Attic: Reflective Barrier

I'm gonna do a cape cod w/ a snap lock panel. We are gonna re-sheet, insulate the attic and also add a reflective barrier.

Not quite sure of my strategy ( under rafters at this point).

Also what about this product (5/8" ) https://products.royomartin.com/products/eclipsetm-radiant-barrier-roof-sheathing

https://products.royomartin.com/sites/default/files/productdocs/eclipse_radiant_barrier_roof_sheathing.pdf

and forget the inside radiant barrier or figure in both?

New territory for the Olde Twillster.....

twill59 Said: What I dont understand, reading the Lit, they want the reflective portion facing down

In my opinion, if the house is air conditioned, it would be a crime not to use radiant barrier decking on a redeck. I have not used regular OSB in 15 years. I use 7/16" solar board or LP Techshield. It is only about $3 a sheet more. I have had only positive results. That 5/8 sounds even better. And yes, the aluminum side must face an air space- minimum 3/4". The reason is physics. Heat is transferred in one of 3 ways: conduction, convection, and radiation. Therefore, there can be no such thing as a radiant barrier under the shingle and on top of the deck. If the shingle touches the aluminum, conduction is the result. If you installed the radiant barrier on top of the deck, you would have to install a batten system.

The biggest problem I have seen in N.Texas is the jack-legs slapping down radiant barrier right on top of the 1x4 lathes. Those lathes must be removed to get the best performance from the radiant barrier.

There's an issue w/ Capes here woody. hard to cool down the upstairs

What I don't understand, reading the Lit, they want the reflective portion facing down

I'm not sure there is any need to for it in Northern climates. Value-wise it wouldn't make sense if that's all you were doing. But if you've got everything torn off to you're just rolling the stuff on, it might eventually payback.

Interesting is the rolls specify that it be draped so it sags an inch between rafters. Whatever advantage that gets you (allowing reflected heat to vent) wouldn't be there if it is bonded to the sheathing.

Lefty Said:The radiant barrier laminated to the plywood looks interesting. Have you gotten a price on it?

On cape cods, I am starting to put it in slanted part of the ceiling and the face of the kneewalls.

I think 5/8" OSb was about $16 / sheet Lefty.....not terribly expensive at all. Has to be ordered tho. All they had in stock is 1/2".

Putting radiant barrier underneath shingles? I thought that radiant barrier has to have an air gap on one side to be useful.

Twill 59, you can put the radiant barrier under the shingles.

The radiant barrier laminated to the plywood looks interesting. Have you gotten a price on it?

On cape cods, I am starting to put it in slanted part of the ceiling and the face of the kneewalls.