This study examined the use of zoned ventilation systems using a coupled CONTAM/EnergyPlus model for new California dwellings. Several smart control strategies were developed with a target of halving ventilation-related energy use, largely through reducing dwelling ventilation rates based on zone occupancy. The controls were evaluated based on the annual energy consumption relative to continuously operating non-zoned, code-compliant mechanical ventilation systems. The systems were also evaluated from an indoor air quality perspective using the equivalency approach, where the annual personal concentration of a contaminant for a control strategy is compared to the personal concentration that would have occurred using a continuously operating, non-zoned system. Individual occupant personal concentrations were calculated for the following contaminants of concern: moisture, CO_{2}, particles, and a generic contaminant. Zonal controls that saved energy by reducing outside airflow achieved typical reductions in ventilation-related energy of 10% to 30%, compared to the 7% savings from the unzoned control. However, this was at the expense of increased personal concentrations for some contaminants in most cases. In addition, care is required in the design and evaluation of zonal controls, because control strategies may reduce exposure to some contaminants, while increasing exposure to others.

This project investigated smart ventilation approaches to minimize energy use for providing indoor air quality (IAQ) in high performance new California homes. Evaluation criteria included annual ventilation-related energy, peak energy and time-of-use

savings, and the indoor air quality relative to a minimally code-compliant ventilation system. The simulations used CONTAM’s air flow and contaminant transport model, combined with the EnergyPlus building loads model. House types representing the

default California Energy Code compliance homes were investigated for four California climate zones, covering a wide range of climate types. Both single and multi-zone smart ventilation controls were investigated. Contaminant sources included contaminants emitted continuously and varying with time, temperature and relative humidity, episodic emissions from occupant activities and outdoor particles. Single-zone ventilation controls that varied ventilation depending on outdoor temperatures were able to consistently save half of ventilation-related energy without compromising long-term IAQ. Ventilation strategies that tracked occupancy were less successful, because this work included generic contaminants with constant background emission rates. Energy performance for occupancy controls improved with a one-hour pre-occupancy flush out strategy. The addition of zoning ventilation controls did not offer significant IAQ to energy improvements compared to non-zonal versions of the same ventilation system type. The best controls had HVAC energy savings of 10-20%, with individual cases reaching up to 40% savings. However, these savings cannot be achieved without worsening personal exposures for at least one contaminant. A metric is needed to assess the competing changes in exposure to different contaminants in order to determine the net-health impacts of a control strategy. Controls that directly sensed contaminants and controlled them to acceptable levels showed that the California OEHHA limit for formaldehyde completely dominates system performance, with homes not able to meet the limit even with continuous operation of a fan sized to twice the current code minimum.

A study to assess how the fidelity of wind pressure inputs and indoor model complexity affect the predicted air change rate for a study building is presented. The purpose of the work is to support the development of a combined indoor-outdoor hazard prediction tool, which links the CONTAM multizone building simulation tool with outdoor dispersion models.

The study building, representing a large office block of a simple rectangular geometry under natural ventilation, was based on a real building used in the Joint Urban 2003 experiment. A total of 1600 indoor model flow simulations were made, driven by 100 meteorological conditions which provided a wide range of building surface pressures. These pressures were applied at four levels of resolution to four different building configurations with varying numbers of internal zones and indoor and outdoor flow paths. Analysis of the results suggests that surface pressures and flow paths across the envelope should be specified at a resolution consistent with the dimensions of the smallest volume of interest, to ensure that appropriate outputs are obtained.

10aIndoor models10amultizone10aPressure inputs1 aHerring, Steven, J.1 aBatchelor, Simon1 aBieringer, Paul, E.1 aLingard, Bry1 aLorenzetti, David, M.1 aParker, Simon, T.1 aRodriguez, Luna1 aSohn, Michael, D.1 aSteinhoff, Dan1 aWolski, Matthew uhttps://ses.lbl.gov/publications/providing-pressure-inputs-multizone01966nas a2200289 4500008004100000022001300041245005900054210005900113260001200172300001200184490000800196520113000204653001801334653001401352653002001366100002401386700002101410700002401431700001701455700002601472700002201498700002001520700002201540700001901562700002001581856007501601 2016 eng d a0360132300aProviding pressure inputs to multizone building models0 aProviding pressure inputs to multizone building models c05/2016 a32 - 440 v1013 aA study to assess how the fidelity of wind pressure inputs and indoor model complexity affect the predicted air change rate for a study building is presented. The purpose of the work is to support the development of a combined indoor-outdoor hazard prediction tool, which links the CONTAM multizone building simulation tool with outdoor dispersion models.

