The RCC Classroom (Radiant Control Coatings)

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The RCC Classroom (Radiant Control Coatings)

A group where energy professionals can learn about all the different energy saving aspects of RCCs.  I have worked with one particular RCC for 30 years.  I have amassed alot of information I can share.  Everyone knows, accepts and understands how RCCs work as a 'Cool Roof' coating.  However, that seems to be where the knowledge on these products different energy saving applications abruptly stops.  I hope to change that with this group. 

There are over 300 protective coatings out there and they all say they save energy. Out of nearly 4,000 members of this forum, only one has stepped up and said he works with an RCC as well.  I hope others will add their experiences with these coatings as well.

Please understand that I do not place myself above or think I am smarter than ANYONE with what I know.  I am an authority on the coating I have worked with and I am willing to share that experience. 

How this coating performs, my website and archive

 

Members: 16
Latest Activity: Nov 28

 

 

Discussion Forum

Rooftop A/C units and exposed ductwork 12 Replies

Started by Hal Skinner. Last reply by Hal Skinner Sep 22.

What this RCC will do on an exterior wall compared to standard paint. 11 Replies

Started by Hal Skinner. Last reply by Hal Skinner Oct 16.

The 'Touchy - Feely' sales pitch. 4 Replies

Started by Hal Skinner. Last reply by Hal Skinner Aug 25.

How our ceramic based RCC works 3 Replies

Started by Hal Skinner. Last reply by Hal Skinner Oct 9.

Combining energy efficiency with fire safety 2 Replies

Started by Hal Skinner. Last reply by Hal Skinner Aug 12.

ENERGY SAVING USES OF RCC'S IN / ON /UNDER and near MOBILE HOMES 2 Replies

Started by Hal Skinner. Last reply by Hal Skinner Nov 19.

Perm rating

Started by Hal Skinner Nov 21.

Our RCC and retaining heat

Started by Hal Skinner Nov 11.

Florida Solar Energy Center certification.

Started by Hal Skinner Nov 1.

Our RCC's performance in Yuma, AZ

Started by Hal Skinner Oct 25.

Improved acoustics

Started by Hal Skinner Sep 21.

Walmart goes green in Texas

Started by Hal Skinner Sep 17.

The ice cream freezer and Grandma's house

Started by Hal Skinner Sep 10.

RCC, videos , tests and resulting ENERGY CALCS

Started by Hal Skinner Aug 10.

Our RCC to different types of roofs

Started by Hal Skinner Aug 9.

A little clarification

Started by Hal Skinner Aug 8.

Using an RCC to stop interior mold.

Started by Hal Skinner Aug 4.

Comment Wall

Comment

You need to be a member of The RCC Classroom (Radiant Control Coatings) to add comments!

Comment by Craig Bird on September 2, 2014 at 12:32pm

Now back to your question - the best data for radiant barriers is the DOE studies from the ORNL. Just google "Radiant Barrier Fact Sheet". As far as a comparison for a sheet radiant barrier compared to a foil faced rigid board, I refer you to the foam manufacturer. Check if their foil facing has an "Emissivity Rating". Now compare that rating to your sheet product. Most sheet products have around a 0.05 or less. If your rigid foil face has that type of rating, you should see no difference in performance. This assumes of course you do not cover the foil facing with anything like additional insulation - which would negate the savings due to eliminating the all important air gap for a radiant barrier to work.

Sometimes the rigid product is not being used for a thermal advantage, but rather is added strictly to maintain a ventilation pathway. If the coating on the insulation does not have an adequate emissivity rating or it has been covered in insulation negating the air gap, you will not have an effective radiant barrier.

Comment by Craig Bird on September 2, 2014 at 12:20pm

Kurt - Radiant heat transfer does not heat the air. It is the passing heat directly from hot object to cold object. The hot object heats the cold object directly through infrared heat transfer. Think about it -  the heat we get on the earth is from the sun - does the sun heat the air/gases between us and that in turn heats the earth? The same thing happens in the attic 1) Sun heats the roof - roof gets hot  2) The underside if the hot roof deck emits infrared heat, which travels to the next solid object and passes its energy to that body. 3) Once the surfaces in the attic are heated, the air that is in contact with them is heated, which is what increases the air temperature. This is exactly why attic fans do not work to save energy in a house - They reduce the temperature of the air in the attic, but the insulation/attic floor is still hot, and the temperature of the attic floor dictates how much heat goes through the ceiling. The attic air temp can have an effect if there is a leaky air barrier between house and attic, but that creates a whole other problem when you have a 1500 cfm fan pulling air out of your attic (along with all the conditioned air from your house)

Comment by Kurt Shafer on September 2, 2014 at 11:56am

And, Mr. Bird, in my experience the attic floor is not heated by radiation from the roof so much as by the air that is heated by the roof surface. 

