What is the R-value?

Insulation is the most important part of keeping your house warm and cozy during those cold winter months. It can be found in many places throughout the home, but what exactly does it do? Insulation stops heat from escaping from the walls, flooring, windows, and ceiling. It can also prevent heat from penetrating inside of a building, keeping the interior cool. Insulating materials are measured by their r-value; the higher the insulation value (r-value), the better it will insulate against the elements outside .

But what exactly is the r-value? Well, the r-value is how scientists measure the effectiveness of an insulation material. Insulation is rated according to how well it resists heat passing from one point in space, or media, to another. The better the resistance to this transfer of energy (r-value), the less heat energy will be able to flow through that particular material.

R-value stands for resistance value, and a higher value indicates a more effective insulator. Insulation values are rated on a scale from 0 to over 100. For example, fiberglass insulation has an r-value of about 23 while the foam-lok spray foam insulation used at Evergreen Insulation can achieve and r-value of up to 39, depending on the thickness.

A material’s r-value is determined by its thickness and thermal conductivity, which determines how quickly heat energy can travel from one place to another. Insulation with a higher density will have a higher resistance value than insulation that has gaps or holes. An example would be fiberglass insulation vs. open cell polyurethane. Fiberglass can be porous allowing heat to escape easily. Much of the “blown in” insulation you might in attics is just loose insulation material sitting on the top of the ceiling. On the other hand, spray foam creates a nearly impenetrable barrier, locking in heat energy and ultimately saving you money over time.

You can probably imagine that r-value is measured using a very complicated equation. Since we aren’t accomplished mathematicians, we wont be going over the details of that equation in this article (not to mention it would probably bore you to death). However, we hope that you can glean from this post a basic understanding of what insulation is, what it does, and some of the reasons why!