The study building, representing a large office block of a simple rectangular geometry under natural ventilation, was based on a real building used in the Joint Urban 2003 experiment. A total of 1600 indoor model flow simulations were made, driven by 100 meteorological conditions which provided a wide range of building surface pressures. These pressures were applied at four levels of resolution to four different building configurations with varying numbers of internal zones and indoor and outdoor flow paths. Analysis of the results suggests that surface pressures and flow paths across the envelope should be specified at a resolution consistent with the dimensions of the smallest volume of interest, to ensure that appropriate outputs are obtained.

10aIndoor models10amultizone10aPressure inputs1 aHerring, Steven, J.1 aBatchelor, Simon1 aBieringer, Paul, E.1 aLingard, Bry1 aLorenzetti, David, M.1 aParker, Simon, T.1 aRodriguez, Luna1 aSohn, Michael, D.1 aSteinhoff, Dan1 aWolski, Matthew uhttps://ses.lbl.gov/publications/providing-pressure-inputs-multizone-002678nas a2200241 4500008004100000022001300041245007300054210006900127260001200196300001400208490000700222520194400229653002702173653001502200653002202215653002102237653002202258653001602280100002202296700002602318700002202344856007002366 2014 eng d a0360132300aImplementing state-space methods for multizone contaminant transport0 aImplementing statespace methods for multizone contaminant transp c01/2014 a131 - 1390 v713 aThe “well-mixed zone” approximation is a useful model for simulating contaminant transport in buildings. Multizone software tools such as CONTAM [1] and COMIS [2] use time-marching numerical methods to solve the resulting ordinary differential equations. By contrast, the state-space approach solves the same equations analytically [3]. A direct analytical solution, using the matrix exponential, is computationally attractive for certain applications, for example, when the airflows do not change for relatively long periods. However, for large systems, even the matrix exponential requires numerical estimation. This paper evaluates two methods for finding the matrix exponential: eigenvalue decomposition, and the Padé algorithm. In addition, it considers a variation optimised for sparse matrices, and compares against a reference backward Euler time-marching scheme.

The state-space solutions can run several orders of magnitude faster than the reference method, with more significant speedups for a greater number of zones. This makes them especially valuable for applications where rapid calculation of concentration and exposure under constant air flow conditions are needed, such as real-time forecasting or monitoring of indoor contaminants. For most models, all three methods have low errors (magnitude of median fractional bias <3·10−5, normalised mean square error <3·10−7, and scaled absolute error <4·10−4). However, for the largest model considered (1701 zones) eigenvalue decomposition showed a dramatic increase in error.

10aConcentration solution10aEigenvalue10aIndoor dispersion10aMultizone models10aNumerical methods10aState-space1 aParker, Simon, T.1 aLorenzetti, David, M.1 aSohn, Michael, D. uhttps://ses.lbl.gov/publications/implementing-state-space-methods01469nas a2200265 4500008003900000022001300039245006000052210005700112260001200169300001400181490000700195520074600202653001400948653001100962653001600973653001000989653001400999653001501013653001401028100002601042700001701068700002401085700002201109856007201131 2013 d a0360132300aA stiff, variable time step transport solver for CONTAM0 astiff variable time step transport solver for CONTAM c09/2013 a260 - 2640 v673 aWe describe the implementation of a new transport solver for CONTAM, a whole-building airflow and contaminant transport model developed by the National Institute of Standards and Technology. Based on CVODE, a general-purpose code for ordinary differential equations, the new solver features variable time steps, high-order integration methods, and automatic error control. These techniques can make CONTAM more accurate when simulating fast transport mechanisms such as high air change rates, sorption, and chemical reactions. We present the relevant theory, then describe the modeling decisions needed to integrate CVODE into CONTAM. Testing with two realistic building models shows that CVODE can run faster than the legacy solvers.

