Attic insulation


Old 12-18-01, 01:22 PM
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Attic insulation

I have a 74 year old home with an unheated attic. For insulation, there is about 3 inches of fiberglass on the floor (vapor barrier against the ceiling below) with about 2-3 inches of old rockwool on top of the fiberglass. Over the central part of the attic there is tongue and groove wood flooring (over the current insulation). The boards are not real tight. I want to lay another 6 inches of fiberglass on top of the current insulation. Can I lay the new insulation layer right on top of the wood floor as there is not room under the boards for any additional insulation.
Where there are no boards I just plan to place the insulation on top of the existing insulation.

Anything problems with my approach?


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Old 12-18-01, 01:31 PM
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sounds like a good method to me...use unfaced Insulation and be sure not to block off any soffit vents if they exist..

Good Luck

Old 12-19-01, 09:09 AM
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If you have 6" of bulk insulation, adding another 6" will probably not pay for itself. I doubt if you would see any difference in the summer time. Keep in mind that FG is only about 10% efficient.

You don't say what the vapor barrier material is. If it is paper, then you have no vapor barrier. Vapor barriers are usually not installed in ceilings because of the condensaton factor. A considerable amount of water can pool in the ceiling if there is plastic.

I would recommend a radiant barrier(RB). Sinmce you have enough bulk insulation to take care of your winter needs, it will be the summer heat you want to control. The RB will reflect 97% of the summer heat energy. It will also help a little with winter.

If you would like to know how to get the best results for your time a money, let me know.

Thank you for considering my opinion.
Old 12-19-01, 03:01 PM
Join Date: Dec 1999
Location: South Dakota
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Yes, what you want to do is fine. Lay down bats of un sides insulation. Use R 19 or better. The piece you call an vapor barrier is not really a vapor barrier. It is what is called a heat barrier. It keeps the warm air from below from escaping upwards.
These are very seldom used anymore. Good Luck
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