R14 and R15 are the most popular types of underlay for radiant barriers. They were designed specifically to address all of the issues that come with having poor insulation. R15 is more expensive but if installed properly will keep your home cooler in the summer and warmer in the winter. Here is a quick breakdown of how they work and what you should know before deciding between the two.
Radiant barriers are installed over your exterior walls, ceilings, and floors. The insulating layer is a thick vapor barrier that is affixed to both sides of the wall or floor. It is sandwiched between two edge forms. Typically, r 13 prefabricated radiant barriers are created using aluminum, but other materials such as sheet metal or vinyl may be used.
Radiant heat is emitted from the top of the vapor barrier, while it is blocked by your ceiling or floor materials. That creates an invisible thermal envelope around your home that just needs to be filled in with unfaced or cathedral style R 15 insulation. When the heat in the envelope reaches your windows and doors, they warm up the space even more. This effect is the opposite of what you get with faced or unfaced R-values.
There are many benefits to using a cathedral or unfaced R-values on both your exterior walls and ceiling. The R-values are created by calculating the surface area of your home using the U-values and the reflective properties of the material you are using. The interior of the space is then mapped onto your exterior walls and ceiling. A thin vapor barrier is applied as the surface layer, while the interior is left intact. The R-value is typically much less than you would get with faced or unfaced insulation.
Other benefits include a reduction in moisture absorption and energy costs. A cathedral ceiling has twice the amount of air space between the outer surface and the insulation compared with traditional attic insulation. Also, the cathedral ceiling is not completely enclosed. Attic insulation is completely enclosed and there are several gaps for moisture to move in. These gaps also allow rain, sleet, and snow to slide off the exterior walls of your home.
Keep in mind that the r-value you choose is not determined solely by how reflective it is. If all you want to do is create an intentional design, you can. Cathedral ceilings are commonly referred to as “spaghetti clusters”. If applied correctly, the structure of these clusters can be highly reflective. However, their lack of direction and overall thickness means that they are not highly effective at insulating your home. The r-15 or r-rated fibreglass is a highly reflective material that will greatly increase your R-value.
Unfinished ceiling is generally more expensive to install and if you’re looking to reduce costs even more, an unfinished ceiling should be avoided. The reason for this is because they are typically much colder and have higher R-values than the prefabricated varieties. Prefabricated ceilings come with all the R-value they are advertised with and at a much lower cost than unfinished versions. Also, if you decide to use unfaced insulation you will need to purchase a specially designed sprayer to apply it, which costs extra.
It’s important to note that both R-values are measured in meters. Therefore, when comparing the differences between the two types of exterior wall insulation materials, you should also factor in the cost of installation. Prefabricated versions usually come with an installation manual with easy-to-follow instructions that make the job much easier than using sprayer applications. Cathedral ceilings can be a great choice if your goal is to create a more dramatic effect on the exterior walls of your home, but if your budget is restrictive, you may want to go for the cheaper R-value.