Divide the square footage of your ceiling joist cavities by the square footage covered per bag of insulation. Round up to the nearest whole number. The result is the number of bags of insulation you need to buy.
To do so, take the square footage of the space and divide it by either the depth or the desired R-value. Our blow-in insulation calculator can help take the guesswork out of scoping and pricing for your next cellulose insulation project.
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.
You just need to measure the attic's width and length and multiply both figures to arrive at your home's square footage. For triangular attics, you'll need to measure the triangle's height and width and divide the base in half.
Both cellulose and fiberglass are energy-efficient insulation materials, but cellulose has a slight edge due to its higher R-value. The R-value for cellulose insulation is approximately 3.2 to 3.8 per inch, while fiberglass insulation typically has an R-value of 2.2 to 2.7 per inch.
If the federal recommendation is R60, then you can save yourself plenty of money on energy bills and HVAC repairs by having a minimum of R60 installed. This can be any combination of batts and blown-in insulation.
U-value = ƛ-value / thickness of the insulation
The quotient of these two figures (the U-value) is therefore expressed in W/m2K, which stands for the number of Watts (W) per square metre (/m2) at a temperature difference of 1 degree Kelvin (K).
While loft insulation is an effective way to improve energy efficiency and reduce heating costs, over-insulating can lead to several potential issues. Firstly, over-insulation can lead to poor ventilation in the attic, which can cause moisture buildup and increase the risk of mould growth.
Blown-in insulation costs $1.00 to $2.80 per square foot, depending on the type, location, R-value, and whether it's cellulose, fiberglass, or Rockwool. Blown-in attic insulation costs $900 to $3,600 on average.
For example, if the square footage of the room you're planning on insulating is 1,000 square feet and you want to achieve an R-value of 60, you will need approximately 17 bags to fully insulate your room. If you are using loose fill insulation, the coverage varies based on the R value that is needed.
You can do it yourself for about $500. Blowing attic insulation isn't hard, but it's dusty, sweaty work. To make insulating an attic easier, grab a helper and set aside two days: one for attic prep and the second to actually blow the insulation. By the end of the weekend you're going to be sore and tired.
Fiberglass is by far one of the most thoroughly tested building materials and can be installed in the form of batt or blown-in insulation. Fiberglass is eco friendly, non-flammable, safe to install and maintains its thermal performance for the life of the building.
While cellulose insulation itself is treated to be mold-resistant, the surrounding structure may not be. Understanding how and why mold is likely to occur can help you prevent serious structural damage. Given these risks, swift action is imperative if you suspect your cellulose insulation has become wet.
Air Leakage
Fiberglass insulation is less dense than other types of insulation and does not create an airtight seal, which means air can travel freely through the insulation. This is called air leakage and it's one of the most common sources of energy loss in a house.
Most local building codes require compliance with either the 1/150 method or the 1/300 method exception (refer to local code). These methods can dictate that one (1) square foot of ventilation is provided for every 150 or 300 square feet of attic floor space.
According to Energystar.gov, most attics' recommended cellulose insulation level is to insulate to R-38 (about 10 to 14 inches).
In general, staircases and closets count as finished square footage, while spaces like garages, three-season porches and unfinished basements or attics are not included. When in doubt on the square footage of a home, refer to MLS information, your purchase agreement or your own measurements.
You can use faced or unfaced batting when installing between the roof rafters of finished attic spaces. When using paper or plastic batting insulation, that moisture barrier should face outward toward the attic space. Even if the attic space is unheated, it's typically warmer than the outside air in winter.