Blown-In vs. Spray Foam Insulation for Michigan Attics

By NEXT Exteriors • February 19, 2026 • 12 min read

I've been crawling through Michigan attics since 1988, and I can tell you this: the question isn't whether you need more insulation — it's which type will actually solve your problem without creating new ones.

Homeowners in Sterling Heights, Troy, and Royal Oak call us every winter with the same complaints: ice dams tearing up their gutters, $400 heating bills, bedrooms that feel like walk-in freezers. They've read online that spray foam is the "best" insulation, or that blown-in is "good enough," and they want to know what we'd do to our own homes.

Here's what 35 Michigan winters have taught us about attic insulation in Metro Detroit: both blown-in and spray foam work — when installed correctly, in the right application, with realistic expectations about cost and performance. The contractor who tells you there's only one right answer is probably selling you the only thing they know how to install.

This guide breaks down the real pros and cons of each insulation type, what they actually cost in Southeast Michigan in 2026, and how to decide which one makes sense for your home. No sales pitch. Just 35 years of jobsite experience.

Understanding R-Value and Michigan Building Code Requirements

Before we compare insulation types, you need to understand what R-value actually means — because it's the only number that matters for thermal performance.

R-value measures resistance to heat flow. Higher R-value means better insulation. In Michigan's climate zone (Zone 5), the residential building code requires a minimum of R-49 in attic spaces. That's roughly 14-16 inches of blown-in fiberglass, 11-13 inches of cellulose, or 8-9 inches of closed-cell spray foam.

Here's the reality: code minimum is exactly that — the bare minimum. Most homes we work on in Macomb County and Oakland County were built between 1960 and 1990, and they typically have R-19 to R-30 in the attic. That was fine when natural gas cost $0.50 per therm. In 2026, with energy costs triple what they were in 1985, R-49 is the practical target, and R-60 isn't overkill if you're planning to stay in the house long-term.

Michigan Building Code Reality: The 2015 Michigan Residential Code (still in effect as of 2026) specifies R-49 for ceilings with attic spaces in climate zone 5. However, many municipalities in Southeast Michigan allow R-38 as an acceptable alternative if you meet specific air sealing requirements. Always check with your local building department before starting work.

R-value alone doesn't tell the whole story. Air sealing — stopping actual air movement between your living space and the attic — matters just as much as the insulation thickness. You can have R-60 of blown-in insulation, but if cold air is pouring through gaps around recessed lights, plumbing penetrations, and attic hatches, you're still going to have ice dams and high heating bills.

This is where the blown-in vs. spray foam debate gets interesting. Blown-in insulation provides excellent R-value per inch, but it doesn't stop air movement. Spray foam provides moderate R-value per inch, but it's also an air barrier. Which one you need depends on what's actually wrong with your attic — and that's something a qualified exterior services contractor should evaluate before giving you a price.

Blown-In Insulation: The Michigan Standard

Blown-in insulation — either fiberglass or cellulose — is what we install in about 70% of the attic projects we do in Southeast Michigan. It's cost-effective, proven, and when installed correctly over proper air sealing, it performs exactly as it should for decades.

Blown-In Fiberglass

Fiberglass is the pink or white fluffy material you see in most attics. Brands like Owens Corning ProPink and CertainTeed Insulsafe SP dominate the market because they're consistent, non-combustible, and don't settle significantly over time.

R-value: R-2.2 to R-2.7 per inch. To hit R-49, you need about 15-16 inches of settled depth.

Pros:

• Cost-effective: Blown-in fiberglass is the most affordable way to add significant R-value to an attic. Material costs are low, installation is fast, and labor is straightforward.
• Non-combustible: Fiberglass won't burn. This matters in attics with recessed lights, old knob-and-tube wiring, or any heat-generating equipment.
• Doesn't settle much: Modern fiberglass products settle about 1-2% over their lifetime. You install it at 16 inches, it stays at 16 inches.
• Doesn't absorb moisture: If you get a roof leak, fiberglass dries out. It doesn't hold water, mold, or rot.
• Removable and replaceable: If you need to run new wiring or fix a leak, you can vacuum out fiberglass and blow it back in. Try that with spray foam.

