Radiant Barrier Foil. Any Good?

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  #1  
Old 08-13-04, 08:46 AM
bstruthers
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Radiant Barrier Foil. Any Good?

My attic gets so hot during the summer months in N. VA that the AC can't keep the top floor of the house cool, even if I keep the first floor AC unit at some icy cool temp. The attic has a ridge vent, but I'm looking to do something more to cool it off. Any recommendations on using the radiant barrier attic foil? Don't know if it works, would cause condensation in the winter months, etc. Don't know much of anything about it. Should I just go with turbines or an attic fan? Thanks.

bstruthers
 
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Old 08-13-04, 11:45 AM
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OK, if your attic is more than about 10 degrees hotter than outside temp your ridge vent isn't doing it's job. The most common causes of this are (1) not enough, or any openings at the soffit/ insulation is blocking air from the soffit to the ridge, air can't go out unless air is coming in, (2) ridge vent was attached without a "slot" being cut in the decking at the ridge (don't laugh, I've seen this more than once), (3) your gable vents are open, preventing the air circulating from the soffit to the ridge.

After checking these 3 you may still find that you want the radiant barrier, you guys get enough heat to justify it but with proper ridge and soffit vents you may not need it.

Good luck.

Frank
 
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Old 08-13-04, 11:49 AM
bstruthers
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Will check and let you know. Thanks for your help.
 
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Old 08-13-04, 01:16 PM
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For get the R/B the US gov. said its down hill and after 5 its done for. Get some good power vent fans up there in the attic. You dont say if you have vents in the overhang there at all they are a must.

ED
 
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Old 08-13-04, 01:34 PM
bstruthers
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It's a pretty new house so I do have vents, but I have no idea (yet) if they are plugged up, most likely with insulation if they are.
 
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Old 08-13-04, 02:21 PM
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Check at home depot and lowes. They have a called rafter vent made out of foam that can slide over the insulation next to the roof and let the air up from the vents in the over hang up into the attic. This is put in all new homes now.

ED
 
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Old 08-14-04, 04:46 PM
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Radient Barrier Won't Help

Originally Posted by bstruthers
My attic gets so hot during the summer months in N. VA that the AC can't keep the top floor of the house cool, even if I keep the first floor AC unit at some icy cool temp. The attic has a ridge vent, but I'm looking to do something more to cool it off. Any recommendations on using the radiant barrier attic foil? Don't know if it works, would cause condensation in the winter months, etc. Don't know much of anything about it. Should I just go with turbines or an attic fan? Thanks.

bstruthers
Radient barrier won't help.

You need to increase not only the insulation in your attic to an approved modern level (probably R-30 minimum) but also will need to increase your attic ventilation.

Some type of attic ridge vents have been known to fail or not operate at all (like Cobra Vents).

You also may need to replace your ridge vent and assure properly operating eave vents as well.

Also, utilizing a ridge vent along with a gable or other type vent will rendert the ridge vent useless.
 
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Old 08-23-04, 10:02 AM
jarrejs
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Ed,

In one of your posts you menitoned that "the US gov. said its down hill and after 5 its done for." Could you elaborate on that a little please? Was this concerning dust accumulation or the material breaking down or? I've been doing so research on radiant barriers, specifically retrofitting existing structures, and I haven't ran across anything negative so far. Any information you can share would be appreciated.
 
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Old 08-23-04, 10:18 AM
bstruthers
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Soffit vents are wide open. Plenty of air coming in through there. Ridge vent runs almost the entire length of the roof and is about 3-4 inches wide. Covered by about a half inch of something that looks a bit like a black brillo pad with the shingles on top. For someone who doesn't know much in this area, it all looks pretty well set up, but upstairs AC was working hard the other day just to keep the top floor around 78-79 degrees. Couldn't get it any cooler until evening. Had someone out to look at the AC unit about a month ago, and he said all is well.
 
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Old 08-23-04, 10:29 AM
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Covered by about a half inch of something that looks a bit like a black brillo pad with the shingles on top.
They have been comeing up with that filter like you have there gets stopped up with dust. Like you air filter on the AC.
You say you get air from the overhang so put a power vent fan there on the roof. Is you insulation up to the R 30 or better. do you have all the vent you need up there. You need 1 sq" per 1 sq ft of attic 1/2 in and 1/2 out. Attic vent fan attic sq ft X 0.7=== CFM of fan

Yes the gov said the dust on the R/B kills it in about 5 years.

ED
 
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Old 08-23-04, 01:35 PM
jarrejs
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Ed,
Thanks for answering. So can I assume that if I install it on the bottom (attice side) of the roof decking, or perhaps some other design where dust won't accumulate, the barrier's effectiveness won't be compromised after five or more years?

Bstruthers,
Do you have two separate A/C units? Central, window, or ?
 