10abuildings10acontam10acontaminant10aCVODE10apollutant10asimulation10atransport1 aLorenzetti, David, M.1 aDols, Stuart1 aPersily, Andrew, K.1 aSohn, Michael, D. uhttps://ses.lbl.gov/publications/stiff-variable-time-step-transport01575nas a2200205 4500008003900000245005900039210005900098260001200157300001600169490000700185520097100192653001101163653001901174653001701193653002101210100001901231700002601250700002201276856007101298 2012 d00aSiting Samplers to Minimize Expected Time to Detection0 aSiting Samplers to Minimize Expected Time to Detection c12/2012 a2032 - 20420 v323 aWe present a probabilistic approach to designing an indoor sampler network for detecting an accidental or intentional chemical or biological release, and demonstrate it for a real building. In an earlier article, Sohn and Lorenzetti developed a proof of concept algorithm that assumed samplers could return measurements only slowly (on the order of hours). This led to optimal “detect to treat” architectures that maximize the probability of detecting a release. This article develops a more general approach and applies it to samplers that can return measurements relatively quickly (in minutes). This leads to optimal “detect to warn” architectures that minimize the expected time to detection. Using a model of a real, large, commercial building, we demonstrate the approach by optimizing networks against uncertain release locations, source terms, and sampler characteristics. Finally, we speculate on rules of thumb for general sampler placement.

10acontam10aindoor airflow10aoptimization10asampler networks1 aWalter, Travis1 aLorenzetti, David, M.1 aSohn, Michael, D. uhttps://ses.lbl.gov/publications/siting-samplers-minimize-expected01493nas a2200157 4500008004100000022001400041245008100055210006900136260001200205300001800217490000700235520097800242100002601220700002201246856006701268 2011 eng d a0013-936X00aNumerical Solution of the Polanyi-DR Isotherm in Linear Driving Force Models0 aNumerical Solution of the PolanyiDR Isotherm in Linear Driving F c09/2011 a10091 - 100950 v453 aThe Polanyi-Dubinin-Radushkevich isotherm has proven useful for modeling the adsorption of volatile organic compounds on microporous materials such as activated carbon. When embedded in a larger dynamic simulation—e.g., of whole-building pollutant transport—it is important to solve the sorption relations as quickly as possible. This work compares numerical methods for solving the Polanyi-DR model, in cases where transport to the surface is assumed linear in the bulk-to-surface concentration differences. We focus on developing numerically stable algorithms that converge across a wide range of inputs, including zero concentrations, where the isotherm is undefined. We identify several methods, including a modified Newton-Raphson search, that solve the system 3-4 times faster than simple bisection. Finally, we present a rule of thumb for identifying when boundary-layer diffusion limits the transport rate enough to justify reducing the model complexity.

1 aLorenzetti, David, M.1 aSohn, Michael, D. uhttps://ses.lbl.gov/publications/numerical-solution-polanyi-dr01539nas a2200121 4500008004100000245002600041210002600067260001700093520120000110100002201310700002601332856005901358 2009 eng d00aIndoor Sampler Siting0 aIndoor Sampler Siting aBusan, Korea3 aContaminant releases in or near a building can lead to significant human exposures unless prompt response is taken. U.S. Federal and local agencies are implementing programs to place air-monitoring samplers in buildings to quickly detect biological agents. We describe a probabilistic algorithm for siting samplers in order to detect accidental or intentional releases of biological material. The algorithm maximizes the probability of detecting a release from among a suite of realistic scenarios. The scenarios may differ in any unknown, for example the release size or location, weather, mode of building operation, etc. The algorithm also can optimize sampler placement in the face of modeling uncertainties, for example the airflow leakage characteristics of the building, and the detection capabilities of the samplers. In anillustrative example, we apply the algorithm to a hypothetical 24-room commercial building, finding optimal networks for a variety of assumed sampler types and performance characteristics. We also discuss extensions of this work for detecting ambient pollutants in buildings, and for understanding building-wide airflow, pollutant dispersion, and exposures.