Cons:

• Doesn't stop air movement: Fiberglass insulates, but it doesn't seal. Cold air can still flow through it if you have gaps in your ceiling plane. You need separate air sealing work before you blow insulation.
• Lower R-value per inch than spray foam: If you have limited attic depth (common in ranch homes with low-slope roofs), you may not be able to fit enough fiberglass to hit R-49.
• Requires proper ventilation: Fiberglass works best in vented attics. You need soffit vents, ridge vents, and clear airflow above the insulation. If your attic ventilation is inadequate, you'll have moisture problems.

Blown-In Cellulose

Cellulose is made from recycled newspaper treated with fire retardants. It's denser than fiberglass, settles more over time, and has a loyal following among energy efficiency advocates.

R-value: R-3.2 to R-3.8 per inch. To hit R-49, you need about 12-14 inches of settled depth.

Pros:

• Higher R-value per inch: Cellulose gives you more insulating power in less space compared to fiberglass. If you have a shallow attic, this matters.
• Better air sealing properties: Cellulose is denser and fills gaps more completely than fiberglass. It's not an air barrier like spray foam, but it does reduce air movement better than fiberglass.
• Environmentally friendly: If recycled content matters to you, cellulose is 85% post-consumer recycled material.

Cons:

• Settles significantly: Cellulose can settle 15-20% over the first few years. We install it at 16 inches knowing it'll compact to 13-14 inches. You need to account for this when calculating installed depth.
• Absorbs moisture: Cellulose holds water. If you get a roof leak and it saturates the insulation, you're dealing with mold, weight load on your ceiling drywall, and potential replacement. We've pulled out 200+ pounds of water-soaked cellulose from a single leak in a Warren home.
• Can be dusty: Installation kicks up fine dust that gets everywhere. It's treated to be fire-resistant, but the borates used can be irritating during install.
• More expensive than fiberglass: Material costs are 20-30% higher than fiberglass, though still far cheaper than spray foam.

What We Actually Install: In Southeast Michigan, we install blown-in fiberglass in about 85% of our attic insulation projects and cellulose in the remaining 15%. Fiberglass is more forgiving in our climate — it handles roof leaks better, doesn't settle as much, and performs consistently in vented attics. Cellulose makes sense when attic depth is limited or when homeowners specifically request higher R-value per inch.

Spray Foam Insulation: When It Makes Sense

Spray foam gets a lot of hype in online forums and from contractors who specialize in it. It's an excellent product — in the right application. The problem is that it's often oversold as a universal solution when blown-in would work just as well for half the cost.

There are two types of spray foam: open-cell and closed-cell. They're completely different products with different applications.

Open-Cell Spray Foam

Open-cell foam is soft, squishy, and expands dramatically during application. It's typically light gray or tan and has a texture similar to a dense sponge.

R-value: R-3.5 to R-3.6 per inch. To hit R-49, you need about 14 inches of foam.

Pros:

• Excellent air sealing: Open-cell foam expands into every crack, gap, and penetration. It creates a continuous air barrier that stops drafts and air leakage.
• Less expensive than closed-cell: Open-cell costs about half what closed-cell does, making it more accessible for larger areas.
• Sound dampening: Open-cell foam significantly reduces sound transmission. If you have a bedroom above a garage or a home theater, this is a real benefit.

Cons:

• Absorbs water: Open-cell foam is permeable to water vapor. If you get a roof leak, the foam will soak it up like a sponge. You can't see the leak because the foam hides it, and by the time you notice water stains on your ceiling, you may have significant rot in your roof deck.
• Not a vapor barrier: Open-cell foam allows moisture to pass through. In Michigan's climate, this means you need to be very careful about where and how you use it. We rarely install open-cell in attics because of moisture concerns.
• Lower R-value per inch than closed-cell: You need nearly as much thickness as blown-in fiberglass to hit R-49, so you're paying spray foam prices for fiberglass performance.

Closed-Cell Spray Foam

Closed-cell foam is rigid, dense, and provides both insulation and structural strength. It's the premium product in the spray foam world.

R-value: R-6.0 to R-7.0 per inch. To hit R-49, you need about 7-8 inches of foam.

Pros:

• Highest R-value per inch: Closed-cell foam gives you the most insulating power in the least space. If you have a shallow attic or cathedral ceiling with limited cavity depth, this is your best option.
• Complete air and vapor barrier: At 2 inches or more, closed-cell foam is an air barrier, vapor barrier, and insulation all in one. It stops air movement, moisture transmission, and heat loss.
• Adds structural strength: Closed-cell foam is rigid enough to add racking strength to walls and roofs. In storm-prone areas, this can be a real benefit.
• Doesn't absorb water: Closed-cell foam sheds water. If you get a roof leak, you'll see it immediately because water runs off the foam and shows up on your ceiling. The foam itself doesn't get damaged.

