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What input is needed?

Zoning

A building simulation model consists of one or more zones. A zone can represent a single room or a group of rooms with uniform conditions. The zone represents an air space inside the building and therefore is modelled using the net room volume (internal dimensions). More about the Geometry in ICE you find here: Geometry in ICE.

Floor plan with a single zone over several rooms (red) and a zone for a single room (green)

The different zone models

IDA ICE provides three different zone models: the "Energy" zone model, the "Climate" zone model and the "Climate with stratification" zone model. 

Single-layer (not stratified) zone models

Basically, the not stratified zone model is a single-node model: It describes a volume of well-mixed air that is bounded by surfaces shaped as non-self-intersecting polygons. This volume is regarded as a closed physical system in which the basic conservation laws as, conversation of mass and energy are applied. More detailed information about the zone you find in the model description (SimZone).

This zone model is called "Energy" in  IDA ICE.

“Energy” vs. “Climate” Model

By default, IDA ICE uses the simplest available zone model, called “Energy” model. For more detailed indoor climate modelling (with accurate radiative temperature distribution), the “Climate” zone model is needed. Only the “Climate” zone model can be set to the status “with stratification”, which means that the air space is divided into more than one layer and air flow elements will be considered to reach a correct stratification.

The Energy model has a more conventional level of precision and is based on a mean radiant temperature. All zone models are based on the same description of the building, given in the standard level. All models of components in and around the zone, such as windows, radiators, controllers, leaks, terminals etc., are common to the Energy, Climate and Climate (with stratification) models.

The following table gives an overview of the differences between the three models

Zone model	Energy	Climate	Climate (with stratification)
Model name	SimZone	GgZone
Long wave radiation	Central	View factors
Layer(s)	One	One	More
Balance(s)	One	One	For each layer
Flow elements	No	No	Yes
Description	Well-mixed with simple longwave radiation	Well-mixed with detailed longwave radiation	Stratified with flow elements and detailed longwave radiation
Level of precision	Convenient	Detailed	Very detailed
Simulation Time	Low	Medium	High
Usage	Energy demand, big models, lot of zones	More detailed analysis of indoor air climate	Very detailed analysis of single zones regarding indoor air climate in different layers

The stratified zone model (SZM)

The stratified zone model (SZM) is a "Climate" zone model with different layers. Therefore it is called "Climate (with stratification)" in IDA ICE.

It allows the user to find the temperature, carbon dioxide (CO₂) and vapor fraction distributions along the vertical direction. This is achieved by discretizing the zone in horizontal layers, and by numerically solving balance equations for the flow of these quantities across the layers. Moreover, this 1D vertical finite difference model is augmented with explicit disturbances in the form of jets, plumes, and wall-currents. This is important to get a correct stratification. No stratification without flow elements, and no flow elements without stratification! Finally – as for the non-stratified “Climate” model – the view factors for non-convex geometries with obstacles are properly computed, thereby improving the prediction of the longwave radiation between walls.

The stratified zone model quickly gives the impression of being a three-dimensional model, particularly because of the way the results are displayed. However, this impression is misleading. The three-dimensional impression is created by the fact that two different one-dimensional phenomena (the vertical stratification and the flow elements along a trajectory line in a changing direction) overlap in three dimensions.

Compared to full 3D CFD modelling, the SZM uses a simplified approach focused on the vertical temperature stratification within a zone. Boundary layer flows and supply/exhaust air jets are represented by separate simplified analytical models and coupled through boundary conditions. Interactions between different flow phenomena, turbulent vortices, and airflow around internal objects are not resolved. This significantly reduces computational effort while still capturing the dominant thermal behaviour of the space. However, unlike a CFD simulation (which captures a snapshot), the SZM can provide results dynamically over the entire simulation period.

Strafified Zone Model (SZM)                                       vs.	CFS Model

You can learn more about the Climate model (with stratification) in "IDA ICE 5.0 - Climate (with stratification) model Tutorial". A theoretical description of the model is given in the document “The Climate Model with stratification”.

User defined zone controls

By default, the different objects in a zone (heating, cooling, ventilation, shading, opening, etc.) are controlled by setpoints. But it is also possible to control by user defined zone controls. Controls on the zone level can connect the control of different objects. More about control and the different control layers you find in Control systems.

Zone level domestic hot water use

The domestic hot water use can be defined either in building level (Domestic hot water building level) or zone level or both. If it is defined on both levels, the consumptions are added together.

Zone types (zone templates)

Zone types are predefined templates that are assigned based on the intended use of a zone. They are independent of the zone model and contain default values and assumptions required for the modelling:

• setpoints
• room units
• furniture
• room air
• constructions
• internals load (values and schedules) for occupants, equipment, and lighting

These templates serve as an input aid and help ensure consistent and efficient model creation by providing standardized settings for typical usages. These zone types can individually be defined. Depending on the selected localization, a set of predefined zone templates is available that reflects regional standards and requirements.

See this Video tutorial for more information.

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