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R-Values and What They Mean (and Don’t Mean) to You

by | Jun 29, 2017

If you’re trying to make a decision about what kind of insulation to install in your home, barn, or other structure, there’s one obvious question on your mind: “How well does it work?” Scientifically, the property you’re looking for is called thermal resistance, and the most common way that we measure that property is with something called an R-value.

Thermal resistance measures how difficult it is for heat to transfer through an object. It’s what keeps the hot air from getting into your house in summer, and escaping it in winter. The R-value is calculated using a complicated formula that involves measuring temperature difference across a given thickness and over a certain timeframe, but essentially what you need to know is this: the higher the R-value of an object, the better it is at blocking heat loss.

Let’s run a quick example. If you want to improve your insulation—but you’re not ready to tear out your walls—your best choice is probably our namesake product, RetroFoam. When injected into the wall cavity, RetroFoam can provide an R-value of up to 16 for 2x4 walls, and up to 23.7 for 2x6 studs. (The wider the wall cavity, the more room for insulation, and therefore the greater potential thermal resistance). If you were doing a new home construction or remodeling, a polyurethane spray foam might manage R-values closer to 25 for 2x4 or 38 for 2x6. By comparison, fiberglass can only manage R-values of up to 11 and 13, respectively.

So, all you have to do is look at the R-value to know how good your insulation is, right? Well, not quite.

See, R-values are measured under strict laboratory conditions, and lots of “real world” situations and problems can influence how well a certain type of insulation will actually perform in your home.

Take fiberglass batting. The manufacturer might say that the R-value is “11,” but that might only be the case if the insulation is new, properly installed, and in perfect weather. But often, fiberglass is installed improperly, or leaves gaps around switches, electrical boxes, and other obstructions that allows heat to escape. At the same time, factors like air infiltration, humidity, and even rodents and pests can degrade the quality of the insulation. In the end, you might get a lot worse than what you thought you were paying for, with the installed fiberglass insulation performing well below the advertised R-value, and only getting worse as the years go on. On the other hand, foam insulation generally reaches and retains its R-value much better, since it does a better job filling in the gaps and blocking air transfer.

It’s also worth noting that heat resistance isn’t the be-all, end-all measure of insulation. Other attributes you might want to consider are how well the insulation blocks sounds, resists flame, or prevents air infiltration. Most of these secondary factors tips the balance even further in foam’s favor.

At RetroFoam, we offer 6 different types of foam insulation, and can help you determine which is going to provide the best performance for your home or structure. We’ll also make sure its installed correctly the first time, so you get the absolute best insulation for the product and price. To schedule your free consultation, give us a call at (269) 751-2000.