Types of Insulation: R-Value, Cost & Best Picks for Attic, Walls, Basement

The “best insulation” is rarely one material—it’s a match of form + material + location + performance needs (air sealing, moisture control, fire safety, and budget). In this guide, we break down the most common types of insulation used in homes—such as spray foam, rigid foam board, fiberglass, loose-fill, batts/blankets, cellulose, reflective insulation, and radiant barriers—so you can understand what each one is designed to do and where it typically performs best.

We also explain the key factors that actually determine insulation performance beyond “R-value,” including air sealing ability, moisture resistance, fire safety considerations, sound dampening, installation complexity, and budget. Finally, we answer practical “best insulation for…” questions for areas like attics, crawl spaces, interior and exterior walls, basements, ceilings, and garages, so you can choose the right insulation type for your specific building part and climate.

What Are The Common Types Of Insulation?

There are many insulation options on the market, but most residential projects fall into a few common categories. The best insulation choice usually comes down to form + material + location: how it’s installed (sprayed, rolled, blown, or boarded), what it’s made of (foam, glass fiber, recycled paper), and where it will live (attic, wall cavity, basement wall, crawl space). Below are eight widely used insulation types, with practical guidance on strengths, typical use cases, and common mistakes.

1. Spray Foam Insulation (Open-Cell vs Closed-Cell)

Spray foam insulation is created by a chemical reaction that expands rapidly after application, allowing it to fill cracks, gaps, and irregular cavities. Because it expands and adheres to surfaces, it can reduce heat transfer and help limit air leakage—one of the biggest drivers of real-world energy loss.

Spray foam typically comes in open-cell and closed-cell forms. Closed-cell generally delivers higher R-value per inch and stronger resistance to moisture and air leakage, while open-cell is lighter and less expensive—but DOE advises open-cell should not be used below ground level where it could absorb water.

Numbers (typical ranges)

• Open-cell R-value (per inch): ~R-3.6/in (typical)

• Closed-cell (guide reference): DOE’s insulation guide lists ~R-6.5 at 1 inch for closed-cell polyurethane spray foam (as a reference point).

• Cost (labor example): Spray foam labor may range about $0.44–$3.20 per sq ft depending on conditions (project-dependent).

Best for

• Rim joists, penetrations, and irregular cavities

• Crawl spaces and hard-to-reach areas

• Projects where air leakage is a top concern

Watch-out: installation quality and assembly design matter (especially moisture strategy).

2. Foam Board Insulation (Rigid Board: EPS / XPS / Polyiso)

Foam board insulation comes in rigid panels designed to deliver strong thermal resistance with relatively thin thickness—helpful when space is limited. These boards are often used as continuous insulation to reduce thermal bridging through studs and framing.

Foam boards commonly include EPS, XPS, and polyiso. DOE’s Building America guidance documents frequently cite foam-board R-values per inch as a quick reference for assemblies (product specs vary by manufacturer).

Numbers (typical ranges)

• R-value @ 1 inch (reference): EPS R-3.8–4.4, XPS ~R-5, Polyiso ~R-6.5

• Thickness: commonly 0.5"–4" depending on sheathing/basement/foundation assembly

• Cost (installed): rigid foam board installation is often cited around $0.90–$1.88 per sq ft (project dependent).

Best for

• Exterior wall sheathing (continuous insulation)

• Basement walls, foundations, and some under-slab applications

• Projects targeting thermal bridging reduction

Watch-out: unsealed seams/gaps quietly undermine performance.

3. Fiberglass Insulation (Batts/Rolls or Loose-Fill)

Fiberglass insulation is made from fine glass fibers and is one of the most common residential insulation materials. It’s popular because it’s affordable and available in multiple forms. Its real-world performance depends heavily on fit—gaps and compression reduce effective R-value.

Home Depot notes that standard fiberglass rolls have about R-2.9 to R-3.8 per inch.

Numbers (typical ranges)

• R-value (batts/rolls): R-2.9 to R-3.8 per inch

• Thickness: commonly matched to cavity depth (e.g., ~3.5" for 2×4 walls, ~5.5" for 2×6 walls)

• Cost (installed): fiberglass batts are commonly cited around $0.30–$1.50 per sq ft (varies by product and market).

Best for

• Standard wall cavities and attic floors

• DIY projects (batts/rolls)

• Budget-focused upgrades

Watch-out: compressing batts or leaving voids is the #1 performance killer.

4. Loose-Fill (Blown-In) Insulation

Loose-fill (blown-in) insulation is installed by blowing small particles into place so they flow around wires, pipes, and irregular framing. It’s commonly used in attics and retrofits because it improves coverage in areas where batts might leave gaps.

Loose-fill insulation can be made from fiberglass, cellulose, or mineral wool. DOE emphasizes that installed R-value depends on multiple variables—type, thickness, density, moisture, aging, and temperature—so “depth to a target total R-value” is usually more reliable than chasing a single inches-based number.

