R-Value

What is R Value, Insulation R Value, R Value of Insulation?

R-Value is a measurement of the resistance of heat flow (heat transfer) through a given thickness of a material.  A higher number indicates better insulating properties.  So basically r-value describes how long it takes for heat to pass through or be absorbed by a material or product.  Keep in mind that this only accounts for Conductive Heat Transfer, which is heat transferred by direct contact. Conductive heat can only be transferred through a solid object.

Examples:

    1” of wood has an r-value of 1, so that would be shown as R-1.

    1” of fiberglass insulation has an r-value of 3.9, displayed as R-3.9.

    1” of standard polystyrene (Styrofoam) board is R-3.5. (Commonly used to make coolers and coffee cups.)

So, what is the R-Value of Radiant Barrier Foil?

Radiant Barrier Foil by itself has no r-value. What? Then how does it work?  It works by reflecting radiant heat away from an object so that the object does not absorb heat.  Let’s look at some instances where r-value is not necessarily the only thing to consider when determining heat transfer.  On a hot day, if you set a Styrofoam cooler of ice directly in the sun and a Styrofoam cooler of ice in the shade, which one will melt faster?  Obviously the one setting directly in the sun will melt faster, but why?  The ambient temperature is the same whether you’re standing in the sun or under the shade tree so why would one melt faster? The reason is because of radiant heat, which is a form of invisible heat that travels through air waves. Even though the temperature of the air outside is the same, the bag of ice that is shaded from the radiant heat waves will melt slower because it is protected from the sun’s radiant heat energy.  The shade is acting as a Radiant Barrier!

Another example would be walking barefoot on a concrete sidewalk during a hot summer day.  The concrete that is un-shaded will burn your feet but if you walk under a shade tree the concrete is much cooler. This is because the concrete that is un-shaded has absorbed a lot of radiant heat from the sun, whereas the shaded concrete was protected from it.  Radiant Barrier Foil not only creates a shade but it reflects radiant heat waves away from its surface.

So, how does a Radiant Barrier work in an attic?

The idea of installing radiant barrier in an attic is to keep radiant heat waves from being absorbed by your homes interior building materials such as wood framing, drywall and fiberglass insulation.  This will reduce the heat load in the attic.  In the summer, the building materials that make up the roof of your house will absorb a large amount of heat from the sun throughout the day.  This heat will be re-transmitted by the roof materials long after the sun goes down and heat naturally moves toward cold.  Therefore, if you are cooling your living space below your roof/attic, and your attic temperature is much hotter than your living space temperature, the hot air is always fighting to overtake the cool air below in your living space. That means your air conditioning unit must work harder to keep your living space at a desired temperature.  When you properly install a radiant barrier in an attic, it will keep the overall temperature of your attic much lower, allowing your living space to be cooled more efficiently.

Radiant heat accounts for up to 93% of all heat that builds up in your attic in summer months.  Learn how EcoFoil Radiant Barrier can block that heat and save you money on energy bills 

Why does Bubble Insulation R-Value vary per application?

Single Bubble and Double Bubble Insulation is fairly thin in comparison to mass insulation such as fiberglass or Styrofoam. Therefore the product R-Value is typically lower than these other mass insulation.  But there is more to the story than just product r-value when considering how well a product will insulate.  If you are comparing reflective insulation and r-values you will often notice that companies will speak of an “assembly r-value”.  This refers to an achievable r-value that insulation is capable of providing if you take into consideration other elements of the installation such as dead or trapped air space.  Dead air space is trapped air that has been sealed in a cavity and does not circulate. Therefore, each inch of dead air space accounts for an approximate R-1.

Example: Let’s use a stud wall cavity as an example. Assume a typical stud wall cavity is 3-1/2” deep and you install 3-1/2” of fiberglass insulation. Let’s assume the fiberglass insulation has an r-value of 11 (R-11). The insulation will determine the r-value of the assembly because you are filling the airspace with it, so the “assembled r-value” is still R-11.  Now let’s use Bubble Insulation to cover a stud wall cavity and the bubble insulation has an r-value of 3 (R-3).  Since we have sealed the wall cavity off creating 3-1/2” of dead air space, the “assembled r-value” will be R-3 (bubble r-value) + 3. 5 (r-Value of 3.5" of dead air space). 

  • Double Bubble R-Value = R-3
  • 3.5" Dead Airspace = R-3.5
  • Total Assembly = (3 + 3.5) R-6.5

Choose from our selection of EcoFoil Bubble Insulation here!

So the total assembly R-Value = R-6.5 as long as the insulation is properly taped and sealed. Now keep in mind that foil insulation will also create a radiant heat barrier to reflect those heat waves back towards their source, fiberglass insulation will absorb those heat waves. The reflectivity will count for thermal value but it cannot be measured with R-Value. It is measured in reflective rate and Ecofoil reflects up to 96% of radiant heat. Click the following link to learn more about: How Radiant Barriers Work

Follow the link below to see a PDF chart of common applications and the approximate “assembled r-value” that can be achieved by using bubble insulation or radiant barrier and air space. (Coming Soon)