R-value is a term that you may hear a lot in the world of home insulation. As a homeowner, you may be asking what this means, exactly. R-value is an insulating material’s resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value – the higher the R-value, the greater the insulating effectiveness. Many factors go into the R-value of specific insulation, such as temperature, aging, and moisture accumulation.
If you have multiple layers of insulation anywhere in your home, be sure to add each individual layer’s R-value to find a total number. That being said, the more insulation layers you have, the higher the R-value. However, as the installed thickness increases for loose-fill insulation (such as fiberglass), the settled density of the product increases due to compression of the insulation under its own weight. In other words, fiberglass insulation is an exception to the layering benefit because it works best when it is loosely packed into the area it’s insulating. Fiberglass functions by trapping hot or cold air in the actual air pockets within the material. Therefore, packing this material tightly will reduce the R-value by decreasing the space inside the fiberglass to trap that air.
The location of your insulation will have an impact on its resistance to heat flow. You can also think of materials used to build your ceiling or wall as having an R-value in addition to the insulation. The R-value can vary here because of other factors such as joints, studs, and other building materials conducting heat, for example. All of these factors go into the total calculation of R-value in different areas of your home.
Another variation in R-value will depend on your climate zone. Virginia’s climate falls in zone 4. You can use the chart below as a helpful tool when calculating your home’s R-value.
If you don’t feel confident in your knowledge of R-value, be sure to call a trusted insulation company to come evaluate your current situation and help you figure out the next steps!