Radiant barrier questions


Old 01-10-11, 02:09 PM
Thread Starter
Join Date: Jan 2011
Location: USA
Posts: 2
Radiant barrier questions

I have an old 1950's house with a pitched roof made from 2x6 24"OC trusses. I'm converting the attic space to living space, and need to insulate against the Louisiana summer heat. With only a 6" deep cavity to work with between the top cords, what is the most effective way to insulate?

I'm thinking of using a reflective radiant barrier, hung 1.5" below the roof sheathing, over 3" fiberglass batting, followed by sheetrock. Do others have better ideas or previous experience with cathedral ceilings?

How should I address moisture concerns in the attic? I just have a single ventilation fan through the roof at the moment.

Finally, to improve heat distribution, should I insulate between the ceiling rafters, between the first-floor ceiling and second (attic) floor subflooring? Or remove the insulation, to facilitate greater air movement?

Thanks for any suggestions!

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Old 01-10-11, 07:20 PM
Join Date: Mar 2009
Location: WA
Posts: 1,167
The joists need to support 30# per sq.ft. live load for an attic. If they are SPF-S, rated #2- can span 83, if rated #3- span 66. You will want to check that before you get the building permit; Maximum Span Calculator for Joists & Rafters

Attics now require egress stairs and an egress window for living space; Powered by Google Docs

Old 01-10-11, 07:43 PM
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Join Date: Apr 2009
Location: Maryland
Posts: 334
Were you thinking of bringing the sheetrock up to the top of the ceiling or were you going to box out the top to create room for a gable vent? Do you have soffit vents installed already? Are you thinking of installing a ridge vent? If your installing gable vent,both sides should be of 1 square foot of vent for every 144 square feet of attic floor.
Old 01-19-11, 10:49 AM
Join Date: Feb 2008
Location: Lake Wales, FL
Posts: 463
Your home is basically heated by conduction.
The heat of the sun shining on the roof and walls is conducted through the framing into your home.
The best way to deal with this is a new SIPS roof.
SIPS is a system of polystyrene insulation sheet covered on both sides by plywood or oriented strand board.
Using this system, there is no direct connection between the roof covering and the interior of your home.
The SIPS panels are fixed to the frame of your home, carefully leaving no holes or cracks, then the roof is put back on.
This leaves the interior of your home looking exactly as it does now, but a lot cooler.

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