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The ultimate goal of home insulation beyond energy efficiency is to maintain the desired temperature in a house all year round. The case is no different for Attic Insulation– it adds effective resistance against hot or cold air trying to escape your home, thus ensuring the temperature you set on your thermostat is what you get.

But what is all about attic insulation? This guide compiled by experts at Conejo Valley Home Services. is precisely what you need to learn the essentials of insulating your attic for maximum comfort and energy savings. Let us dive in.

How Much Does Attic Insulation Cost?

According to Conejo Valley Home Services, the reputed name of Home Insulation contractor in Conejo Valley and surrounding areas, the cost for insulating your attic depends on following main factors:
  • Your attic size
  • Type of the insulation material you pick
  • The amount of work needed
  • The local labor rates

The total insulation project cost will be offset over time, but the payback time will largely depend on how much you save on your air conditioning bills. According to the US Department of Energy, attic insulation can offer homeowners 10% to 50% utility bill savings, depending on the inefficiency of the old insulation and the R-Value of the new insulation.

R-Value, short for Resistance Value, denotes a material’s ability to resist heat flow.

Insulate the Attic Floor

If you do not use your attic that much, heating it does not make sense. The best, cheapest, and most straightforward solution is insulating your attic floor. However, a floor covered with plywood cannot accommodate enough insulation beneath it. So, part of the attic insulation project will be removing the flooring and adding new insulation material to the old.

If you intend to use the attic for storage, cover the floor insulation with some boarding type, such as the Oriented Strand Board.

Insulate the Attic Floor

Pick Insulation Types and Materials

Typically, there exist two choices for DIY attic insulation: batt (blanket insulation) and loose fill. You can add both to an uninsulated attic or layer them over existing material. Following is a quick overview of these insulation types and material options best suited for them.

1) Batts

The most common and widely available insulation type, batt/ blanket insulation is a flexible material available in long insulation fiber rolls. Batt rolls are available in various thicknesses and standard widths and can be hand-cut and trimmed to fit specific spaces. Batts may or may not include a facing (think vinyl, kraft paper, or foil-kraft paper), which serves as a vapor barrier and/or air barrier.

This insulation type is the recommended option for attics with:

  • Few obstruction or penetrations to work around
  • Standard joint spacing of joists
  • Enough headroom for maneuvering around during installation

It also the best choice for homeowners who do not mind trimming the material to fit around obstructions. The following are the material options available for batt insulation:

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Encompassing a high recycled material content ranging between 82% and 85%, cellulose insulation is made of fibers from recycled paper products, largely newsprint. Accounting for the remaining portion is mineral borate, often combined with ammonium sulfate, for permanent fire resistance.

Manufacturers first reduce the paper into small pieces and then fiberize it to create a product that snags in building cavities and restricts airflow. Cellulose has an R-Value lying somewhere between 3.7 and 3.8 per inch. Additionally, cellulose is non-toxic, and there is no risk of fibers entering your breathing system or causing long-term effects when inhaled.


The most frequently bought attic insulation material, fiberglass consists of extremely delicate glass fibers made of recycled glass and sand melted and rolled into fibers. This material boasts high moisture-resistance, making it less vulnerable to mildew and mold growth. It is also non-combustible, and its R-Value ranges between 2.9 and 4.3 per inch.

Among the downsides of fiberglass is its lower efficiency in blocking airflow. When inhaled, glass fibers can irritate the nose and throat and aggravate bronchitis and asthma. New manufacturing methods promise to minimize this risk.

Mineral Wool

Mineral wool refers to either of these two types of insulation materials: slag wool (artificial material blast furnace slag) or rock wool (synthetic material comprising natural minerals such as diabase and basalt). Typically, post-industrial recycled content accounts for 75% of this insulation material.

Mineral wool does not require additional chemicals to make it fire-resistant. It is costlier than other materials, and its R-Value ranges between 3.0and 3.3 per inch.


