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COMIS Multizone Air Flow Model

Conjunction Of Multizone Infiltration Specialists

About COMIS -- User Information (and Getting COMIS)

Background -- Capabilities -- History -- COMIS Related Projects at LBNL -- Related Websites

The air flow pattern in a building influences indoor air quality and thermal space conditioning loads. Correct sizing of HVAC (heating, ventilation and air-conditioning) systems should also be based on indoor air flow considerations.

Air flows and their distribution in a given building are caused by pressure differences that can be induced by wind, thermal buoyancy, mechanical ventilation, or a combination of these factors. Building-related properties such as the distribution of openings in the building shell, inner pathways, and occupant activity can also create indoor pressure differences. Two methods exist for characterizing indoor air flow rates: performing air flow measurements using tracer gas techniques, and using mathematical models to model the indoor air flows.

Measurements based on tracer gas techniques can determine the air flows between the inside and the outside of the building, as well as interzonal air flows. However, because tracer gas measurements reflect the prevailing leakage and weather conditions at measurement time, their use in characterizing general building leakage is limited. To describe indoor air flows for any leakage and weather conditions, a number of mathematical models describing interzonal air flow have been developed. One advantage to using these mathematical models is that, in addition to air flows, they can also simulate indoor contaminant transport.

COMIS is one of the most recently developed air flow models. It can be used as a stand-alone program with input and output features, or as an infiltration module that can be integrated into thermal building simulation programs. COMIS is a FORTRAN-based code.


COMIS Capabilities
COMIS models the air flow and contaminant distributions in buildings. The program can simulate several key components influencing air flow: cracks, ducts, duct fittings, fans, flow controllers, vertical large openings (windows and/or doors), kitchen hoods, passive stacks, and "user-defined components".

COMIS allows the user to define schedules describing changes in the indoor temperature distribution, fan operation, pollutant concentration in the zones, pollutant sources and sinks, opening of windows and doors, and the weather data. The flexible time step implemented in COMIS enables the modeling of events independent of the frequency with which the weather data are provided.

The COMIS air flow calculation is based on the assumption that indoor air flows reach steady-state at each time step. The contaminant transport is based on a dynamic model and has its own time step, based on the time constant of the most critical zone. The two models are coupled. Results for air flows and contaminant levels are reported in terms of tables by COMIS and in graphical form by some of the user-interfaces.


History of COMIS
COMIS (Conjunction Of Multizone Infiltration Specialists) was developed in 1988-89 by ten scientists from nine countries, during a twelve-month workshop hosted by the Lawrence Berkeley National Laboratory (LBNL). During the review of the workshop, members of the review panel suggested that COMIS should be "validated" against experimental data.

COMIS participants and Review Panel (1989)

In 1990 the Executive Committee of the International Energy Agency's Buildings and Community Systems Agreement instituted a working group focusing on multizone air flow modeling (Annex 23). Annex 23 was supported between 1990 and 1996 by nine participating nations: Belgium, Canada, France, Greece, Italy, Japan, Switzerland, The Netherlands, and USA. Its objectives were to study the physical phenomena causing air flow and pollutant transport in multizone buildings, develop numerical modules to be integrated in the COMIS multizone air flow modeling system, and evaluate the COMIS code. Annex 23 was dissolved at the end of 1997. The programs developed within the frame of Annex 23 will be maintained by participating countries, and the official COMIS code was handed over to the Swiss agency EMPA in 1998.


COMIS-Related Projects at the Lawrence Berkeley National Laboratory
The Lawrence Berkeley National Laboratory is conducting several ongoing COMIS related projects. Funding has recently been dedicated to integrating COMIS into EnergyPlus, the next generation of thermal building simulation model under development by LBNL and the University of Illinois. Furthermore, COMIS will be enhanced by integrating an aerosol deposition model for rooms and for ducts. The room model (MIAQ4) is in its final stage of development at the University of California, Berkeley. The deposition model for ducts is also under development. Furthermore, we are planning a new module dealing with air flow through staircases. In the frame of IEA/ECBCS Annex 35, Concordia University is developing a zonal model, which also should be implemented into COMIS.


Related Websites
Air Infiltration and Ventilation Centre
EMPA Homepage
International Energy Agency, Annex 23
IISiBat Homepage

LBNL Homepages
LBNL's Homepage
LBNL's Environmental Energy Technologies Division
LBNL's Building Technology and Urban Systems Department

International Energy Agency (IEA)
U.S. Department of Energy

This page was last updated on February 24, 2003

If you have any technical comments or questions about COMIS, please send mail to David Lorenzetti (

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