When is the last time you poked your head up in the attic? Maybe you were retrieving holiday decorations, or storing your summer clothes up there? Chances are if you are like most homeowners, we tend not to think about attic insulation until we notice a problem. Now is a good time of year to take a peek up there and make sure your insulation is in good shape.
Why insulate?
The insulation in your attic is like a thick hat on your head while you are out in the snow – it can make all the difference between being freezing cold or sufficiently warm. Heat rises and in doing so, it can escape your home, requiring you to turn the furnace up. This effect is generally well-understood here in Colorado and isn’t typically a concern with newer construction. Older homes however may have substandard insulation which can lead increased energy costs and strain on the HVAC system.
In an insulated attic, we typically see several inches of fiberglass batt insulation (the pink stuff) or blown-in cellulose (off-white and fluffy) or mineral wool (yellow to grey dense fiber) but do you have enough? In order to make that determination first we need to understand R-Value.
R-Value is the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power.
Hint: If your insulation is only as high as the joists, it's probably insufficent!
Insulation requirements in Colorado?
Fortunately for us, are several organizations which provide guidance as to the right amount of attic insulation. We prefer to go right to the top with the U.S. Department of Energy (DOE) and the International Energy Conservation Code (IECC), which designates Colorado as a complicated mix of Zone 5, Zone 6 and Zone 7 which varies by County. This is simplified somewhat, as all three zones have the same recommendation for an attic space: R49-R60.
R-value per inch varies between insulation types as well as from manufacturer to manufacturer, but the general guideline from the DOE for the common types of residential insulation is as follows:
Insulation Type: R-Value per Inch:
Fiberglass (loose) 2.2 – 2.9
Fiberglass (batts) 2.9 – 3.8
Cellulose (loose) 3.1 – 3.8
Stone Wool (loose) 2.2 – 3.3
Stone Wool (batts) 3.3 – 4.2
Cotton (batts) 3.0 – 3.7
What does all this mean? Well, in Denver, working with an average R-value of 3/inch the general rule of thumb is that you should see 14+” of insulation. Many folks we have spoken with seem to think that “14 inches of insulation is Code” which isn’t necessarily the case. As demonstrated above, there are several variables at play here so be sure to ask your inspector for help in determining if the insulation in your attic is sufficient.
Stay warm and enjoy the holiday season!