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2) Loose Fill

Loose-fill or blown-in insulation consists of tiny particles of foam, fiber, or other materials that form an insulation material that fits any place without disturbing finishes and structures.

Using an insulation blower machine rent from a home improvement store, a homeowner can package the fibers in a bag and blow in place to the desired thickness. Alternatively, you can pour the material in place and spread it manually; however, this option is labor-intensive and produces less desirable results.

Blown-in insulation is best suited for attics with:

  • Lots of penetrations and obstructions with to work around
  • Nonstandard or irregular joist spacing
  • Existing insulation to be topped
  • Limited headroom

This insulation type is also your best bet if you are comfortable working with a power machine and want the job completed quickly.

Blown-in insulation material options include:

 Loose Fill Insulation


  • 82%-85% recycled material
  • Made of paper reduced into small pieces, fiberized, and chemically treated for fire and insect resistance
  • Non-toxic
  • R-value lies between 3.7 and 3.8 per inch.
  • Susceptible to mold and mildew growth when exposed to moisture


  • Extremely delicate glass fibers made of recycled glass and sand
  • R-value of 2.9-4.3 per inch
  • Lighter in weight than mineral wool or cellulose, meaning you need to use a thicker layer for perfect insulation.
  • Non-combustible
  • Highly resistant to moisture- no risk of mildew or mold growth

Mineral Wool

  • Can either be slag wool (artificial material blast furnace slag) or rock wool (synthetic material comprising natural mineral such as basalt)
  • R-value per inch hovers between 3.0 and 3.3
  • Naturally fire-resistant
  • More expensive than other loose-fill insulation materials

How to Measure Attic Insulation?

Measuring your existing attic insulation level is a straightforward process that does not demand any special training. You only need to take a ruler and push it down through different spots on your insulation. Record how far the ruler goes before reaching the bottom of your insulation.

To calculate your home’s insulation R-value, multiply the depth of your attic’s insulation(in inches) by its corresponding R-value. Below is a list of R-values for different types of existing insulations:

  • Loose-fill cellulose: 3.7
  • Loose-fill fiberglass: 2.5
  • Loose-fill mineral wool: 2.8
  • Batts fiberglass: 3.2
  • Loose rock wool: 2.8

Determine the Ideal R-Value for Your Attic Insulation

Energy Star recommends the following attic insulation R-values, depending on the climate zones:

Zone Add attic insulation to:
Uninsulated attic Existing 3-4 inches attic insulation
1 R30 to R49 R25 to R30
2 R30 to R60 R25 to R38
3 R30 to R60 R25 to R38
4 R38 to R60 R38
5 to 8 R49 to R60 R38 to R49

Check for Tax Credits and Rebates

The federal tax credits for home insulation, which offered homeowners 10%. But your state or city might offer you some financial incentives for insulating your home, including product rebates and discounts. Find home insulation policies and incentives within your area by entering your zip code here.

How Much Insulation Should You Buy for Your Attic?

The first step to finding how much insulation material you need is measuring your attic’s area in square footage.

To find the number of rolls/batts you need, calculate the area of the product you intend to use by multiply length and width. Dividing your attic’s area by the product’s area yields the number of rolls you need.

If you intend to use loose-fill materials, read the labels carefully. Each bag lists the ideal depths for various R-values and the number of bags required to cover 1000 square feet at those depths.

Regardless of the insulation types you choose, always buy an extra roll or bag to avoid a scenario where you run out of material just when you are about to complete your attic insulation project.

Seal Air Leaks and Improve Insulation

Insulating your attic is only half the energy- and bill-saving equation. Complete the equation by sealing all gaps in the attic and openings penetrating the attic floor. Among the areas to check include:

  • Openings between attic floor framing and flues and chimneys– Seal these gaps with furnace cement or metal flashing sealed with high-temperature caulk.
  • Openings for ductwork, electrical boxes, pipes, and wiring– Seal gaps of ¼ inch or less using fire-blocking caulk and larger gaps of up to ½ inch with fire-blocking spray foam.
  • Around attic windows- Seal leaks around the casing using canned, minimally-expanding spray foam. For gaps around the jambs and sash, use weather stripping foam.

