Insulation, Radiant and Vapor Barriers - Cellulose insulation
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Sharons
01-12-01, 05:42 AM
I have heard that cellulose blown in insulation does not have to be as thick to achieve the same R value but have also heard that if it gets wet it is ruined and you have to start over. As for fiberglass, I guess the only draw back is that it tends to settle. Am I on the right track? Thanks.
lefty
01-12-01, 07:08 PM
You're asking good questions, but you have gotten some less than perfect answers.
The thickness required by either cellulose or fiberglass to acheive a certain "R" value is virtually the same. Either reqire about 4 inches to acheive an R-13; either require about 12" to acheive an R-38.
If cellulose gets wet, yes, it is ruined and needs to be removed and replaced. The same is true of fiberglass. (Did somebody forget to mention that little detail to you?)
Given enough time, ALL insulation will settle. It also gets filled with dust and eventually has it's "R" value reduced because of it. So you need to replace your insulation every 40 or 50 years. (Or at least add more over the top of it, in the case of an attic.)
The 3 areas where cellulose is better than fiberglass are in noise attenuation, fire retardency, and repelling critters.
The thickness required by either cellulose or fiberglass to acheive a certain "R" value is virtually the same. Either reqire about 4 inches to acheive an R-13; either require about 12" to acheive an R-38.
If cellulose gets wet, yes, it is ruined and needs to be removed and replaced. The same is true of fiberglass. (Did somebody forget to mention that little detail to you?)
Given enough time, ALL insulation will settle. It also gets filled with dust and eventually has it's "R" value reduced because of it. So you need to replace your insulation every 40 or 50 years. (Or at least add more over the top of it, in the case of an attic.)
The 3 areas where cellulose is better than fiberglass are in noise attenuation, fire retardency, and repelling critters.