Comment by Kurt Shafer on September 2, 2014 at 11:54am

Mr. Byrd, 

I did not accept my IR camera data off hand, I could FEEL the heat. What I am hoping to learn here from you and Hal and others is what data you have on other materials such as the coatings and the rigid foams. 

Comment by Craig Bird on September 2, 2014 at 11:42am

Kurt Schafer - I would be careful measuring temperatures with an IR Camera as a part of a comprehensive analysis/comparison of products that contain a reflective surface. You will not get accurate measurements using an infrared camera when you are shooting such a surface. Often the reflective coating on a rigid foam product is a radiant barrier. It should perform very similarly to a sheet radiant barrier product. A more accurate measurement you may want to perform is checking the temperatures of the attic floor. This is the first surface heated by the radiant heat transfer of the hot roof and will not have the measurement issues created by reflective surfaces. Of course I am sure you realize to get an accurate result, you would need to measure on the same day, same temperature, same roof construction/orientation to be near accurate.(yet still too crude for legitimate building science research)

Comment by Hal Skinner on September 2, 2014 at 11:32am

"you need spectral analysis by wavelength to get directional transmission rates black-body style to be able to compare them.:.

Is this what you are referring to?

Comment by Tom Mallard on September 2, 2014 at 11:11am

To those with coatings as products, my reaction is that you need spectral analysis by wavelength to get directional transmission rates black-body style to be able to compare them.

This info can then be put into radiative thermal modeling to compare them to other materials and to each other and mainly to predict performance more accurately in estimates.

So working backwards with the spectral proportions to actual performance for so long should get a high degree of reliability when correlated and bets then can be reduced to equations.

Comment by Hal Skinner on September 2, 2014 at 10:27am

Hi Kurt.  I am in Modesto.  If you have the grey comp shingled on your roof (Roofing industry calls it white) it will reach 150 degreesF at 1:30pm on a 90 degree day. 

I have 30-years worth of data on the RCC I have worked with.

 

Find the discussions in the ''RCC clasroom' group and you will probably learn quite a bit at what they can do.

Some of the applications available will probably set you back in your chair.  You wouldnt be alone there.

 

The RCC classroom

 

Comment by Kurt Shafer on September 2, 2014 at 10:15am

All, I have been trying out a radiant barrier from atticfoil.com (not my co.) 

I see that you have this group named " radiant control coatings." which appears

to be limited to coatings. Is there another thread on barriers? Anyone out there who knows the real difference in effectiveness?

And, as you know, new homes are being built with a 1/2 inch thick silver coated foam between the rafters and the roofing. As a home inspector I recently had the chance to test that. I have a FLIR IR camera and looked at the temperature of the underside of that 1/2 inch thick material. It was already 90 degrees at 11 AM in Temecula CA. So it appears that it might impede some heat transfer but it does not reduce the surface temperature a bit. 

In contrast, I put up about 500 square feet of atticfoil radiant barrier that is 2 sheets of thin silver plastic like mylar attached to each other every 1/2 inch and perforated every 1/2 inch. I put up 28 inch wide strips stapled to the bottom edge of my rafters. I measured the roof underside at 102 F at 11 AM in July and after installing the foil the underside of it was 85, the temp of the air we were working in. 

Do you have any comparable data?

 

Comment by Hal Skinner on August 1, 2014 at 11:39am

Hi Ryan and welcome aboard.

No doubt we can learn from each other for sure, I am the proverbial student.  I have worked with one coating for 30 years and have been given many invitations to prove our coating works well.

We are one of those "Sonds too good to be true" kind of products.   Had to find ways our sales reps could overcome that big hurdle in their presentations to prospective customers.

 

I was the engineering rep that actually got dirty and had tp pick our coating out from under my fingernails almost every day. .

 

Hopefully we can show some others in this forum something they can use to help convince the homeowners radianr barriers are something they do need.

If the proof is in the pudding, you have to give them pudding.

This could get very interesting.

 

 

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