R19 Insulation Thickness [How Much Insulation Do You Need]

This article lists the R19 insulation thickness for different materials like fiberglass, spray foam, cellulose, Rockwool, form board, and aerogel.

R19 insulation is commonly used to insulate the outer walls of newer buildings. If you are insulating your new construction, you will want to know how thick the insulation needs to be to reach R 19 heat resistance.

The thickness of R19 insulation ranges from 2.1 inches to 6.3 inches. It is the least for aerogel and most for fiberglass and Rockwool. The R 19 thickness needed for spray foam insulation is 5.2 inches.

The following table lists how much insulation thickness is needed for each material to achieve R19. 

Insulation MaterialRequired Thickness (inches)
Fiberglass (Batts)5.2 inches
Fiberglass (Loose-fill)6.3 inches
Spray Foam (Open Cell)5.2 inches
Spray Foam (Closed Cell)3.1 inches
Cellulose (Loose fill)5.5 inches
Rockwool (Batts)5.2 inches
Rockwool (Loose-fill)6.3 inches
Foam board3.8 inches
Aerogel2.1 inches
R19 insulation thickness for different insulation materials
R19 insulation chart
R19 insulation thickness chart

Fiberglass insulation thickness

The R19 thickness for fiberglass loose-fill insulation is 6.3 inches and for fiberglass batt insulation is 5.2 inches.

Fiberglass is the most common insulation solution in the market. It is widely available in the form of both batts and loose-fill. Fiberglass batts can easily fit between joists, studs, and walls with gaps. However, for tight spaces where batts might not be fully able to insulate, loose-fill gets the job done. In terms of effectiveness, fiberglass is a reliable material to choose from as it trims down the amount of airflow to a great extent.

As the name suggests, the material is made from tightly packed glass fibers. Fiberglass is derived from pure glass that goes through an intense heating session until it becomes soft. Afterward, the material makes its way through miniature divisions that result in a thread-like end product. The final touch involves cooling these fibers and making either batts or loose-fill out of them. Due to fiberglass’ widespread availability, ease of installation, and affordable price tag, homeowners consider it to be their first choice when the subject of insulation is being discussed.

R19 Spray foam thickness

R19 spray foam insulation thickness is 5.2 inches for open-cell type and 3.1 inches for closed-cell type insulation. Closed-cell spray foam requires less thickness due to the higher heat resistance per inch of its densely packed cells.

Spray foam is considered to be one of the best insulation materials due to its accuracy and effectiveness. It is blown in tight spaces, walls, attics, and other such places with the help of a blower. Thanks to its foamy texture, the insulation material can be sprayed almost everywhere. Whether it’s in small openings around an electric outlet or cavities between joists and beams. Once sprayed, the foam expands and dries quickly, becoming a barrier to stop both heat and cold.

The thing that makes spray foam special is its effectiveness. Unlike batts, the foam can make its way into anywhere guaranteeing extraordinary results. However, the cost is a bit high due to spray foam’s excellent insulation performance. Since it’s also blown by a professional, the installation procedure is an expense too. In terms of longevity, there’s no denying that spray foam insulation will not sag or deteriorate for a long while. To sum it up, you’re making a safe investment when you choose spray foam.

Cellulose thickness

5.5 inches is the minimum thickness required for R19 cellulose insulation. This is when the cellulose is loose-filled. Its R-value will increase if the filling is more compact.

Cellulose is derived mostly from discarded paper which initially made it prone to fires. It wasn’t until the mid-20th century that the inclusion of fire retardant resulted in cellulose becoming a widely used insulation material. Fortunately, this material has managed to stay accepted to this date. Other than protecting homes from extreme weather conditions, cellulose is also a noticeably good option for noise insulation.

Cellulose is perhaps the only material that has over 80% recycled ingredients. It is also relatively inexpensive due to the material mostly being derived from paper. Installation should not be a hassle either as cellulose can be put up with a typical blower by anyone with basic DIY knowledge. Not to mention the involvement of boric acid and aluminum sulfate in the recipe of cellulose makes the product highly resistant to fire and mold. Note that these two are the top reasons behind most insulation materials expiring before they should. This makes cellulose an ideal pick for adding new insulation to an existing one or simply adding a new layer altogether.

