This free collection of Revit families focuses on duct attenuators, which are used to lower the sounds generated from fans and HVAC systems. The collection builds on our work with industry expert Ben Drake from Rushing Co.

Ben highlighted to us how manufacturer Revit families for attenuators tend to take a variety of conflicting approaches. This can prove cumbersome within Revit projects, especially if you need to coordinate systems using more than one manufacturer.

Our collection contains reactive, absorptive and cross talk attenuators for use in both square and round duct. The cross talk attenuators are available in U, Z and L shapes, and the inline attenuators have both type-driven and duct size instance-driven versions.

Issues with manufacturer content

Duct attenuators are normally created as a duct accessory family and are set up to break into the duct. On the other hand, Price Industries attenuators, which Rushing Co. frequently use, are set up as Mechanical Equipment. That category is really meant for something that would create the systems, such as an air handling unit.

Using the incorrect category isn’t the biggest problem. It just means the user has to pay extra attention to object styles, and it could conflict with filters or system setups. However, the part type is set as Normal, so the attenuator doesn't break into ductwork.

Manufacturer attenuator Revit family with incorrect category and part type.

Meanwhile, the family's connectors are set as Supply Air, which means it will conflict with any other system and it will only create supply air systems.

Manufacturer attenuator Revit family showing incorrect system type.

Normally the orientation of the family is left/right, rather than up/down. And the use of an instance parameter to drive the half length, which is tied to the named reference plane, means that in a project there are two grippies which both increase the length of the attenuator and in both directions of the duct.

Incorrect family setup creates two sets of grippies when loaded into a project.

This is not the first time we’ve seen manufacturers veer away from industry and Autodesk standards, and it can be questioned whether they actually know they are doing something wrong. Personally, when I was doing coordination I don't think I ever had the time to email a manufacturer about issues with their Revit families. We’re all too busy modelling and pushing out drawings.

Reactive attenuators

Our collection contains two reactive attenuators from IAC Acoustics and Ruskin. Both attenuators are rectangular with square duct connections. They come in set sizes and lengths from their manufacturers and, as such, are controlled by a type catalog with over 60 types. The Ruskin model has slip joint connection method and the IAC Acoustic model is flanged at both ends.

Reactive attenuators with symbol in plan view (left). Slip joint and flanged connections (right).

Absorptive attenuators

We have five absorptive attenuators which have their width and height set as instance specific, so they are defined by the duct size they are dropped into. From Price Industries, we created their rectangular RL/RM/RH model. The family has four internal types defined by the various lengths.

From Price Industries and Linx Industries, we have created their circular absorptive attenuator models. All of these families have eight types defined by the various lengths and are available with standard and extended insulation thicknesses.

Circular absorptive attenuators from Price and Linx Industries.

Cross talk attenuators

Last but not least, the collection also contains three cross talk attenuators (L, U and Z shaped), again from manufacturer Price Industries. Cross talk attenuators are designed to maintain sound transmission ratings in low velocity (below 750 fpm) applications where air is transferred between adjoining spaces.

All of these cross talk attenuators have been built so they can attach to the grille, and when the length changes they do NOT move the grille itself. They also rotate about the grille and the width/height will change to suit the grille.

Attenuator dropped into existing grille in project (left). Attenuator can be rotated about the grille (center). The attenuator changes to suit grille orientation and the respective connection width and height (right).

The attenuators also have instance parameters to control collar height, thickness and overall length. This ensures that the families can be modified by the end user to suit any design or construction requirements.

L shaped attenuator dropped into grille (left). Values for length and collar can then be changed (right).

L and U shaped cross talk attenuators in side view.

The L & U shaped cross talk attenuator are both designed to be used in the ceiling void and can connect to a ceiling grille. The U shape has downward and upward facing types so it can be placed manually when the design does not require any grille connection.

U shaped cross talk attenuator with downward and upward facing types.

Developed in partnership with Ben Drake, BIM Manager at Rushing.

In order to bring you the best Revit content, we continue partnering with industry experts to identify the most relevant and useful products for our collections. Ben Drake is BIM Manager at Rushing, a ‘technology-driven off-site’ construction company based in Seattle.

If you work in a specialised industry and feel like the Revit families available to you are missing the mark, please let us know and we’ll see what we can do to help.

Get the Collection

Click here to view and download the full collection.

Collection Content List

1. Two absorptive circular attenuators from Linx Industries.
2. Two absorptive circular attenuators from Price Industries.
3. Absorptive rectangular attenuator from Price Industries.
4. Reactive rectangular attenuator from Ruskin.
5. Reactive rectangular attenuator from IAC Acoustic.
6. Z shaped cross talk attenuator from Price Industries.
7. U shaped cross talk attenuator from Price Industries.
8. L shaped cross talk attenuator from Price Industries.