Can You Mix Different Types of Insulation?

When it comes to insulating your home, one size doesn’t always fit all. Homes are built with unique designs, materials, and energy needs—and sometimes, the best insulation solution involves combining different types of insulation. But is that a good idea? Can it cause problems? Or is it a smart way to boost energy efficiency?

At Koala Insulation of Greater Ann Arbor, we get this question from homeowners all the time. The short answer is yes, you can mix different insulation types, but you need to do it correctly to avoid moisture issues, reduced performance, or safety concerns.

In this blog, we’ll explain when it’s appropriate to combine insulation types, the pros and cons, and which combinations work best for Michigan’s climate and housing stock.

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Why Consider Mixing Insulation Types?

Most homes don’t have uniform insulation needs. Different areas—attics, walls, crawl spaces, basements—may face different challenges, including:

• Drafts and air leaks
• Moisture buildup or poor ventilation
• Temperature fluctuations
• Aging or outdated insulation materials

In some cases, the original insulation may still be effective, and you’re simply looking to supplement it. In others, you may want to use one insulation type for air sealing and another for thermal resistance.

At Koala Insulation of Greater Ann Arbor, we evaluate every part of your home to determine the best blend of materials for maximum efficiency and performance.

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Common Types of Insulation You Might Combine

Here are the most common types of insulation used in homes—and how they may be used together:

1. Fiberglass (Batts or Blown-In)

• Cost-effective and widely used
• Great for attics and wall cavities
• Non-combustible and moisture-resistant

2. Spray Foam (Open-Cell or Closed-Cell)

• Excellent for air sealing
• High R-value
• Acts as both insulation and vapor barrier

3. Cellulose (Blown-In)

• Eco-friendly and effective
• Great for retrofits
• Better air sealing than fiberglass but can absorb moisture

4. Rigid Foam Board

• Durable and moisture-resistant
• Ideal for basements, exterior walls, or under flooring

5. Mineral Wool (Rock Wool)

• Fire-resistant and sound-dampening
• Excellent for high-temperature areas

Each material has strengths and limitations. Mixing them strategically can improve your home’s overall thermal envelope and air sealing performance.

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Best Practices for Mixing Insulation Types

Mixing insulation materials isn’t just about piling one on top of the other. To do it right, you need to consider:

1. Moisture Management

This is the biggest concern when mixing insulation. If you trap moisture between layers of insulation, you can create a perfect environment for mold and rot. That’s why you need to understand which material serves as the vapor barrier—usually spray foam or rigid foam board.

Pro Tip: Never install a vapor-impermeable layer on the wrong side of your insulation in cold climates like Michigan. Moisture should always be able to escape to the exterior.

2. Thermal Layering

Different materials have different R-values (thermal resistance). You can layer them to achieve higher overall R-values, especially in the attic.

For example:

• Use closed-cell spray foam on the attic floor to air seal and prevent moisture
• Add blown-in fiberglass or cellulose on top to boost the R-value

This combo is commonly recommended by Koala Insulation of Greater Ann Arbor to help homeowners meet and exceed Michigan’s energy codes.

3. Fire and Code Compliance

Each insulation product has specific fire ratings. Be sure the materials you mix are compatible and approved for the space you’re insulating. Attics and basements, in particular, must follow strict fire safety rules.

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Smart Insulation Combinations That Work

Here are some combinations that are both safe and effective in Michigan homes:

✅ Spray Foam + Blown-In Fiberglass

Use spray foam to seal air leaks and create a thermal barrier in tricky spaces (rim joists, crawl spaces, attic edges), then add blown-in fiberglass to cover larger areas.

✅ Rigid Foam Board + Fiberglass Batts

Commonly used in basement walls. Foam board goes against the concrete or block to resist moisture, and fiberglass batts go in the stud cavities for added thermal resistance.

✅ Closed-Cell Spray Foam + Open-Cell Spray Foam

In rooflines, closed-cell can provide moisture control while open-cell adds extra R-value and sound insulation.

At Koala Insulation of Greater Ann Arbor, we routinely design hybrid insulation systems like these to ensure long-term comfort and efficiency.

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When You Shouldn’t Mix Insulation Types

While mixing insulation can work well, it’s not always the right move. Avoid mixing when:

• The existing insulation is wet, moldy, or damaged—remove it first
• The insulation types have incompatible vapor barrier properties
• You’re unsure about the location of your home’s dew point
• You’re stacking insulation in a way that may compress and reduce its R-value

Koala Insulation of Greater Ann Arbor always performs an insulation inspection before adding any new material. That way, we can address any underlying issues first.

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How We Help

When you contact Koala Insulation of Greater Ann Arbor, we provide:

• ✅ A full insulation inspection
• ✅ Infrared scanning to detect hot and cold spots
• ✅ Recommendations tailored to your home’s structure and age
• ✅ Safe removal of old or ineffective insulation
• ✅ Expert installation of hybrid systems using proven techniques

We make sure every material we use is compatible and installed to meet Michigan’s energy code requirements.

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Call Us for a Free Estimate Today

So, can you mix different types of insulation? Absolutely—as long as it’s done with care, strategy, and expert knowledge. Combining materials can enhance your home’s energy performance, soundproofing, and indoor comfort all year long.

Call Koala Insulation of Greater Ann Arbor at (734) 834-3455 or visit our website to schedule your free estimate today. Our team will evaluate your current insulation and recommend the best approach to keep your home cozy in the winter and cool in the summer.