Rockwool thickness

R19 insulation thickness for Rockwool batts is 5.2 inches and for loose-fill is 6.3 inches.

Rockwool is known for its mold-resistant, waterproof, and thermal insulation properties. Living up to its name, rockwool/mineral wool is made from minerals such as stones. These minerals are put through extreme heat until they reach their melting points. Afterward, they are spun like cotton candy to achieve a thin texture. Once in the form of spun fibers, what we know as rockwool comes into being. 

Thanks to its ingredients being excellent insulators, rockwool is a very reliable insulation solution. It is commonly used for soundproofing structures as well. Consider rockwool to be similar to fiberglass, except the former is derived from rocks while the latter is from glass. However, the use is pretty much the same. Rockwool can be installed almost everywhere such as attics, walls, ceilings, and likewise.

Foam Board thickness

A thickness of 3.8 inches is required for foam board insulation to attain an R19 value. Foam board is an insulation material quite similar to fiberglass in terms of composition. However, it is more effective in stopping airflow and more resistant to moisture. Also known as rigid board insulation, it is commonly found in the form of batts, which makes it relatively easy to install as well. Simply cut the batts as needed and put up the insulation to secure your house. Before you go for foam board, ensure that you’re going for the right type as there are mainly three of them, expanded polystyrene, polyisocyanurate, and extruded polystyrene. 

Note that foam board is known to be closed-cell insulation, unlike other popular insulation materials which are open-cell such as fiberglass. Closed-cell insulations are more powerful and better at stopping airflow as compared to open-cell. Foam board is a cheap insulation solution that has been around for a while. The best part about it is its brilliant resistance to moisture. even if an old pipe starts leaking onto it, foam board insulation can still continue doing its job very well. You’ll find different thickness levels of foam board batts in the market, starting from a half-inch to around three inches.


Aerogel is undoubtedly the uncrowned king of insulation materials but it’s not too popular for a number of reasons. It has the highest R-value and the highest price tag in the market. That’s why only around 2 inches of aerogel blanket would easily land you an R19 rating. This is even less than half of what is needed for fiberglass to achieve R19! Primarily used in space missions, aerogel was not around until the last decade when some manufacturing companies stepped up to offer the product to homeowners. Although it still is nowhere near the popularity of fiberglass, its performance is at the top.

The most effective insulator comes into being after the removal of liquid molecules from gels. Once the liquid is gone, all that is left is 90% air in the material. This low-density material does a great job by letting almost no airflow get through it. Due to its technologically advanced recipe, aerogel is by far the thinnest and lightest insulation material introduced. Therefore, even a couple of inches in thickness will offer an incredibly high R-value. Aerogel is capable of trimming down utility bills up to a whopping 80%. This shows that the material is indeed an elite-level insulation material.

When to go for R19 insulation?

Standard R-value for homes ranges around R13 to R21 and R19 comes somewhere in between. The R19 grade is usually chosen for newly-built structures and houses as well as attics and basements. In several states, R 19 is considered to be the standard rating. Particularly for the states in the Southern region of the country, R19 is considered to be the basic. However, homeowners are welcome to upgrade to R21 if the need arises. Another factor that plays a role here is the region where insulation is being applied. For areas that witness extreme weather conditions, R19 would likely be insufficient and R21 would be recommended.

Achieving R 19 should not be too expensive as it’s considered to be the standard R-value in several states. However, the costs are also dependent upon the material you’re choosing. We’ve provided a table to show the required thickness of different insulations and their distinct characteristics, composition, and subdivisions. 

Charles John

Experienced HVAC technician with 8 years of experience in the industry. Capable of handling all sorts of heating and cooling equipment as well as proficient in operational management, construction-related techniques such as preventative maintenance, electrical troubleshooting and AutoCAD

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