Your Home Insulation: R-Value VariablesNot all insulation is created equally. Insulation R-value can vary based on a number of factors, and is not constant like you may think. Learn more about how R-values can vary in your Phoenix or Scottsdale, Arizona home.

What is an R-value?

The R-value indicates the ability of the insulation to resist the heat trying to travel through it. Generally, higher R-values indicate better thermal performance. Insulation products usually state the R-value on the packaging.  In order to determine the R-value of the product, they are tested using American Society of Test Methods (ASTM) standards. Most R-value testing is performed with temperatures varying 50 degrees between indoor and outdoor temperatures, which is not realistic for every home, though in Arizona, our summers can certainly create those types of conditions!

Insulation R-value variables

So if the product states its R-value on the packaging, how can it vary? One variable your insulation is constantly exposed to is the temperatures indoors and outdoors. Different types of insulation have been found to perform better at certain temperatures. This means your insulation may not always be performing at the level stated on the packaging. At certain temperature levels, it could offer less thermal resistance or increased thermal resistance.

  • Fiberglass batting has been found to perform better when the temperatures outside are colder.
  • The performance of expanded polystyrene (EPS) insulation also improves at colder temperatures.

While these two types of insulation have shown an improvement in performance during colder weather, one type of insulation performs poorly when outdoor temperatures drop. Polyisocyanurate insulation, which is also referred to as polyiso, actually can lose R-value when temperatures drop. Studies have found that polyiso loses up to 25 percent of its insulation R-value when exposed to colder temperatures.

So you see, R-value isn’t really the constant you may think it to be. It appears that the performance of insulation R-values is really dependent on the conditions it is exposed to. Learn more about how to properly insulate your home by calling Wolff Mechanical. Our technicians can explain more about how insulation R-value varies in your Phoenix or Scottsdale home.

Our goal is to help educate our customers in the Phoenix Valley area of Arizona about energy and home comfort issues (specific to HVAC systems). 

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