I loved reading the article, you totally knocked it out of the ballpark! I have sent a link to my bro, and will definately be back for more.

[...] www.bdcnetwork.com is one useful source on this issue,[...]

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Jeff, thank you for your opinion. However, this article was about DAYLIGHTING and the GREATEST opportunity with Skylights in industrial and commercial buildings includes the use of controls. People, such as Walmart, that utilize daylighting as an energy savings technique use lighting controls to shut their lights off and save substantially!. Otherwise, if you didn't use controls, then the most efficient model for your building would be to take out the skylight and roof it properly as the skylight would be less thermally efficient then the roof it was cut into. The skylights that Walmart utilizes actually have a .75 U with a .51 SHGC which is actually even greater solar heat gain. However, you forgot to mention that they also have a 67.8% VLT with 100% diffusion which is 53% more VLT then the common double glazed acrylic white dome. This means more hours of natural light properly diffused available to shut the lights off in their buildings. That is why Walmart alone has installed them in 2,400 properties world wide for toplighting and save annually around $250,000,000 in energy through their use. The reality is, if you are not using controls with skylights, you aren't daylighting, period. Your right, if you aren't putting lighting controls in the building with skylights, you are actually increasing your cost of energy through loss of heat and increase in solar heat gain. At that point, it doesn't matter what your U-Value is if it is less then the R-Value of the roofing insulation. It will be an energy loss for the building model. However, the single greatest opportunity with daylighting from skylights isn't in it's thermal efficiency, but in it's ability to fully replace artificial electrical lighting for a majority of daylight hours. Lighting is a year round use. Heating, even in northern climates, is at most, a 6 month issue and Natural Gas and Heating Oil is approximately 1/3rd the cost of electricity per BTU. If Walmart was to use the skylights you prescribed above, they would actually reduce the amount of savings they are realizing through the use of their current daylight harvesting system with controls SUBSTANTIALLY. The reason for the skylight is to bring in light properly diffused for the most amount of hours of off. ASHRAE 90.1-2007 recognizes this, the U.S. Department of Energy recognizes this, LEED 2009 follows this prescriptive, and even the State of California Title 24 energy requirements recognizes this. Don't listen to me, check it out for yourself. A claim of 40%-60% VLT with .14-U doesn't match the marketing literature or actual ASTM D- 1003 testing for VLT and Haze of multiple skylight manufacturer's literature using Nanogel and I would have to argue that the misinformation being submitted here needs to be taken with a grain of salt. It is simple, you use lights year round. You also have the heat that light produces. Electricity is more expensive then heating fuels and you even pay a summer demand for electrical energy. If you shut off the lights with the maximum amount of visible light transmission (not the minimum prescribed level of 40%) with 100% diffusion, you will by far be more successful in your energy efficiency measures with skylights. If you aren't using controls with skylights, you should be as it is actually costing you more money and increases your carbon footprint, not decreases as suggested above. There is a reason that the largest daylighting users in the world use high visible light transmission with 100% diffusion daylighting solutions including controls. Otherwise, as an energy professional, if lighting controls didn't exist, I would have to argue that the more efficient building model would be to take out the skylights! Discover the truth for yourself! Do a little research. The true passive solar opportunity with skylights is through daylighting with controls!

There is a significant amount misinformation presented in this article. The reality is that over 95% of the buildings in the United States with skylights do not have lighting controls. For these applications, any of the modeling programs referenced above will tell you that the higher the thermal efficiency, the greater the energy savings and overall building carbon footprint will be. Although the author is correct that HVLT skylights are critical in overall lighting strategy, this DOES NOT mean that you have to use skylight s with poor U values and solar heat gain coefficients. Case in point: the prismatic skylights that are used in the author’s Wal-Mart example have a U value of .82 (1.2R) and a SHGC of .49. This is very poor from a thermal efficiency perspective. There are skylights that would meet the authors HVLT minimums (40%) and haze value in excess of the mentioned 90% that would have u-values 6 Xs the U-values of the Wal-Mart skylights. A Nanogel skylight for instance, will have U-values up to .14 (almost 6 Xs more energy efficient) with VLTs between 40% -60% (this is dependant of the thickness of the Nanogel panel)