When you install insulation in your attic, you expect your home to become more affordable to heat and cool. However, the effectiveness of your attic insulation depends on its R-value. Here’s a look at exactly what R-value means and the factors that impact its real-world effectiveness.
What Is R-Value?
R-value is an efficiency rating for insulation. It refers to a particular insulation’s ability to resist heat flow. R-values vary based on:
The higher the value, the more insulating ability the product has. To achieve a higher attic insulation R-value, simply add another layer of insulation.
How Much Insulation Does the Attic Need?
Different areas of your home have different R-value recommendations, and homes in different areas of the country have different recommendations based on the climate and cost effectiveness of the insulation.
For homes in the DC area, the attic should achieve an R-value between R-38 and R-60. Most areas of the country have a higher minimum R-value recommendation, but just about everywhere recommends up to R-60.
Nominal R-Value vs. Effective R-Value
The R-value indicated on the packaging tells how much thermal resistance the insulation provides per inch. Of course, this number is merely the nominal R-value. Other factors in the real world impact how well the insulation lives up to its rating.
If the insulation needs to be compressed so it fits into the space, this decreases attic insulation R-value by minimizing air pockets within the product and thus lowering its thermal resistance.
A variety of insulation types—including fiberglass batts, expanded polystyrene (EPS) and extruded polystyrene (XPS)—can be more effective when the temperature drops outside. Oddly, when it’s above 60 degrees, the insulation can performs below its nominal R-value.
Temperature has the opposite effect on one popular type of insulation called polyisocyanurate, often simply called polyiso. This insulation decreases in R-value as it gets colder outside. Solutions for this problem include using more polyiso, covering it with another type of insulation to keep it warmer, or counting on exterior insulation instead of cavity insulation to meet your requirements.
Attic Insulation in the Washington, DC Area
We’ve thrown a lot of information at you and it can seem overwhelming, but when it comes down to it, you won’t be on your own! Professionals can complete your insulation installation so it’s done correctly.
Need insulation services in Washington, DC or the surrounding Maryland areas? Accurate Insulation can help. If you’re looking to boost your attic insulation R-value, contact us today!