R-Values might sound a bit like something a pirate would say, but in fact, they're an important characteristic of all forms of insulation. To the uninitiated, they can seem a bit confusing at first, but with a little bit of explanation, you'll see that even a captain's parrot can understand this fairly simple measure of a material's ability to resist heat flow. More importantly, you'll be able to calmly make the correct insulation decisions for your next project without feeling like someone just asked you to walk the plank.
Insulation is one of the most important parts of your home's envelope, the imaginary barrier that separates the interior environment from the outdoors. Without insulation, your home would lose more heat than a leaky pirate ship. Of course, heat (mostly) doesn't work like leaking water. Instead, heat moves between your home's interior and exterior by transferring through materials. This type of heat transfer is known as conduction, and it's the primary type of transfer that insulation is designed to protect against. Convection hews a bit closer to the ship analogy; convective heat transfer occurs as warm or cold air circulates around a house or enters from the outside.
There's also a third type of heat transfer: radiation. When you're standing on the deck of your pirate ship on a warm, sunny day, the heat that you're feeling on your face is radiative heat transfer from the sun. The typical type of insulation installed in walls or ceilings isn't designed to block radiative heat transfer, although various types of reflective insulation exist for this purpose.
What's Up With Arrrrr — Ahem, R-Values?
Remember conductive heat transfer? Your insulation's R-Value is simply telling you how effective that particular insulating material is at resisting conductive heat transfer. Most in-wall insulation also helps with convective air transfer, but the R-Value doesn't tell you much about its ability to block heat in this way. Instead, it works by simply filling the spaces between walls or in ceilings and preventing drafts. By stopping air from circulating into or out of the house, convective heat transfer is significantly reduced.
On the other hand, blocking conductive heat transfer is largely a function of the type of insulating material and its overall thickness. A higher R-Value tells you that the insulation blocks more heat transfer than a material with a lower R-Value. Choosing the right value depends on where the insulation will be installed in your home and where your home is located.
If you are replacing insulation, installing installation in a new addition to your house, or adding insulation to an existing home, you should consult with a local insulation company to determine the exact amount and type of insulation that will be cost-effective for your needs. A good insulation company will make sure that you aren't shivering in your timbers once winter rolls around!