THE SEALS THAT WERE USED IN THE SOUND TEST TO ATTAIN THE STC.
In the beginning when flat panel operable wall systems were new you could have any kind of top & base seals that you wanted as long as they were fixed finger sweeps. And life was simple & good and controversy did not exist. But now there are so many different types, combinations, operating clearances, ways to actuate & operate as well as confusing names & descriptions it is difficult for the specifier/consumer to properly select what is best for his application.
What is the specifier to think? What should he “choose”? Or should he even try to choose relying instead on the preferred manufacturer to choose for him? There are many factors to consider as the correct choice (if in fact options are available) will have an impact on the success & operation of the installed system.
Acoustics: The primary rule is to read the sound test associated with the manufacturer & STC selected. The sound test will describe the type of top & base seals used to achieve the selected STC and those seals should be specified as it pertains to that particular manufacturer. If the sound test says “automatic” seals than the specifier should ask for “automatic” seals. On the other hand if a different manufacturer is selected and they have achieved the desired STC value using a different type of seal but does not have a test using the specified seals, should they be rejected? Of course not as long as the “intent” of the specification is achieved. The “intent” in this case is to achieve the STC value: it is not
to use a particular type of seal. As an example one manufacturer is constantly having his high STC product specified but the seals specified do not match those indicated in the sound test. This should be challenged in a positive, educational, non derogatory way.
Aesthetics; Seals have different appearances. Fixed sweeps are pieces of vinyl that wrinkle, overlap where panels meet, can wear & tear over time, typically come in only one color and most often used only as top sweeps. They can be unattractive aesthetically especially over time. So choosing fixed sweeps for an upscale, high profile wall, especially ones that are less than 15’ tall, often results in an unattractive appearance that will worsen over time. Fixed sweeps also continuously contact the finished ceiling/track soffit which could result in marks, especially when reconfiguring panels around switches or when stacking. Retractable seals on the other hand may be painted, anodized or powder coated in almost any color to complement the panel finish and never come in contact with the finished ceiling. Retractable seals are uniform in appearance and will retain their aesthetics over time.
Ease of Movement: No contest here. Lever actuated retractable top seals are as good as it gets simply because there is no contact with the ceiling when the panels are being moved. Continuous contact sweeps whether top and/or base are in constant contact with a building interface creating friction. The problem is exacerbated when taller and/or heavier panels are required.
Set-up considerations: Many field applications require wall set-ups other than straight line configurations. These would include “T’ing”’ into another wall, wanting to secure individual panels within the room space in order to use to attach or display items or to use built in marker boards, closing against a finely finished permanent wall that is not able to withstand any abuse, alternate locations of panels so that lead & trail edges are reversed etc. In these cases automatic seals (see definition below) are not the best choice. Lever actuated retractable seals should be used. This is where you should work with your designer to provide assistance and anticipate problems.
There are other factors such as accommodating deflections but addressing all or some of the above should provide enough information so that the best selection can be made.
#!. The manufacturer specified should provide the seals indicated in the sound test that achieved the specified STC. Other acceptable manufacturers should be able to supply the seals that they used to achieve the equivalent STC and as indicated in their sound tests as long as the intent of the specification is met.
#2. If aesthetics are a concern then lever top actuated seals are the best choice.
#3. Ease of movement is best achieved by the use of lever actuated retractable top & base seals.
#4. Lever actuated retractable base seals in conjunction with automatic seals should be used when needed for unique set-up needs (Moderco recommends the use of lever actuated seals wherever possible).
Glossary of terms:
Sweep Seal: A top or base seal with fingers and/or a bulb shape installed on the top and/or base of a panel designed to be in constant contact with the soffit or floor at all times.
Adjustable sweep seal: As above but fixed to a panel mounted adjustable extrusion/shape such that the seal may be vertically adjusted to conform to fixed floor elevations thus providing continuous contact.
Automatic Seal: A top and/or bottom seal that will extend/retract when the panel in which it is contained is pushed against/retracted from its immediately adjacent panel, pocket door or fixed wall.
Manual Retractable or Actuated or Operable Seal: A top or bottom seal that is manually extended/retracted by a person using force (as with an automatic seal) by the use of a key, wrench or lever (lever operated) inserted in the panel operating mechanism and applying pressure.
Mechanical Seal: Automatic or Manual or Operable – all can be considered “mechanical”
Lever Actuated: Top and/or Base seals that are extended/retracted by a person using a lever (wrench, key) inserted into the seal operating mechanism.