Are Insulation Boards Flammable? Understanding Fire Safety in Insulation Materials
If you’re picking insulation for your home or a job site, fire safety isn’t just a fine-print detail—it’s something you need to think about up front. I’ve been in this business since bell bottoms were still in style, and let me tell you: not all insulation boards are created equal when it comes to handling heat.
So, are insulation boards flammable? Well… some of them absolutely are. Others? Built like a fireman’s jacket. Here’s the no-fluff rundown on the main types we work with, and what you need to know to keep your space safe.
1. Polyisocyanurate (PIR): The Overachiever With a Caveat
PIR boards are stiff, high-performance foam panels—popular in walls, roofs, and anyone looking for big R-values in a slim package.
🔥 Will it burn? Eventually, yes. PIR boards are less flammable than other foam boards because they’ve got fire retardants baked in. They tend to char instead of going up like a tiki torch. But hit them with serious heat, and they’ll still catch and send off toxic smoke.
✅ What to do: Always cover PIR with a fire-rated barrier—like drywall. Never leave it exposed in finished spaces.
2. XPS: Tough Against Moisture, Not Against Flame
Extruded polystyrene (XPS) is what you’ll find behind a lot of foundation walls and under slabs. Great for water resistance, not so great for fire.
🔥 Will it burn? Like dry pine in August. Even treated XPS can ignite and gives off thick, nasty smoke when it does.
✅ What to do: XPS should never be left uncovered indoors. Wrap it up tight behind something non-combustible—gypsum board is your friend here.
3. EPS: Cheap, Light, and Quick to Catch
Expanded polystyrene (EPS) is kind of the little brother to XPS—lightweight, inexpensive, and used in packaging, walls, and roofs.
🔥 Will it burn? Oh yeah. Faster than XPS, in fact. It’s got a lower melting point and will absolutely feed a fire if you let it.
✅ What to do: If you’re going to use EPS, bury it completely behind non-combustible materials. Think of it like kindling—treat it with caution.
4. Mineral Wool (aka Rockwool): Built From Lava, Basically
Now we’re talking. Mineral wool is made from spun rock and industrial slag. It’s dense, durable, and basically fireproof.
🔥 Will it burn? Not a chance. It’s non-combustible and holds up to temps north of 1,800°F. I’ve seen it used in fire-rated assemblies, and it doesn’t even blink.
✅ What to do: If fire resistance is your top concern, this is your MVP. No special treatment needed—install and sleep easy.
5. Fiberglass: The Old Reliable (With a Caveat)
Fiberglass boards are another non-combustible option made from—you guessed it—glass fibers. Great for ductwork, ceilings, and wall cavities.
🔥 Will it burn? The glass itself won’t. But if your board has a kraft paper or foil facing? That can ignite if exposed to flame or heat.
✅ What to do: Keep faced fiberglass away from open flames, light fixtures, or anything that gets hot.
Fire Safety 101 (From a Guy Who’s Seen Some Things)
Whatever insulation you’re working with, there are a few universal rules that’ll keep you out of trouble:
✔ Cover your foam. XPS and EPS should never be exposed in a finished space. Always wrap ‘em up in drywall or cement board.
✔ Know your codes. Every town has its own rules. Follow your local building codes like your roof depends on it—because it does.
✔ Vent properly. Trapped heat can turn a safe attic into a fire trap. Good airflow helps prevent that.
✔ Install smoke detectors. Especially near new insulation work. Cheap insurance.
✔ Use fire-rated products when you can. Mineral wool and fiberglass might cost a bit more, but they’re way safer in a pinch.
So… Are Insulation Boards Flammable?
Some are. Some aren’t. If you’re using foam—like XPS or EPS—just assume it burns and plan accordingly. If you want the peace of mind that comes with fire resistance, mineral wool or fiberglass is the way to go.
And if you're not sure what makes sense for your home? That’s why we’re here. At Nealon, we’ve been insulating Connecticut homes since 1977. We know the products, we know the codes, and we know how to do the job right the first time.