1 aSohn, Michael, D.1 aLorenzetti, David, M. uhttps://ses.lbl.gov/publications/indoor-sampler-siting01582nas a2200157 4500008004100000245008900041210006900130300000600199520101600205653003001221653002201251100002601273700003001299700002201329856007301351 2007 eng d00aEffect of room air recirculation delay on the decay rate of tracer gas concentration0 aEffect of room air recirculation delay on the decay rate of trac a73 aTracer gas measurements are used to estimate the ﬂow rate of fresh air into a room or building. These methods commonly account for the decay of tracer gas concentration as the result of ventilation air supply and inﬁltration, using a well-mixed model of the space. Some researchers also have considered the effect of leakage in the ventilation ductwork.

This paper considers the effect of recirculation through ventilation ducts on the calculated fresh air supply rate. Transport delay in the ducts can signiﬁcantly alter the time evolution of tracer concentration, and hence alter the estimated air change rate.

This result could be important when interpreting experimental measurements of tracer gas decay in a space with recirculating ventilation. For instance, transport delays longer than ten minutes have been observed due to low airspeeds in a ceiling return plenum. This paper shows that such long delays can have a signiﬁcant impact on the estimated building air change rate.

10arecirculating ventilation10atracer decay rate1 aLorenzetti, David, M.1 aKristoffersen, Astrid, H.1 aGadgil, Ashok, J. uhttps://ses.lbl.gov/publications/effect-room-air-recirculation-delay00370nas a2200121 4500008004100000245003700041210003600078300001200114490000700126100002200133700002600155856006700181 2007 eng d00aSiting Bio-Samplers in Buildings0 aSiting BioSamplers in Buildings a877-8860 v271 aSohn, Michael, D.1 aLorenzetti, David, M. uhttps://ses.lbl.gov/publications/siting-bio-samplers-buildings01806nas a2200253 4500008004100000245007000041210006800111260005500179300001400234490000900248520093000257653004201187653002101229653001001250653005501260653002301315653001301338653003401351653002101385100002201406700002401428700002601452856007401478 2005 eng d00aAssessing Sheltering-In-Place Responses to Outdoor Toxic Releases0 aAssessing ShelteringInPlace Responses to Outdoor Toxic Releases aBeijing, ChinabTsinghua University Pressc09/2005 a1792-17960 v2(6)3 aAn accidental or intentional outdoor release of pollutants can produce a hazardous plume, potentially contaminating large portions of a metropolitan area as it disperses downwind. To minimize health consequences on the populace, government and research organizations often recommend sheltering in place when evacuation is impractical. Some reports also recommend "hardening" an indoor shelter, for example by applying duct tape to prevent leakage into a bathroom. However, few studies have quantified the perceived beneficial effects of sheltering and hardening, or examined the limits of their applicability. In this paper, we examine how sheltering and hardening might reduce exposure levels under different building and meteorological conditions (e.g., wind direction). We predict concentrations and exposure levels for several conditions, and discuss the net benefits from several sheltering and hardening options.

10aairflow and pollutant transport group10aairflow modeling10acomis10acountermeasures to chemical and biological threats10aemergency response10aexposure10aindoor environment department10ashelter-in-place1 aSohn, Michael, D.1 aSextro, Richard, G.1 aLorenzetti, David, M. uhttps://ses.lbl.gov/publications/assessing-sheltering-place-responses00914nas a2200133 4500008004100000245007500041210006900116260004200185520040900227100002700636700002600663700002200689856006900711 2004 eng d00aCoupled model for simulation of indoor airflow and pollutant transport0 aCoupled model for simulation of indoor airflow and pollutant tra bLawrence Berkeley National Laboratory3 aUnderstanding airflow in buildings is essential for improving energy efficiency, controlling airborne pollutants, and maintaining occupant comfort. Recent research on whole-building airflow simulation has turned toward protecting occupants from threats of chemical or biological agents. Sample applications include helping design systems to reduce exposure, and selecting optimal sensor locations.

