Blown-in insulation dramatically improves a home’s energy efficiency by filling gaps and voids that traditional insulation methods often miss. It creates a continuous thermal barrier that reduces heat loss in winter and heat gain in summer, thereby cutting energy costs and enhancing indoor comfort. This insulation method works by using specialized machines to blow loose fibers or particles into attics, walls, or crawl spaces, allowing it to conform tightly to irregular spaces and hard-to-reach areas.
By targeting these vulnerable points, blown-in insulation can reduce overall heating and cooling energy use by up to 30%, making it a cost-effective retrofit for older homes and a strong option for new construction upgrades. This article provides an in-depth look at the types, performance, and considerations of blown-in insulation to help you understand how it can transform your home’s energy profile.
Types of Blown-In Insulation and Their Performance
The choice of insulation material directly affects how well the insulation performs over time and in different environmental conditions. There are three primary types of blown-in insulation: cellulose, fiberglass, and mineral wool. Each has distinct characteristics that influence thermal resistance, moisture control, fire resistance, and durability.
Material Characteristics and Thermal Resistance
Cellulose insulation, made from recycled paper treated with fire retardants, offers high density and excellent air-sealing capabilities. It typically has an R-value between 3.2 and 3.8 per inch, making it efficient at slowing heat transfer. Its dense fibers trap air effectively, which also makes it one of the best options for soundproofing.
Fiberglass blown-in insulation is composed of tiny glass fibers. While its R-value per inch is lower, generally between 2.2 and 2.7, it is highly resistant to moisture and does not settle much over time. This makes fiberglass a preferred option for areas prone to dampness or where long-term stability is critical.
Mineral wool, derived from rock or slag, combines good thermal resistance with exceptional fire and moisture resistance. With an R-value around 3.0 to 3.3 per inch, it performs well in extreme conditions and also provides superior sound dampening, similar to cellulose.
| Material Type | R-Value per Inch | Fire Resistance | Moisture Resistance | Settling Over Time | Typical Use Case |
|---|---|---|---|---|---|
| Cellulose | 3.2 – 3.8 | Moderate | Moderate | Settles ~10-20% | Attics, walls in dry climates |
| Fiberglass | 2.2 – 2.7 | High | High | Minimal settling | Damp areas, crawl spaces |
| Mineral Wool | 3.0 – 3.3 | Very High | Very High | None | Fire-prone areas, soundproofing |
Bonus Tip: For colder climates, cellulose’s air-sealing ability often results in better overall energy savings despite its settling tendency. However, pairing it with proper air sealing before installation helps maximize performance.
Installation Process and Impact on Energy Efficiency
The installation of blown-in insulation involves specialized blowing machines that propel the material into cavities or open spaces. This method allows for dense, uniform coverage, which traditional batt insulation struggles to achieve due to gaps, compression, or improper fitting.
In attic applications, installers often add insulation in layers, carefully monitoring depth to meet recommended R-values. The ability to fill irregular cavities means less air infiltration, which is a significant contributor to energy loss. Studies have found that air leakage accounts for roughly 25–40% of energy consumption in heating and cooling, so reducing these gaps through blown-in insulation translates directly to energy savings.
In existing wall cavities, blown-in insulation can be installed by drilling small holes and filling the space without removing drywall. This minimally invasive approach allows older homes to benefit from modern insulation standards without extensive renovation.
Market data supports the energy-saving potential of blown-in insulation. The U.S. Department of Energy reports that upgrading insulation and sealing air leaks can reduce energy bills by up to 50%. Nationally, homes retrofitted with blown-in cellulose insulation see average energy savings of $430 per year, demonstrating its strong return on investment.
Factors That Affect Insulation Performance
While blown-in insulation offers clear benefits, certain factors influence its effectiveness and longevity. Understanding these will help in making an informed decision that aligns with your home’s needs.
Moisture and Climate
Moisture control is critical in preventing mold growth and maintaining insulation integrity. Cellulose is more susceptible to moisture absorption, which can reduce its insulating properties and encourage settling. For homes in humid climates or areas with high moisture exposure, fiberglass or mineral wool is usually recommended.
Settling and Maintenance
Over time, cellulose insulation tends to settle by 10-20%, potentially reducing its R-value. While this isn’t an immediate problem, homes with older cellulose installations may need occasional topping up to maintain effectiveness. Fiberglass and mineral wool generally retain their volume and insulating power longer.
