Most people have an intuitive understanding of R-Value, maybe they’ve seen or heard the term in advertising, and know that it is somehow connected with the energy efficiency of their home. But what does the R-Value measure, what do those numbers in the advertising mean, and why should you care?
WHAT IS R-VALUE?
First, what does the R-Value measure? R-Value measures how well a barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists or slows the conductive flow of heat. I should point out here that heat flow doesn’t care if we are talking about keeping winter-time heat inside or summer heat out. The barrier works equally well in either situation. A closely related term is U-Value, which is simply the inverse of R-Value; that is U-Value = 1 / R-Value. The U-Value is a measure of well a material conducts heat. In the U.S. window efficiency is expressed in terms of U-Value, while the rest of the house is expressed in R-Value; so confusing, right?
WHAT DO THE NUMBERS MEAN?
Second, what do the numbers mean? You may have noticed in your local home improvement store, bags of insulation labeled R-13, R-19, or R-38, etc. Simply put, the higher the number, the better that insulation is at resisting heat flow. For these three insulation values, R-19 offers approximately 46% more resistance to heat flow than the R-13 does. While the R-38 offers double the resistance compared to R-19, and nearly three times more resistance than R-13.
R-Value Preparation For The Winter Season
Finally, why should you care? In the winter, you are paying good money (that you worked hard for) to heat your home to comfortable temperature. Everything else being equal, doubling the insulation in your walls and ceiling will cut your heating bills in half. The same is true in the summer, doubling your insulation will cut your cooling bill in half. I personally know people who spend on average $400 per month heating their homes in winter, I’ll bet they would like to save $200 per month.
In future blogs, I will discuss the various types of insulation and their pros and cons. I’ll also discuss various modern building techniques that can dramatically improve the efficiency of the house compared to traditional building methods. Plus, I’ll cover some the strategies to consider for existing homes that need a make-over.