What is the R-Value of Fiberglass Insulation? [With Chart]

When it comes to insulating your house, you may have heard the name fiberglass insulation.

Fiberglass insulation is cost-efficient and provides good insulation at an affordable price. It is used for insulating houses for a very long period.

If you have been considering installing fiberglass insulation in your house then, it will be advisable for you all to know all about the types, cost, and most importantly the R-value of the material.

We present you with this article which has all the information to answer your queries.

What is the R-Value of Fiberglass Insulation?

What is the R-Value of Fiberglass Insulation

The R-value of insulating material is a measure of the thermal resistance of the material that it can provide against external factors. The higher the R-value of the material, the better insulation it can provide.

Fiberglass insulation has various types, and these types have different R-values. The R-value of these types, which includes batt insulation, attic insulation, or wall insulation ranges between 2.2- to 4.3 per inch.

Fiberglass insulation is manufactured by the spinning of fine glass into layers or small particles. It is cost-effective and can last you up to fifty years. Yeah, we know a long-lasting lifespan at an affordable price! What else does one need?

Moreover, there are different types available based on your different needs, so it makes it further easier to decide which insulation you want to get installed in your space.

The R-value of fiberglass ranges between 2.2-and 4.3 per inch. It is sufficient for insulating your walls and attics.

Here is a table that will quickly answer your questions regarding the R-values per inch of thickness of the different types of fiberglass insulation:

Type of Insulation

R-Value

Batts

3.1 to 3.4 per inch of thickness

Loose-fill (attic)

2.2 to 4.3 per inch of thickness

Loose-fill (wall)

3.7 to 4.3 per inch of thickness

Rigid Fibrous

4 to 5 per inch of thickness

To better your understanding, read on to know about the different types of fiberglass and their R-values.

Batt Insulation

Batt insulation comprises layers of glass strands structured into long rolls. The layers are made up of very fine glass strands. It appears to be a very thick blanket of glass rolls. To install it, you just have to measure the size, and cut off the required size from the sheets.

Batt insulation has a defined form and structure to it. It is available in various depths and fits the wall just like a glove fits your hand.

The R-value of Fiberglass batt insulation is 3.1–3.4 per inch of thickness. It makes up for the perfect choice for wall insulation. You can either hire a professional or turn it into a fun family DIY project.

Loose-Fill Insulation

Contrary to batt insulation, loose-fill insulation lacks a structured form. It is sold in bags. Due to its particle nature, you can install it almost anywhere. Most people install it on their walls and attics. It has a flexible nature in its application and can be installed in diverse spaces.

Loose-fill fiberglass insulation is made of particles that can be hazardous if inhaled, so it is advised to wear proper health gear before installing this insulation. It will be advisable to hire a professional to carry out this installation for large areas. They usually place a mesh fabric on the installation to keep it steady in its place and prevent movement. The R-value for loose-fill fiberglass insulation is between 2.2-and 4.3 per inch of thickness.

Rigid Fibrous or Fiber Insulation

This insulation has been designed especially for certain specific applications. It is used in ducts and other areas exposed to high temperatures. It is used by HVAC contractors in their fieldwork while installing ducts.

The greatest benefit of rigid fibrous or fiber insulation is that it can withstand high temperatures. The R-value for this type is 4-5 per inch of thickness.

What is the R-value of 2-inch fiberglass insulation?

In the case of batt insulation, the R-value of 2 inches thickness is between 6.2-6.8.

For loose-fill insulations for attics, the R-value is between 4.4-and 8.6.

For loose-fill insulation for walls, the R-value is between 7.4-and 8.6. For rigid fibrous insulation, the R-value of 2 inches thickness is between 8-and 10.

What is the R-value of 3 1/2 inch fiberglass insulation?

For batt insulation, the R-value of  3 ½ inches thickness is between 10.9-11.9. For loose-fill insulations for attics, the R-value is between 7.7-15.05.

For loose-fill insulation for walls, the R-value is between 12.95-and 15.05. For rigid fibrous insulation, the R-value of 3 ½  inches thickness is between 14-and 17.5.

What is the R-value of 4-inch fiberglass insulation?

For batt insulation, the R-value of 4 inches thickness is between 12.4-13.6. For loose-fill insulations for attics, the R-value is between 8.8-and 17.2.

 For loose-fill insulation for walls, the R-value is between 14.8-and 17.2. For rigid fibrous insulation, the R-value of 4 inches thickness is between 16-and 20.

What is the R-value of 6-inch fiberglass insulation?

For batt insulation, the R-value of 6 inches thickness is between 18.6-and 20.4. For loose-fill insulations for attics, the R-value is between 13.2-and 25.8.

For loose-fill insulation for walls, the R-value is between 22.2-and 25.8. For rigid fibrous insulation, the R-value of 6 inches thickness is between 24-and 30.

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Does fiberglass insulation lose R-value over time?

Does fiberglass insulation lose R-value over time

The simple answer is no! Even though it does not lose its R-value for a very long period, it has been observed that under certain external conditions, the R-value has been seen to decrease.

But, if the insulation is kept away from extremely low temperatures and moisture, there is no reduction in the R-value of the insulation.

It was observed that when the temperature fell below 20 degrees Fahrenheit, R-19 insulation was as effective as R-9 insulation, that is, the R-value decreased under low temperatures. Also, when the moisture content is increased by 1.5%, the R-value dropped by around fifty percent. So, if the external conditions are not suitable, the R-value has decreased. The installation also plays a major role in maintaining the R-value of the insulation.

 If installed correctly, the fiberglass insulation lasts for a long time and maintains its R-value over time. It has a lifespan of about 50-100 years

R-values of other insulating materials compared to fiberglass

R-values of other insulating materials compared to fiberglass

We all know that spray foam insulation has the highest R-value per inch compared to all other insulating materials available on the market.

Fiberglass insulation does not have the highest R-value, but it has the biggest benefit, and that is, it is cost-efficient. But it has sufficient R-value to insulate your attics and walls on a budget.

If installed correctly it can even last for a very long time.

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The Bottom Line

Even though fiberglass insulation does not possess the highest R-value, it can be effectively used for insulating. It is affordable and provides good enough insulation to your walls and spaces.

Based on your need and the space you are applying to, you can choose between the batt insulation or the loose-fill insulation. Fiberglass batt insulation has an R-value of 3.1–3.4 per inch of thickness. Whereas, loose-fill fiberglass insulation has an R-value of 2.2–4.3. Now that you know the fiberglass insulation R-value, you can start searching for the right type of insulation.

You can try to make it a fun DIY project too when installing batt insulation. But for other types, we will suggest getting help from a professional. And remember, if you are trying it on your own then, do take the necessary precautions.

 These chemicals can be harmful also. Wear your proper heath gear and safety equipment. But we will suggest you better contact a professional to get the insulation installed.