Cons:

• Expensive: Closed-cell spray foam costs 3-4 times more than blown-in insulation per R-value. For a typical 1,500 sq ft attic, you're looking at $7,000-$12,000 for closed-cell vs. $2,000-$3,500 for blown-in fiberglass.
• Permanent: Once you spray closed-cell foam, it's there forever. If you need to run new wiring, fix a leak, or inspect your roof deck, you're cutting through rigid foam with a saw. It's not removable like blown-in insulation.
• Requires professional installation: Spray foam installation requires specialized equipment, training, and safety equipment. This isn't a DIY product, and bad installation can create serious problems (off-ratio foam that doesn't cure, overspray, odor issues).
• Creates an unvented attic: When you spray foam to the underside of the roof deck, you're creating an unvented attic. This changes how your roof system works. You lose the ability to inspect your roof deck from below, and you need to be very careful about moisture management.

When Spray Foam Actually Makes Sense

We install spray foam in about 15-20% of our insulation projects. Here's when it's the right choice:

• Cathedral ceilings with no attic space: When you have a vaulted ceiling with rafters as the only cavity, closed-cell spray foam is often the only way to get adequate R-value in a limited depth.
• Bonus rooms over garages: These spaces are notoriously hard to insulate with traditional methods. Spray foam to the underside of the floor deck creates a thermal barrier that actually works.
• Severe ice dam problems: If you've tried everything else (air sealing, more insulation, better ventilation) and you still get ice dams every winter, spray foam to the roof deck eliminates the temperature differential that causes them. It's expensive, but it works.
• Attics with HVAC equipment: If your furnace, air handler, or ductwork is in the attic (common in ranch homes), spray foam to the roof deck brings that equipment inside the building envelope. Your HVAC doesn't have to work as hard, and you eliminate duct losses.
• Historic homes with plaster ceilings: Old homes with lath-and-plaster ceilings are nearly impossible to air seal from below. Spray foam to the roof deck creates the air barrier you need without disturbing the historic plaster.

If your situation doesn't match one of these scenarios, blown-in insulation will likely give you 90% of the performance for 30% of the cost. That's not a knock on spray foam — it's just the reality of cost-benefit analysis.

Cost Comparison: What You'll Actually Pay in Southeast Michigan

Let's talk real numbers. These are based on our 2026 project costs for a typical 1,500 square foot attic in Sterling Heights, Troy, or Warren. Your actual costs will vary based on attic access, existing insulation removal, air sealing needs, and how much R-value you're adding.

Insulation Type	R-Value Target	Material Cost	Labor Cost	Total Cost
Blown-In Fiberglass	R-49	$800-$1,200	$1,200-$1,800	$2,000-$3,000
Blown-In Cellulose	R-49	$1,000-$1,500	$1,200-$1,800	$2,200-$3,300
Open-Cell Spray Foam	R-49 (14" depth)	$3,500-$5,000	$2,000-$3,000	$5,500-$8,000
Closed-Cell Spray Foam	R-49 (7" depth)	$5,500-$8,000	$2,500-$4,000	$8,000-$12,000

These prices include:

• Air sealing work (caulking penetrations, sealing around chimneys and plumbing stacks, weatherstripping attic hatch)
• Installation of insulation baffles at soffit vents (for blown-in applications)
• Insulation material and installation
• Cleanup and disposal

These prices do not include:

• Removal of old insulation (add $1.50-$2.50 per square foot)
• Attic ventilation improvements (ridge vent installation, soffit vent cutting)
• Electrical work to move or replace recessed lights
• Structural repairs (roof deck replacement, rafter reinforcement)

Energy Savings Reality Check: Homeowners always ask: "How long until this pays for itself?" Here's the honest answer: If you're going from R-19 to R-49 with blown-in fiberglass ($2,500 project), you'll save about $400-$600 per year on heating costs in Southeast Michigan. That's a 4-6 year payback. If you're installing closed-cell spray foam ($10,000 project), you'll save about $500-$700 per year. That's a 14-20 year payback. The spray foam provides other benefits (ice dam elimination, air sealing), but purely on energy savings, blown-in insulation wins the ROI calculation.