What About Cellulose, Fiberglass, and Spray Foam? Are They Flammable?
Glad you asked—because this comes up a lot.
- Cellulose is made from recycled paper, so yeah, it can burn. But before you panic: it’s treated with borate, a fire retardant that slows ignition and helps it smolder instead of flame up. Think of it like a campfire log that's been dipped in fire-resistant gravy.
- Fiberglass is made of spun glass and is naturally non-combustible. The catch? If it’s faced with kraft paper or foil, that facing can burn. So it’s not the insulation you’re worried about—it’s the clothes it’s wearing.
- Spray Foam—especially closed-cell—can ignite if exposed directly to flame. It typically has flame retardants mixed in, but don’t let that lull you. It must be covered with drywall or a thermal barrier in finished spaces to meet code and stay safe.
Bottom line: Every insulation type has its own fire personality. The trick is knowing how to install and cover it correctly. And that’s where we come in.
Common FAQ's about Insulation Boards
Can I leave foam board insulation exposed in a basement or utility room?
No, foam board insulation cannot be left exposed in basements or utility rooms. Building codes require a thermal barrier, such as 1/2" drywall, over foam types like XPS, EPS, or PIR for fire safety. Exposed foam poses a fire risk and can lead to code violations.
What’s the difference between “fire-retardant” and “non-combustible” insulation?
The main difference between fire-retardant and non-combustible insulation is that fire-retardant materials slow flame spread but can still burn, while non-combustible materials will not ignite. Foam boards are typically fire-retardant; mineral wool and bare fiberglass are non-combustible and offer higher fire safety.
How do I know if the insulation I’m using meets local fire code?
To know if insulation meets local fire code, check for a Class A fire rating and compliance with ASTM E84. Then confirm with your local building inspector, as Connecticut towns may have different requirements. Always verify with professionals before installation to avoid code violations.
What happens if I don’t cover foam board insulation as required?
If you don’t cover foam board insulation, you risk fire hazards, code violations, and failed inspections. Exposed foam can spread flames quickly and emit toxic smoke. It may also void insurance coverage and require removal during resale or renovations, leading to costly delays.
Can I use mineral wool or fiberglass around recessed lights or chimneys?
Yes, you can use mineral wool or unfaced fiberglass around recessed lights and chimneys. Mineral wool is fire-resistant up to 1,800°F and ideal for high-heat zones. Always choose products rated for heat contact and maintain required clearances to meet safety codes and prevent fire risks.
Final Word: Fire Safety Isn’t Optional—It’s the Standard
Whether you’re building new, remodeling the attic, or beefing up your basement walls, insulation isn’t just about R-value—it’s about risk management. Fire safety needs to be baked into your plan from day one. That means choosing the right materials, installing them the right way, and never cutting corners when it comes to code.
At Nealon, we don’t just insulate—we protect homes. We’ve seen what happens when foam is left exposed or the wrong product ends up next to a heat source. Trust us: it’s cheaper (and a lot less stressful) to do it right the first time.
If you’re unsure about which insulation boards are safe, which need to be covered, or how to meet code in your specific Connecticut town, we’re here for that. No upsells. No guesswork. Just real-world experience from a company that’s been doing this since 1977.
👉 Ready to fireproof your insulation strategy? Contact us today—we’ll help you choose materials that work hard, stay safe, and keep your project code-compliant.
Related Articles
Which Attic Insulation Type Offers the Best Energy Efficiency—and Why?
Let’s get one thing out of the way: insulation isn’t sexy. But you know what is? Lower energy bills, a more comfortable home, and not hearing your HVAC wheeze like it’s running a marathon.
Let’s get one thing out of the way: insulation isn’t sexy. But you know what is? Lower energy bills, a more comfortable home, and not hearing your HVAC wheeze like it’s running a marathon.
If your attic is under-insulated—or insulated with the wrong stuff—you’re basically paying to heat the outdoors. And in Connecticut, where the seasons come in hot and cold (literally), that’s a losing game.
So which attic insulation type actually delivers when it comes to energy efficiency? Let’s break it down.
