• Winona Building Products

FSK vs. PSK: What is the Difference?

The two main products offered by Winona Building Products are FSK and PSK. FSK stands for Foil-Scrim-Kraft and PSK stands for Polypropylene-Scrim-Kraft. These are both types of vapor barriers that are commonly used in facing for metal buildings, in particular for insulation. Both of these products use scrim and kraft — scrim being a heavy duty lining and kraft being kraft paper that has been coated in asphalt to help make it impermeable to water vapor. The real difference between FSK and PSK lies in the F and the P — foil vs. polypropylene.

Before diving into the difference between these two types of vapor barriers and where they are best suited, we should first talk about the value of vapor barriers in general. Installing vapor barriers is an invaluable way of extending the life of a system, making things more combustion-proof, preventing water damage, and improving the appearance of things like the outward-facing, exposed surfaces of HVAC ductwork. Vapor barriers are useful for many different types of industries, in particular construction, metal building, automotive, and aerospace.

Winona Building Products specializes in creating premium-quality insulation facing for all these various industries, with a specific focus in creating insulation facing for various mechanisms and appliances with a variety of different insulation types. Call us now to learn more about how we can help your business or order vapor barriers today!


Protecting insulation is a crucial way to increase its lifespan and maximize its strength, weather-resistance, and cost-effectiveness. Winona Building Products constructs all our vapor retarders with three separate layers. That’s where FSK and PSK come in.

What is FSK?

FSK is a commonly used type of insulation that uses foil that looks like aluminum foil — shiny and silver. The foil is bound together with the scrim and kraft to create a fire-proof insulation solution. FSK is used widely by manufacturers during the construction of duct boards, duct wraps, and for other HVAC applications. This type of insulation facing works as both a vapor barrier as well as a way to control moisture and add a protective layer over an insulation’s fiberglass.

What is PSK?

Instead of foil, the kraft and scrim with PSK are adhered to a plastic blend of polypropylene. This type of insulation facing is commonly used for ductwork, metal building insulation, and basement wall facings. The polypropylene helps prevent moisture from reaching the inner layer of your insulation, which helps contribute to longer lasting, safer insulations solutions. PSK will help as a fire retardant, seal any gaps, and increase the tensile strength of your insulation or other product, along with a number of other benefits.

What’s the Difference?

The difference between PSK and FSK come down primarily to issues of price and appearance. Because polypropylene is more expensive than foil, PSK tends to be moderately more expensive than FSK. For this reason, PSK is generally more used for indoors while FSK is used more both indoors and outdoors. Another difference is that PSk has a smooth, white-colored finish, while FSK looks like aluminum foil. Because of this, PSK tends to be more appropriate for inside insulation of exposed systems where aesthetics are a priority.

The Bottom Line

Though there are some differences in price and appearance, at the end of the day, both PSK and FSK will be excellent vapor barriers for your needs. If you need vapor barriers attached to, for example, fiberglass insulation from a major manufacturer, adding either of these vapor barriers will help prevent moisture from entering or exiting the building. They will also both help contribute to the reduction of condensation between wall layers, reducing the risk of mold growth and corrosion.

All the vapor barriers sold by Winona Building Products will provide adequate fireproofing for your insulation as well. What really makes Winona Building Products different, however, is our commitment to using eco-friendly vapor barriers. Our adhesive formula is fire-retardant, extremely strong bonding, and, free of any chemicals considered by the International Living Future Institution to be dangerous to humans and the environment. We believe that eco-friendly vapor barriers are the future.

To learn more about Winona Building Products services and products, feel free to reach out to us online or by phone. We will be happy to answer all of your questions!


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