For most homeowners in Macomb County, Oakland County, and St. Clair County, blown-in insulation offers the best balance of performance, cost, and payback period. Spray foam makes sense when you have specific problems that blown-in can't solve — but it's not the automatic choice that some contractors make it out to be.

Which Insulation Type Is Right for Your Michigan Attic?

Here's the decision framework we use when evaluating attics in Southeast Michigan. This is based on 35 years of real-world performance, not marketing materials.

Choose Blown-In Fiberglass If:

• You have a standard vented attic with adequate soffit and ridge ventilation
• Your attic floor is accessible and relatively clear
• You're primarily concerned with adding R-value cost-effectively
• Your home doesn't have severe ice dam problems
• You want the flexibility to access wiring and roof deck in the future
• Budget is a primary concern (and it should be — this is the most cost-effective solution for most homes)

Choose Blown-In Cellulose If:

• You have limited attic depth and need higher R-value per inch than fiberglass provides
• Your attic has good ventilation and no history of roof leaks
• You prefer recycled content and environmental considerations matter to you
• You want slightly better air sealing properties than fiberglass without the cost of spray foam

Choose Closed-Cell Spray Foam If:

• You have cathedral ceilings or bonus rooms with no attic access
• You have chronic ice dam problems that haven't been solved by other methods
• Your HVAC equipment and ductwork is in the attic
• You have a historic home with plaster ceilings that can't be easily air sealed from below
• You're willing to pay 3-4x more for the added benefits of complete air sealing and vapor control
• You understand you're creating an unvented attic system that requires different maintenance and monitoring

Avoid Open-Cell Spray Foam In Michigan Attics

We almost never install open-cell spray foam in Michigan attics. The moisture permeability creates too much risk in our climate, especially with the freeze-thaw cycles we experience. If you're considering spray foam, closed-cell is the right choice — or stick with blown-in insulation and invest the savings in proper air sealing.

What About Combining Methods? Some contractors suggest spray foam to the roof deck at 2-3 inches for air sealing, then blown-in insulation on top to reach R-49. This can work, but it's expensive and complex. You're paying spray foam prices for air sealing that can be achieved with caulk, foam, and weatherstripping for a fraction of the cost. Unless you have a very specific situation (like HVAC in the attic), this hybrid approach usually doesn't make financial sense.

The reality is that most homes in Rochester Hills, Shelby Township, and Clinton Township need straightforward solutions: proper air sealing followed by blown-in fiberglass to R-49 or R-60. That combination solves 90% of attic insulation problems for 30% of what spray foam costs.

Signs Your Attic Insulation Is Failing

How do you know if your current attic insulation is underperforming? Here are the symptoms we see most often in Southeast Michigan homes:

Ice Dams Every Winter

Ice dams form when heat escapes from your living space into the attic, warms the roof deck, melts snow, and the meltwater refreezes at the cold eaves. If you get ice dams every year, your attic insulation and air sealing are inadequate. This is the #1 reason homeowners call us for insulation services in Detroit and surrounding areas.

High Heating Bills

If your natural gas bills are $300-$500 per month in January and February, you're losing heat through your attic. A well-insulated 2,000 sq ft home in Metro Detroit should run $150-$250 per month in the coldest months (assuming a reasonably efficient furnace and normal thermostat settings).

Uneven Temperatures Between Rooms

If your master bedroom is 68°F and the spare bedroom is 62°F with the same thermostat setting, you have insulation or air sealing problems. Heat is escaping unevenly through your ceiling plane.

Attic Frost in Winter

If you go up in your attic on a cold January morning and see frost on the underside of the roof deck or on the nails poking through, you have an air leakage problem. Warm, moist air from your living space is escaping into the attic and condensing. This can lead to mold, rot, and structural damage.

Visible Gaps or Compressed Insulation

If you can see your ceiling joists because the insulation has settled or been compressed, you've lost R-value. Insulation only works when it maintains its loft. Compressed fiberglass or settled cellulose needs to be topped off or replaced.

Drafts Around Light Fixtures

If you feel cold air coming down around recessed lights or ceiling fans, air is flowing from the attic through gaps in the ceiling. This is a classic air sealing problem that no amount of insulation will fix without addressing the penetrations first.