What Makes Insulation “Energy Efficient,” Anyway?
Let’s get one thing straight: energy-efficient insulation isn’t just about stuffing something fluffy in your attic and hoping for the best. It’s about controlling how heat moves through your home—and more importantly, how to stop it from escaping like a dog that figured out the screen door.
The first thing folks bring up is R-value. That’s the measurement of how well a material resists heat flow. Higher R-value = better insulation performance. But here’s the kicker: R-value alone doesn’t tell the full story.
Imagine wearing a thick winter coat full of holes. That’s high R-value with bad air sealing. Doesn’t matter how “warm” the material is if drafts are whistling right through it. That’s why air sealing is the unsung hero of insulation. A well-sealed attic paired with the right material will keep your home warmer in winter, cooler in summer, and your HVAC system from running a marathon every day.
Another piece people overlook? Moisture control. Insulation that gets damp (looking at you, open fiberglass batts in a leaky attic) won’t perform well for long. And in a Connecticut climate, where humidity swings like a mood on Monday morning, that stuff matters.
So when we talk about energy-efficient insulation, we’re looking for:
- High R-value (per inch, especially in tight attic spaces)
- Strong air sealing (no sneaky drafts)
- Moisture resistance (so performance stays strong over time)
In short, the best insulation for energy efficiency does more than sit there. It seals, insulates, and holds up to weather, time, and the messiness of real life.
Comparing the Main Types of Attic Insulation
Alright, now that we know what actually makes insulation energy efficient, let’s talk about your options. Not all insulation is created equal—and each type brings something different to the table. Some are air-sealing ninjas. Others are more like paper towels: cheap, common, and not great under pressure.
Here’s the plain-English breakdown.
Spray Foam Insulation (Open-Cell & Closed-Cell)
The Cadillac of attic insulation. Spray foam is high-performance and high-budget—and for good reason.
- Closed-cell spray foam has the highest R-value per inch (around R-6 to R-7), acts as an air and vapor barrier, and basically hardens into a weatherproof seal. It’s ideal for tight, irregular spaces or when you need max performance in minimal depth.
- Open-cell spray foam is softer, cheaper, and still seals air leaks—but it absorbs moisture like a sponge, so we don’t recommend it below-grade or in humid Connecticut attics.
Best for: Energy efficiency, homes with weird attic geometry, or when air sealing is non-negotiable
Downside: Expensive, and it’s not a DIY weekend warrior kind of job
Blown-In Cellulose Insulation
The workhorse. Cellulose is recycled newspaper treated with borates (which handle mold, fire, and pests like a bouncer at the door). It’s dense, it fills every nook, and it’s one of our go-to choices in Connecticut homes.
- R-value sits around R-3.5 to R-4 per inch
- Blown in over attic floors or dense-packed into rafter bays, it settles in tight and stops air movement better than fiberglass
- It’s also eco-friendly and cost-effective—without being flimsy
Best for: Retrofitting older homes, topping off existing insulation, and environmentally conscious upgrades
Downside: Needs proper air sealing underneath to shine. Can settle slightly over time if not dense-packed
Fiberglass Batt Insulation
The old standby. You’ve seen fiberglass: pink or yellow rolls shoved between attic joists. It’s cheap and easy to install, which is why it’s everywhere—but that doesn’t mean it’s the most efficient.
- R-value ranges from R-2.9 to R-3.8 per inch
- Doesn’t seal air gaps at all—so unless it’s paired with perfect air sealing, heat escapes right around it
- Works better in open spaces with standard joist spacing and minimal obstacles
Best for: New builds on a budget, wide-open attic spaces
Downside: Gaps, drafts, and poor performance in real-world conditions if not installed carefully
Each of these materials has its place. But if you're chasing real energy efficiency in your attic—especially in the unpredictable climate we get here in Connecticut—you want to pick the one that does more than just check the R-value box. You want something that actually seals, resists moisture, and lasts.
Energy Efficiency Comparison Table: The Good, The Better, and The Drafty
Now that we’ve walked through the big three insulation types, let’s put them head-to-head in a no-fluff comparison. Because at the end of the day, you’re probably asking: “Which one gives me the most bang for my buck?”