1 aJayaraman, Buvaneswari1 aLorenzetti, David, M.1 aGadgil, Ashok, J. uhttps://ses.lbl.gov/publications/coupled-model-simulation-indoor01408nas a2200169 4500008004100000245007900041210006900120260005100189300001000240490000700250520084700257100002501104700002001129700002201149700002601171856004101197 2003 eng d00aImproving Long-Range Energy Modeling: A Plea for Historical Retrospectives0 aImproving LongRange Energy Modeling A Plea for Historical Retros bInternational Association for Energy Economics a75-920 v243 aOne of the most striking things about forecasters is their lack of historical perspective. They rarely do retrospectives, even though looking back at past work can both illuminate the reasons for its success or failure, and improve the methodologies of current and future forecasts. One of the best and most famous retrospectives is that by Hans Landsberg, which investigates work conducted by Landsberg, Sam Schurr, and others. In this article, written mainly for model users, we highlight Landsberg's retrospective as a uniquely valuable contribution to improving forecasting methodologies. We also encourage model users to support such retrospectives more frequently. Finally, we give the current generation of analysts the kind of guidance we believe Landsberg and Sam Schurr would have offered about how to do retrospectives well.

1 aKoomey, Jonathan, G.1 aCraig, Paul, P.1 aGadgil, Ashok, J.1 aLorenzetti, David, M. uhttp://www.jstor.org/stable/4132301302400nas a2200205 4500008004100000245010600041210006900147520166600216100002301882700002201905700002201927700002201949700002601971700002901997700002402026700002402050700002502074700002302099856007202122 2003 eng d00aProtecting Buildings From a Biological or Chemical Attack: actions to take before or during a release0 aProtecting Buildings From a Biological or Chemical Attack action3 aThis report presents advice on how to operate a building to reduce casualties from a biological or chemical attack, as well as potential changes to the building (e.g. the design of the ventilation system) that could make it more secure. It also documents the assumptions and reasoning behind the advice. The particular circumstances of any attack, such as the ventilation system design, building occupancy, agent type, source strength and location, and so on, may differ from the assumptions made here, in which case actions other than our recommendations may be required; we hope that by understanding the rationale behind the advice, building operators can modify it as required for their circumstances. The advice was prepared by members of the Airflow and Pollutant Transport Group, which is part of the Indoor Environment Department at the Lawrence Berkeley National Laboratory. The group's expertise in this area includes: tracer-gas measurements of airflows in buildings (Sextro, Thatcher); design and operation of commercial building ventilation systems (Delp); modeling and analysis of airflow and tracer gas transport in large indoor spaces (Finlayson, Gadgil, Price); modeling of gas releases in multi-zone buildings (Sohn, Lorenzetti, Finlayson, Sextro); and occupational health and safety experience related to building design and operation (Sextro, Delp). This report is concerned only with building design and operation; it is not a how-to manual for emergency response. Many important emergency response topics are not covered here, including crowd control, medical treatment, evidence gathering, decontamination methods, and rescue gear.

1 aPrice, Phillip, N.1 aSohn, Michael, D.1 aGadgil, Ashok, J.1 aDelp, William, W.1 aLorenzetti, David, M.1 aFinlayson, Elizabeth, U.1 aThatcher, Tracy, L.1 aSextro, Richard, G.1 aDerby, Elisabeth, A.1 aJarvis, Sondra, A. uhttps://ses.lbl.gov/publications/protecting-buildings-biological-or00704nas a2200193 4500008004100000245008500041210006900126520003400195100002300229700002200252700002200274700002400296700002600320700002400346700002200370700002500392700002300417856007000440 2002 eng d00aAdvice for first responders to a building during a chemical or biological attack0 aAdvice for first responders to a building during a chemical or b3 aNo Abstract available.