  #12  
Old 08-23-04, 07:25 PM
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Lightbulb

Originally Posted by bstruthers
Covered by about a half inch of something that looks a bit like a black brillo pad with the shingles on top.
That "brillo pad" stuff is extremely restrictive and blocks 90% of the airflow. It's just a poor design. In our part of the country (Oklahoma) wind turbines are popular and work well, but we have one of the highest average wind speeds in the country. Electric fan WILL cool the attic but the cost to run them can exceed the savings in A/C costs when compared with a well designed passive solution. Fan motors have an average life of about 5 years, the PSC (capacitor motor) types last much longer than the fans that use shaded pole motors.
 
  #13  
Old 12-04-04, 08:28 AM
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Do you have whole house forced air ? Maybe its just a matter of circulation.

Close off supply vents in your lower levels somewhat, and make sure that upper story vents are open fully. If your upper story return-air vents are only located at floor level - consider tying in ceiling return air vents, and change the lower vents to have dampers.

That way you'll push the heavy cold air to the upstairs supply vents, and siphon off hot air from the ceiling return for cooling.

Here's a link:

http://www.askthebuilder.com/printer...Problems.shtml
 
  #14  
Old 02-01-06, 01:56 PM
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Radiant Barrier is quite effective

I have found radiant barrier to be quite effective. In my own house stapling the RB up to the roof joists reduced my attic temperature by about 25 degrees on a sunny day. I live in Texas and no amount of attic ventilation can keep an attic cool. Powered attic vents can suck conditioned air out of your house.

Dust is not an issue when you staple Radiant Barrier up to the roof joists. Dust doesn't hurt all that much anyway, (15% or so) when you install a double sided Radiant Barrier on top of the ceiling insulation.

The link below will help with more information on installing RB
Installing Radiant Barrier
 
  #15  
Old 03-04-07, 09:47 AM
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Originally Posted by Danwalter View Post
I have found radiant barrier to be quite effective. In my own house stapling the RB up to the roof joists reduced my attic temperature by about 25 degrees on a sunny day. I live in Texas and no amount of attic ventilation can keep an attic cool. Powered attic vents can suck conditioned air out of your house.

Dust is not an issue when you staple Radiant Barrier up to the roof joists. Dust doesn't hurt all that much anyway, (15% or so) when you install a double sided Radiant Barrier on top of the ceiling insulation.

The link below will help with more information on installing RB
Installing Radiant Barrier
Thanks Dan. I bought some RB on Wednesday but I haven't installed it yet. I am going to staple it up to the roof joists. I saw Ed mention several times the RB wouldn't be any good and it had me worried. I bought mine from Innovative Insulation http://www.radiantbarrier.com/ because they are close to me in Arlington. I couldn't get a hold of the guy at http://www.blocktheheat.com/FoilHome.htm and I didn't know about www.energyefficientsolutions.com at the time.
 
  #16  
Old 05-21-07, 08:56 PM
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Radiant Barrier Foil is Very Effective.

Understanding the dynamics of heat gain into a home is pretty simple. First, you must understand that all an air conditioner does is remove or suck out heat from a home. The LESS heat it has to remove the lower the cost. So anything to reduce the heat gain into a home will help. Here are the main areas to focus on. Everybody is trying to find the silver bullet, but it's always a combination of several things.

Glazing - windows are a huge source of heat gain. You can either use film or solar screens.

Kneewalls - If you have them, you must encapsulate them on the attic side with foamboard, bubble foil or similar product. These are called "Hot Walls"

Open Chases - Basically this is air getting between the floors from the attic. usually "blocking" was not done in the construction process. Batt insulation stuffed in the trusses WILL NOT stop air infiltration. Read the EPA/EnergyStar Thermal Bypass Checklist here:

http://www.energystar.gov/ia/partner...ypassGuide.pdf

Duct Sealing - the most neglected area in most homes. Why bother putting more money into other areas if 20-50% of the cold air you ar buying ends up in the attic? SEAL THE DUCTS!!

Attic Ventilation - Good ventilation is critical to reduce heat gain into the ducts by lowering the temperature differential between the attic and the ducts (just stay away from mechanical ventilation methods - Fans etc.) Wind turbines are best, but the most common problem is dirty or clogged soffit vents. I've cleaned the soffit vents on a home and the attic temperature dropped 20 degrees in 15 minutes. Ventilation is TWO PARTS - air IN the bottom and OUT the top. MUST have both.

RADIANT BARRIER (www.AtticFoil.com) - Will make a HUGE difference in the heat gain into the attic only. You must COMBINE radiant barrier foil with good attic ventilation to be fully effective. Finally, HOME SEALING to reduce air infiltration. Start with the can lights, attic door and all sources of potential outside air.
 

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  #17  
Old 03-31-08, 09:11 PM
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I have been reading about Radiant Barriers and have a question. How does this product affect the roof decking and shingles life? do they not get hotter with the RB attached to the rafters?
 
  #18  
Old 03-31-08, 09:26 PM
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Generally roof temperatures will increase between 2-10F. This is from the department of energy website:
http://www.ornl.gov/sci/roofs+walls/radiant/rb_03.html
From personal experience this is generally true. This small increase is well within the temperature range for all shingles and most (if not all) shingle manufacturers warranty the shingles over a radiant barrier. However, most attics are under-ventilated. This will cause more of an increase in shingle temperature than radiant barrier foil. In fact, MOST roofs warranties are technically void for not meeting the ventilation requirements.