Mike’s Take:
- Want top-tier efficiency with the budget to match? Closed-cell spray foam is hard to beat. It insulates and air seals in one shot.
- Want real performance without breaking the bank? Dense-packed cellulose gives great results—especially when paired with proper air sealing.
- Looking at batts or open-cell foam in a Connecticut attic? You might save upfront, but you’ll likely pay it back (and then some) on your energy bills.
Bottom line: The best attic insulation for energy efficiency isn’t just about R-value—it’s about how well it works in real homes, through real winters, with real utility bills on the line.
What’s the Best Attic Insulation for Connecticut Homes?
Let’s narrow it down. Because while charts and specs are nice, you’re not insulating a lab—you’re insulating a house in Connecticut, where winter winds can rattle your windows and summer humidity turns your attic into a sauna.
For Older Connecticut Homes
Most of the houses we work on—especially along the shoreline—are 50+ years old, drafty as a barn, and built long before energy efficiency was a thing. If that sounds like your place, blown-in cellulose is usually the sweet spot.
- It settles into every nook and cranny in your attic floor
- It plays well with uneven framing and weird attic shapes
- When dense-packed, it seals up air leaks surprisingly well—especially when combined with attic air sealing and baffles
It’s also green, affordable, and it won’t attract pests or mold if installed correctly. We've installed it in homes from Branford to Old Saybrook, and it’s made a night-and-day difference.
For Homes with Moisture Concerns or Complex Rooflines
If your attic looks more like a jungle gym of trusses or you’ve had issues with condensation, damp rafters, or ice dams, closed-cell spray foam is the better long-term play.
- It offers both insulation and a vapor barrier
- It locks in heat and blocks moisture from the roof deck down
- It’s pricier, but in the right situation, it can save you thousands in energy loss and roof repairs
Perfect for homes where you're insulating under the roof deck (cathedral ceilings, conditioned attics, etc.) or when you want your attic space within the thermal envelope.
What We Don’t Recommend
- Open-cell spray foam? Skip it in unvented attics here—it absorbs moisture like a sponge and can lead to rot.
- Fiberglass batts? They’re fine in new builds but don’t hold up well in real-world conditions. Gaps, compression, and air leakage are all too common.
So What’s “Best”?
If we’re talking about the best attic insulation for energy efficiency in Connecticut, the real answer is: it depends on your house. But most of the time, it comes down to dense-packed cellulose for cost-effective upgrades, or closed-cell spray foam for max performance in moisture-prone or complex spaces.
Final Verdict: What’s the Most Energy-Efficient Attic Insulation?
If you’ve stuck with me this far, you now know more about attic insulation than most contractors on Facebook Marketplace. So let’s cut to it:
- Want top-tier efficiency with the budget to match? Go with closed-cell spray foam. It insulates, seals, and shrugs off moisture like a champ.
- Want serious performance without torching your wallet? Dense-packed cellulose is the MVP—especially in older, drafty New England homes.
- Looking at fiberglass batts or open-cell foam for your attic? Be cautious. They have their place, but that place isn’t usually in a Connecticut attic.
Remember, the “best” insulation isn’t just about R-value—it’s about how it performs in your home, with your roof, and your climate. That’s why we don’t do cookie-cutter solutions. We do what works.
And what works? Quality materials, smart air sealing, and an installer who knows the difference between cutting corners and doing it right.
👉 Want us to take a look at your attic and lay out the smartest path forward? Contact Nealon Insulation and let’s make your home more efficient, comfortable, and quiet—without the guesswork.
Common Attic Insulation FAQ's
How do I know if my attic is under-insulated?
You can tell your attic is under-insulated if rooms are hard to heat or cool, ice dams form in winter, or the insulation looks thin, patchy, or dusty. Seeing exposed joists is another red flag. In Connecticut, attics should meet R-49 to R-60. A professional audit confirms insulation levels.
Can I mix different types of attic insulation?
