Attic Insulation Question

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  #1  
Old 01-12-12, 09:02 AM
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Attic Insulation Question

I have a home with an unfinished second floor. Before completing it, I want to insulate better because most of it is not insulated to the proper R value. Since its unfinished, I have access to everything. It has a metal roof. One thing the previous owner and builder did was put R19 insulation between the roof rafters (2x10) AND in the cieling of the second floor. Should I remove the insulation between the roof rafters and add it to the second floor cieling or should I simple leave the insulation in the roof rafters and then insulate MORE on the floor of the attic? There is an 'air gap' between the decking and R19. I have never seen a home built with insulation in the rafters except in specific cases where it is warranted.
 
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Old 01-12-12, 09:14 AM
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Is there any ventilation above the second floor, soffit vents, ridge vents, or gable vents?

You are correct that both is not the way to go, one or the other. Is the second floor a full floor or half walls with a sloping roof? I also assume you are in southern tx, where heat in the summer is a greater concern than cold in the winter. The difference involves the use of a vapor barrier, ie on the warm side of the insulation.

Bud
 
  #3  
Old 01-12-12, 12:53 PM
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Yes, there are soffits in the three very large true dormers on that floor.

And a ridge vent the length of the house. The second floor is a full second floor, 8' ceilings. Due to the shape of the house, however, it has a knee wall about 5' high, the sloping roof and then the ceiling. So, above the second floor ceiling, there is a mid sized attic space.

Because of the insulation in the roof rafters, their is airflow from the first floor soffits between the insulation and decking all the way up to the ridge vent.

Is the setup 'bad'? Is there any reason a builder would go to the expense and effort to have insulation in the ceiling AND roof rafters? Its a metal roof, perhaps for noise insulation.

Insulation used is all faced toward conditioned space.
 
  #4  
Old 01-12-12, 04:55 PM
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Your short walls on the second floor are different than this link, but the air gap, if I'm understanding you correctly, is to allow ventilation to flow between the insulation and the roof. Heat that escapes through the ceiling will heat the roof and melt snow causing those miserable ice dams. Also moisture carried by leakage or diffusion needs to be vented out so it will not condense on cold surfaces and cause moisture damage or mold.

Energy Savers: Knee Wall Insulation and Air Sealing

Bud
 
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