The Importance of U and R Values and a Heat Efficient Home

Insulation - R Value

Anywhere in your house where one side of a wall is exposed to the outside world is a place where heat can escape your home and dissipate into the external environment. This means that a poorly insulated home will incur higher heating bills during the winter. Similarly, in hot climates, insulation keeps the cool air inside and the heat out. Critical to interior climate control, insulation essentially reduces the amount of effort your climate control (air conditioning or heating) has to expend an order to maintain a certain temperature. Energy efficiency can not only improve bills costs, it also impacts the value of a home in a positive way. But how can you ensure that your home is as efficient as possible? There are measurements for the insulation quality of different materials, measured in U and R values.

R-Values of Insulation

This is a value that corresponds with an insulation's thermal resistance, that is, any material's resistance to conduct heat. This only applies to the convective and radiative heat transfer through the material and does not account for the any of those same properties at that same material's surface.

Every material at a temperature above absolute zero radiates heat. All material absorb a certain amount of heat from conduction (physical contact) and this includes the surrounding atmosphere. Therefore thermal resistance is a value attributed to how well a material blocks heat transfer from its surroundings and into itself. The technical number that is reached has to do with the thickness of the insulation material and the 'K' value, that is the basic heat conductivity of the material. The equation looks like this : R-value = thickness / K-value. That means the thicker the substance, the larger the R value. As well, the smaller the K value (the worse the heat conductivity) then the larger the R value. The bottom line is an insulation product's R value determines its efficiently at blocking heat transfer. The larger the number, the better the heat blocking ability. Since part of the equation is thickness, you can manually increase the R value by layering more insulation into the same space.

U-Values of Insulation

While R-values pertain exclusively to the insulation product, U-Values are values attributed to the system as a whole, that is the heat/cooling system along with the insulation and the area where the two are working in conjunction. Technically, the value measures thermal transmittance. The calculation that determines U values is fairly complex and takes into account most of the properties of the insulation used, the material used for walls, siding, vapour barrier etc. Unlike R values that measure the amount of heat transfer blocked, U values measure the amount of heat transfer that is allowed in a system. This means that a low U value is desirable, where the heat transfer is as low as possible.

You can improve the U value of your home through renovations of doors, windows and even walls. By opting for better materials with low U values, these investments can have dramatic effects on the heat efficiency of a building.

Things to Consider

From the above explanations, any do-it-yourself project should strive for a low U value and you can obtain that by using insulation materials with a high R value. As a rule of thumb, more insulation is better, but there are physical and cost restrictions involved as well there is a case diminishing returns when you reach an outer limit, depending on the climate of your environment. Warmer climates won't need as much insulation as colder climates, as a rule. Still, insulation against losing cooling in your home is valid as well.

When purchasing insulation or replacing exterior doors/windows then consider whether you can access the respective U and R values of the products through their producers. Customers are more aware of the benefits of insulated products so you are more likely to find them when conversing with a producer or even presented on their website. External door Producer Vufold offers the U values of their products collected together on one page and it’s part of FTC law that procedures of insulation must provide fact sheets detailing the R value of their products.

This article was intended to be a short rundown of some of the technical aspects of insulation and renovation with efficiency in mind. When in doubt, always contact a professional, but heat efficiency is an investment that can make your money back relatively quickly in many cases. And you certainly have nothing to lose by learning how it works.


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An Overview of the Different Types of Home Insulation
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