You can mix attic insulation types, like adding cellulose over fiberglass, if the existing material is dry, stable, and air sealing is completed first. Mixing requires care—done improperly, it can trap moisture or reduce performance. Consult a pro to ensure compatibility and code compliance.
Does adding attic insulation qualify for any rebates or tax credits?
Yes, adding attic insulation may qualify for rebates or tax credits. In 2025, the federal Energy Efficient Home Improvement Credit offers up to 30% back (up to $1,200) for qualifying upgrades. Connecticut homeowners may also receive additional rebates through Energize CT based on utility provider and income.
How long does attic insulation typically last?
Attic insulation typically lasts 20–30 years if installed properly and kept dry. Cellulose maintains performance well over time, while fiberglass may settle or degrade. Spray foam can last the lifetime of the home if protected from UV exposure and moisture. Longevity depends on material type and environmental conditions.
Will insulating my attic reduce noise too?
Yes, insulating your attic can reduce noise. Dense materials like cellulose and spray foam absorb sound, helping to block outside noise such as rain or reduce indoor noise like HVAC equipment. While thermal performance is the main benefit, attic insulation also improves home acoustics and quietness.
What Is the Best Insulation for a Crawl Space?
If your floors feel cold in winter or your home smells a little... earthy after a rainstorm, your crawl space might be the reason. Most folks never give it a second thought—until they’re dealing with mold, drafts, or energy bills that look like a second mortgage. That’s the thing about crawl spaces: they’re out of sight, but not out of mind when it comes to how your home performs.
If your floors feel cold in winter or your home smells a little... earthy after a rainstorm, your crawl space might be the reason. Most folks never give it a second thought—until they’re dealing with mold, drafts, or energy bills that look like a second mortgage. That’s the thing about crawl spaces: they’re out of sight, but not out of mind when it comes to how your home performs.
In Connecticut, where weather swings from humid summers to icy Nor’easters, insulating your crawl space isn’t just a nice-to-have—it’s essential. Done right, it keeps moisture out, warm air in, and critters where they belong (anywhere but under your house). Done wrong—or not at all—and you’re inviting mold, rot, and sky-high heating costs.
So what’s the best crawl space insulation? Spray foam? Fiberglass? Foam board? We’ve tested them all. This guide breaks it down in plain English—no sales fluff, just real-world pros and cons—so you can make the right call for your home and your wallet.
The Real Question: What Makes an Insulation Type “Best”?
Let’s clear something up: there’s no one-size-fits-all answer when it comes to the best crawl space insulation. Anyone who tells you otherwise probably sells one product and calls it a day.
Here’s the truth—what works best depends on what you’re working with. Got a vented crawl space with good airflow? That’s a different playbook than a damp, musty crawl with a dirt floor. Planning to fully encapsulate with a vapor barrier and seal it tight? Now we’re talking a whole different set of rules.
To figure out the right material, we look at six things:
- Moisture resistance – Can it handle humidity without growing a mold farm?
- Air sealing – Does it block drafts and keep outdoor air from creeping in?
- R-value – How well does it slow down heat loss?
- Durability – Will it stay put, or fall to the floor in five years?
- Install method – Are we insulating the subfloor, the walls, or the whole crawl?
- Cost vs. performance – What gets you the most bang for your buck?
If your crawl space is damp or flood-prone, for example, you need something that won’t absorb water or fall apart—spoiler alert: fiberglass doesn’t make the cut. That’s where options like closed-cell spray foam or rigid foam board shine, especially when paired with proper crawl space encapsulation insulation.
Bottom line: The best insulation does more than just pass code—it solves your specific problem. That’s what we aim for every time.
Option 1: Closed-Cell Spray Foam (The Gold Standard for Encapsulation)
If you’re serious about sealing your crawl space tight—like “forget-it’s-even-there” tight—closed-cell spray foam is the heavyweight champ. It’s what we reach for when a homeowner wants long-term performance, moisture control, and insulation all in one shot.
