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Old 08-16-2013, 09:40 PM   #1
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Insulation board vs Radiant barrier...or both


I have a very badly insulated attic. Its destroying the temperature of my evaporator in the attic and causing the temperature of the air return to be well over 80 degrees.

My dilemma:
I want maximum cooling in the attic. I see the reflective board and radiant barrier.

Reflective board looks like its mounted to the actual plywood in the attic on a new home. How does that compare to Radiant barrier?

I see radiant barrier mounted on all the rafters. Is that because it NEEDS the space to capture the heat and uses the space between the plywood and the barrier to move it out the soffets and edgevents? If not can I just mount it on the plywood?

Lastly what do you guys think about putting Reflective Insulation on the Plywood itself directly mounted and then radiant barrier on the Rafters?

Im just looking for MAXIMUM MAXIMUM attic insulation. Even .1 degree will help me at this point so don't let your responses go unposted!

Lastly which is better? Reflective insulation barrier or radiant barrier?
Do you think both is effective?

PS MY ATTIC IS FFFFkn SMALLLL! WITH the HVAC in the attic crawling around the attic is like crawling in a cave that a human can barely go in. I mean smallllll......So consider the idea that reflective board allows me to put my head closer to the ceiling so I can work on different things and store things....But keep MAXIMUM heat resistance to be the number 1 priority

Thanks in advance

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Last edited by ang1dust; 08-16-2013 at 09:43 PM.
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Old 08-16-2013, 10:37 PM   #2
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Insulation board vs Radiant barrier...or both


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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Old 08-16-2013, 10:48 PM   #3
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Insulation board vs Radiant barrier...or both


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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Old 08-16-2013, 11:06 PM   #4
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Insulation board vs Radiant barrier...or both


South Texas, Houston. Soffets.. Basic vents, passive spinny thingys ( :D ) 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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Old 08-16-2013, 11:52 PM   #5
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Insulation board vs Radiant barrier...or both


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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Old 08-17-2013, 12:00 AM   #6
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Insulation board vs Radiant barrier...or both


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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Old 08-18-2013, 10:32 PM   #7
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Insulation board vs Radiant barrier...or both


Depends on the application. I'm not really interested in radiant, but here are some library links; http://www.ecobuildingpulse.com/arti...flections.aspx

http://www.radiantbarrierguru.com/es...-barrier-foil/

http://www.rfoil.com/pdf/8-Effect-of...erformance.pdf

http://www.fsec.ucf.edu/en/publicati...1-01/index.htm

http://www.fsec.ucf.edu/en/publicati...N-15/index.htm

Some good test results there, hope they help you.

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Old 08-19-2013, 07:06 AM   #8
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Insulation board vs Radiant barrier...or both


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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Old 08-27-2013, 02:29 PM   #9
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Quote:
Originally Posted by Windows on Wash View Post
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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