cross-section of a wall displaying all the components

Whenever you have a conversation about insulation, the term “R-value” comes up frequently because it is essential for understanding the insulation’s effectiveness. 

But what exactly is it, and what value do you need?   

This article will discuss everything you need to know about R-value and how it relates to insulation. We’ll also discuss some of the most common insulation materials, their pros and cons, and their R-values. 

So, let’s dive in!

What is R-Value? 

R-value means how much a material withstands heat conduction and how resistant it is to thermal conductivity. Effective insulation has a higher value and can efficiently keep a room warm. It’s the key metric for insulation because it measures how productive your insulation system is.

Why Is R-Value Important for Insulation? 

R-value, which is short for resistance value, is an essential metric for insulation because it measures its effectiveness. The higher this value is, the better the material is at slowing the airflow and maintaining a comfortable temperature. 

R-value, also known as thermal resistance, measures how effectively insulating material prevents heat conduction or the flow of heat from one area to a colder area. 

Thermal resistance is an essential metric for insulation because the purpose of insulation is to keep cold air out and warm air in during the winter and to do the opposite in the summer. 

As a result, homes with high-quality and effective insulation typically have lower energy bills because you spend less on heating and cooling costs.  

You shouldn’t underestimate the importance of insulation. If your insulation has a suitable R-value for your geographic location, you can save up to 15% on your heating and cooling bills and 11% of your overall energy usage. These results can save you approximately $110 every year. 

Not only will you save money, but you will also reduce your carbon footprint because you won’t have to use as much energy to keep your house at a comfortable temperature. For more information, we recommend reading our article on how much money and energy insulation saves. 

An attic in a home prepared for insulation to be blown in

However, you must ensure that your insulation has a sufficient R-value to get these results. The US Environmental Protection Agency and the Department of Energy have divided the country into eight zones, each with specialized recommended ranges for insulation.

Generally, colder climates require a higher R-value and warmer regions require a lower one. The standard for US homes is R-13 insulation for 3 x 4 walls and R-30 or R-40 for roofs.  

The following table outlines the recommendations for various parts of the house based on geographic regions: 

Region Attic 2×4 Walls 2×6 Walls Floors 
North & NortheastR-49 to R-60R-13 to R-15R-19 to R-21R-25 to R-30
West & Midwest R-38 to R-60 R-13 to R-15R-19 to R-21R-25 to R-30 
South & Southeast R-30 to R-60 R-13 to R-15R-19 to R-21R-19 to R-25

Before selecting an insulation material, we recommend researching your area to determine the suitable rating for you. 

How Is R-Value Determined? 

An insulation’s R-value depends on the following factors: 

  • Thickness 
  • Density
  • Type of material
  • How it handles moisture

You can calculate the figure mathematically if you know the following figures: 

  • The temperature difference between the inside and outside of the house in Fahrenheit
  • The area of the wall, floor, or roof simulated in square feet.
  • How long the measurement takes place in seconds
  • How much heat is lost in British thermal units

Once you know these values, you multiply the temperature difference by the area and the time, then divide by the heat loss. The result of this calculation gives you the R-value per inch. Then you can increase the overall R-value of the insulation by adding additional layers.  

What Insulation Has the Best R-Value? 

The kind of insulation material and the quantity used affect the R-value. Therefore, you must get the best insulation with the correct R-value to save money and energy and ensure your home is comfortable year-round.  

The most widely-used materials for insulation include fiberglass, mineral wool, and cellulose. However, these are not necessarily the materials with the highest R-values. 

A picture of un-faced pink fiberglass insulation batts in the wall, with a man installing it

The highest R-value insulations are: 

  • Vacuum insulated panels
  • Polyurethane rigid panels
  • Polyisocyanurate rigid panels
  • Formaldehyde panels
  • Molded polystyrene foam

For more about insulation with high R-values, we suggest reading our article on the highest R-value insulation per inch

Common Insulation Materials and Their R-Value 

Your insulation is most likely made of one of the following materials: 

  • Polyurethane foam 
  • Mineral wool 
  • Cellulose
  • Fiberglass
  • Polystyrene
A pair of cupped hands holding cellulose of the type that is high r-value and often used to insulate interior walls.
Cellulose is an eco-friendly material that can be used to insulate interior walls.

The following table outlines the pros and cons of using each of these materials, including their R-values: 

Material R-Value (Per inch of thickness) Pros Cons 
Polyurethane Foam R-6.3The foam is ideal for harsh environments because of its high R-value and heat and cold-insulating properties. 
It is lightweight. 
It is a durable, stable material. 
Polyurethane foam is more expensive than alternatives. 
Some foams are flammable. 
Some foams have poor weatherability. 
Some of the foams utilize toxic isocyanates. 
Mineral Wool R-3.1Mineral wool is naturally moisture-resistant. 
It blocks sound more effectively. 
Mineral wool performs as a fire barrier and slows down house fires. 
Mineral wool installation can be difficult and expensive. 
Some types of mineral wool can cause lung disease when inhaled. 
Cellulose R-3.7Cellulose is an eco-friendly insulation material. 
It is heat-resistant. 
The high R-value is ideal for homes in harsh climates. 
It is treated with fire-retardant substances, making it less dangerous during a fire. 
It is relatively affordable, especially considering its high R-value. 
It is resistant to mold and mildew. 
Installation is complex and can cause a lot of dust. 
The material requires a vapor barrier. 
Some cellulose insulation sags and settles, so it isn’t as long-lasting as some alternatives. 
Fiberglass R-3.1Fiberglass is one of the most affordable insulation materials available. 
Most fiberglass insulation can last around fifty years. 
Fiberglass is made of recycled glass, which is eco-friendly. 
It is fire-resistant, which makes it safer in the event of a fire.  
Installation is difficult and potentially dangerous because it can irritate the skin upon contact. 
Inhalation can cause lung disease. 
Fiberglass sags and settles over time, so the R-value decreases and loses effectiveness. 
Polystyrene R-4It is extremely lightweight. 
The material is resistant to fungal infections and does not decay. 
Polystyrene has a relatively high R-value, so it is better for homes in harsh climates. 
Polystyrene doesn’t provide as much sound insulation as other materials. 
The material is not environmentally friendly. 
Some types of polystyrene can be pretty expensive. 
It will start to suffer relatively quickly if exposed to direct sunlight. 

The suitable insulation material for you depends on your living and budget. However, keep in mind that it is more cost-effective to invest in high-quality insulation, as you’ll save money on heating and cooling. 

If you would like more information about fiberglass, we have an article on the pros and cons of using it for your insulation material. We also have a similar discussion of the pros and cons of cellulose insulation.    

Final Thoughts 

R-value, or resistance value, is a critical metric for insulation because it measures how effective a material is in keeping the heat in or out of a home. 

Since this is the primary purpose of insulation, the R-value is helpful when determining what kind of insulation to use to save as much money as possible and maintain a comfortable temperature in the home. 

The most common insulation materials have different R-values and various other pros and cons. We hope this article helped you determine which is the best fit for your home!


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