Why? Because this stuff doesn’t just insulate—it air seals and acts as a vapor barrier, too. Spray it on the crawl space walls and rim joists, and you’ve created a shell that blocks moisture, drafts, and even pests.
What makes it great:
- High R-value per inch
- Water resistant
- Air sealing power
- Adds structural strength
Now, is it the cheapest option? Not by a long shot. But if you're after a one-and-done solution that performs year-round and pays you back on your energy bills, this is the one to beat.
Option 2: Rigid Foam Board (Budget-Friendly for Encapsulation)
If spray foam is the Cadillac, rigid foam board is the dependable pickup. It gets the job done without draining your wallet.
These boards (typically polyiso or XPS) are installed on crawl space walls and sealed at the seams. When combined with a floor vapor barrier, they create a solid moisture and thermal barrier.
Why we use it:
- Good R-value
- Moisture resistant
- Long-lasting and clean
- More affordable than spray foam
This setup works great in encapsulated crawl spaces where you want durability and performance—without breaking the bank. Just make sure the seams are sealed, or pair it with some spray foam for a tighter air seal.
Option 3: Fiberglass (What Not to Use in a Damp Crawl Space)
Let’s just say it: fiberglass insulation and crawl spaces don’t get along. We find it all the time—soaked, sagging, and moldy. It may be cheap up front, but it often turns into a money pit down the line.
Why it fails in most crawl spaces:
- Absorbs moisture
- Supports mold
- Falls down over time
- Rodents love it
Unless you’ve got a bone-dry, well-vented crawl space (rare around here), skip it. And if you’ve got old fiberglass under there now? Check out our insulation removal service—we’ll get rid of it and set you up with something that works.
Option 4: Blown-In Cellulose (Only in Certain Crawl Space Setups)
We love blown-in cellulose for attics and walls—but it has a very specific use case in crawl spaces.
If you’ve got a dry, vented crawl space and want to insulate the floor joists from below, cellulose can be a smart move. It air-seals better than fiberglass and resists pests and mold (thanks to its borate treatment).
But if there’s any chance of moisture, it’s a no-go. Cellulose absorbs water and will settle or rot over time. Use it only in the right conditions, and you’ll be happy. Use it in a damp crawl, and you’re back to square one in a few years.
Bonus Consideration: Vapor Barrier vs. Insulation – What’s the Difference?
A vapor barrier is not insulation, and insulation is not a vapor barrier.
- Vapor barrier: a plastic sheet laid across the crawl floor to stop ground moisture.
- Insulation: blocks heat transfer—either along the floor or the crawl space walls.
If you want your crawl space to stay dry and efficient, you need both. A vapor barrier keeps moisture out. Insulation keeps heat in. Skipping either one usually leads to problems—either comfort issues or moldy headaches.
When in doubt, ask us to take a look. We’ll tell you what you need—and what you don’t.
Real Talk: Is Crawl Space Insulation Worth It in Connecticut?
Here’s the bottom line: insulating your crawl space is absolutely worth it—especially here in Connecticut, where the weather throws everything at your home in a single year.
What you gain:
- Warm floors in winter
- Lower energy bills
- No more musty smells
- Less mold and rot
- Better home value
We’ve been fixing crawl spaces since 1977. When it’s done right, you only have to do it once.
How Much Does Crawl Space Insulation Cost in Connecticut?
Here’s a rough idea of what homeowners around here are paying:
- Fiberglass (floor only): $1.50–$2.50/sq ft
- Blown-in cellulose: $2.00–$3.50/sq ft
- Rigid foam board: $3.50–$5.50/sq ft
- Spray foam (full encapsulation): $5.00–$8.00+/sq ft
Your price depends on crawl size, access, current condition, and whether you’re adding a vapor barrier or drainage. We’ll give you a clear, honest quote before we touch a thing.
Common Crawl Space FAQ's
How do I know if my crawl space needs new insulation?
You’ll know your crawl space needs new insulation if you notice cold floors, musty odors, rising energy bills, or visible issues like sagging insulation, mold, or rodent activity. Moisture on the vapor barrier is another red flag. These signs often mean your crawl space insulation is failing or missing entirely.
