Insulation levels are specified by R-Value. R-Value is a measure of insulation's ability to resist heat flow. The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.
What is an R value in insulation?
Insulation level are specified by R-Value. R-Value is a measure of insulation's ability to resist heat traveling through it. The higher the R-Value the better the thermal performance of the insulation.
According to ENERGY STAR®, you can put new insulation over old insulation, “unless it is wet. The vapor retarder on top of or between layers of insulation can trap moisture. Any existing batt or roll insulation in the attic should have the facing against the attic drywall floor or no facing at all.
First, always place the insulation tight to the living space. The insulation should not be installed in the roof rafters unless the ceiling finishes are applied directly to the roof rafters. Unfinished attic storage areas are cold in winter. There is no advantage in insulating a cold attic from the cold outdoors.
Seal small gaps. Even though most of the gaps spilling warm air into your attic are buried under insulation, you might be able to find evidence of them. Use expanding foam or caulk to seal the openings around plumbing vent pipes and electrical wires.
If you need to add insulation in your attic, save big by blowing in cellulose insulation yourself. The pros charge $1,500 to $2,000 to do a 1,200-sq.-ft. house. You can do it yourself for about $500. Blowing attic insulation isn't hard, but it's dusty, sweaty work.
You can use either faced or unfaced batting for this installation. When using insulation that has either paper or plastic facing, that moisture barrier faces outward, toward the attic space. Even if the attic space is unheated, it typically is warmer than the outside air in winter.
Can You Over-Insulate Your Home? Homes need insulation, and more is generally a good thing. Without proper ventilation, a home can build up too much moisture, especially in the attic (warm air rises), which can cause mold problems and, overall, lower indoor air quality.
Spray foam is available in two different types: open-cell spray foam which is usually $0.44 to $0.65 per board foot and closed-cell spray foam which is about $1 to $1.50 per board foot. The average cost to have spray foam professionally installed is about $2,259.
Attics are awful places to work, and there is a strong incentive to cut corners, especially when the work will be buried beneath R60 of insulation. A second, related thought is whether there are any ducts in the attic that may have been damaged during the work, thereby connecting the super heated attic to your house.
Cost: The average cost per square foot is between $0.64 - $1.19. So, for a 500 square foot area, your estimate will vary between $145 to $200, if you do it yourself. For a professional job, add between $150 to $300 for labor, and you're looking at around $300 to $500 for 6 hours of work.
Fiberglass Batt Insulation. Standard fiberglass insulation batts or blankets provide an R-value of 2.2 to 3.8 per inch of thickness. Most manufacturers produce an R-13 batt that fits into a 2-by-4 wall cavity, which is typically 3.25 to 3.5 inches in total thickness.
Faced insulation is a type of blanket insulation that is typically made of fiberglass. It differs from unfaced insulation only in that it has a vapor barrier (also called vapor retarder) that blocks moisture from moving from one space to another. The vapor barrier is usually made of kraft paper.
At the technical level, R-value is a measure of resistance to heat flow through a given thickness of material. In theory, the higher the R-value, the greater that resistance. That's true to a point, but it's just one of four key factors that determine the effectiveness of an insulation material.
An example would be compressing R-19 insulation (typically 6 ¼”) thick into a 2x4 stud cavity that is 3 ½” deep. A. When you compress fiber glass batt insulation, the R-value per inch goes up, but the overall R-value goes down because you have less inches or thickness of insulation.
|Component||R-Value Studs||R-Value Cavity|
|Plywood Sheathing - 1/2"||0.63||0.63|
|3 1/2" Fiberglass Batt||13.00|
|3 1/2" Stud||4.38|
An insulating material's resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value -- the higher the R-value, the greater the insulating effectiveness. The R-value depends on the type of insulation, its thickness, and its density.
Enter the dimensions of your attic.
- Measure the depth of your existing insulation and enter this number below. Current Depth: in. Current Insulation Type: Fiberglass Cellulose.
- Determine Your Desired R-value. Estimated Current R Value: Your Desired R Value:
- Enter the dimensions of your attic. Width: ft. Length: ft.
R-value is a measure of apparent thermal conductivity, and thus describes the rate that heat energy is transferred through a material or assembly, regardless of its original source. The SI unit for R-value is kelvin square meters per watt (K. m²/W).
The R-Value of Wood. A material's thermal resistance or resistance to heat flow is measured by its R-value. In a solid log wall, the logs provide both structure and insulation. The R-value for wood ranges between 1.41 per inch (2.54 cm) for most softwoods and 0.71 for most hardwoods.
The fiberglass comes in rolls, also known as batts, which vary in size. An R-38 fiberglass batt should be approximately 6 1/4 inches thick, while the thickness of cellulose insulation of a finished, fitted product will be around 12 inches.