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Does fiberglass insulation need a vapor barrier?

Asked by Arthur Briggs on September 09, 2021

Categories: Home and garden Indoor environmental quality


Rating: 4.1/5 (73 votes)

Like other batt-type insulation, fiberglass has a predictable R-value if not compressed but is difficult to fit around obstacles without leaving gaps. In most climates, it needs a vaporbarrier.

What is the best type of insulation to use in my attic? From a performance standpoint, the best type of insulation is spray foam. There are two types; closed-cell and open-cell, aka 2-pound and ½-pound, respectively. They have insulation values of approximately R-6.5 and R-3.6 per inch,respectively.

What happens if you don't use vapor barrier? If water vapor diffuses or infiltrates into the wall cavity and finds the cool surface, moisture problems can occur. Of course, you can have moisure problems here even without the exterior vapor barrier because of what Bill Rose calls the rule of materialwetting.

Is Fiberglass Insulation mold resistant? Fiberglass, a non-biodegradable substance is resistant to mold. With its sharp, ground glass, mold spores puncture before they can attach to it. Mold can grow on the fiberglass insulation backing, which is made of paper and is a mold food source. Fiberglass insulation without backing may be the bestchoice.

How do you properly insulate? Transcript

  1. Get your stud and joist dimensions.
  2. Choose an insulation type.
  3. Cut batt insulation to size.
  4. Make sure insulation fits tight against framing.
  5. Staple tabs (if present) on inside of framing.
  6. Tape any seams or torn kraft-faced insulation.
  7. Don't block air vents with ceiling insulation.