NIST Multizone Modeling Website
Weather and Wind
CONTAM enables you to incorporate the effects of weather on a building. Weather parameters include ambient temperature, barometric pressure, wind speed, wind direction and also outdoor contaminant levels. The type of weather data you require for a simulation depends on the type of simulation you are performing, whether you want to account for the effects of wind, and whether or not you are simulating contaminants. If you are performing a steady-state airflow and contaminant simulation, you will only need steady state weather, wind data and contaminant data. If you are performing a transient airflow simulation, you can use either steady state or transient weather data. Transient weather data is implemented through the use of weather files or WTH files. If you are performing transient contaminant simulations, you can use either steady-state or transient ambient contaminant data as well. Transient ambient contaminant data is implemented via the use of ambient contaminant files or CTM files.
NOTE: Both the WTH and CTM files assume a single set of values for the ambient zone at any given point in time, i.e., there is no spatial variation in either the pressure or contaminant fields. However, CONTAM also allows the use of transient wind pressure and contaminant files (WPC file) with which you can account for spatial variation in both the pressures and contaminant concentrations over the surface of a building envelope (See Working with WPC Files).
Wind
Wind pressure can be a significant driving force for air infiltration through a building envelope. It is a function of wind speed, wind direction, building configuration, and local terrain effects. CONTAM enables you to account for the effects of wind pressure on flow paths through the building envelope (external airflow paths). You define how you want to account for wind effect for each external flow path on a case-by-case basis. In ContamW, you can either choose to ignore the effects of wind on an envelope penetration, define wind pressure to be constant for each envelope penetration, or implement variable wind pressures for envelope penetrations.
CONTAM provides a general approach to handling the variable effects of wind on the building envelope. This approach requires you to provide CONTAM with information related to the determination of a local wind pressure coefficient for the building surface.
For a general introduction to the effects of wind pressure on buildings, see Chapter 16, Air flow Around Buildings, in the 2005 ASHRAE Fundamentals Handbook [ASHRAE 2005].
WPC Files
A new method to account for the variation of external wind pressures and outdoor contaminant concentrations over the building envelope has been implemented in CONTAM. This method addresses the need to allow for the use of general, spatially varying wind pressure and ambient contaminant concentrations such as those from wind tunnel experiments or atmospheric models, e.g., plume or puff dispersion simulation tools. This method involves the implementation of a Wind Pressure and Contaminants file (WPC file). This file provides exterior pressure and/or contaminant concentrations time histories for every flow path that connects to the ambient zone including duct terminals and outdoor air intakes of CONTAM's simple air handling systems.
