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Both unfaced and faced insulation serve the same purpose–providing thermal resistance to heat conduction. Ensuring that buildings remain warm or cool as required. The differences between them involve where they are used and how they are used.
What is Unfaced Insulation?
Unfaced fiberglass batts or rolls are insulation without anything added. No vapor barrier. It is probably the most popular type of insulation for all types of applications. Many jurisdictions do not mandate faced insulation but they may require a vapor barrier. Unfaced batts are less expensive and usually easy to obtain. Unfaced insulation is considered non-combustible. It can help slow flame spread and even prevent fire.
Where to use?
Unfaced insulation can be used anywhere that requires a barrier between warm and cold areas. Exterior walls. Crawl spaces. Vaulted roofs. Attic floors. It can be added to existing insulation for more R-value as long as it is not compressed. Compressed fiberglass loses its insulation value. It also provides good soundproofing when used in interior walls to keep bedrooms quiet and bathroom noises inside.
In colder climates, a vapor barrier should be added over unfaced insulation on the warm side of walls to prevent moisture penetration.
What is Faced Insulation?
Faced insulation is the same fiberglass batts or rolls with kraft paper applied to one side. The kraft paper–sometimes vinyl or light aluminum foil–provides a vapor barrier when applied correctly. Faced insulation prevents moisture from entering wall cavities. Which helps reduce mold and mildew and protect framing from moisture damage and possibly rot.
Where to use?
Faced insulation should be used where moisture protection is required in addition to thermal protection. Such as exterior walls or vaulted roofs. It may also be beneficial to use faced insulation in the interior walls of kitchens and bathrooms to prevent moisture passing from room to room. Install the faced side towards the humid room. Faced insulation can be layered over unfaced insulation to add a vapor barrier and more R-value; provided the cavity is deep enough to accept it without compression reducing the R-value.
Layering Unfaced and Faced Insulation
Unfaced insulation can be layered over top of unfaced insulation without any problem. Such as double batts in wall cavities or double layers on attic floors. A layer of faced insulation can be installed over unfaced insulation provided that the kraft paper side is on the warm side of the wall, floor, or roof.
Never install multiple layers of faced insulation. This sets up a double vapor barrier that can trap moisture between the layers. Which can cause rot, mold, and mildew. Or it is absorbed by the fiberglass. Wet fiberglass has next to zero insulation value.
Installing Unfaced and Faced Insulation
Unfaced insulation is used in almost all situations. The product relies on friction between studs, rafters, or joists to stay in place. It is light enough that it should not sag–especially after the drywall is installed to create a tight sandwich. If drywall is not being installed in places like rafters, strapping may be required to keep the batts in place.
Faced insulation is generally considered easier to install because the kraft paper provides stability to the batt. The paper side tabs are folded out and stapled to the sides or faces of studs, rafters, or joists. Some local building codes specify which method. Non-standard-sized wall cavities require cutting the insulation to size and manufacturing a tab. They can also be covered with poly to keep the vapor barrier intact.
In hot climates installing faced insulation with the kraft paper on the outside may help to keep moisture outside. Some hot humid climate jurisdictions ban the use of faced insulation altogether.
Take care installing either type of insulation so that the fiberglass fits snuggly against all framing members. Even small gaps and holes compromise the wall’s insulation integrity.
Difference in Insulation Costs
Unfaced insulation typically costs $0.10 – $0.25 per square foot of installed area less than faced insulation–depending on thickness and R-value. For locations requiring a vapor barrier on the warm side of the exterior walls, 6 mil poly is usually acceptable. Add $0.05 – $0.20 per square foot of covered area for the poly. Plus the time to install it.
