cdru
Go Colts
Premium,MVM
join:2003-05-14
Fort Wayne, IN
| reply to dj_figgy
Re: Insulation Question
Fiberglass has a R-value of about 3 per inch. If you have 14 inches of blown in insulation plus batting (figure 4"-6" for a truss or 8"-10" for stick built attics) you are looking at a minimum of 18"-20" of insulation which would give you beyond your R-49 rating. I would agree with SparkChaser  that you probably don't need to add insulation.
If your attic is quite hot in the summer, you may be much better off checking into the attic ventilation. Home builders often put only enough venting in to pass code, but then the blown in insulation subsequently covers up the vents or otherwise blocks the airflow. There are multiple different types of vents available from passive to active that can help. It's recommended to have ventilation in a 1:150 ratio, meaning 1 sq ft of vents for every 150 sq ft of attic space (not roof surface). If you go with a powered vent, each cubic foot/minute is sufficient to maintain the 1:150 ratio. You can also use a combination of the two and set the powered vent on a thermostat/humidistat to only kick on for additional help when needed.
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