I am one of those people involved with ‘a’ radiant barrier product, just one. Over the years I have tested ours vs a few dozen of our competitors.
There are different types of radiant barrier materials out there. Ours is a radiant barrier coating, an ENERGY STAR ‘Cool Roof’ coating. I wish someone in charge of these would create a seperate classification just for the coatings.
I hate it when the coating classification gets lumped in with the aluminum foil types and the others. If you staple up aluminum foil to the attic rafters or floor, how do they prevent convected heat transfer? Aluminum foil is great for protecting the tender skin of a Thanksgiving turkey from getting burnt, but it still turns brown and crispy. Am I wrong??
A reputable radiant barrier coating will form and maintain what the industry refers to as “An intimate bond”. The bonding ability should be questioned and considered just as importance as the coating’s Reflectivity and Emissivity.
Many radiant barrier coatings do NOT maintain an intimate bond, they just sit on top of whatever they are applied to.
Some should not be applied where it gets too cold, some should not be applied where it gets too hot. Why? THEY LOSE THEIR ABILITY TO MAINTAIN ANY BONDING, thus the roofing industry has temperature zones now that one must assume is because of that very reason. Almost none of those coatings can be applied to a vertical surface or ceiling because they fall off!.
I cannot speak of the other coatings out there on this matter, RETAINING HEAT. We have applied our coating to the outside of boilers, steam pipes, incinerators, industrial air pollution control equipment, exhaust piping, etc. and had great results. We have had surface temperature reductions from 75 degrees all the way up to 330 degrees.
As with any other types of products, there are good ones and bad ones. Some coatings are exceptionally good. Some should be considered criminally bad, at least in my opinion. Our industry gets enough black eyes from the lousy coatings out there without being compared to the tin foil types claiming one thing and then performing differently.
It’s just not fair to lump them all together.
I have just posted three videos to youtube, very large files.
I hope you find them useful and informative as to what a 'Good' coating can do.
http://www.youtube.com/watch?v=GGaKytKT8XQ 1988. This URL is the video from our testing at an ice cream plant in Fresno, Cal. Tested on mineral capsheet and galvanized walls. Energy calcs and company statement attached.
http://www.youtube.com/watch?v=v-7Vv6x_bpE 1989. This is the video URL for the Anheuser - Busch Nevada distributorship test. I tested Cerama-Tech on mineral capsheet, metal roof, large roll up metal doors, AC units and several smaller applications. We had the energy calcs performed by SDG&E engineers, also attached.
http://www.youtube.com/watch?v=M1Vq74oMoQY This is the video of some homeowners in Mariposa Calif. They did their own real life test of Cerama-Tech on their own mobile home. It does not look real impressive but the temperature readings are a great demonstration of Cerama-Tech vs standard white paint.
These VHS videos were thought to be lost for almost 20 years.
Someone found one in a box in their storage building and sent it to me. I had them put to digital format. The video quality of the ice cream plant video is not great, it had degraded a little over those years.
We have been producing results of 50%+ reductions in BTU’s and heat transfer for well over 20 years. For more recent results, check our websites.
Just added all 3 of these to our website
Despite the title being a little misleading and some of your questions being legitimate, I would have hoped for a little more civility and less hostility on the threads here. You're last reply is pretty harsh.
An "expert" on only one product is no expert at all, but merely a salesman.
I regretfully came across as somewhat hostile in my first reply to Hal even though I feel my argument is still valid - but we don't have to discredit someone's expertise in order to make a point do we?
From what I've read - Hal has been professional, courteous and a good example so far.....
Sorry, but there's a difference between a discussion among energy professionals and a sales pitch complete with YouTube videos.
You need to take the blinders off, your talking about being a professional rater. I am not a home energy rater, nor have I ever claimed to be one.
The lesson has now ended and the test will begin.
1. If you apply a reflective barrier coating to a residential asphalt shingle roof will it have an effect on thermal shock?
2. If that coating has solar reflectivity of 83% and thermal emissivity of 90%, how much of that heat energy actually enters the structure?
3. If the reflective roof coating has those same numbers, what effect will those specific numbers have on the thermal shock on that same asphalt shingle roof?
Robert, you are a professional energy rater. You deal with energy efficient materials, including reflective roof coatings apparently. Dropping the electric bills is not the only thing that these materials do. They have other money saving effects for the customer. If you are the expert you say you are, you should not have a problem answering those questions. Any time I talk to a home owner, Plant Operations Manager or Engineer all these things that I have mentioned in this thread I must have an answer for including what it is going to do to their electric bill and why.
You deal with energy efficient roof coatings. You surely must know the other positive effects these coatings have on a structure. It is part of your business to know and explain these things to any prospective customer, these other added benefits of the reflective roof coatings.
I will be very interested in hearing your response.
I never claimed to be an energy rater. I've been designing and building cold-climate super-insulated homes for 30 years and have been teaching sustainable design and hygro-thermal engineering for the past half dozen.
If by "themal shock" you mean the differential expansion and consequent internal stresses felt by a material undergoing rapid temperature change, then that's an issue only for fully-adhered roofing materials, not for most roofings.
As for how much heat enters the structure, that depends not just on surface characteristics but on the conductivity and emissivity of the roof membrane, whether the attic is ventilated, how much thermal insulation separates the roof/attic from conditioned space, how well the conditioned space is pneumatically isolated from the attic, and the pressure differential between attic and conditioned space.
In cold climates, with most roofs vented and the code-required R-38 to R-49 insulation in the attic, the surface characteristics of roofing materials makes little difference.
We don't foolishly put HVAC mechanicals in attics, and our energy efficiency depends far more on heat load than cooling load.
So your "test" is not applicable to most homes in America and not at all to homes here in cold country.
But, if you only have a hammer, everything looks like a nail.