If you have an idea that there is something called an R Value that relates to insulation, then congratulations! You already know more about insulation and how it works to keep your home energy efficient than almost everyone else.
The R Value refers to how thermally conductive a material is. In very simple terms, if you were to add all the R values of the materials in your home together you would get an R value for the entire building. In this instance, we’re referring to the material the insulation is made of (there is some more complicated maths to get this number accurately, but we don’t need to know it when we’re talking about insulation).
Thermal Conductivity means how easily heat passes through the material in question. The higher an R value, the better a material stops heat passing through it. So, in practical terms of insulation, the higher the R value of your insulation the more insulation it will provide.
One of the great things about modern insulation today is that many manufacturers actually put the R value of their product on the product itself (for example, a roll of loft insulation may have it on the packaging), or if it isn’t on the product, it is already calculated and available to check. This saves you having to worry about doing the maths to work it out on your own.
Something that is worth noting when it comes to R values of materials is that they can change. Depending on the location something is placed, the thickness of the product, its material and its density can all affect the R rating and effectiveness of insulation. Environmental factors like age of the insulation, exposure to moisture and temperature can all affect the R rating.
In some instances, the materials around the material you’re using to insulate can even make a difference, for example a joist or roof beam has a low R value in itself, so would need to be insulated better than the roof or ceiling around it to overcome this. Although, this really only applies when you’re considering the R rating of the home as a whole, rather than thinking about the R rating of a type of insulation in isolation.
Ultimately, the R value of insulation is the way you can tell how effective your insulation is going to be. Adding insulation to your home is only ever going to make your home warmer and more energy efficient, but when you’re getting into the more detailed aspects of assessing which kind of insulation is going to suit your home the best, or have the biggest impact know the R value of your choices is going to be crucial.