by: Todd Bryson, Pacific Insulation

Many homeowners would like to insulate their attics, but don’t know how to do it. Attic insulation is a wise investment, considering that most houses experience the greatest heat loss through attic spaces. This not only reduces energy efficiency but can also end up costing homeowners due to expensive heating bills. Therefore, proper and effective attic insulation is one of the smartest projects to take on for your home.

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So, how do you insulate your attic?

Much of the work when it comes to insulating your attic will be making decisions about the type of insulation to use and preparing the space for installation. Once those tasks are complete, you can install insulation in your attic in the proper manner, depending on whether it is a finished or unfinished space.

Like any do-it-yourself (DIY) home project, insulating your attic requires attention to safety. When you are working with insulation, it’s essential to wear gloves, eye protection, and a particle mask—especially if using fiberglass material. Understanding the basics of insulation and what best suits your space is the first step to insulating your attic.

Insulation Basics: What You Need to Know About Insulation

Insulation materials are measured by “R-value,” which indicates the amount of insulation the material provides. A higher R-value results in more effective insulation.

The most common types of insulation used in attics are:

  • Spray foam—This is considered the most effective insulation in that it fills the space to create a solid air barrier. However, spray foam is costly and not recommended for installation by anyone other than a professional.
  • Loose-fill fiberglass—This material is commonly used in new-construction houses and has a good R-value. Loose-fill fiberglass requires a machine to be blown in during installation. It’s vital to understand that fiberglass can be a skin and lung irritant, so protection is necessary.
  • Cellulose—This material is made from recycled, ground-up paper mixed with boric acid for insect control and fire resistance. Cellulose can be purchased for DIY installation with the rental of an insulation blower. This insulation is an excellent choice for attics as its density controls air movement.
  • Fiberglass batts—This is considered the easiest way to add insulation to an attic space. Fiberglass batts measure lower in R-value than other materials, but they are easy to acquire and roll out for installation.

Choosing the right insulation material for your attic is a matter of deciding the best combination of R-value effectiveness and affordable cost to suit your space.

How to Prepare Your Attic for Insulation

It’s essential to do some preparation before you begin insulating your attic. There are three essential steps to take for this preparation in order to ensure proper installation and maximum results:

  • Sealing air leaks: Properly removing old insulation and sealing attic air leaks will lead to maximum insulation results. Key areas in which to ensure sealing are attic doors, pull-down stairs, and chimneys. Sealing these areas will prevent air leaks and enhance the effectiveness of installed attic insulation.
  • Proper ventilation: Proper attic ventilation allows moisture to escape, which helps to prevent water damage. A build-up of moisture or ice dams can damage a home’s roof and walls. Attic ventilation systems should balance the level of air taken in and then exhausted through soffit vents or ventilation chutes.
  • Preventing fire hazards: Properly treating attic lighting and electrical wires help prevent fire hazards. To prevent such safety risks, recessed lights should be covered, and insulation must be kept a few inches away from all lighting fixtures. In addition, any exposed electrical wiring in your attic should be attended to and fixed before insulation.

Making these preparations and taking these precautions before insulating your attic will ensure that your efforts at optimizing energy efficiency and reducing utility costs are effective.

How to Insulate an Unfinished Attic

Insulating an unfinished attic keeps the rooms in a house cool in the summer and warm in the winter through insulating the attic floor and installing roof vents. Blanket insulation that comes in the form of batts or rolls is recommended for attics with standard-spaced beams and joists, with few obstructions. Loose-fill insulation is recommended for attic installation where there is little headroom and multiple obstructions such as vents and crossbeams.

Installing a Vapor Barrier

Batt and blanket insulation generally come with a vapor-retardant facing, whereas other varieties of rigid foam insulation don’t require extra barrier protection. For other materials, it’s recommended to install a thin barrier or polyethylene on the underside of insulation to prevent moisture damage. It’s important to use unfaced insulation near flues and chimneys or when adding new insulation layers to old.

Installing Batt and Blanket Insulation

Blanket insulation is available as batts or rolls, made of fiberglass, mineral wool, plastic, or natural fibers.
For vapor-retardant facing material, install with vapor-retardant side down. It’s best to begin at one wall of the attic and work toward the center of the floor or entryway. Carefully place insulation between joists and ensure a good fit without compressing the material when pressing it in place.

Insulation should overlap the top plate of the exterior wall and be installed across the tops of joists as well. Batts and blankets should be cut to run the proper lengths of areas and trimmed carefully to snugly fit around vents so as not to compromise R-value effectiveness. Pricing for this type of insulation varies based on the thickness and material of blankets and batts.

Installing Loose-Fill Insulation

Installing loose-fill insulation is available in fiberglass, cellulose, and mineral wool, though cellulose is the most effective material. This insulation can be spread manually, but usually requires a loose-fill blower, which can be rented from most home improvement retailers. In some cases, these blower machines may be rented for free, depending on the amount of insulation purchased at the time.

To install this material in your attic, it’s best to begin filling the area between joists with insulation, starting with the walls and slowly move toward the center of the room or attic entry. Vents should be left uncovered, and attention should be paid to areas where insulation fills in around obstructions.

Often, it’s helpful to install loose-fitting insulation with another person who can load the blower as the other fills the space completely and evenly with insulation. Loading and operating the blower while installing the insulation is difficult to manage for one person and may compromise safety.

It’s also essential to leave attic vents uncovered. Any uneven spots of insulation can be leveled with a rake.

How to Insulate a Finished Attic

Insulating a finished attic keeps the attic space comfortable through insulating the walls and ceilings. Most likely, a finished attic is already at least partially insulated. However, you can raise the R-value in some areas.

If the living space of a finished attic needs insulation, it can be installed around the walls, ceiling, and continued along the floor of any non-living space. The roof above must be ventilated in order to prevent winter ice dams, which can cause serious damage. For ventilation in a roof that is already insulated, special rafter vents can be installed in order to prevent exposure to moisture and potential mold problems.

If your home’s attic is finished but just used for storage, it may be beneficial to pull up parts of the flooring and install loose-fill insulation with a blower. Insulating the attic floor in this way retains heat in the lower portion of the house and leaves the attic cold. However, if you wish to then turn this finished attic into living space as opposed to storage, an additional heat source such as a space heater may be required.

If your finished attic has preexisting insulation, you can purchase a different type of material and layer it over the existing material. Loose-fill insulation, in particular, can be effectively blown over existing insulation.

Why You Should Insulate Your Attic

A home’s attic has more purpose than just storage. It’s also a protective barrier when it comes to cold, heat, and humidity. Therefore, attic insulation provides many benefits, including:

  • Lower utility bills
  • Safer home structure
  • Better indoor air quality
  • Indoor comfort
  • Less wear and tear on HVAC system

Uninsulated or under-insulated homes will end up costing homeowners more for trying to maintain comfortable temperatures through heating and cooling. In addition, attic insulation can prevent damage to houses due to heat and moisture. An insulated attic prevents water vapor from entering and eroding walls, slows heat buildup in the attic, which can cause damage to roof shingles and mitigates outdoor pollutants such as dirt and mold for a cleaner environment.

Older homes, in particular, tend to have poor insulation, which can result in heating and cooling systems working harder than necessary to maintain consistent temperature. Attic insulation, when done properly, prevents cool air from remaining at lower levels and warm air from rising. This leads to greater indoor comfort and less wear and tear on a home’s HVAC unit. Less heat gain or loss as a benefit of attic insulation will lower utility bills and improve energy efficiency as well.