When you are in the process of either building a new house or renovating your existing home, the insulation material for your home is a very important aspect to discuss with the building contractors. During these discussions, the contractors often mention the insulation’s “R-value.” By now you’ve gathered that the higher the R-value, the better the insulation. But is it as simple as using the insulation with the highest R-value you can afford? It also seems to you that the contractors will use insulation with R19 and/or R21 value. What is the difference?
In principle, there are two main differences between R19 and R21 insulation materials. The first difference is that the R21 insulation material is denser than the R19 material and thus insulates your home better. The second difference is that R19 material is less expensive than R21 insulation, but in the long run, the R21 insulated home will save the homeowner money every month on the utility bill.
The R-value of insulation is a very important aspect to keep in mind. The number indicates the density of the insulation material. But you are right, there is more to it than only using the insulation with the highest R-value you can afford. Aspects like the normal summer and winter temperatures in your area, the size of your home, the type of HVAC system that will be used in the home and the material the walls, floors and roof are made of all play a role. And it is customary to use insulation with R19 and/or R21 values in domestic homes.
In this article, I’ll explain what the R-value is and how it influences your home’s insulation. In the discussion, I’ll indicate the differences and similarities between R19 and R21 insulation materials.
Table of Contents
Why is insulation needed in your home?
You may wonder why your home should be insulated.
Simply put the answer is that insulation is installed in a building, and thus your home as well, to help the HVAC’s air conditioner and/or furnace to keep your home at a comfortable temperature during the summer’s heat and the winter’s cold.
The insulation material resists heat flow in or out of your home.
What is the R-value for insulation?
It can be overwhelming when you sort of simultaneously have to decide on insulation material and the type of HVAC system for your home, while working out the monthly cost of keeping your home’s temperature comfortable. And with all this, you also have to get used to new technical terms you’re not familiar with like the R-value of insulation material.
But I’ll make it easier for you by telling you in simple terms in this article what the R-value is and specifically tells you the difference and similarities between R19 and R20 insulation values.
The R-value for insulation is a recognized measurement to indicate how much resistance against airflow insulation material offers. The higher the R-value, the more resistance is offered by the material. And the more the resistance, the better can the insulating material resist the heat flow.
As the resistance given is directly related to the density of the insulation material, the R-value actually refers to the insulation’s density. R21 insulation has a higher density than R19 and is therefore slightly thinner because of its density. But although the density differs, R19 and R21 can fit into the same wall space.
Differences and similarities between R19 and R21 Insulation material
There are differences and similarities between R19 and R21 insulation materials. For your convenience, I’m providing you with a table listing the main differences and similarities. After that, I will discuss the list and other aspects in more detail.
| Aspect | R19 insulation material | R21 insulation material | Different/Similar |
| Density | Less dense than R21 | Denser than R19 and this offers more insulation. | Different |
| Thickness | 6.5” | 5.5” | Different (although both fit into the same space). |
| Most commonly used walls | Walls of homes framed with 2 x 6-inch lumber | Walls of homes framed with 2 x 6-inch lumber | Similar |
| U.S. Department of Energy recommended | Yes | Yes | Similar |
| Purchase price | Less expensive than R21 material. | More expensive than R19 material. | Different |
| Long-term cost/ Value over time | Utility bills can stay high because electric HVAC devices have to work hard to keep the temperature inside the home comfortable. | Very cost-effective over time because the electric HVAC devices have to work not so often – the R21 insulation keeps the home’s temperature comfortable for longer. | Different |
| Efficiency | Efficient if the HVAC system is sophisticated and very efficient. | To be used when the HVAC system is not very sophisticated – using electric baseboards for instance. | Different |
Both R19 and R21 insulation are used in homes
When you talk to contractors in the building and insulation fields it becomes clear that both R19 and R21 insulation are commonly used to insulate walls of homes framed with 2-by-6-inch lumber. They fit tightly in the wall and prevent air from flowing through gaps in the walls.
Both of them are also recommended by the U.S. Department of Energy to efficiently insulate new homes. In many regions of the United States, R19 insulation is seen as good enough for use in the outer walls of new construction projects.
Why and when to use R21 instead of R19 material
Although R19 and R21 insulation fit into the same space, R21 insulation has a higher density than R19 and is more efficient because it prevents the transfer of heat better than R19.
If the home’s HVAC system is sophisticated and very efficient, R19 insulation can normally be used and the temperature in the house will always be comfortable.
However, if a home is heated by a not-so-efficient HVAC system and uses devices such as electric baseboards, R21 insulation is a better choice. With better insulation, the house retains more heat in the winter months so that the electric heater or furnace can be used less often. During the summer months, the heat is efficiently kept outside the house and the air-conditioning devices don’t have to work non-stop.
So, the homeowner saves every month on the utility bill and can within a few months recoup the investment made when the R21 insulation has been installed. However, for very large construction projects the less expensive R19 should probably be the better option because it can take quite a long time to recoup the difference in insulation costs.
