Enclosing space in an attic: radiant barrier


  #1  
Old 12-13-18, 01:21 PM
L
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Enclosing space in an attic: radiant barrier

I want to claim an 8-foot by 7-foot walk-in closet space in my unheated/uncooled attic.
Near freezing in winter and 125 degrees in summer is not uncommon in this Georgia home's huge unfinished second-floor bonus space.
I've solved all the framing and finishing problems, but I would like some advice on the topic of insulating the enclosed area. I've put R 38 in all of the ceiling areas except for a couple of duct locations. I used Kraft-faced, R 19 bats and then overlaid it with a second layer of the same bats but with the Karft facing removed. The walls are 2X6 and I used more R 19 bats with the Kraft on the inside of the new room. Now, to augment the R factor AND to get a radiant barrier against the summer heat, I want to cover the other side of the walls with foil-faced, closed cell foam sheets. I would put the foil side toward the raw attic space... the HOT space.
I plan to run an HVAC duct to the 56 square foot space and to relieve the overpressure with a jumper vent back to the main living space.
Given this generous approach to the insulation and the introduction of moving HVAC to the enclosure, do I still have to worry about moisture/condensation/mold in those walls that are Kraft paper on the inside and foiled-foam on the outside? Please consider BOTH very hot and very cold conditions for different times of year.
I won't buy the foiled foam until after I've heard your advice.
Thanks to all.
 
  #2  
Old 12-13-18, 01:42 PM
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During winter you would be sending warm moisture laden air into that box with no air barrier to prevent it from seeping through the insulation and reaching the inside surface of that foil faced foam. In a colder climate that would be a problem, yours not so much.

As a good practice you should have a rigid air barrier in the inside like drywall.

Electrical penetrations need to be air sealed as well.

Bud
 
  #3  
Old 12-13-18, 05:30 PM
L
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Thank you, Bud.
I do have every intention of hanging dry wall on the interior walls and priming and painting them... the ceiling, too.
Given your advice, I will give close attention to all seams and wall penetrations, as well.
 
 

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