This document provides guidance on modeling Atrium type spaces in Design Database.
The following information should help with modeling different height adjacencies, for e.g. A sports hall connected to adjacent ground-floor classrooms.
For the most accurate consideration of atrium type spaces we would recommend using Simulator and implementing Atrium keywords.
If you wish to consider these spaces for steady state and PartL calculation within Design Database then the following should help.
This involves modeling the taller room as multiple separate rooms – for e.g. one ground floor room and one 1st floor room. As the walls and partitions will be defined correctly, this method will give accurate results in relation to the heat transfer between side-by-side rooms.
However, as there will be an internal ceiling/floor you will need to create and use a ceiling & floor with a very high U-value, so that its effects are negligible. While suitable for Steady State calculations, the increased floor are may cause issue with PartL results.
This method would be more suited to Part L calculations. This involves drawing the atrium room on one floor only, and then editing the wall height and type accordingly (Rooms>Change surface).
The main drawback with this method is that all of the double height surface will be defined as external and will not connect to the ground floor rooms, so heat flow across this surface may be compromised.
The third option, and possibly the most accurate, would be to draw your model in CAD Input, and then use Room Data to manually edit the surfaces of the rooms. Please see this document for information on switching to Room Data mode.
The final design choice must be down to the engineers best reading of the project. It may prove prudent to keep a number of backups of your project, each considering different methods.