Dynamic Thermal Modelling

Dynamic Thermal Modelling can be used where overall figures for temperature or humidity in a space are required. A model can include a whole building or a small section of it, but it will generally be divided up into the separate rooms, and possibly zones within the rooms. E.g. the bottom 2m or 'occupied zone' and above 2m i.e. above head height.

Such models can also be used to provide information on heating or cooling plant requirements, and can now also be run for checking Carbon Emissions compliance with the new Part L2 of the Building Regulations (2002).

The software requires entry of the following parameters:

• The basic geometry of the building
• The materials that make up the walls, floors, doors windows and roof etc.
• The orientation and global position
• Windows and doors can be opened by specified percentages and to specified schedules, or in accordance with the weather.
• Internal conditions can be set for each zone and for different periods during the day or week. These include lighting gains, occupant and small equipment latent and sensible gains, infiltration and mechanical ventilation rates.
• The planned heating/cooling plant can also be included or the software can be sued to size this automatically.

The weather data used for the simulations is real and can be imported from Meteonorm for anywhere in the world, there is also CIBSE design day data available to work from.

The results include plots of air temperature, humidity, resultant temperature etc for each zone throughout the chosen day. Figures can also be obtained for air movement both to/from external or other internal areas, and plant loads for single or multiple zones.

The above image shows a building where thermal analysis was done to ascertain the effects of covering a central courtyard with an ETFE roof.

The model includes the effects of solar gains, wind speed and direction, and can include various shading and sheltering mechanisms. Some examples of what thermal modelling is useful for include:

- Analysing the effects on internal summer or winter temperatures of different glazing options.

- Assessing air change rates for naturally ventilated spaces with differing opening sizes and locations.

Unlike CFD models, thermal models in TAS are very quick to run, so many scenarios can be run in a relatively short space of time. The time required to initially put the model together varies with the complexity of the building, but does not usually take longer than a couple of days once all the required information has been supplied.