How to Prepare Your Attic for Insulation

The first preparation step for home attic insulation is cleaning and organizing your attic. Remove anything not needed in the attic and properly store all valuables in a secure area. Make sure to remove as much dust and debris as possible.

The next step is checking for water leaks. Evaluate your attic thoroughly to discover any water damage. Excess moisture encourages mold and mildew growth and ruins the air-trapping pockets responsible for blocking heat flow. Typical signs of water leaks include damp areas, moldy spots, and water stains.

Next, protect all lighting fixtures in your attic. Never allow the insulation material to come into contact with your lighting fixtures unless the fixture is rated safe for contact with the material or you are using mineral wool insulation; otherwise, you increase fire hazard risk. To prevent this risk, create a box around all the lighting fixtures using a metal flashing or plywood while ensuring a 3-inch safety gap all around each fixture.

Lastly, direct all vents and exhaust fans to your home’s exterior. If your vents dump in the attic, the humid exhaust air will create a breeding ground for mildew and mold growth.

Prepare Your Attic for Insulation

DIY Attic Home Insulation Tips

When insulating your attic, start from the perimeter wall and work toward the door/hatch to avoid tramping your new insulation. Also, cover the top of your ceiling joist to ensure correct insulation depth for your target R-value and prevent heat loss through the wood framing. Keep reading to discover tips specific to the two types of attic home insulation.

For Batt Insulation

Always use unfaced batts- you can buy the insulation unfaced or remove the foil or paper backing. Cover any old insulation gaps by placing a new layer of batt insulation perpendicularly over the old layer.

Avoid placing heavier batts over lighter ones- otherwise, you compromise the lower layer’s efficiency.

Stuffing batts around obstructions and penetrations compresses the material’s air pockets, thus reducing its insulating qualities. Because of this, always cut the material to fit. Avoid leaving any gaps between the batts and butt adjoining batts snugly together but not tightly enough to compress them.

For Loose Fill Insulation

Close the attic door or hatch to keep the loose-fill material inside the attic during the installation. Ensure the fill’s depth is uniform across your loft using depth guides screwed to the joists.

Always use power tools specifically designed for loose fill insulation. Do not attempt to place your hand in front of the blower to control the insulation’s direction, as this may cause an injury.

To achieve the right density, hold the insulation blower’s hose parallel to the floor and floor joists, and blow in the material between and over the joists.

Self-Protection when working with Insulation

Wear long pants, a long-sleeved shirt, work gloves, safety goggles, a dust mask, and a hat when insulating your attic to protect your skin, eyes, and respiratory tract from the fibers. Use hand tools to cut the insulation material whenever possible. And ensure the power tools have a dust-collecting mechanism.

You will also want to illuminate your work area- use an electrical working light or battery-powered lantern. NEVER use candles for illumination because they may ignite the insulation material. When done with the insulation, shower thoroughly to remove fibers from your skin and wash your work apparel separately from other clothes.

Conejo Valley Home Services?
  • We Offer 24-hour Emergency Services
  • We Charge by the Job – Not by the Hour
  • We Offer Only the Most Dependable Customer Satisfaction With Each Job Completed

Ready to Insulate Your Attic? Conejo Valley Home Services Can Help!

If you want to learn more about home attic insulation or schedule an attic insulation appointment with a certified HVAC contractor, do not hesitate to contact Conejo Valley Home Services. Our experts are trained, certified, and experienced to handle blown-in fiberglass and cellulose insulation and batt fiberglass insulation.

Call us today at 805-499-0448 or contact Insulation experts online for a free in-home consultation or information about our other HVAC services in Conejo Valley and the surroundings.