Should I insulate the crawl space walls or the subfloor?
Insulate crawl space walls if the space is encapsulated, as this keeps it within your home’s thermal envelope. For vented crawl spaces, insulate the subfloor between joists. Using the wrong method can lead to cold floors or moisture problems, so the choice depends on whether the crawl space is sealed or ventilated.
Can I insulate my crawl space myself?
You can insulate your crawl space yourself, but it’s risky unless the space is dry, accessible, and you understand proper materials and methods. DIY attempts often skip critical steps like air sealing or moisture control, which can lead to mold, rot, or insulation failure—resulting in costly redos.
What’s the difference between open-cell and closed-cell spray foam in a crawl space?
The main difference between open-cell and closed-cell spray foam in a crawl space is moisture resistance. Closed-cell foam is dense, water-resistant, and doubles as an air and vapor barrier—ideal for Connecticut’s damp conditions. Open-cell is cheaper but absorbs moisture, making it unsuitable for below-grade use.
Will insulating my crawl space help with humidity in the rest of the house?
Absolutely. A poorly sealed crawl space acts like a moisture engine, pumping damp air into your home’s living areas—especially if you’ve got hardwood floors or HVAC ducts running overhead. A properly insulated and sealed crawl helps control indoor humidity, improves air quality, and even protects your flooring from warping or cupping.
Conclusion: Choosing the Right Insulation for Your Crawl Space
So, what’s the best crawl space insulation?
That depends on your setup. But the right choice will block moisture, seal air leaks, and actually last.
We’ll help you choose the right material for your home—not just the most expensive one.
At Nealon Insulation, we’ve been doing this since 1977. Crawl spaces, attics, walls—you name it. We don’t do shortcuts, and we don’t push products you don’t need. Just smart solutions that make your home feel better and cost less to run.
👉 Ready to fix your crawl space for good? Schedule your free inspection here. We’ll crawl it, quote it, and fix it like it’s our own.
What Is the Best Insulation for Walls?
Your walls are doing more than just holding up your roof. They’re the front line in your battle for comfort, efficiency, and quiet. So let’s make sure they’re pulling their weight.
Your walls are doing more than just holding up your roof. They’re the front line in your battle for comfort, efficiency, and quiet. So let’s make sure they’re pulling their weight.
If your home’s walls are hollow, poorly insulated, or stuffed with 1970s-era fiberglass, it’s time for an upgrade. But with all the choices—spray foam, fiberglass, cellulose, mineral wool—how do you know which one actually works best?
Short answer: it depends on your home, your goals, and your budget. Long answer? You’re about to find out.
Welcome to your guide to the best insulation for walls, brought to you by a team that’s been insulating homes across Connecticut since bell bottoms were cool the first time.
Why Wall Insulation Matters More Than You Think
Most people don’t think about the insulation behind their walls—until they feel a draft, get slapped with a sky-high energy bill, or hear every step their kids take in the next room.
Wall insulation plays a critical role in:
- Regulating temperature between rooms and across floors
- Lowering heating and cooling bills
- Reducing noise from outside or within the house
- Blocking moisture and air leaks that lead to mold and rot
In older Connecticut homes especially, exterior walls are often under-insulated—or not insulated at all. That means you're paying to heat or cool the outdoors, and probably not enjoying the comfort you should indoors.
Know Your Options: Common Types of Wall Insulation
Let’s break down the top players when it comes to wall insulation. Each one has its pros and cons—and the right one depends on your goals.
1. Fiberglass Batts (The Budget Classic)
Cheap, fast, and available at every big box store. Fiberglass batts are great for open wall cavities and new construction, but they can leave gaps and don't stop air movement well.
Good for: Budget jobs, open framing, simple installs
Not ideal for: Air sealing or older homes with weird wall layouts
🔗 Discover more about fiberglass insulation
2. Dense-Packed Cellulose (The Retrofit Hero)
Cellulose is made from recycled paper, but don’t let that fool you—it’s a beast at filling wall cavities, sealing air leaks, and dampening sound. We often use it to insulate existing walls without tearing them open.