1 aPrice, Phillip, N.1 aDelp, William, W.1 aSohn, Michael, D.1 aThatcher, Tracy, L.1 aLorenzetti, David, M.1 aSextro, Richard, G.1 aGadgil, Ashok, J.1 aDerby, Elisabeth, A.1 aJarvis, Sondra, A. uhttps://ses.lbl.gov/publications/advice-first-responders-building01122nas a2200133 4500008004100000245005200041210005200093260003600145300001200181490000600193520069800199100002600897856006500923 2002 eng d00aAssessing multizone airflow simulation software0 aAssessing multizone airflow simulation software bIndoor Air 2002, Santa Cruz, CA a267-2710 v13 aSeveral standard multizone modeling programs, in order to improve their computational efficiency, make a number of simplifying assumptions. This paper examines how those assumptions reduce the solution times and memory use of the programs, but at the cost of restricting the models they can express. Applications where these restrictions may adversely affect the program's usefulness include: (1) natural ventilation, when buoyancy effects dominate mechanically-driven flow; (2) duct system design, when losses in T- junctions affect the system performance; and (3) control system design, when the dynamic transport of pollutants plays a significant role in the simulated system.

1 aLorenzetti, David, M. uhttps://ses.lbl.gov/publications/assessing-multizone-airflow01511nas a2200121 4500008004100000245006100041210006100102300001400163490000700177520110400184100002601288856007501314 2002 eng d00aComputational Aspects of Nodal Multizone Airflow Systems0 aComputational Aspects of Nodal Multizone Airflow Systems a1083-10900 v373 aThe multizone approach to steady-state airflow problems models a building as a network of discrete mass flow paths. A nodal formulation of the problem writes the governing equations in terms of the unknown pressures at the points where the flow paths connect. This paper proves conditions under which the nodal equations yield symmetric positive-definite matrices, guaranteeing a unique solution to the flow network. It also establishes relaxed conditions under which a nodal airflow system yields asymmetric matrices with positive eigenvalues, guaranteeing at least one solution. Properly exploiting the system properties greatly reduces the cost of numerical solution. Thus, multizone airflow programs such as Contam and Comis depend on symmetric positive-definite systems. However, the background literature neglects or simplifies the underlying assumptions, does not assert existence and uniqueness, and even contains factual errors. This paper corrects those errors, states the implicit assumptions made in the programs, and discusses implications for modelers and programmers.1 aLorenzetti, David, M. uhttps://ses.lbl.gov/publications/computational-aspects-nodal-multizone00587nas a2200157 4500008004100000245007200041210006900113520003400182100002300216700002600239700002200265700002200287700002200309700002300331856007500354 2002 eng d00aInformation for first responders to a chemical or biological attack0 aInformation for first responders to a chemical or biological att3 aNo Abstract available.

1 aPrice, Phillip, N.1 aLorenzetti, David, M.1 aGadgil, Ashok, J.1 aSohn, Michael, D.1 aDelp, William, W.1 aJarvis, Sondra, A. uhttps://ses.lbl.gov/publications/information-first-responders-chemical01351nas a2200169 4500008004100000245004800041210004800089260003600137300001200173490000600185520082300191100002401014700002601038700002201064700002401086856007101110 2002 eng d00aModeling the spread of anthrax in buildings0 aModeling the spread of anthrax in buildings bIndoor Air 2002, Santa Cruz, CA a506-5110 v43 aThe recent contamination of several U.S. buildings by letters containing anthrax demonstrates the need to understand better the transport and fate of anthrax spores within buildings. We modeled the spread of anthrax for a hypothetical office suite and estimated the distribution of mass and resulting occupant exposures. Based on our modeling assumptions, more than 90% of the anthrax released remains in the building during the first 48 hours, with the largest fraction of the mass accumulating on floor surfaces where it is subject to tracking and resuspension. Although tracking and resuspension account for only a small amount of mass transfer, the model results suggests they can have an important effect on subsequent exposures. Additional research is necessary to understand and quantify these processes.

