For 2×6 walls, you need an R-value of 19, and the recommended wall insulation R-value for all zones falls between 19 to 21. If you decide to insulate the ceilings, they should have a minimum ceiling insulation R-value of 30.
Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces.
I would not put anything less than R5. Even R6 if you can get it. Good insulation is one of the best bang for your buck improvements you can make. It really isn't worth saving a little on lower R values, for something you will have in there for 20+ years.
R13 insulation is commonly used in ceilings in moderate climates. It helps to prevent heat loss in the winter and heat gain in the summer, which can improve energy efficiency and comfort. R15 insulation is used in ceilings in colder climates or buildings with high energy usage.
Foam Board or Rigid Foam
For ceiling applications, rigid board roof insulation types are ideal. The foam is easy to install and performs efficiently. It is possible to achieve spray foam levels of sufficient R-value density. Rigid foam is waterproof.
R30 insulation is frequently installed in ceilings, particularly in multi-story homes. It helps reduce noise transmission between floors and improves energy efficiency by minimizing heat exchange between levels.
It is possible to over-insulate your house so much that it can't breathe. The whole point of home insulation is to tightly seal your home's interior. But if it becomes too tightly sealed with too many layers of insulation, moisture can get trapped inside those layers.
R-value is used to judge thermal insulation performance and the higher the number, the better the product's insulating ability. So R19 has better insulating ability than R13. Now R-Value ranges widely across products and home applications.
Fiberglass: This is a popular choice due to its affordability and effectiveness. It's available in various R-values to suit different climates. Cellulose: Made from recycled paper, cellulose batts are eco-friendly and provide good thermal performance.
Most climates require a vapor barrier to cover ceiling insulation, but not all insulation requires a vapor barrier. It's always important to refer to your state's building codes.
CEILING INSULATION THICKNESS
For instance, to achieve a U-value of 0.16 W/m²K for a flat ceiling, you'll need a minimum of 170mm thick mineral fibre insulation placed between the ceiling joists, along with an additional 100mm thick layer covering the joists.
Kraft-faced insulation includes a paper vapor retarder, which helps prevent mold and mildew. Kraft-faced insulation should be installed in exterior walls, exterior basement walls, and attic ceilings by pressing the product into the wall cavity with the paper side facing outward, towards the installer.
Effective ceiling insulation is the best barrier against the summer heat and the winter cold, saving you up to 20% on your heating and cooling energy costs.
If you live in the Southern part of the U.S., the recommended insulation level is a minimum of R-38 or about 13-14 inches of insulation. If you live in the Northern part of the U.S., the recommended insulation level is a minimum of R-49 or about 16-18 inches of insulation.
R15 insulation offers slightly better thermal insulative properties than R13. Some of its formats are a fraction of an inch thicker than R13, making it more effective at helping with energy efficiency. However, the difference is minimal.
ABOUT INSULATION
The thermal barrier of a home should consist of a continuous layer of insulation on all sides—including the lowest floor, the exterior walls, and the ceiling or roof. Doubling the thickness of insulation will double the insulation's R-value, cutting heat loss in half.
Foil-faced batt insulation is often used in cathedral ceilings because it provides the permeability rating often required for use in ceilings without attics. A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel.
Foam insulation: Spray foam insulation seals all areas of the cavity, including walls, floors, and ceilings, as well as structural members, holes, cracks, and seams. Spray foam cannot lose its shape except under extreme pressure and will not sag or settle over time.
If the existing attic insulation is an R-19, you may choose to add another layer of R-19. Two layers of R-19 at 6¼ ” thick will achieve a total R-value of 38. So adding an R-19 batt to an existing R-19 batt will give you a total insulation value of R-38.
As mentioned above, you can always increase your R-Value simply apply an extra layer of insulation over your initial layer.
R13 batt insulation is typically used to attenuate sound in interior wall cavities. It is akin to a large blanket, designed specifically to fill a wall, floor, or ceiling cavity.
The optimal R-value for most homes is 30, but you can go as high as 38 if you live in a tropical climate. Anything higher than 38 indicates an over-insulated space. While you might think that too much insulation can't be bad, there are some significant consequences to consider.
You should always install a vapor barrier to protect exposed ceiling insulation even if it's temporary. Consult with a building or safety expert to confirm where else in the structure a vapor barrier may be required.
When it comes to insulation, it's generally recommended to leave a gap between the insulation material and any other surfaces, such as walls, ceilings, or roofs. This gap provides ventilation and prevents moisture buildup, which can lead to mould and other problems.