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Choosing The Right Type Of Insulation For The Attic

Adding more insulation for the attic is a great way to lower your heating and cooling bills for decades to come. One of the easiest and most affordable ways to increase the thermal protection in the attic is to blow in insulation using loose fill. It’s a reasonably easy and affordable project that will last for decades, as long as you choose the right insulation for our climate.

The U.S. Department of Energy recommends that you have at least 8 inches of insulation in the attic to achieve an R-value of 25. Each inch of fiberglass or cellulose insulation provides a little more than three hours of protection from heat gain, which gives you nearly 25 hours of protection from heat gain or loss. While each type has its merits, fiberglass may be the better choice for homes in our area.

  • Cellulose insulation can compress by as much as 20 percent over a few years, which means that you’ll lose some of its insulating value. Air spaces between the insulation narrow, diminishing its effectiveness.
  • Since cellulose is made primarily from recycled paper, it tends to absorb water vapor more readily. Although much of the year is dry in the San Joaquin Valley, the winter rainy season and summer thunderstorms raise the humidity. When insulation gets damp or wet, mold can grow on it, creating a toxic situation in your attic. Fiberglass fill can’t absorb water vapor or excess humidity since the product comes from a mineral, making it a better choice for insulation for the attic.
  • Because our climate is moderate, freezing weather occurs rarely, which means that insects can be an issue year-round. Cellulose is usually treated with borates to deter pests, but over time, the chemical coating can degrade. Fiberglass is inorganic and does not attract insects of any kind.
  • Fiberglass insulation can’t burn, while cellulose will burn at 450 degrees F, which is the surface temperature of a 75-watt light bulb.

If you would like more information about insulation for the attic, contact Donald P. Dick Air Conditioning. We’ve provided superior HVAC services for the Fresno area for more than 40 years.

Our goal is to help educate our customers in the greater Fresno, California area about energy and home comfort issues (specific to HVAC systems).  For more information about attic insulation and other HVAC topics, download our free Home Comfort Resource guide.

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