radiant heat barrier?


Old 06-09-05, 02:23 PM
nola mike
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radiant heat barrier?

looking at installing radiant heat barrier in the attic. looks like i have a choice between bubble wrap barrier (in the middle) or plain foil with no core. which do i want? i guess the bubble wrap barrier gives me some extra insulation, which i probably need. anything else to it?
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Old 06-09-05, 02:38 PM
Ed Imeduc's Avatar
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Location: Mountain Williams Missouri
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if you check the gov www they say that the RB is no good . It goes down hill for what it can do from the day you put it in. A good R 38 to R 40 insulation in the attic and good attic vents. Attic vent fan on a stast is the best way to go.

Old 06-10-05, 08:56 AM
nola mike
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actually, i've read differently on the government web pages:

both of these sites were linked from the government energy star site. where is the info that you're talking about?
Old 06-10-05, 10:38 AM
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Location: Mountain Williams Missouri
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I cant seem to find it right now. But what it said is yes you get a return on it at first then it goes down hill and is no good in 5 years.Cause of the dust that gets on it What I have found over the years is. Good insulation and good vents with a power vent fan on a stat work the best. Im down in FL now and Ill stay with my power vent fan for sure. If you want to save put a hot water recovery unit on your AC there and get free hot water.At the same time kick up the seer of the unit with it

Old 06-16-05, 07:22 AM
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Ed opinion seems correct. Direct from the web site you linked to:

The attic floor application is most susceptible to accumulation of dust, while downward facing reflective surfaces used with many roof applications are not likely to become dusty. When radiant barriers are newly installed, some testing shows that the attic floor application will work better than the roof applications. As dust accumulates on the attic floor application, its effectiveness will gradually decrease. After a long enough period of time, a dusty attic floor application will lose much of its effectiveness. Predictive modeling results, based on testing, suggest that a dusty attic floor application will lose about half of its effectiveness after about one to ten years.
Old 06-17-05, 10:13 AM
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RB alternative


I'd like to suggest our radiant barrier coating

Dust is not an issue with it (as with foil), it has the additional benefit of insulating ceramics, and is the only RB coating that is 100% water based and environmentally friendly.

I'll be happy to answer any questions you may have.


Last edited by Ed Imeduc; 06-18-05 at 06:41 AM. Reason: No adds
Old 06-18-05, 03:43 PM
Join Date: Nov 2001
Location: USA
Posts: 1,873
There are three mechanisms for heat loss/gain, namely RADIANT, CONVECTION and CONDUCTION. All 3 have distinct characteristics from each other which means all three influence heat loss/gain at the same time. A product may address a specific mechanism, that same product will have little affect on the other two mechanisms. For example, AIR SEALING addresses CONVECTIVE HEAT TRANSFER, but has little affect on RADIANT or CONDUCTIVE HEAT TRANSFER. RADIANT BARRIERS addresses RADIANT HEAT TRANSFER but has little affect on CONVECTIVE or CONDUCTIVE HEAT TRANSFER. INSULATION addresses CONDUCTIVE HEAT TRANSFER but has little affect on CONVECTIVE or RADIANT HEAT TRANSFER.

While all 3 influence Heat Loss/Gain, one of the 3 will always dominate the other two. For example, the majority of Heat Loss in the winter is through CONDUCTION. There is still RADIANT and CONVECTIVE Heat Loss during the winter, but not nearly as much as CONDUCTION under normal circumstances.

On ther other hand, during the summer the dominant heat transfer mechanism for Heat Gain is RADIANT. However, unlike during the winter where the other two mechanisms do not address heat loss well, in the summer, CONDUCTION is a very close second when addressing Heat Gain.

This makes insulation very effective all year round and regardless of the area in which you live. In fact, CONDUCTIVE HEAT TRANSFER (Insulation) influences Heat Loss/Gain calculations significantly. Whereas Radiant Barriers and/or Air Sealing have an insignificant role in this calculation and usually have a small default value concerning the calculation.

To put this into perspective, the Heat Loss/Gain calculation determines the size of your heating and cooling systems. It is there to replace/extract the amount of BTU's per hour in order to maintain a design temperature. The larger the size of your heating or cooling systems are, the more it costs you to heat or cool your home. Since insulation has a dramatic effect on the calculation, it influences the costs to heat and cool your home.

Let's say your home is not insulated and you had a heating and cooling systems installed. A year later you decided to insulate the house. If a Heat Loss/Gain calculation was done at that time, the heating and cooling systems would be found to be oversized. If you did the same with either Air Sealing or Radiant Barrier, the calculation would show the size of the units to be within tolerable differences.

This does not mean that Air Sealing or Radiant Barriers are useless, what it does mean is that they are most effective when they are used in conjunction with insulation.
Old 06-23-05, 08:41 PM
Join Date: Sep 2004
Location: Canada
Posts: 71
Do your homework

I would suggest you do your homework regarding the RB coatings. Im afraid the following quote is not quite accurate though.

"the only RB coating that is 100% water based"

I believe you will find there are others.
You will also find that dust does affect the performance of some of these products more so than others simply due to the fact that they only carry a single ceramic type.
We have tried an assortment of these products over the past 15 years.

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