Numbers (typical ranges)

• Typical project total: average around $1,725 with a range $750–$3,800 depending on material and scope.

• Cost (by material examples): blown-in fiberglass can be around $0.50–$1.10 per sq ft, while dense-pack cellulose can exceed $2 per sq ft (see detailed cellulose section below).

• Thickness: set by target total R-value and even coverage, especially in attics

Best for

• Attics and retrofit projects

• Spaces with obstructions and irregular geometry

• Filling coverage gaps over large areas

Watch-out: air seal first, then blow-in—otherwise you’re insulating moving air.

5. Blanket or Batt Insulation

Batt or blanket insulation comes in pre-cut batts or rolls designed to fit between studs and joists. It’s common in walls and floors because it’s easy to place and cost-effective—when cut and fitted correctly.

Batts are especially useful for wall cavities, floors above unconditioned areas, and interior walls where some sound reduction is helpful. The biggest difference between a “good” and “bad” batt installation is whether it’s cut and fit carefully around wires and plumbing without leaving voids.

Numbers (typical ranges)

• R-value: depends on material; fiberglass batts/rolls are commonly R-2.9–3.8 per inch.

• Thickness: typically matched to cavity depth (2×4, 2×6, floor joists)

• Cost (installed benchmark): for many wall applications, installed batting is often cited around $1.00–$1.50 per sq ft (varies by region and scope).

Best for

• Wall cavities and floors

• DIY installations with standard framing spacing

• Interior walls needing basic sound control

Watch-out: most “bad installs” are just batts cut too short or left with edge gaps.

6. Cellulose Insulation

Cellulose insulation is typically made from recycled paper products treated for fire and pest resistance. It’s often used as blown-in attic insulation or dense-packed into retrofit wall cavities, where its ability to fill voids can be a major advantage.

Cellulose performance depends heavily on install method and density. Dense-pack wall installs are designed to reduce settling and improve long-term consistency, while attic installs prioritize even coverage to the intended depth.

Numbers (typical ranges)

• Cost (installed average): around $1.20 per sq ft for cellulose overall in blown-in contexts.

• Wet-spray cellulose: $0.60–$1.80 per sq ft

• Dense-pack cellulose: $2.00–$2.30 per sq ft

• Thickness: set by target total R-value and density (especially in walls)

Best for

• Attics (blown-in)

• Retrofit wall cavities (dense pack)

• Projects prioritizing coverage and recycled content

Watch-out: density is the difference between “great” and “settles over time.”

7. Reflective Insulation

Reflective insulation uses foil-based layers to reduce radiant heat transfer (different from conductive heat). This makes it most relevant when radiant heat is a dominant issue, such as hot-climate attic assemblies.

Reflective systems are assembly-dependent. The reflective surface generally performs best when installed with the proper air space; without it, the radiant benefit is reduced.

Numbers (typical ranges)

• Cost and performance vary widely by assembly; best treated as a radiant-control layer rather than the primary thermal layer.

Best for

• Hot climates and radiant heat control scenarios

• Pairing with bulk insulation to improve overall results

Watch-out: without an air gap, effectiveness drops sharply.

8. Radiant Barrier Insulation

Radiant barriers are reflective sheets installed in attics to reduce radiant heat gain from the roof deck. They’re most useful in hot, sunny regions where cooling loads dominate.

Radiant barriers do not replace bulk insulation; they complement it by reducing radiant heat entering the attic space.

Numbers (typical ranges)

• Highly climate- and assembly-dependent; treat as an add-on comfort/cooling layer rather than “R-value replacement.”

Best for

• Attics in hot, sunny climates

• Homes with high cooling demand

Watch-out: don’t skip adequate bulk insulation.

Quick Comparison Table (Standardized)

Type	Typical R-value (reference)	Typical thickness	Typical installed cost	Notes
Open-cell spray foam	varies; board-foot pricing common	assembly dependent	labor can range $0.44–$3.20/sq ft	DOE cautions against below-grade use where it can absorb water
Closed-cell spray foam	up to ~R-7/in	assembly dependent	project-based; higher than open-cell	strong moisture/air control; higher cost
Rigid foam board (EPS/XPS/Polyiso)	@1": EPS R-3.8–4.4, XPS ~R-5, Polyiso ~R-6.5	0.5"–4"	$0.90–$1.88/sq ft	good continuous insulation; seal seams
Fiberglass batts/rolls	R-2.9–3.8/in	cavity depth (3.5", 5.5"+)	$0.30–$1.50/sq ft	performance drops with gaps/compression
Blown-in (general)	target total R; depends on density/moisture	depth to target R	avg $1,725 (range $750–$3,800)	great retrofit coverage; air seal first
Cellulose (dense-pack)	target total R	density-dependent	$2.00–$2.30/sq ft	strong coverage; density matters
Cellulose (wet-spray)	target total R	density-dependent	$0.60–$1.80/sq ft	often used for walls in some contexts
Reflective/radiant barrier	assembly dependent	installed as layer	varies	best as add-on in hot climates

What Are The Factors When Choosing Insulation?

