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Adding Attic Insulation Over Fiberglass Batts

I recently got a quote from a repair guy doing other work on my house for blown in fiberglass insulation. He will apply over the existing batting. I currently have existing fiberglass batting (old about 6 inches between rafters). The attic area is approx. 1,050.00 square feet. His quote was $500.00 and he said he would use about 8 bags. He said it would provide an r factor of 38. How does this sound to you? 

Thanks for your help, Debbie

Hi Debbie

OK. You have 6" of existing fiberglass batting in the attic. That translates to a R-19 as long as it's not mashed down or compressed. If so than it's lost some of the r-value. To achieve an R-38 you would need to add an additional 8" of blown in fiberglass. If I were you I'd opt to add an additional 10" of blown in fiberglass, just to make sure you are getting all of the low areas covered.

As far as how many bags it will require that depends on the manufacturer as bag weights differ and coverages will vary. You can look at the chart on the bag to determine how much coverage you'll get.

Make sure your repair guy knows what he's doing before he gets started. The lower vents should have baffles installed to make sure he doesn't clog them when blowing in the insulation. Also, any light fixtures, fans or chimneys need to be isolated from the insulation. If not it could be a potential fire hazard.

Having a "repair guy" insulate your attic kind of bothers me. If I were you I would get a couple of estimates from actual insulation contractors. Some will add baffles and isolate electrical heat sources as part of the package.

Or, you could do it yourself. You can read my instructions for blowing in insulation into an attic for more details. It's an easy project that could be done in a day. 

Hope this helps and good luck with your project. 

Related Tips and Advice:

How To Measure For Attic Insulation

How To Install Baffles

How To Install Fiberglass Batts In An Attic

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