Blown-in fiberglass insulation is one of the most effective methods for sealing air leaks and improving comfort in residential and commercial buildings. Whether the goal is to reduce drafts in older homes or bring a commercial property up to energy efficiency standards, this technique offers practical advantages that align with modern building needs.
This guide covers the use of blown-in fiberglass in attics and walls, focusing on what property owners need to know when addressing draft issues. The structure is designed to match search intent, answer real questions, and improve relevance across AI ranking systems.
How Blown-In Fiberglass Works
Blown-in fiberglass is made from tiny glass fibers and installed using a machine that distributes it into enclosed spaces. This method allows installers to reach irregular or tight areas in attics and wall cavities where traditional batts can’t fit properly.
Key Installation Process
- Loose fiberglass is loaded into a blowing machine
- The machine breaks up and fluffs the fibers for even coverage
- A hose feeds the material into attic floors or wall cavities
- It fills gaps and voids, creating a dense thermal barrier
Application Areas
- Unfinished attic floors
- Enclosed wall cavities (existing or new construction)
- Narrow or obstructed ceiling spaces
- Crawl spaces with limited access
This technique is used in both retrofits and new builds to improve insulation levels without removing drywall or doing major renovations.
Why Drafts Happen in Attics and Walls
Drafts occur when uncontrolled air moves between conditioned and unconditioned areas. Insufficient insulation is often the cause, especially in older buildings or improperly sealed newer ones.
Common Causes of Drafts
- Gaps around attic hatches or recessed lighting
- Settled or compressed insulation
- Missing insulation in wall cavities
- Air leaks around wall outlets, windows, or framing joints
Blown-in fiberglass addresses these by filling voids more thoroughly than batt insulation, especially around irregular shapes or obstructions.
Benefits of Blown-In Fiberglass for Draft Control
Blown-in fiberglass stands out for its coverage, speed of installation, and long-term reliability. It works particularly well in existing structures where full wall or attic renovation isn’t feasible.
High Coverage and Thermal Resistance
- Uniform fill prevents gaps common with batt insulation
- Maintains consistent R-value across space
- Reduces air movement, which improves HVAC efficiency
Fast Application with Minimal Disruption
- Installers can insulate an attic in a few hours
- No drywall removal required for wall applications
- Ideal for occupied properties needing quick fixes
Safe and Fire-Resistant Material
- Non-combustible
- Resists moisture and mold growth
- Contains no formaldehyde or harsh chemicals
Comparing Blown-In Fiberglass to Other Insulation Types
Understanding how blown-in fiberglass compares with alternatives helps property owners choose the best solution based on needs, access, and performance.
Comparison Table: Blown-In Fiberglass vs Alternatives
| Feature | Blown-In Fiberglass | Cellulose | Spray Foam |
|---|---|---|---|
| R-Value per Inch | ~2.2 – 2.7 | ~3.2 – 3.8 | ~6.0 – 7.0 |
| Fire Resistance | High (non-combustible) | Moderate (treated paper) | High (closed-cell) |
| Moisture Resistance | Good | Low | Excellent |
| Settling Over Time | Minimal | Moderate | None |
| Application Time | Fast | Fast | Slower |
| Wall Retrofitting | Yes | Yes | Rarely feasible |
| Odor or Off-Gassing | None | Mild odor | Strong (curing phase) |
When to Choose Blown-In Fiberglass Over Other Methods
Choosing insulation isn’t just about thermal value. It’s about fit, cost-effectiveness, and ease of installation in existing structures.
Ideal Scenarios for Blown-In Fiberglass
- Older homes with uninsulated walls
- Properties needing fast attic upgrades
- Buildings with limited access points
- Owners seeking low-odor, non-toxic materials
Less Suitable Situations
- Spaces requiring vapor or air barriers (spray foam is better)
- Projects demanding the highest R-values in limited space
- Walls that are completely open and being rebuilt (batts may be easier)
Common Signs You Need Blown-In Fiberglass Insulation
Draft complaints and uneven temperatures aren’t always easy to trace, but certain indicators point to insulation problems.
Watch for These Issues
- Cold spots near exterior walls or ceiling corners
- Rising energy bills despite no HVAC changes
- Ice dams on roofs during winter
- Dust or outdoor smells coming through walls
These often suggest air leaks that blown-in fiberglass can correct without requiring full demolition or structural changes.
Steps to Retrofit Existing Walls with Blown-In Fiberglass
Adding insulation to finished walls might seem difficult, but the process is relatively simple using blown-in methods.
Retrofit Process Overview
- Small access holes are drilled near the top of each wall cavity
- A hose is inserted to blow in the fiberglass material
- Cavities are filled from top down to prevent voids
- Holes are sealed and patched afterward
This makes it possible to insulate without removing drywall or interrupting interior finishes.
How Fast Can Blown-In Fiberglass Be Installed?
Speed is one of the main reasons property owners prefer blown-in fiberglass, especially in occupied buildings.
General Time Estimates
- Attic insulation (1,000–1,500 sq ft): ~3–5 hours
- Wall retrofitting (entire home): 1–2 days
- Small commercial retrofits: 1–3 days depending on access
Installers often complete residential attic upgrades in a single visit.
Conclusion
Blown-in fiberglass insulation services are one of the fastest and most practical solutions for fixing drafty attics and walls. It delivers wide coverage, quick installation, and effective thermal control with minimal disruption. Whether insulating an older home or improving energy performance in a commercial space, blown-in fiberglass offers a cost-effective upgrade.
Its compatibility with retrofit scenarios, fire-safe properties, and long-term durability make it a logical choice for anyone dealing with temperature inconsistencies or air leakage issues. For property owners looking to address drafts quickly without major renovations, this method often provides the most efficient return on investment.
FAQs
How long does blown-in fiberglass insulation last?
Blown-in fiberglass can last 30 to 50 years if installed correctly and kept dry. It resists settling, maintaining consistent thermal performance over time.
Can blown-in fiberglass be used in both walls and attics?
Yes. It’s frequently installed in attics, enclosed walls, ceilings, and crawl spaces, making it versatile for both horizontal and vertical applications.
Is blown-in fiberglass safe for indoor environments?
Fiberglass is non-combustible and contains no formaldehyde. Once installed, it does not release fibers into the air or pose indoor air quality risks.
Will blown-in insulation stop all drafts in my house?
It significantly reduces drafts by sealing gaps and improving coverage, but for best results, it should be combined with proper air sealing around penetrations and access points.
Does blown-in fiberglass settle over time like cellulose?
Blown-in fiberglass has minimal settling compared to cellulose. This helps maintain insulation effectiveness and avoids gaps forming over time.
Author: With 15 years of banking experience and five years managing H&R Foam Insulation, Edith is passionate about building strong relationships with customers. Her favorite part of the role is connecting with clients and ensuring their needs are met as she works alongside them to improve the health, comfort, and energy efficiency of their homes.
Reviewer: With 7 years in the spray foam insulation business, Ella Adams offered useful feedback on this post, helping make sure the tips were both realistic and easy to apply.