
n recent years, we’ve noticed a growing confusion in the industry over design and performance requirements for sensitive compartmented information facilities (SCIF). Part 2 of this article is intended to highlight the significant difference in the performance of radiofrequency (RF) shielding between facilities designed per ICS/ICD-705[1] and those intended to meet NSA 94-106[2] performance requirements. We will also highlight some of the design and construction methodologies that lead to significant differences in performance.
Part 2 of this article will highlight some of the methods utilized in ICS/ICD-705 that limit RF shielding performance and some alternate methods that could increase the RF shielding performance. Further, we will discuss other common deviations that often increase project costs without providing any enhanced RF performance. Finally, Part 2 will document the significant differences in potential RF performance utilizing measurement data collected from a facility built per ICS/ICD-705 construction methods and a facility designed to meet NSA 94-106 requirements.
Despite a clear process for design direction and general construction recommendations established in ICS/ICD-705, many project documents deviate from the typical ICS/ICD-705 direction. Those deviations can range from specifying alternate shielding materials to utilizing alternate construction methods to establishing RF performance requirements not supported by the project’s design. These deviations often have a variety of adverse effects from increased project costs to designs that do not support the shielding requirements. This puts all involved, including the facility owners, facility designers, and general contractors, in the challenging position of having to work through the disconnects between design and specified performance, often during the construction phase of a project.

Based on their assessment, the CTTA may provide recommendations or require the shielding of floors and ceilings and request the inclusion of filters, treated penetrations, and RF doors. But this does not mean the design will meet NSA 94-106 performance without substantial changes to the general design recommendations provided in ICS/ICD-705.
The second facility design utilized the ICS/ICD-705 Wall A construction for interior walls and along exterior building perimeters. The facility design provided shielding enhancements beyond those identified in ICS/ICD-705, including RF doors, electrical filters for power and building management systems, HVAC RF waveguides, and RF waveguides for plumbing, which enhanced performance over the typical recommendations provided in ICS/ICD-705. Finally, the facility also included windows, which are typically discouraged under ICS/ICD-705 but are occasionally included in a SCIF design. This facility’s project requirement identified custom RF shielding performance at 90 MHz, 900 MHz, and 6 GHz with attenuation requirements of 10 dB to 30 dB.
Since the SCIF facility performance requirements identified frequencies that did not coincide with NSA 94-106 test frequencies, only the 100 MHz, 1 GHz, and 10 GHz test frequencies of the facility designed to meet NSA 94-106 were provided to achieve as relevant a comparison as possible. There is clearly a significant difference in the performance, with average differences of 55 dB or more and peak differences of up to 80 dB. The ICS/ICD-705 Wall A calls for the shielding layer to be sandwiched between two layers of drywall, but the finish layer of drywall had not been installed at the time that these measurements were recorded and the shielding performance would likely decrease further once the drywall is added.
In this specific application, the windows are one factor that limited performance. There are a few different types of protection for windows, including RF film, RF glass, and RF shielded windows, which incorporate an RF shielded screen. These technologies are typically limited to between 40 dB and 80 dB at 10 GHz, depending on the performance of a specific product, and vary in performance from 1 kHz to 10 GHz.
To overcome the limited performance in some frequency ranges, some designs will specify thicker copper foil or aluminum sheets. But the specified materials may still not meet NSA 94-106 if identified as a performance requirement. Further, in the next section of this article, we will identify some construction challenges that will degrade RF shielding performance and limit the benefit of specifying a different material
It is also common to see many issues overlooked in designs that are critical to RF performance, resulting in incremental degradation of RF shielding performance. Common issues include not identifying all items that require filtering. Whether it is used for power, communication, data, or building management systems, a component than includes or uses conductive cables or wires needs to be filtered to maximize the RF performance of a shielding system.
There are multiple examples of a facility filtering all power sources but choosing not to filter all data lines because the data is entering through the floor, which is slab on grade. However, it does not matter the location from where that cable or wire is entering. If it is conductive, it has the ability to carry signals and radiate similar to an antenna. Similarly, critical or protected signals are at risk of coupling to those cables or wires and leaving the secured space. In some cases, this lack of protection may be a concern over costs associated with data filters or communication filters. However, a cost-effective solution may be to use fiber-optics in the secure space that can penetrate the shielding through an inexpensive RF waveguide or series of RF waveguides.
Other common design issues include allowing untreated mechanicals and plumbing not specific to the SCIF to penetrate and pass through the SCIF RF shielding. This simply creates additional points where RF signals can leak into or out of the SCIF. Again, if the purpose is to maximize RF shielding performance, then any penetration into or out of the shielded space must be properly treated. To avoid potential RF performance issues, it is recommended that only items being utilized in the RF shielded space of a SCIF pass through the RF barrier and that any other items supplying other areas of the facility be routed outside the shielded space. Of course, there are exceptions, but those should be evaluated individually based on an assortment of factors including the cost and the impact on RF performance.
Other common construction challenges when building a SCIF include shielding at the ceiling, RF-shielded doors, and treatment of penetrations when specific RF performance requirements have been identified as part of the design requirements. Many SCIF designs may require that the wall foil turns onto and overlaps the ceiling around the perimeter of the SCIF when the ceiling is a metal pan deck. However, RF performance will be limited by the existing penetrations through the metal deck.
Additionally, projects may identify that a shielding material must be applied to a ceiling. In most cases, the ceiling is also used to support electrical and mechanical systems and components such as plumbing and HVAC. This is often accomplished using threaded rods or angles that are attached through the ceiling. An example is shown in Figure 5.
Unfortunately, this technique may result in hundreds, if not thousands, of penetrations through the ceiling, creating the potential for RF leakage. RF shielding companies know how to treat these connections to maximize the RF shielding performance, but an HVAC contractor or plumber with no RF shielding experience is not likely to know how to manage the penetrations. Regardless, these additional penetrations of the shielding can have a negative impact on the overall RF shielding performance.

To mitigate these issues, we recommend that SCIF design teams review the actual requirements with the CTTA before a project specification or request for quotation is finalized. It’s also a good idea to include an RF shielding consultant on the design team to assist in coordinating the RF shielding design and to ensure that the finished structure meets the performance requirements.
- ICS/ICD-705, “Technical Specification for Construction and Management of Sensitive Compartmented Information Facilities.” Available at https://www.dni.gov/files/Governance/IC-Tech-Specs-for-Const-and-Mgmt-of-SCIFs-v15.pdf.
- NSA 94-106 (not available for public reference).
- “SCIF and Radio Frequency Secured Facility Design: An RF Shielding Design Guide to Navigating ICS/ICD 705 and NSA 94-106 Requirements,” In Compliance Magazine, June 2021. Available at https://incompliancemag.com/article/scif-and-radio-frequency-secured-facility-design.
- TEMPEST is a U.S. National Security Agency specification and a NATO certification used in reference to secure facilities.
- IEEE 299, “IEEE Standard Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures.”
