# Insulation board vs Radiant barrier...or both



## ang1dust (Jul 28, 2012)

So i saw a couple videos and it seems you MUST have the gap between the plywood and rafter. 

My questions to follow - which is better: Reflective insulation or radiant barrier or both?

Would painting the plywood with radiant barrier, reflective insulation and then radiant barrier be the ultimate protection? 

Would the paint + the reflective insulation be just as good if not better than radiant barrier? 

What are your ultimate radiant heat reflection or barrier suggestions for the attic regardless of money?


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## GBrackins (Apr 26, 2012)

adding your location to your profile may aid in getting useful information. Insulation recommendations is based upon your physical location.

is the HVAC equipment/ductwork insulated? do you have a vented attic, if so how is it vented (soffit/ridge vents, power vents, gable end vents?)


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## ang1dust (Jul 28, 2012)

South Texas, Houston. Soffets.. Basic vents, passive spinny thingys (  ) but no edge vents (yet). I dont care about my current AC setup i have done all the research and i am at max for my ducts / hvac / condenser just trying to give it a helping hand by lowering attic temp.


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## Windows on Wash (Aug 30, 2011)

Radiant barrier application works well in Texas.

You do need an air gap and be sure to have the ridge open so that the attic can still vent.


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## ang1dust (Jul 28, 2012)

I am really wanting to know if there is a MAJOR difference between reflective insulation (Like RMax Polyion) and radiant barrier. It is more expensive i know. I dont care. I am just wanting to know the major differences. I see tons of Hot boxes of people demonstrating radiant barrier and they are fantastic. But i dont see anyone demonstrating reflective insulation such as what RMax offers .


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## Gary in WA (Mar 11, 2009)

Depends on the application. I'm not really interested in radiant, but here are some library links; http://www.ecobuildingpulse.com/articles/energy-efficient-construction/reflections.aspx

http://www.radiantbarrierguru.com/e...ey-compare-to-atticfoil-radiant-barrier-foil/

http://www.rfoil.com/pdf/8-Effect-of-attic-ventilation-on-performance.pdf

http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1231-01/index.htm

http://www.fsec.ucf.edu/en/publications/html/FSEC-EN-15/index.htm

Some good test results there, hope they help you.

Gary


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## Windows on Wash (Aug 30, 2011)

Don't get sucked into the bubble foils and other things that are supposed improvements on the standard radiant barrier.

Once the barrier is a radiant barrier, it is doing all of its job at that point.

You aren't moving your insulation layer to the rafters, just trying to divert some of the radiant heat gain from the sun out of the attic and very quickly to the ridge/roof vents.

Whatever you can most cost effectively install and source is your best option.


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## AtticFoil.com (Aug 27, 2013)

Windows on Wash said:


> You aren't moving your insulation layer to the rafters, just trying to divert some of the radiant heat gain from the sun out of the attic and very quickly to the ridge/roof vents.


This is exactly true. With attics they are ventilated or sealed and it really depends if you want to or intend to move your thermal envelope to the bottom of the roofline. Adding r-value like foam board products will really only help if you completely seal the attic and make an airtight insulated box. Otherwise, you just want to reflect the heat coming off the roof and keep the surface temperatures of the insulation (and everything else inside the attic) cooler.


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