Good for: Older Connecticut homes, energy upgrades, air sealing
Not ideal for: Places with high moisture exposure unless paired with proper vapor barriers
🔗 Learn more about cellulose insulation
Here's How the Dense Pack Cellulose Works
3. Spray Foam (The Premium Performer)
Closed-cell spray foam gives you high R-value, strong air sealing, and moisture resistance—all in one shot. It’s more expensive, but it performs like a champ and adds structural strength.
Good for: Cold climates, tight spaces, moisture-prone areas
Not ideal for: Tight budgets or retrofits in finished walls
🔗 Explore spray foam insulation
How to Choose the Best Insulation for Your Walls
Here’s what really matters when deciding:
- Age of your home: Old homes? Cellulose is often the MVP.
- Wall access: Open walls = more options. Closed walls = think dense-pack.
- Moisture risk: Go with closed-cell spray foam or mineral wool in damp spots.
- Noise issues: Use mineral wool for quiet, or cellulose for a solid balance.
- Budget: Fiberglass wins on price, spray foam wins on performance.
When Should You Insulate or Re-Insulate Your Walls?
There’s no universal timer, but here are 5 moments when wall insulation becomes a smart move:
- Your walls feel cold in winter or hot in summer
- You’re renovating, replacing siding, or opening up walls
- Your energy bills have climbed for no obvious reason
- You hear outside noise clearly from inside
- Your home was built before the 1980s (when insulation wasn’t required)
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7 Big Benefits of Proper Wall Insulation
- Lower Energy Bills: Cut heating and cooling costs by 15–25%.
- More Consistent Temps: No more hot rooms upstairs or freezing spots in the corner.
- Noise Reduction: Stop hearing your neighbors—or your teenager’s stereo.
- Improved Air Quality: Proper insulation helps block dust, allergens, and outdoor pollutants.
- Moisture Control: Avoid condensation, mold, and wood rot.
- Increased Comfort: A well-insulated home simply feels better.
- Higher Resale Value: Buyers love efficient, well-sealed homes.
FAQs: Wall Insulation in Connecticut
Can you insulate existing exterior walls without removing drywall?
Yes, you can insulate your walls without removing drywall. Nealon Insulation installs dense-packed cellulose or injection foam through small exterior holes, which are patched after. This method upgrades comfort and efficiency without damaging your home’s interior.
What’s the recommended R-value for walls in Connecticut?
The recommended R-value for walls in Connecticut is R-13 to R-21. Older homes with 2x4 walls typically reach R-13 to R-15, while newer homes with 2x6 framing can achieve R-21. Dense-packed cellulose can help improve performance by sealing air gaps, especially in drafty or under-insulated walls.
Does insulating my walls add resale value to my home?
Yes, insulating your walls can increase resale value by boosting energy efficiency and comfort. Buyers appreciate lower utility bills and consistent room temperatures. In older Connecticut homes, upgraded insulation with documented R-values or savings can be a strong selling point.
How do I know what’s currently inside my walls?
To know what’s inside your walls, professionals inspect behind outlet covers or drill small test holes to view or sample insulation. Tools like borescopes or core samplers reveal whether insulation exists and what type it is. This quick, non-invasive check helps determine if upgrades are needed without damaging your walls.
Final Take: Wall Insulation That Works As Hard As You Do
Your walls can be a money pit or a comfort fortress—it depends on what’s inside them. If your energy bills are climbing, rooms feel drafty, or your home’s just not holding temperature, wall insulation might be the missing piece.
And don’t worry—you don’t need to have it all figured out. That’s our job.
At Nealon Insulation, we’ve been helping homeowners across Connecticut insulate smarter for nearly 50 years. From dense-packed cellulose in old beach homes to spray foam in new builds, we know how to match the right solution to your space, your needs, and your budget.
👉 Get your free wall insulation assessment today and let’s make those walls work for you.
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Ready to transform your home into an energy-efficient haven? Schedule your free energy assessment today and experience the Nealon difference for yourself.