We recently hosted our live webinar, “Insulation Systems as a Design Element,” where we received a variety of excellent questions. Below, you’ll find the answers to the top 10 questions from the webinar (plus an honorable mention). Many of the answers have links to resources where you can find additional information on the question topic.
- What does PSK Stand for?
PSK describes a type of facing used on an insulation material and it stands for “Poly- scrim-kraft.” This type of facing is made from a scrim-reinforced kraft paper with a polypropylene coating on top. Traditionally, PSK facings are white, but JM offers a black-coated PSK for aesthetic versatility. This chart gives you a detailed description of the various mechanical and HVAC insulation facings that are available, including PSK.
- Is PVC jacketing non-plastecized?
There are two types of PVC, rigid (non-plasticized) and flexible (plasticized). JM’s Zeston® PVC formulation is a rigid PVC formulation, and therefore, by design, does not use or incorporate any phthalates (or “plasticizers”).
- Typically, architects work with STC ratings not NRC values. Why do insulation manufacturers use NRC values rather than STC ratings to measure acoustical performance of insulation?
STC Ratings, or Sound Transmission Class ratings, refer to how well a building partition prevents sound from traveling between rooms. In the simplest of terms, STC essentially refers to how well a wall or floor can reduce sound from traveling through it. It measures the reduction in noise between two rooms in decibels. One of the most important distinctions of an STC rating is that it measures the acoustical performance of the entire wall or floor system (studs, dry wall, and insulation) as a whole, not just its individual components.
In contrast, a Noise Reduction Coefficient (NRC) rating relates specifically to asinglematerial’s ability toabsorbsound. While the STC looks at the entire system an NRC looks at the individual material exposed directly to the sound source. In theory, each of the materials that go into a wall could potentially have a unique NRC rating.
For practical use, NRC ratings can help building designers evaluate and compare materials to determine which materials are best suited to controlling sound transmission in their applications. In contrast, STC ratings can help building designers look at the acoustical properties of the building as a whole to ensure consistency and performance throughout rooms.
- We typically only insulate exposed ductwork when condensation control is a requirement. Do you recommend doing it in all cases?
While condensation control is certainly a key benefit of insulating an exposed duct system, particularly in humid climates, you shouldn’t neglect insulation simply because you aren’t worried about condensation. Insulation is one of the few investments you can make that will offer potential returns (e.g., in energy savings) throughout its lifetime.
Systems that are properly insulated maintain more consistent air temperatures throughout the duct. This, in turn, puts less stress on the fan and HVAC system as a whole by ensuring that the system doesn’t have to work harder to heat or cool the occupied space. The potential long-term energy savings insulation provides make insulation one of the building components that can be considered an investment, rather than a depreciating expense.
In addition to potentially improving energy efficiency and temperature control, certain duct insulations, like duct liners, offer acoustical control. This can be tremendously helpful for building occupants because properly installed duct liners can help to reduce fan noise and noise generated from cross-talk (sounds traveling through the ducts from other rooms).
While insulation may not be needed in every single application, it is worth taking a second look at the long-term benefits of insulation in terms of potential energy savings and building occupant comfort before you write it off entirely.
- How does the printed artwork image on wall panels get applied and does it degrade the NRC rating at all?
Wall panels may be manufactured from fiberglass panels wrapped in an aesthetically pleasing fabric. The fabrics may be adhered to the insulation panels or stretched over or around the insulation in a frame. Designers can choose a solid color fabric, or they can choose to have a design printed on the fabric by the wall-panel manufacturers. Many manufacturers have the ability to make custom shapes, colors, and designs that meet the unique aesthetics of the applications while still offering valuable acoustical control for the space.
If we want to take a closer look at the impact the printed artwork or fabric applied over the insulation has on the NRC rating of the fiberglass, we would have to look at the performance literature of individual acoustical wall panel manufacturers. There are many wall panel manufacturers who offer custom printed acoustical wall panel systems. It is best to consult the product literature of these manufacturers or contact them directly for information on the specific NRC rating of their finished wall panel products.
- Are there concerns that fiberglass will enter the airstream if used to line ducts?
In order to meet the Air Erosion Requirement for Duct Liner (ASTM C1071), our duct liner insulations have undergone incredibly rigorous testing prior to being approved for use in HVAC systems. Duct liner has to undergo an Air Erosion test developed by UL (Underwriters Laboratories) that requires duct liners to be tested at air velocities that are 2.5 times the speeds that would be encountered in their recommended HVAC applications. So, for example, JM’s Linacoustic® Duct Liner is rated for a maximum air velocity of 6,000 fpm This means that it has been tested at air velocities of 15,000 fpm. These wind speeds are equivalent to what would be encountered in a hurricane. In order to pass the test, the duct liner cannot show signs of erosion, breaking, or delamination during or after exposure to these air velocities.
This rigorous testing speaks to the product’s ability to withstand a high-velocity HVAC application without eroding into the airstream when properly handled and installed. We took a deeper look at this topic and more in our recent webinar, “The Truth Behind the Health & Safety of Fiberglass & Mineral Wool.”
- Does a lined duct restrict the volume or velocity of the duct?
Yes, a lined duct restricts the volume or velocity of the duct. To account for this, both the ASHRAE Fundamentals Handbook and the SMACNA HVAC Duct Design Manual provide duct friction loss charts to help designers determine pressure drop in a variety of insulated and uninsulated ducts. It’s important to understand, however, that pressure drop is influenced by a myriad of factors, including the air velocity, the shape, size, and length of the duct run, and the interior surface roughness of the duct or the insulation.
- When using PSK duct wrap, are mechanical fasteners required or is it all reliant on the tape?
When using JM’s duct wrap of any kind (PSK or FSK), mechanical fasteners are required on the underside of ducts that are 24” (610 mm) across or larger. This helps prevent sagging. On ducts smaller than 24” across, installers using JM insulation can simply use a UL approved tape. JM offers PSK tapes that match the color and scrim patterns of our PSK-faced duct wraps to help ensure a consistent aesthetic appearance. Bear in mind, this applies largely to ducts that run horizontally; vertical ducts of any size may require additional pinning to ensure the material does not shift.
- Does the spiral duct liner come with a foil facer on the airstream surface?
No. JM’s spiral duct liner, Spiracoustic Plus®, comes with an antimicrobial coating on the airstream surface and a foil facer on the surface that sits flush against the duct.
- Is there anypaint that can be used on exposed fiberglass?
JM does not test any of its fiberglass HVAC or mechanical insulations with paint on them. As a result, any time any type of paint is used on the insulation or the insulation facing, the UL Fire Hazard Classification rating will be voided. This may cause the material to become non-compliant with building codes, and in a worst-case scenario, could put building occupants at risk in the event of a fire. For more information, read this blog.
- Honorable Mention: How are lined ducts cleaned?
We received this question several times, and as a result, wanted to provide a link for anyone looking for more information on how to clean ducts insulated with fiberglass insulation. Instructions on how to clean lined ducts can be found in these two guides produced by the North American Insulation Manufacturer’s Association (NAIMA).
1. Cleaning Fibrous Glass or Lined Sheet Metal Ducts
2. Cleaning Fibrous Glass Insulated Air Duct Systems
If you have any additional questions, please don’t hesitate to contact our technical services team at 1-800-654-3103 or fill out the form on our Contact Us Page.