Modeling Mechanical Systems

BIM for Architecture, Engineering, and Construction Curriculum


Copying Shared Elements into a Mechanical Model

What elements and features of a model would you want to see to assist with mechanical design tasks?

You would want to see the location of the room boundary elements\u2015including the walls, doors, windows, and ceilings\u2015to understand the thermal loads and requirements. You would also want to see the structural members to avoid their locations while placing elements of the mechanical system.

What other types of equipment and systems should be considered when placing HVAC equipment and ducts?

You should consider the location of any equipment that will contribute to the heating or cooling. You should also consider the locations of other systems that could interfere when placing elements of the mechanical system.

Which views are best for placing HVAC equipment and ducts in a ceiling space?

Typically, ceiling plan views, sections, and 3D views will provide the most useful information when placing ductwork.

Modeling Exposed HVAC Systems

In what types of spaces are exposed HVAC system typically used?

Exposed HVAC systems are typically used in retail spaces, restaurants, lofts, and spaces where the architectural intent is to reveal and not hide the building systems. This is often associated with more modern and dynamic architectural styles.

What factors determine the size requirements for an air handling unit?

Air handling units are sized in accordance with the amount of air flow required to handle the supply and return diffusers. 

Could a central air handling unit be used rather than a local unit in the space?

Yes, central air handling units are an efficient strategy for conditioning air for a large number of spaces.

Where could it be located? How would you modify the design to route air to and from the central unit?

Central air handling units are typically located on rooftops, below grade, or in dedicated utility spaces. When central air handling is used, mechanical chases and shafts must be provided to accommodate the ductwork required to distribute the air.

How does the shape of the ducts and number bends in ductwork affect the efficiency of the system?

Increasing the number of bends decreases the efficiency of the system because of air drag. When bends are used, 45-degree bends are more efficient than 90-degree bends. Similarly, round and oval are more efficient than rectangular ductss.

Modeling Closed Plenum HVAC Systems

Why are return ducts not needed in a closed plenum HVAC system?

The plenum between the ceiling and the floor above provides a closed channel that is used for drawing the return air back to the air handling units. 

What types of HVAC systems are typically used for residences? For offices? For hotel rooms?

For residences in the United States, central forced air systems with closed supply and return ductwork are used. In other parts of the world, split system air handlers, which control the heating and cooling locally, are more common.

In large offices and public spaces, central air handling systems are typically used to condition the air for the open spaces<\/p>\nHotel rooms typically use split systems that allow occupants to control the comfort settings in the individual rooms.

What factors determine the best placement for supply diffusers in a room?

Supply diffusers are often placed near the windows or doors, as the largest temperature differences occur there.