Air Sealing and Installation Quality
Blown-in insulation works best when paired with a comprehensive air sealing strategy. Gaps around windows, doors, electrical outlets, and recessed lighting should be sealed prior to insulation installation. Poor installation that leaves voids or compresses material can undermine insulation performance.
Building Structure and Access
The installation method depends on the building’s structure and accessibility. Retrofitting walls may require drilling holes and patching afterward, which might not suit every homeowner. Attic spaces are more straightforward to insulate but require adequate ventilation to avoid moisture buildup.
Comparing Blown-In Insulation to Other Methods
Blown-in insulation is often compared to batt and spray foam insulation. Each method has trade-offs based on application, cost, and performance.
| Insulation Type | R-Value per Inch | Air Sealing Ability | Installation Impact | Cost per Sq Ft | Best Use Case |
|---|---|---|---|---|---|
| Blown-In (Cellulose) | 3.2 – 3.8 | High | Low (retrofit-friendly) | $0.50 – $1.50 | Existing walls, attics |
| Batt (Fiberglass) | 3.1 – 3.4 | Low to Moderate | Moderate (labor-intensive) | $0.30 – $0.90 | New construction, open cavities |
| Spray Foam | 6.0 – 7.0 | Very High | High (requires expertise) | $1.50 – $3.50 | Air sealing, irregular spaces |
While spray foam offers the highest R-value and air sealing, its cost and complexity often put it beyond reach for many homeowners. Batt insulation is less effective at sealing air gaps and tends to leave cold spots due to compression and poor fitting. Blown-in insulation strikes a balance between cost, performance, and ease of installation, especially in retrofit projects.
Things to Consider Before Making a Decision
Several critical considerations should guide your choice to install blown-in insulation:
- Climate and Moisture Levels: Choose insulation material appropriate to local weather patterns. Avoid cellulose in areas with persistent dampness.
- Existing Insulation Condition: If your current insulation is compressed or degraded, blown-in insulation can serve as an effective supplement or replacement.
- Access for Installation: Ensure that installers can safely and effectively reach areas needing insulation without major structural alterations.
- Long-Term Maintenance: Factor in potential settling, particularly with cellulose, and plan for occasional inspections.
- Energy Goals: Align insulation upgrades with broader home energy improvements such as air sealing, HVAC upgrades, and window replacements for best results.
- Budget: Understand the upfront costs versus potential long-term savings. Blown-in insulation offers a moderate initial investment with strong payback through energy savings.
Common Questions About Blown-In Insulation
Will blown-in insulation settle unevenly and cause gaps?
Cellulose does settle, but professional installation includes techniques to minimize settling and ensure consistent density. Fiberglass and mineral wool settle minimally.
How quickly can blown-in insulation pay for itself?
Depending on your climate and existing insulation quality, payback periods range from 3 to 7 years based on reduced heating and cooling bills.
Is blown-in insulation safe around wiring and plumbing?
Yes. Blown-in materials do not compress or damage wiring or pipes. However, electrical boxes should be sealed beforehand to prevent fire hazards.
Can blown-in insulation improve indoor air quality?
By reducing air infiltration and dust entry, blown-in insulation can contribute to a healthier indoor environment, but proper ventilation remains essential.
Make the Right Decision
Blown-in insulation offers a practical, cost-effective way to enhance home energy efficiency, particularly in older buildings where wall cavities are inaccessible and attics need thick coverage. Understanding the different materials and their long-term behavior will help you select the best fit for your climate and budget.
Consider your home’s unique conditions—moisture levels, existing insulation, structural access—and prioritize comprehensive air sealing alongside insulation upgrades. A well-executed blown-in insulation project not only lowers energy costs but also improves comfort and reduces environmental impact.
Author: With over two decades of hands-on experience, Robert Lamothe, owner and lead installer of Lamothe Insulation, brings unparalleled expertise in spray foam insulation, carpentry, and building science. Since 2002, he has earned a reputation for precision, quality craftsmanship, and delivering energy-efficient solutions that stand the test of time. Lamothe Insulation is a family-owned and family-operated business, and Robert also owns the Goddard School of Auburn, an early childhood education school.
Reviewer: Ethan Taylor has 8 years of experience in spray foam insulation. He reviewed this content and suggested ways to simplify business outreach while keeping trust and professionalism intact.