What are communicating doors?
Communicating doors are two doors, generally single doors, installed on each side of an opening. Imagine the two door setup commonly seen in adjoining hotel rooms. Not every wall has space for a communicating assembly, as the wall must be thicker than a standard 2x4 or 2x6 construction to fit both doors.
- Two IsoDoor SD/V - Minimum wall thickness, 6-1/2".
- One IsoDoor SD/V, One IsoDoor HD - Minimum wall thickness, 7-1/4".
- Two IsoDoor HD - Minimum wall thickness, 8".
The door handles can be on the same side of the opening if space allows, otherwise the door handles would have to be on opposite sides so both doors can close without the handles hitting each other. The jamb is built separately for each door, but more on that later in the article.
This video was sent in from a customer that built their own professional recording studio. The live room has around 95-100 dB of sound on the other side of a IsoDoor HD LF and IsoDoor SD communicating assembly.
Including a sealed sliding barn door in a communicating assembly
A well sealed wall mounted barn door allows for a communicating assembly to exist without requiring unusual wall thickness. There are other benefits to this approach as well.
- Ability to retrofit if the customer wants to increase performance of their already installed door, whether a standard door or an IsoDoor HD, SD, or V. This allows a second door to be added without significant reworking of the door opening.
- Allows for communicating doors in walls thinner than 6-1/2". The entire thickness of the door is wall mounted and the hardware is generally low profile or flush mounted to the door. Even a 4-1/2" thick wall can fit a communicating assembly.
- In standard residential construction, a communicating assembly can sometimes be cumbersome. Especially for the significant other that is not as excited about the new sound room and the idea of having to deal with two doors to enter a space. With a wall mounted sliding door, the second door can remain fully open and out of the way, and only closed when truly needed to be closed.
When are communicating doors appropriate?
Communicating doors are the result of the limiation of a single door in an assembly. Most of our customers will be satisfied with one of our single door solutions, the IsoDoor HD, SD, or V. However, when performance expectations are at a maximum and space is limited, communicating doors are the only reasonable solution. The purpose of communicating doors is to accomplish what an individual door simply cannot. Individual doors are limited for various reasons, generally from thickness, weight, and structural stability in the design. Certainly a 5" thick door would perform better than even our 2-1/2" thick IsoDoor HD, but how much better really, what door hardware would you use on a door that thick, and how would you install a door that heavy? The design of a massive door seems like it would be a success, but taking a solid 1-3/4" door and adding another solid 1-3/4" door for a massive 3-1/2" thick door will not accomplish what you think it might. The mass-air-mass created with communicating door assemblies is a value that cannot be re-created within a resonable design for an individual door.
The only reasonable way to achieve an STC and OITC of 50 plus is with a communicating assembly. Only a 450 pound or heavier steel door with steel jambs back-filled with concrete will achieve the performance of a standard IsoDoor communicating assembly. Such a door generally costs upwards of $15,000 and is very difficult to install.
Wow.
Ron Sauro, NWAA Labs, 2012In-person response to our communicating door assembly performance.
What performance can be achieved with communicating doors?
Performance is limited to the overall mass of the assembly and distance between the two doors. Assuming a pretty standard 8" wall thickness that would allow for any combination of our IsoDoors, here's a rough chart showing performance options with communicating assemblies:
- Two flush panel 1-3/4" solid core/solid wood doors - For walls up to STC 50 (about equal to the performance of one IsoDoor V)
- One IsoDoor V, one 1-3/4" solid core/solid wood door - For walls up to STC 55 (about equal to the performance of one IsoDoor SD)
- One IsoDoor SD, one IsoDoor V - For walls up to STC 60 (about equal to the performance of one IsoDoor HD)
- Two IsoDoor SD (one with a slightly different core to avoid resonance) - For walls up to STC 65 (better than one IsoDoor HD)
- One IsoDoor HD, one IsoDoor HDLF - For walls up to STC 70 (good enough for even the highest rated walls that exist)
We would recommend that each of the doors are at least 100 pounds and the thickness of the wall is at least 7" (unless you include a sliding barn door that is sealed). The more you can push the limits from there, the better the performance in all frequencies. All frequencies will improve evenly as you increase the distance between each door. Most dramatic improvements are from significant changes in distance, 3" increased to 6", 6" increased to 12", 12" increased to 24".
Can I improve the performance of a communicating assembly?
The simplest way to improve the performance of a communicating assembly is to mount acoustic panels to the interior side of the doors. This way, when both of the doors are closed, they don't act as an echo chamber. Much like how we wouldn't want to leave any open wall cavity uninsulated, the same is true with communicating door assemblies. A standard 2" acoustic panel in 2' x 4' size on one door or both doors will suffice.
What else should I know about communicating doors?
The most common misconception of communicating doors is in regards to the door jamb. You must have two separate jambs for a communicating assembly with an air space maintained between those two jambs. The larger the span between the doors, the larger the air gap between the jambs. Generally ranging from 1/4" to 1" for walls that are between 6-1/2" and 24" in overall depth.
For the threshold, there are many options. If the wall is thick enough, then simply one acoustic threshold on each side. Our standard threshold is 5", so this would work on any wall that is 10" or thicker. Otherwise have one acoustic threshold on one side and no threshold on the other (possible if the finish floor beneath the door without a threshold is a solid surface), no threshold on either side (possible if the finish floor beneath booth doors is a solid surface), or supply your own custom rabbeted threshold that spans the entire opening.
Resonance issues will hurt performance if the door on each side is exactly the same. We always specify different door types in a communicating assembly, this can be done in a multitude of ways.
- IsoDoor V with IsoDoor SD
- IsoDoor SD with our alternate core IsoDoor SD
- IsoDoor HD with IsoDoor SD or IsoDoor V
- IsoDoor HD with IsoDoor HDLF
The different materials within those doors should be substantially different to avoid resonance issues by having the same exact materials repeated in an assembly. Two solid wood doors, for instance, can be used in a communicating assembly, but the full gains of the communicating assembly won't be realized at several frequencies if the doors are identical.
Have more questions about communicating assemblies or need to know something that wasn't covered on this page? Email us, we're happy to help!