1 aSextro, Richard, G.1 aLorenzetti, David, M.1 aSohn, Michael, D.1 aThatcher, Tracy, L. uhttps://ses.lbl.gov/publications/modeling-spread-anthrax-buildings01678nas a2200205 4500008004100000245007500041210006900116260002500185300001200210520100000222653001801222653000901240653003801249100002901287700001501316700002501331700002601356700002201382856006801404 2002 eng d00aModeling Transient Contaminant Transport in HVAC Systems and Buildings0 aModeling Transient Contaminant Transport in HVAC Systems and Bui aMonterey, California a217-2223 aA mathematical model of the contaminant transport in HVAC systems and buildings is described. The model accounts for transients introduced by control elements such as fans and control dampers. The contaminant transport equations are coupled to momentum equations and mass continuity equations of the air. To avoid modeling variable transport delays directly, ducts are divided into a large number of small sections. Perfect mixing is assumed in each section. Contaminant transport equations are integrated with momentum equations in a way that guarantees mass continuity by using two non-negative velocities for computing the mass transport between elements. Computer simulations illustrate how the model may be used to analyze and design control systems that respond to a sudden release of a toxic contaminant near a building. By coupling transient flow prediction with transient contaminant prediction, the model overcomes a number of problems with existing contaminant transport codes.

10aAir transport10ahvac10aModeling pollutant concentrations1 aFederspiel, Clifford, C.1 aLi, Huilin1 aAuslander, David, M.1 aLorenzetti, David, M.1 aGadgil, Ashok, J. uhttps://ses.lbl.gov/publications/modeling-transient-contaminant01082nas a2200097 4500008004100000245009100041210006900132520069200201100002600893856006500919 2002 eng d00aPredicting Indoor Pollutant Concentrations, and Applications to Air Quality Management0 aPredicting Indoor Pollutant Concentrations and Applications to A3 aBecause most people spend more than 90% of their time indoors, predicting exposure to airborne pollutants requires models that incorporate the effect of buildings. Buildings affect the exposure of their occupants in a number of ways, both by design (for example, filters in ventilation systems remove particles) and incidentally (for example, sorption on walls can reduce peak concentrations, but prolong exposure to semivolatile organic compounds). Furthermore, building materials and occupant activities can generate pollutants. This paper surveys modeling approaches for predicting pollutant concentrations in buildings, and summarizes the application of these models.

1 aLorenzetti, David, M. uhttps://ses.lbl.gov/publications/predicting-indoor-pollutant01160nas a2200097 4500008004100000245004100041210004100082520083900123100002600962856007400988 2001 eng d00aAssessing Multizone Airflow Software0 aAssessing Multizone Airflow Software3 aMultizone models form the basis of most computer simulations of airflow and pollutant transport in buildings. In order to promote computational effciency, some multizone simulation programs, such as COMIS and CONTAM, restrict the form that their flow models may take. While these tools allow scientists and engineers to explore a wide range of building airflow problems, increasingly their use has led to new questions not answerable by the current generation of programs. This paper, directed at software developers working on the next generation of building airflow models, identifies structural aspects of COMIS and related programs that prevent them from easily incorporating desirable new airflow models. The paper also suggests criteria for evaluating alternate simulation environments for future modeling efforts.

1 aLorenzetti, David, M. uhttps://ses.lbl.gov/publications/assessing-multizone-airflow-software01714nas a2200145 4500008004100000245005500041210005500096260009100151300001200242490000600254520118600260100002601446700002201472856007401494 2000 eng d00aImproving Speed and Robustness of the COMIS Solver0 aImproving Speed and Robustness of the COMIS Solver bThe University of Reading, P.O. Box 219, Whiteknights, Reading RG6 6AW, United Kingdom a241-2460 v13 aThe numerical investigation of airflow and chemical transport characteristics for a general class of buildings involves identifying values for model parameters, such as effective leakage areas and temperatures, for which a fair amount of uncertainty exists. A Monte Carlo simulation, with parameter values drawn from likely distributions using Latin Hypercube sampling, helps to account for these uncertainties by generating a corresponding distribution of simulated results. However, conducting large numbers of model runs can challenge a simulation program, not only by increasing the need for fast algorithms, but also by proposing specific combinations of parameter values that may define difficult numerical problems. The paper describes several numerical approaches to improving the speed and reliability of the COMIS multizone airflow simulation program. Selecting a broad class of algorithms based on the mathematical properties of the airflow systems (symmetry and positive-definiteness), it evaluates new solution methods for possible inclusion in the COMIS code. In addition, it discusses further changes that will likely appear in future releases of the program.

1 aLorenzetti, David, M.1 aSohn, Michael, D. uhttps://ses.lbl.gov/publications/improving-speed-and-robustness-comis