If you're experiencing any of these issues, it's time to have a qualified contractor evaluate your attic. At NEXT Exteriors, we start every insulation project with a thorough attic inspection — we look at existing insulation depth, ventilation, air leakage points, and moisture issues before we recommend a solution. That's how you get a project that actually solves the problem instead of just covering it up.

Beyond insulation, we also handle related exterior improvements that impact your home's energy performance. If you're dealing with drafty windows, our Detroit window experts can evaluate whether replacement makes sense. If ice dams are tearing up your gutters, our seamless gutters in Detroit, MI installation includes proper ice-and-water shield and gutter apron details that work with improved attic insulation. And if your roof is nearing the end of its life, our Detroit roofing services include attic ventilation upgrades that complement new insulation.

Attic insulation isn't a standalone project — it's part of a complete building envelope system that includes your roof, siding, windows, and air sealing. When you work with a contractor who understands how all these systems interact, you get solutions that actually work instead of band-aids that fail in three years.

Ready to Fix Your Attic Insulation?

NEXT Exteriors has been insulating Michigan homes since 1988. We'll evaluate your attic, explain what's actually wrong, and give you honest recommendations — blown-in or spray foam — based on what your home needs, not what's most profitable for us. No pressure, no gimmicks, just straight answers from a contractor who's been doing this for 35 years.

Get Your Free Attic Evaluation

Or call us: (844) 770-6398

We also offer comprehensive house siding in Detroit services that can address exterior envelope issues contributing to heat loss. And if your home needs a fresh exterior finish, our Southeast Michigan painting professionals use Sherwin-Williams products exclusively for lasting protection. For a complete overview of what we offer, visit our exterior services in Detroit page.

Frequently Asked Questions About Attic Insulation in Michigan

Is spray foam insulation worth the extra cost in Michigan?

Spray foam is worth the cost in specific situations: cathedral ceilings with limited depth, severe ice dam problems that haven't been solved by other methods, attics with HVAC equipment, or bonus rooms over garages. For standard vented attics, blown-in insulation provides 90% of the performance for 30% of the cost. The payback period for spray foam based purely on energy savings is 14-20 years, compared to 4-6 years for blown-in insulation.

How much attic insulation do I need in Southeast Michigan?

Michigan building code requires R-49 minimum for attic spaces in climate zone 5 (all of Southeast Michigan). In practical terms, we recommend R-49 as the baseline and R-60 if you're planning to stay in the house long-term. That's about 15-16 inches of blown-in fiberglass, 12-14 inches of cellulose, or 7-8 inches of closed-cell spray foam.

Can I add insulation on top of existing insulation?

Yes, in most cases. If your existing insulation is dry, not compressed, and free of mold or pest damage, we can blow new insulation on top. However, we always do air sealing work first — adding insulation on top of air leaks doesn't solve the underlying problem. If your existing insulation is wet, moldy, or severely compressed, removal and replacement is the better approach.

Will more attic insulation stop my ice dams?

Maybe. Ice dams are caused by heat escaping into the attic, warming the roof deck, and melting snow. More insulation helps, but only if you also address air leakage. We've seen homes with R-60 of insulation that still get ice dams because they have massive air leaks around recessed lights and plumbing penetrations. The solution is proper air sealing first, then adequate insulation, then proper attic ventilation. All three need to work together.

What's the difference between open-cell and closed-cell spray foam?

Open-cell spray foam is soft, squishy, and provides R-3.5 per inch. It's an air barrier but not a vapor barrier, and it absorbs water. Closed-cell spray foam is rigid, dense, and provides R-6 to R-7 per inch. It's both an air barrier and vapor barrier, and it sheds water. For Michigan attics, closed-cell is the right choice if you're using spray foam — open-cell creates too much moisture risk in our climate.

How long does blown-in insulation last?

Blown-in fiberglass lasts 80-100 years with minimal settling (1-2%). Cellulose lasts 20-30 years but settles 15-20% over the first few years, which reduces its effective R-value. Both materials maintain their insulating properties indefinitely as long as they stay dry. If you get a roof leak, fiberglass dries out and continues working, while cellulose may need to be removed and replaced.

Do I need to remove old insulation before adding new?

Not usually. If the existing insulation is in good condition (dry, not compressed, no mold or pests), we can add new insulation on top after completing air sealing work. However, we do recommend removal if: the existing insulation is wet or moldy, there's evidence of rodent infestation, the insulation is severely compressed, or you need to do extensive air sealing work that requires clear access to the ceiling plane.