels with simulated occupancy were maintained below 1000 ppm. Finally temperature settings were met and controlled accurately. The goals of the laboratory testing phase were met and this system is ready for further study in a field test of occupied classrooms.« less

We investigated the relationship between ventilation rates and individual work performance in a call center, and controlled for other factors of the indoor environment. We randomized the position of the outdoor air control dampers, and measured ventilation rate, differential (indoor minus outdoor) carbon dioxide (DeltaCO(2)) concentration, supply air velocity, temperature, humidity, occupant density, degree of under-staffing, shift length, time of day, and time required to complete two different work performance tasks (talking with clients and post-talk wrap-up to process information). DeltaCO(2) concentrations ranged from 13 to 611 p.p.m. We used multivariable regression to model the association between the predictors and the responses. We found that agents performed talk tasks fastest when the ventilation rate was highest, but that the relationship between talk performance and ventilation was not strong or monotonic. We did not find a statistically significant association between wrap-up performance and ventilation rate. Agents were slower at the wrap-up task when the temperature was high (25.4 degrees C). Agents were slower at wrap-up during long shifts and when the call center was under-staffed.The productivity benefits of ventilation rates that exceed common standards such as ASHRAE Standard 62 may be small (0-2%), and other factors may have a larger impact on productivity. Understaffing and long shifts should be avoided because both showed a negative impact on performance. In this study, high temperature had the largest statistically significant impact on productivity and was caused by occupants fighting over the thermostat setpoint. Care should be taken to avoid high temperatures in call centers. If occupants are allowed to adjust temperature setpoints, then the size and/or duration of the setpoint change should be restricted.

In chamber experiments, we investigated the ventilation effectiveness and thermal comfort of a task ventilation system with an air supply nozzle located underneath the front edge of a desk and directing air towards a heated mannequin or a human volunteer seated at the desk. The task ventilation system provided outside air, while another ventilation system provided additional space cooling but no outside air. Test variables included the vertical angle of air supply (-15 degrees to 45 degrees from horizontal), and the supply flow rate of (3.5-6.5 l/s). Using the tracer gas step-up and step-down procedures, the measured air change effectiveness (i.e., exhaust air age divided by age of air in the breathing zone) in experiments with the mannequin ranged from 1.4 to 2.7 (median, 1.8), whereas with human subjects the air change effectiveness ranged from 1.3 to 2.3 (median, 1.6). The majority of the air change effectiveness values with the human subjects were less than values with the mannequin using comparable tests. Similarly, the tests run with supply air temperature equal to the room air temperature had lower air change effectiveness values than comparable tests with the supply air temperature lower ( approximately 5 degrees C) than the room air temperature. The air change effectiveness values are higher than typically reported for commercially-available task ventilation or displacement ventilation systems. Based on surveys completed by the subjects, operation of the task ventilation system did not cause thermal discomfort.With a desk-edge-mounted task ventilation system it is possible to obtain an increase in the effective ventilation rate of 50%. This could lead to reduced energy use. Also, this improvement can be gained while maintaining thermal comfort for occupants. Thus occupants can be thermally comfortable and save energy at the same time.

PurposeThe goal of this project was to develop practical strategies for preventing building‐related symptoms in office buildings, based on the experience of those who investigate buildings with health complaints, and suitable for use by those who own, lease, or manage office space.Design/methodology/approachIdeas from six experienced building investigators on primary causes and key prevention strategies were gathered and prioritized through consensus and voting in a structured, multi‐day workshop.FindingsIEQ investigators from diverse climatic regions agreed on the most important problems causing symptom complaints in office buildings, and the key strategies for prevention. The top ranked problems identified were, in priority order: excessive building moisture, inadequate outdoor air, excessive dust, pollutant gases and odors, inadequate thermal control, and inadequate attention by management to indoor environments. The highest priority recommended prevention strategies for building‐related symptoms were: managing moisture at building exteriors, operating ventilation systems per design intent, providing at least the minimum recommended ventilation rates, and maintaining indoor temperatures at 72°F±2° (22°C±1°). Available scientific findings were generally consistent with these recommendations.Research limitations/implicationsValidity of these findings, from a subjective synthesis of empirical knowledge, not from scientific research, has not yet been scientifically confirmed.Practical implicationsThese recommendations, including managing moisture at building exteriors, providing adequate ventilation, and controlling indoor thermal conditions, provide practical, empirically based guidelines for those who own, manage, or maintain office buildings.Originality/valueThe empirical knowledge of practitioners, concentrated and synthesized here, offers more direct guidance for health‐protective strategies in office buildings than current science.