# Can you install Tech Shield OSB over skip sheathing roofing deck?



## Windows on Wash (Aug 30, 2011)

Radiant barriers need an air gap to work.

Why would you be facing the radiant barrier towards the attic in this case?


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## crayola110 (Aug 23, 2012)

Windows on Wash said:


> Radiant barriers need an air gap to work.
> 
> Why would you be facing the radiant barrier towards the attic in this case?


So what you're saying is that it won't work where theres already skip sheathing? So I assume it will only work on the parts where there's open air like the roofer I talked to said.


It's always installed with reflective facing down towards attic


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## crayola110 (Aug 23, 2012)

Looks like answer to my original question is NO










the shake wood/ skip sheathing won't allow propper ventilation/ air under the radiant barrier.


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## AtticFoil.com (Aug 27, 2013)

Radiant barrier decking actually works off the emissivity quality of foil and not the reflectivity. This is the ability (or lack of) the foil to EMIT stored energy/radiant heat into the attic. To answer your question, you will still get some benefit to installing over skip sheathing. Assuming you have 50% contact with the foil, you will still have 50% benefit. The less surface contact the larger the benefit. A normal open rafter is best, but considering the low additional cost of radiant barrier decking over normal OSB (today it was $1.60/sheet) it is still worth it even if you only get part benefit.

Another option is to staple up AtticFoil Radiant Barrier in the attic. It's actually more effective then radiant barrier decking at reducing overall heat flow.

Here is my page that explains Why Radiant Barrier Requires An Airspace

I hope this helps.

And a video:


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## crayola110 (Aug 23, 2012)

AtticFoil.com said:


> Radiant barrier decking actually works off the emissivity quality of foil and not the reflectivity. This is the ability (or lack of) the foil to EMIT stored energy/radiant heat into the attic. To answer your question, you will still get some benefit to installing over skip sheathing. Assuming you have 50% contact with the foil, you will still have 50% benefit. The less surface contact the larger the benefit. A normal open rafter is best, but considering the low additional cost of radiant barrier decking over normal OSB (today it was $1.60/sheet) it is still worth it even if you only get part benefit.
> 
> Another option is to staple up AtticFoil Radiant Barrier in the attic. It's actually more effective then radiant barrier decking at reducing overall heat flow.
> 
> ...


Hey I get what your saying about benefit for wherever there is air space below... but is there any NEGATIVE to where the reflective part touches the 1x6 skip sheathing?? Someone had told me that it will actually get more hot there and reflect back to the shingle (if that's the right wording) and then make the shingles get extra hot and void the roofing warranty

has anyone heard about that?


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## AtticFoil.com (Aug 27, 2013)

No worries - NO negatives! Where the foil is between the deck and the sheathing, it simply becomes one solid with multiple layers of density/conductivity. Heat can only travel through a solid by conduction. It can't "reflect" or turn around in a solid. Conductive heat ONLY travels one way. From hot TO cold. Depending on the r-value of something dictates whether it travels faster or slower. Wood - pretty fast, aluminum - even faster (this is why we cook with aluminum cookware). 

You will not void your warranty. All shingle manufacturers warranty their products over a radiant barrier (some areas REQUIRE radiant barrier on new construction). Lack of ventilation is usually what could void a warranty.

Frying shingles is a common myth with radiant barriers. The shingle temperatures WILL increase a few degrees either over radiant barrier decking or stapled up the foil in the attic. This is kinda like a reflector behind a light bulb directing the heat/light in one direction. Our tests and common knowledge in the industry is that shingle temperatures will increase less than 10º over a radiant barrier. This is considered nominal considering the shingles are designed to handle temps approaching 200º.

Here is more info on Do Radiant Barriers Damage Shingles?

Does this help?

Ed

And a video on shingle temps:


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## crayola110 (Aug 23, 2012)

Yes thank you. So now my questions is should I remove some of the skip sheathing to allow the radiant barrier to do it's thing? The only thing I'm afraid of is losing some of structural support that the skip sheathing may be helping with?


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## AtticFoil.com (Aug 27, 2013)

crayola110 said:


> I'm afraid of is losing some of structural support that the skip sheathing may be helping with?


On my old home I removed all the sheathing. They do offer some structural support, but remember the new OSB will be nailed/screwed into the rafters too. So, really no different in strength. Be careful though. You can't assume all the rafters are 24" OC. It's a pain to have a sheet of OSB come up 1/2" short from the rafter (I learned the hard way). One good option I've seen is removing half of them. You can still easily overlay the decking and you will get good benefit from the radiant barrier decking.


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## crayola110 (Aug 23, 2012)

That is excellent advice I will remove every other one but then I guess I'll have to use some shimming over the rafter?


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