Types of Home Insulation: A Detailed Comparison of Fiberglass, Cellulose, and Spray Foam (Benefits and Best Use Cases)

When Massachusetts homeowners look to improve comfort and energy efficiency, insulation is usually the first upgrade that comes to mind. But insulation works best when it’s paired with air sealing, because insulation reduces heat transfer but does not block air movement by itself. If air is flowing through or around insulation, its R value drops dramatically, which is why Mass Save requires air sealing before insulation upgrades.

Below is a practical comparison of the most common insulation materials used in homes, including where each one tends to perform best.

Before You Choose Insulation: Know the Job It Must Do

Insulation slows the movement of heat in and out of your home. Air sealing targets the cracks, gaps, and penetrations that allow conditioned indoor air to escape and outdoor air to enter. Common leak areas include attic penetrations and recessed lighting, chimney chases, pipe and wire openings, rim joists and basement sills, attic hatches, and kneewalls.

Because air leakage can undermine insulation performance, many successful projects start with air sealing and then add insulation where it will deliver the most benefit.

Fiberglass Insulation

Fiberglass insulation is made from fine glass fibers and is used in multiple formats, including blown in fiberglass and fiberglass batts.

Fiberglass Blown In

Material
Made from fine glass fibers

Best for
Attics, walls, and crawl spaces

R value
Around R 2.2 to R 2.7 per inch

Benefits
Lightweight and easy to install
Fire resistant and non combustible
Does not absorb moisture
Cost effective and widely available

Best use cases
Attic floors where you want broad, even coverage
Areas where access is limited and blown in installation is practical
Projects where cost control is a priority while still improving thermal performance

Fiberglass Batts

Rogers Insulation states fiberglass has been the go to insulation product for professionals and homeowners for 80 years and that they only install formaldehyde free fiberglass products.

Best use cases
Open stud or joist cavities where batts can be fitted correctly
Projects where a traditional insulation method is appropriate for the specific area being insulated

Cellulose Insulation

Rogers Insulation describes blown in cellulose as their most recommended product. It is made from recycled newspaper and is described as one of the greenest products available. Rogers also notes that cellulose has been used for nearly 100 years.

Cellulose Blown In

Material
Recycled paper products primarily newspaper
Rogers describes 80 to 85 percent recycled content and also describes cellulose as made from up to 85 percent recycled materials

Best for
Walls, attics, and retrofitting older homes

R value
Around R 3.2 to R 3.8 per inch

Benefits
High R value thermal performance
Treated with borates for fire mold and pest resistance
Dense coverage that fills irregular spaces
Rogers notes it can reduce air infiltration by up to 30 percent
Rogers notes properly installed blown in cellulose can last 20 to 30 years
Rogers states it is treated with non toxic fire retardants such as boric acid and has a Class 1 Fire Rating

Best use cases
Attics where you want even coverage and the ability to fill irregular spaces
Older homes where wall cavities and framing can be irregular
Existing walls where insulation can be installed by drilling small holes into wall cavities and blowing in insulation without major renovations

How it is commonly installed in attics on the Rogers Insulation site
Clear debris and old insulation as needed
Seal air leaks and ensure proper ventilation
Blow insulation evenly across the attic floor
Measure insulation depth to ensure consistent coverage and the desired R value

Spray Foam Insulation

Spray foam is applied as a liquid that expands and hardens. Rogers describes spray foam as providing excellent air sealing and insulation properties and also describes it as creating an airtight seal that helps prevent drafts.

Material
Polyurethane or similar foam based compounds

Best for
Sealing air leaks and high performance insulation applications
Small spaces and irregular cavities

R value
Around R 3.5 to R 6.5 per inch

Benefits
Creates an airtight seal to prevent drafts
Provides insulation performance while also addressing air leakage
Rogers notes it helps control moisture and can reduce risk of mold
Useful for small spaces and irregular cavities

Best use cases
Areas where drafts are driven by air leaks and you want insulation plus air sealing in one approach
Irregular or difficult to seal areas where coverage matters

Foam Insulation Board and Rigid Foam Board

Rogers Insulation describes foam insulation board as having the highest insulating values per inch of nearly any insulation product. Rogers also notes they use it extensively for knee walls and crawl spaces and that it can increase the efficiency and air sealing abilities of fiberglass and cellulose insulation.

Best use cases
Knee walls where air leakage and bypasses are common
Crawl spaces where insulation details must improve comfort and reduce energy costs
Projects where you want a rigid layer to support overall air sealing and thermal performance

Best Material by Area of the Home

Attic spaces
Blown in cellulose or blown in fiberglass are commonly used, with air sealing addressed first

Exterior walls
Blown in cellulose is commonly used for retrofits and older homes and can be installed in existing walls using drilled access holes

Sloped and cathedral ceilings
Material choice depends on access and air leakage conditions, with air sealing playing a major role in performance

Knee walls
Foam insulation board is used extensively by Rogers Insulation for knee walls, and air sealing details are important in these areas

Crawl spaces
Foam insulation board and other insulation strategies are used by Rogers Insulation in crawl spaces, with attention to air sealing to improve comfort and reduce energy costs

FAQ

What’s the best insulation for an attic?

For many homes, the highest-impact approach is air sealing the attic floor first, then adding blown cellulose (or blown fiberglass) to the target depth.

Is spray foam “worth it”?

Spray foam is often worth it in areas where air leakage is hard to stop by other means—rim joists, crawlspaces, complex framing, and certain roofline designs. It’s less compelling as a blanket solution everywhere due to cost.

What’s better: fiberglass or cellulose?

In many retrofit situations, cellulose delivers better real-world results because it covers irregularities well and reduces air movement within the insulation layer. Fiberglass can match or beat it when installed perfectly with robust air sealing.

Can I insulate walls without removing drywall?

Often yes—dense-pack cellulose can be installed through small access holes, making it a strong option for older homes.

Mass Save and Next Steps With Rogers Insulation

Rogers Insulation is a Mass Save Partner and states they have been associated with the Mass Save program for over 25 years. Rogers states that as a Mass Save Partner they are able to offer a 75 percent incentive on insulation and no cost air sealing.

Rogers also states that a Mass Save no cost Home Energy Assessment includes a customized home energy assessment with personalized recommendations and a report on identified energy savings opportunities, plus installation of no cost energy saving products as needed such as advanced power strips, low flow shower heads, faucet aerators, and programmable thermostats or discounted wireless thermostats installed at a second appointment.

Rogers Insulation is family owned and operated since 1979 and on 225 Arlington Street Suite G Framingham MA 01702. Our estimates are always free and informative and offers a no cost no obligation estimate. Contact us today!