Making sure you have the most effective insulation, especially in the attic, is a smart way to increase your home’s energy efficiency. With the right materials and proper ventilation, you can reduce your energy costs and make your home more comfortable. In the video above, Ask This Old House expert Tom Silva explains a few techniques to help maximize the impact of your attic insulation.
Why Attic Insulation Is Important
The attic floor is often where homes lose or gain the most heat. During winter, warm air rises and escapes through poorly insulated attic floors, while in summer, heat from the roof radiates into your home. It’s also typically one of the easiest places to add insulation, particularly in older homes where the existing insulation may be insufficient or compressed.
Over time, insulating your attic can improve your home’s overall comfort and lower your energy bills. Proper attic insulation also helps prevent ice dams from forming on your roof, which can cause damage and lead to costly repairs.
Choosing the Right Insulation
Several factors can impact the best insulation for your home, including the type, cost, and R-value. We’ll go over these factors in more detail below to help you choose the right insulation.
R-Value Ratings
The R-value measures an insulation’s thermal resistance, with higher R-values meaning better insulation. Colder climates require higher R-values to prevent heat loss, while milder climates can get by with lower R-values. Check your local building codes or consult with a professional to determine the right R-value for your region.
Types of Attic Insulation
Several types of insulation work for the attic:
- Blown-in cellulose: Made from recycled materials, blown-in cellulose provides excellent coverage in attics with irregular shapes. It’s also resistant to settling, so it maintains its performance over time.
- Blown-in fiberglass: This option has a high R-value, meaning it offers strong insulation against heat loss. Its loose-fill nature allows it to reach and insulate hard-to-reach areas effectively.
- Fiberglass batts: This type of insulation is lightweight and easy to handle, making it ideal for do-it-yourself (DIY) installation. It fits snugly between attic joists, offering good thermal protection.
- Rigid foam boards: Because of their dense and rigid structure, rigid foam boards provide superior insulation. They’re ideal for areas where moisture and mold are a concern, but they often require professional installation.
Faced vs. Unfaced Insulation
Faced insulation includes a built-in vapor barrier that prevents moisture from passing through. If it’s not installed properly, it can trap moisture between layers, potentially leading to mold growth and decreased insulation effectiveness.
On the other hand, unfaced insulation lacks a vapor barrier, making it ideal for adding on top of existing insulation. It offers better moisture control and minimizes the risk of trapping moisture when used correctly.
Cost Considerations
The upfront cost of insulation varies by type, but the long-term energy savings often outweigh these initial expenses. For example, while blown-in cellulose or fiberglass may cost more initially, they can drastically reduce energy consumption over time.
Investing in insulation with a higher R-value may also make you eligible for energy efficiency rebates from local governments or utility companies. To find available rebates in your area, check the Database of State Incentives for Renewables & Efficiency (DSIRE).
Insulation Installation Techniques
Follow these installation techniques to maximize your insulation’s effectiveness.
Adding Insulation to Existing Attics
If your attic already has some insulation, you can increase its R-value by using unfaced insulation. When adding insulation, fill the space between joists and position the new material slightly higher than the joist tops. For blown-in insulation, make sure it extends above the joists to account for settling over time.
Insulating Bare Attic Floors
For attics with no existing insulation, you have two main options: fiberglass batts or blown-in insulation. If you opt for fiberglass batts, fit them carefully between the joists without compressing them. Alternatively, renting a blower allows you to distribute blown-in insulation evenly for maximum coverage and efficiency.
Working With Floored Attics
If your attic has a floor installed, follow these steps to enhance insulation performance while preserving usable attic space:
- Remove the existing flooring, if possible.
- Add insulation between the joists.
- Add a layer of rigid foam insulation on top.
- Cover the foam with 1/4-inch plywood for a walkable surface.
Maintaining Proper Attic Ventilation
Proper ventilation makes your insulation perform better by expelling excess heat and moisture. During summer, effective ventilation keeps the attic cooler and reduces the strain on your air conditioning system. In winter, it prevents moisture from condensing on cold surfaces, which can lead to mold and mildew growth.
Types of Attic Ventilation
Effective attic ventilation typically involves a combination of intake and exhaust vents working together to create a balanced system. This setup helps maintain a consistent temperature and reduces moisture buildup in the attic.
Common types of home ventilation systems include:
- Soffit vents: These vents allow cool air to enter the attic from outside, helping to maintain a balanced airflow and reduce heat buildup.
- Ridge vents or gable vents: These vents facilitate the escape of warm air from the attic, ensuring that hot air can exit efficiently, which helps to prevent overheating.
- Roof vents: These vents provide additional exhaust for warm air, complementing other ventilation systems to improve overall attic ventilation and cooling.
To maintain proper airflow in your attic, keep soffit vents clear of insulation to allow unobstructed entry of cool air. Make sure there is a clear path for air to move from the soffits to the attic space, preventing any blockages. Also, use baffles or rafter vents to maintain airflow in areas where insulation might otherwise obstruct air movement.
Common Insulation Mistakes
Here are common mistakes that can happen when insulating your attic and the best ways to avoid them.
Air Leaks
Before adding insulation, seal any air leaks in the attic. Common sources of air leaks include gaps around plumbing vents, electrical wires, and chimney chases. Use caulk or spray foam to seal these gaps.
This step prevents warm air from escaping in winter and entering during summer to improve your insulation’s overall efficiency.
Compressed Insulation
Remember not to squish insulation when installing it. This can reduce its effectiveness by making it thinner and decreasing its ability to resist heat transfer. To prevent this, make sure to install the insulation following the manufacturer’s guidelines. Allow it to expand fully and maintain its intended performance. Use the right tools and techniques to fit the insulation neatly between the joists or studs to preserve its insulating properties.
Forgetting the Attic Access Hatch
Many people overlook the attic access hatch when insulating, yet it has the potential to be a significant source of heat loss. Verify that the hatch is properly insulated and weatherstripped to prevent air leakage.
DIY vs. Professional Installation
While many homeowners can successfully insulate their attics themselves, there are situations where professional installation might be better.
When To DIY
DIY insulation can save on labor costs and is manageable for homeowners comfortable with basic home improvement. Consider a DIY approach if your attic is easily accessible, allowing you to move around comfortably and reach all areas. If you’re comfortable working in confined spaces, such as an attic, handling the insulation tasks will be easier.
If the job involves simply adding insulation to the attic floor, rather than insulating walls or dealing with complex features, the project will be more straightforward to DIY.
When To Hire a Professional
For attics with complex features or limited access, or if you need to insulate walls or work around existing hazards like old wiring, we recommend hiring a professional. Professional installation ensures the insulation meets local building codes and is installed correctly. Many professionals also offer warranties on their work, providing added peace of mind.