Stay Cool!
 
  #19  
Old 05-21-08, 10:52 AM
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vapor barrier or not

I live in dallas, it gets hot. Do i need a vapor barrier or not on a double sided RB. also perforated vs not perforated. ALso is there a tensil strength that I need to be looking for, and last, is the bubble RB worth it.
 
  #20  
Old 05-21-08, 12:24 PM
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having a double bubble will help to increase the chance that the barrier will get to your site with a higher % of the bubbles intact.

Me personally..i think it's worth it.
 
  #21  
Old 05-21-08, 02:32 PM
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OK RB do not work unless it is closed cell spray foam or the RB paint!
 
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Old 05-28-08, 06:10 AM
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Originally Posted by willarrington View Post
I live in dallas, it gets hot. Do i need a vapor barrier or not on a double sided RB. also perforated vs not perforated. ALso is there a tensil strength that I need to be looking for, and last, is the bubble RB worth it.
I am in the Dallas area too. For attic applications you do not need or want a vapor barrier. Go with a perforated product to allow moisture vapor to pass through. Double sided is the way to go.

Many people get wound up about the effect of dust on a radiant barrier. This can be disputed all day, but no one can dispute that dust does not affect the side that faces down. This calls on the emissivity quality of the product (ability NOT to emit radiant heat) So it will always work.

As far as strength, radiant barrier foil comes in basically two weights. 14-16 lbs/1000 square feet and 26-28 lbs/1000 square ft. The heavyweight is only about $10 per 1000 ft. more and is worth it since it will never tear and you can pull it tight without tearing after stapling it to the bottom of your rafters. I don't even mess with the midweight and only sell the heavyweight radiant barrier perforated foil.

Bubble foil for attics is not worth it. All you need is a radiant barrier. Bubble foil is great for hot water heater, walls, and metal buildings. It is really intended to be placed against a hot or cold surface and add r-value. In an attic, you have have air flowing on both sides so r-value means nothing. Here is an example: If you are on the beach you want a big umbrella to stop the radiant heat, right? If I gave you an umbrella 2 inches thick made of styrofoam would it work any better than the regular umbrella? No, because the air temperature is the same on both sides. Bubble foil will work fine, but you are paying extra for the r-value (thickness) when you don't need it.

Stay Cool.
 
  #23  
Old 06-06-08, 09:21 PM
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Originally Posted by airman.1994 View Post
OK RB do not work unless it is closed cell spray foam or the RB paint!
Actually Radiant Barriers are VERY effective, they reduce radiant heat gain by 97% (the sheets that is). Also the RB paints are not as effective as the RB sheets as they only reduce radiant heat gain by 93%.

Im not sure what you mean by closed cell spray foam because it is not a radiant barrier, it is an insulator. Radiant heat is a type of thermal radiation and insulation doesn't stop it, but a reflective low emissivity product will. This is why Radiant Barrier does work very well.

A double sided RB will work to keep heat out in the summer and keep heat in during the winter.

I
 

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  #24  
Old 06-07-08, 04:26 AM
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Here we go again! Sheets of RB do work well! For a year or two until they get a dust coating which will eliminate the reflective properties. You said the paint will do 93% Every thing I've seen is in the 60% range. Closed cell foam works best because radiant heat will not travel threw it.
 
  #25  
Old 06-23-08, 06:52 PM
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Whenever I need a boost to my spirits, I find myself looking at either automotive motor oil forums or radiant barrier forums. Reading each should brighten up anyone's day.

My own $.02 regarding radiant barriers. Live in San Antonio, where we've had 90+ daytime highs since early May. Had the entire attic done in the middle of March - perforated foil stapled to undersides of rafters, including area over garage. Have full length ridge vents with unobstructed soffit vents. 3-ton 17+ year old A/C unit appears to be cycling less often & for shorter periods of time. So far, our RB appears to be doing what was claimed for it to do.

Due to month long vacation out of state last summer, won't be able to compare apples to apples about $$$ saved using RB. Will try to keep track for the entire year to see just what savings if any happen.
 
  #26  
Old 06-30-08, 10:13 PM
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Originally Posted by elgrandekazoo View Post
Whenever I need a boost to my spirits, I find myself looking at either automotive motor oil forums or radiant barrier forums. Reading each should brighten up anyone's day.

My own $.02 regarding radiant barriers. Live in San Antonio, where we've had 90+ daytime highs since early May. Had the entire attic done in the middle of March - perforated foil stapled to undersides of rafters, including area over garage. Have full length ridge vents with unobstructed soffit vents. 3-ton 17+ year old A/C unit appears to be cycling less often & for shorter periods of time. So far, our RB appears to be doing what was claimed for it to do.

Due to month long vacation out of state last summer, won't be able to compare apples to apples about $$$ saved using RB. Will try to keep track for the entire year to see just what savings if any happen.
I live in San Antonio too. We were interested in the spray on stuff from mailers we've gotten, until I started reading that it doesn't work as well. Foil seems the way to go. How much did it cost to have the foil installed in your attic and who did it?
 
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