Designing Suspended Ceilings
Get information about the possibilities of modeling rooms with suspended ceilings for building detection.
The clear room height is used to determine the interior volume as well as the enveloping surface for the air tightness test. In residential buildings, the clear room height usually extends from the top edge of the finished floor up to the bottom edge of the ceiling. In non-residential buildings, such as office buildings, ceilings are usually suspended. Since the intention is usually to hide technical components, they are usually opaque, but not necessarily airtight. In most cases, suspended ceilings are not particularly thermally relevant and can be neglected in the calculation, but they may reduce the net volume of the room.
The result is that different cases with regard to the building registration have to be distinguished.
Highly Air-permeable Ceiling (e.g. Lamellas)
For this type of suspended ceiling, the area between the suspended ceiling and the lower edge of the raw ceiling should be included in the net volume of the MEP spaces.
Modeling in Revit
Mostly Airtight Ceiling (e.g. Sheetrock)
This type of suspended ceiling by its design reduces the net volume of the MEP space.
In the case of mostly airtight suspended ceilings, the suspended ceiling shall be defined as a room boundary and the suspended ceiling has to be of the type Ceilings. The volume of the suspended area should not be included in the net volume of the MEP space, since there is no air exchange between the space above the suspended ceiling and the actual room.
If the detection encounters the suspended ceiling as room boundary when the MEP space is placed, the program tries to continue the detection up to another 250 cm to find the raw ceiling. The raw ceiling is detected with a thickness of up to 100 cm, so that a layered component with a total thickness of up to 350 cm can be detected. If the distance between the bottom edge of the raw ceiling and the suspended ceiling is, for example, 70 cm, the raw ceiling is found and identified together with the suspended ceiling as a layer component and, after detection, is also listed as such in the master tables. The correction of gross area as well as storey height is carried out automatically during this step.
If problems still arise when placing the MEP space, an alternative modeling approach can be used to place an unoccupied MEP space with a suitable temperature assignment so that the ceiling delimiting the space is not misinterpreted as being adjacent to outdoor air.
If the distance between the suspended ceiling and the upper edge of the raw ceiling is more than 350 cm, no adjacent rooms or components are detected and the area is detected as outdoor air. In such cases, an unoccupied MEP space with appropriate temperature assignment should be placed between the suspended ceiling and the lower edge of the unfinished ceiling so that components adjacent to this area are not detected as being adjacent to outside air.
Mostly Airtight, but only Partially Suspended Ceiling
The net volume of the MEP space is reduced by the suspended part of the ceiling.
Modeling in Revit
For mostly airtight suspended ceilings that extend over only part of the room, proceed in the same way as for largely airtight suspended ceilings that extend over the entire surface of the ceiling. The suspended ceiling must be defined as room bounding. If the distance to the bottom edge of the raw ceiling is less than 250 cm and the raw ceiling above is max. 100 cm thick, it is not necessary to take any action. If the distance is greater or problems arise when placing the MEP space, an unoccupied MEP space with a suitable temperature assignment should also be placed in such cases for the reasons mentioned above.