R-value is important, but DOE emphasizes that insulation performance also depends on thickness, density, temperature, aging, and moisture accumulation—so you should choose insulation as part of the full assembly, not just a label number. Here are 10 factors that you must consider before choosing insulation for your building. 

• Thermal Resistance (R-Value):

The thermal resistance of an insulation, which is also known as its R-value, is a measure of the material’s ability to resist heat transfer. R-value varies for different types of insulation. The higher the value, the higher the thermal resistance. Closed spray foam insulation offers the highest R-value, while fiberglass insulation offers the lowest.

• Climate And Location:

The climate and location of a building play vital factors when choosing insulation. Buildings in cold climates require a high R-value, such as spray foam insulation, to retain heat. For hot climates, reflective or radiant insulation is a suitable option.

•  Application and Space:

The area of application is important when selecting insulation. Virtually all types of insulation can be used for wall insulation, attic insulation, and floor insulation. However, not all types of insulation can be used for crevices, pipes, or hard-to-reach places such as crawl spaces. Spray foam insulation is a versatile type of insulation that is applied to irregular spaces.

• Cost and Budget:

Installation cost is a major criterion to consider when choosing the type of insulation to use for your building. Evaluate your budget and cost before choosing an insulation. The installation cost varies with different insulating materials. Spray foam insulation is considered the most expensive, while fiberglass insulation is the cheapest. Here is a breakdown of how much spray foam insulation costs.

• Environmental Impact:

It is essential to consider the environmental impact of an insulating material when selecting insulation. Choose insulating materials that are eco-friendly and sustainable. This helps to create a healthier environment and reduce carbon footprint. Get this high-quality carbon-neutral spray foam product from Kraken.

• Ease of Installation:

Ease of installation can affect insulation selection. Fiberglass, Reflective, and foam board insulations are all DIY-friendly. In contrast, spray foam and loose-fill insulation require the services of a professional for efficient installation. 

• Fire Resistance:

The flammability of insulating material is an essential factor to consider when choosing insulation. The insulation should be able to resist fire to a certain degree. Cellulose insulation minimizes fire since they are usually treated with retardants.  

Fiberglass and mineral wool also possess fire-resistance capabilities. Typically, foam insulation supports combustion because of its chemical constituents. However, newly improved spray foam products such as Fast Coat have a Class 1 fire rating. 

• Moisture Resistance:

Moisture accumulation causes gradual deterioration of insulation. Therefore, the ability of insulating material to resist moisture is an essential characteristic to consider before choosing an insulation. Moisture resistance eliminates the risk of mold growth in buildings. Spray foam insulation provides superior moisture resistance. On the other hand, fiberglass insulation absorbs moisture easily. 

• Soundproofing

Insulation is a good way to soundproof your building especially if you are in a noisy environment. However, not all types of insulation provide soundproofing capabilities. Soundproofing a building makes it more relaxing and distraction-free for occupants. Spray foam and fiberglass insulation are effective at dampening sound transmission.

• Building Codes and Regulations

Local building codes and regulations may dictate specific insulation for different parts of a building. Ensure that the chosen insulation meets these building codes to avoid penalties.

FAQs

What Type of Insulation For Attics?

Spray foam insulation offers a high R-value, and it is the most suitable type of insulation for attics. Cellulose and fiberglass insulation are also suitable types of attic insulation that can effectively provide thermal resistance.

What Type of Insulation For Crawl Space?

The best type of insulation for crawl space is spray foam. They are suitable for irregular spaces and provide effective moisture resistance. 

What Type of Insulation For Interior Walls?

Batts and spray foam are the ideal types of insulation for interior walls. They possess soundproofing capabilities, thermal resistance, environmentally-friendly, and fire resistance. Reflective insulation can also be used in combination with other types of insulation to provide thermal resistance in a living space. 

What Type of Insulation For Exterior Walls?

Foam Board is the most suitable type of insulation for exterior walls. They are commonly used for exterior wall sheathing and interior sheathing for basement walls. 

What Type of Insulation For Basement Walls?

Spray and foam board are suitable types of insulation for basement walls. They provide effective moisture and thermal resistance, thereby creating a comfortable and energy-efficient basement environment.

What Type of Insulation For Ceiling?

Spray foam, batts, and cellulose are types of insulation for ceilings. However, spray foam insulation is the ideal type of insulation as it can applied to irregular ceiling shapes and provides a higher thermal resistance.

What Type of Insulation For Garage?

The best type of insulation for a garage is spray foam. Spray foam offers a high R-value, moisture resistance, soundproofing capabilities, and durability.