R-19 and R-21 fiberglass batts are both designed to insulate 2x6 exterior wood walls. R-21 is a premium, high-density product that offers superior thermal performance while being slightly thinner than R-19, making it ideal for tight code requirements, though it comes at a higher upfront cost.
Thermal Resistance: R-21 polyiso boards offer higher thermal resistance compared to R-19, which makes them more effective at reducing heat transfer in colder climates.
The R21 PINK Next Gen Unfaced Batt is a premium fiberglass insulation solution designed for 2x6 wood or metal-framed walls, floors, and ceilings. With a high R-value of 21, it delivers exceptional thermal performance, helping to maintain consistent indoor temperatures and reduce energy costs.
Fiberglass and rock wool batts—2x4 walls can hold R-13 or R-15 batts; 2x6 walls can have R-19 or R-21 products.
Designed for interior and exterior wall applications. Energy-saving thermal insulation. Exceptional sound and noise absorption. Fire-resistant.
The maximum R-value you can achieve in a standard 3.5-inch 2×4 wall cavity is approximately R-21 to R-24, which is accomplished using professionally installed closed-cell spray foam insulation.
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.
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.
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.
What time of year is Insulation cheapest?
Overall, fibreglass insulation is the cheapest and most effective insulation option available, making it a popular choice for homeowners and builders alike.
R19 is 6.5″ thick whereas R21 is 5.5″ thick. Thinner by one inch and yet 2 points higher in R value. The common explanation as to why this is so, is that the R21 insulation is said to be “more dense”.
For roof/ceiling and interior/exterior wall applications Installed in wood or metal framing cavities or between furring channels. Flexible fiberglass insulation 5.5 inches thick.
It is a common measure adopted by manufacturers, retailers, and even some contractors to ascertain the performance of insulation. Although R-value is important, it will not help you save on your power bills. The fact is, the energy efficiency of your home does not just rely on a number.
R13 Insulation: The Standard for 2x4 Walls
If you live in a climate where winters are mild (think Southern California or Florida), R13 might be all you need for exterior walls. Is R13 good enough? For many situations, yes. Energy Star recommends R13 to R15 for wall insulation in warmer zones (Zones 1 through 3).
Attached, non-heated garages should have insulation with an R-value of 7 to 9, since heat loss in this type of garage can affect your home's heating costs. Heated garages should have insulation with an R-value of 10 to 13.
Key takeaways
Natural Smells the Amish Use to Repel Mice
Traditional methods often include using natural deterrents like peppermint, pine, or other strong plant-based smells. Whether it's growing plants near entry points or using oils indoors, these scents can interfere with how mice navigate and make the space less appealing.
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.
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.
10 Insulation Installation Mistakes to Avoid
In basements, installing a vapor barrier on the interior wall in front of the insulation and behind the drywall will keep the basement temperature consistent and protect its contents from water vapor damage.
The number one killer to mice is rodenticide, a type of poison designed to eliminate them quickly and effectively. These poisons work well but can harm pets, kids, and wildlife if mishandled. Mice may be small, but they can cause big problems inside homes and businesses.
"Mice are generally not inclined to crawl on or bite humans, as they are naturally skittish and avoid contact," Dillard says. "They are nocturnal and typically avoid human interaction, instead foraging for food or seeking shelter while you're asleep and the environment is quieter."
Closed-cell spray foam and rigid foam board are hard, unattractive to rodents, and double as air barriers. Mineral wool is dense enough to discourage nesting. Fiberglass batts, especially in crawl spaces and attics, are essentially an open invitation.