Congratulations on your new home (or on enhancing one you’ve cherished for years)! Alongside choosing new furniture and paint, it’s worth dedicating some time to assess your home’s attic insulation.
What is Attic Insulation?
Attic insulation acts as a thermal barrier in your attic, limiting heat transfer from your home’s interior to the exterior in the winter, and vice versa in the summer. With better heat retention or prevention, your living space remains consistently comfortable year-round.
A well-insulated attic also guards against moisture buildup and eases the workload on your HVAC system, helping it maintain your desired indoor temperature efficiently.
Differences Between Attic and Roof Insulation
Both attic and roof insulation can help insulate your home effectively, especially when used together, but they are installed in different places. Attic insulation is installed in the attic, while roof insulation is placed on the roof slope, either above or below the rafters.
Adding both is ideal for energy efficiency, but if you’re limited to insulating just one area, we recommend the attic—it’s more affordable and yields higher savings in the long run.
Though this article focuses on attic insulation, much of the information can also apply to roof insulation.
How Insulation Works
Insulation helps by slowing the transfer of heat through conduction, convection, and radiation:
- Conduction: How heat moves through materials.
- Radiation: How radiant heat travels in a straight line, heating everything in its path.
- Convection: How heat circulates through liquids and gases, explaining why warm air rises and cool air sinks.
Most insulation types work by reducing conduction and convection, while reflective insulation systems prevent radiant heat from entering your home.
Lower Energy Costs Through Proper Insulation
According to the U.S. Department of Energy, about 49% of a home’s energy use goes to heating and cooling. Adding attic insulation can reduce monthly energy bills by preventing air leakage, potentially cutting energy costs by 10-15%. For many, that means around $200 in annual savings.
Before You Buy Insulation Materials
In most cases, adding attic insulation is highly beneficial. However, in certain situations, it could cause issues:
- Older Homes: Some older homes were designed with large gaps for moisture control. Filling these gaps could trap moisture, leading to mold and wood decay.
- Old or Wood-Shingled Roofs: Older roofing materials are meant to dry naturally, so insulation near the ceiling could trap moisture and create problems.
- Knob and Tube Wiring: Common in homes built before the 1940s, this outdated wiring can be a fire hazard if surrounded by insulation.
Inspecting Your Attic Insulation
Start by inspecting your attic and assessing the current insulation. Generally, the U.S. Department of Energy recommends adding insulation if there’s less than 8 inches of cellulose or less than 11 inches of rock wool or fiberglass, though your climate may affect these needs.
What You’ll Need for Inspection:
- Boards for walking (if needed)
- Tape measure
- Flashlight or headlamp
- Hard hat or cap for nail protection
- Safety glasses, gloves, and a dust mask
- Protective suit
Note: Some attics may have vermiculite insulation, which can contain asbestos. If present, don’t disturb it until it has been tested by an approved lab. Contact your local health department for a lab list.
How to Check Insulation Levels Quickly
Looking across the attic, is the insulation level with or below the attic floor joists? If so, more insulation is likely needed. If you can’t see any joists, you probably have sufficient insulation. Make sure it’s evenly distributed without low spots along the edges.
How to Measure Insulation Levels
If you see batts (fiberglass pieces) in your attic, check for the R-value printed on them. Alternatively, you can measure insulation depth with a tape measure.
This step-by-step guide should help you ensure your attic is well insulated, bringing down your energy costs while enhancing indoor comfort.
Understanding R-Values in Insulation
The R-value measures an insulation material’s ability to resist heat flow, with higher R-values indicating better insulating power. The R-value depends on factors like insulation type, thickness, and density, and can also be influenced by age, temperature, and moisture buildup. To determine the R-value for multilayered insulation, simply add up the R-values of each layer. Generally, increasing insulation thickness also raises the R-value, although with loose-fill insulation, the R-value may not increase proportionally due to compression.
Climate Considerations
Insulation needs vary depending on where you live. Homes in colder climates require more insulation than those in warmer areas. The goal is to create a thermal barrier that suits your specific regional climate conditions.
Choosing the Right Type of Insulation
Various insulation types offer different benefits. Selecting the best one for your attic depends on your home’s layout, budget, and specific needs. Here are some common attic insulation types:
- Blanket Insulation: Often made of fiberglass, this is an economical choice for attics but is best used in enclosed spaces to avoid air quality issues. Proper handling is necessary since fiberglass particles can irritate skin and lungs; always wear gloves, a mask, and protective clothing when installing.
- Spray Foam: A popular choice for professional installation, spray foam is excellent for sealing gaps and providing strong insulation against temperature changes. It’s made from liquid polyurethane, which expands to fill spaces and hardens. Although more costly, it offers superior insulation, especially when paired with blanket insulation.
- Foam Boards: Foam boards, usually crafted from materials like polyurethane or polystyrene, are easy to install and resist moisture. While less effective than spray foam or blankets, they are affordable and can be cut to fit various spaces.
- Radiant Foil: Ideal for warmer climates, radiant foil reflects heat away from the home. It’s inexpensive and works well when paired with other insulation types to create an efficient barrier against heat.
Insulation Materials
- Fiberglass: Common in blanket insulation, it has an R-value of 2.7 per inch and is easy to cut and install.
- Rock Wool (Mineral Wool): Made from basalt rock and steel slag, this material has an R-value of 3.3 per inch.
- Cellulose: Often used in loose-fill insulation, it’s made from recycled materials and has an R-value of 3.8 per inch.
- Liquid Polyurethane: A key component of spray foam, with an R-value between 3.5 and 6.5 per inch. Closed-cell spray foam offers the highest R-value.
- Polystyrene: Used for foam boards, with R-values between 3.8 and 5 per inch depending on the specific type.
Cost of Attic Insulation
Attic insulation costs vary based on the material used, averaging from $0.30 to $1.50 per square foot. For example, insulating a 500-square-foot attic could cost between $150 and $700 if you install it yourself. Professional installation typically adds $200 to $500. Additionally, you might qualify for financial assistance through the Weatherization Assistance Program (WAP).
Preparing for Installation
Safety is essential when handling insulation. Gather supplies such as gloves, dust masks, hard hats, and knee pads, and ensure adequate lighting. Use plywood to create safe walking paths and protect yourself from nails and other hazards.
Insulation Installation Tips
- Select Your Insulation Type: Loose-fill and blanket insulation can be layered, and you can mix types if needed.
- Lay Down the Insulation Carefully: Follow recommended methods for your chosen insulation type, especially if using machinery for loose-fill installation.
- Create Protective Barriers: Keep insulation away from recessed lighting unless it’s rated for direct contact.
Helpful Tips
- Unwrap insulation only when ready to install since it expands after unpacking.
- To cut blanket insulation, press it with a two-by-four and slice along the edge with a utility knife, taking care not to over-compress, which reduces R-value.
DIY or Professional Installation?
If you feel confident working in an attic, you may consider insulation installation a DIY project. However, a professional installation offers expertise and precision, potentially maximizing energy savings. Upgrading attic insulation can improve your home’s energy efficiency, leading to long-term savings on utility bills.
