The "warm side" of insulation refers to the side facing the environmentally controlled, heated, or cooled living space. It is the direction of the living space in winter and the side exposed to hot exterior air in the summer.
The facing should always face the warm side of the wall (toward the living space in cold climates). This prevents warm, moist air from penetrating into the wall cavity where it could condense and cause problems.
Unfaced insulation is great for new construction, remodels, walls, floors, ceilings, basements, attics and crawlspaces. It's best used for interior wall applications that do not face the outside and also in rooms that don't need moisture control, like living rooms, dining rooms and studies.
(The general rule for insulation is that the facing always goes toward the conditioned space.)
Properly placed vapor barriers should be installed on the warm, humid side of a wall.
No, you should never put vapor barriers on both sides of insulation. A double vapor barrier essentially creates a moisture trap, sealing any water inside the wall cavity and leading to rot, mold, and structural damage over time.
Because spray foam can trap moisture, hide the condition of the roof, make it difficult for surveyors to inspect, which means risks like timber decay, dry rot, and not forgetting increased fire risk. If you've got it or you're buying a property that does, this is something you need to know upfront.
10 Insulation Installation Mistakes to Avoid
The paper side (vapor barrier) of insulation should always face toward the heated, conditioned living space to prevent moisture from trapping inside walls and causing mold. In walls, this means the paper faces inside toward the room; in attics, it faces down; and in crawl spaces, it faces up.
What time of year is Insulation cheapest?
Mice are curious and always searching for safe, snug, and warm nesting sites. Attics filled with blown-in insulation provide an excellent option–from the mice's point of view. As long as there is a ready food source. Mice are omnivorous and will eat and chew on almost anything including wood and electrical wires.
Yes, you can mix faced and unfaced insulation, but only one vapor barrier should be used. Place the faced layer toward the heated side of the space. Never stack two faced layers, as trapped moisture can lead to mold or damage.
Yes, homeowners can add new insulation over existing insulation in most cases. This approach works well for attics, walls, and floors where the current layer remains intact and undisturbed. Building codes and energy experts often support this method to boost thermal performance without full removal.
Yes, faced or unfaced insulation matters significantly depending on your climate, local building codes, and the specific location you are insulating. The facing acts as a vapor barrier (or retarder) to prevent moisture from condensing inside your walls.
Effective wall coverings for cold walls include thermal insulation wallpaper (PE foam or cork), insulated lining paper, rigid foam boards, and thick acoustic panels to reduce heat loss and improve warmth. Popular solutions include Adhesive Thermal Insulation Wallpaper (3.28 x 32.8 ft) and 19. 7 in. X 16. 4 ft. Thermal Insulation Wallpaper, which offer easy installation for immediate improvement.
Don't Skip Sealing Seams, Edges, and Penetrations
A vapor barrier with unsealed seams fails at every gap. Moisture and soil gases enter through even small openings. Overlap panels by at least 12 inches and tape every seam.
Yes, the direction matters significantly. The rule of thumb is to face the paper or foil vapor barrier toward the conditioned (heated or cooled) living space. This prevents warm, moist air from passing through the insulation and condensing on cold surfaces, which can lead to mold and structural rot.
While it may appear harmless to the naked eye, it actually contains thousands upon thousands of small shards of glass and sand that can make their way onto your skin, eyes or even inside your lungs. If you've ever touched fiberglass insulation with your bare hands, you're probably well aware of its effect on the skin.
Unfaced insulation is a plain batt or roll of fiberglass insulation with no facing. It is Class A fire-rated, which means it can be left exposed, or used in specific fire-rated assemblies. Unfaced insulation can also be used with vapor retarders such as polyethylene or polypropylene (depending on local code).
It's recommended to leave an air gap insulation of at least 25mm or 1 inch for the walls and ceilings. This should be enough to allow for ventilation and prevent moisture buildup. The same rule may be applied when using foil insulation. On roofs, the air gap should be larger, typically around 50mm or 2 inches.
Installing insulation backwards—specifically faced insulation with a vapor barrier—creates a serious moisture trap. The paper or foil backing is meant to face the conditioned (warm) side of the home. If reversed, moisture from inside the house passes through the insulation and condenses against the cold, backward barrier, leading to trapped water, mold, and wood rot.
Foam insulation is a common target because it's easy for them to chew through. The material offers little resistance, allowing mice to create tunnels or nests within the insulation. But mice aren't just interested in chewing for the sake of it—they're also drawn to the warmth and shelter insulation provides.
The healthiest, non-toxic insulation for your home is natural sheep's wool or hemp insulation. These materials contain no chemical binders or formaldehyde, actively regulate indoor humidity to prevent mold, and do not off-gas.
Closed cell spray foam is rigid once set. It is a better thermal insulator and was previously sold to stabilise failing roofs. But if it has been used inappropriately or installed poorly, it might put stress on timbers, restrict air circulation and put them at risk of decaying.