Decoding the Impact of R-Values on Green Building and Insulation

Any experienced green builders understands how the R-Value of your insulation is paramount to the efficiency and success of your project. For builders who are new to green concepts, or for those of us who are trying to meaningfully renovate or remodel existing structures to maximize efficiency, “R-Values” are probably a foreign piece of vocabulary. When you’re confronted with a new table of numbers for the first time, you may be daunted, but understanding R-Values and choosing a type of insulation is easier than you might think.

R-Values measure the effectiveness of a material to retain heat, and the higher the R-Value, the greater a material’s ability to retain heat. You can talk about the R-Value of any material, including your roof, windows, or siding, but its usually used to make comparisons between different kinds and styles of insulation. You also might here the phrase “U-Factor” or “U-Value” thrown around, which are commonly used to discuss the resistance of windows to heat transfer; R-Values refer to the flow of heat through an insulator of any material, and the U-Factor measures how much heat escapes past that insulator, and usually refers to glass.

When most people think of insulation, the first thing that comes to mind is the pink, itchy fiberglass blankets they might find in the roof of an old house, commonly known as “glass wool.” Glass wool is from the old guard of insulation—it was filed for patent in 1933, and though there have been some improvements, it hasn’t really changed much since. Glass wool is, as it sounds, created from glass fibers that are spun together into batting, and exposure to it can irritate the eyes, skin, or respiratory system. Glass wool has not only raises these health concerns, but older glass wool insulators often contained asbestos, which is extremely dangerous. Interestingly, despite all the risks associated with glass wool, it has a pretty low R-Value—this artificially-manufactured insulation that will never decompose and possibly endanger your family isn’t even very efficient. It’s usually only used today because of its low cost, but there’s no reason a truly committed green builder should ever elect to use it.

The Department of Energy ranks fiberglass at the very bottom of its list of potential insulation materials. There are dozens of options out there, many of which are natural and/or made from recycled materials. Polyurethane offers the highest insulating ability, and the DOE estimates that homes insulated with polyurethane insulate 50% better than those using traditional insulators. It seems counterintuitive that an artificially-engineered plastic substance could be the answer to so many questions of green building, energy efficiency, and conservation, but polyurethane is the preferred insulator of many “green” builders. Polyurethane is a spray insulation that is the shape of the space into which it is injected. It was originally invented in the 1940s to be applied to airplanes, which are exposed to extreme temperature drops during flight, and was popularized for use in homes in the 1970s. The American Chemistry Council estimates that, according to a study by Franklin Associates, structures that used plastic building and construction materials like polyurethane insulation over traditional materials saved 467.2 trillion Btu’s of energy in a year—that’s the energy equivalent of the annual energy usage of of 4.6 million US households.

Of course, if you’re trying to stay as natural as possible with your construction or remodel, and you don’t live in an area that might be exposed to extreme sub-zero temperatures, cellulose or other organic insulators are excellent alternatives to artificial plastic insulators. Cellulose insulation is made from 82 to 85 percent recycled paper products, primarily newspaper, and yet requires no moisture barrier, and won’t settle or change shape, and offers a R Value much higher than fiberglass. Other natural insulators include cotton (3.4 R-Value per square inch), wool (3.5 R-Value per square inch),  straw (2.4-3.0 R-Value per square inch), and even hemp (3.5 R-Value per square inch), though hemp is very rarely used in the US. These materials have been used in traditional home building for centuries, and though they’re often more expensive or labor-intensive, you can rest assured that they are completely non-toxic and environmentally friendly.

How do you know what R-Value is necessary for your home or structure? Depending on your climate, the answer can be very different, but good insulation will keep in heat and air conditioning, and can also be a powerful force for keeping it out, so don’t assume that living in a hot or arid climate means that a high R-Value will do you no good. A high R-Value will benefit you no matter where you live, but for structures in far-northern climates, it becomes more of a necessity than a luxury. Many companies that offer structural services or products will also offer their own proprietary insulationsthat can help ensure your building to reach any R-Value necessary, and if you’re starting a ground-up building project, look into what your partners offer. If you’re looking to do a remodel or retro-fit your home for efficiency, the location of your new insulation will partially determine what kind you use—for example, a potentially-dangerous material like glass wool is a lot safer in your attic than in your kitchen wall. Choosing your insulation wisely is one of the most important elements of green building, and deserves to be researched.


  • Drew Hendricks is a tech, social media and environmental addict. He's written for many major publishers such as National Geographic and Technorati.

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Drew Hendricks is a tech, social media and environmental addict. He's written for many major publishers such as National Geographic and Technorati.

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