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Upgrading Building Enveloping Performance By Putting R Value In Its Place

Dennis Roberts's picture
President Energy Efficiency Done Right

About the author: Dennis G. Roberts President of Energy Efficiency Done Right Consultant to Gerson Lehrman Group and TGR Research for Energy Efficiency and Windows Past contributing author...

  • Member since 2005
  • 48 items added with 22,414 views
  • Jan 6, 2023
  • 338 views
For new construction and building retrofits, science and logic have convinced me that we can do a much better job of improving comfort and reducing energy use and carbon emission by putting much less emphasis on the R value and more on reducing heat gain, heat loss, and infiltration. If we have an exsiting building with comfort and performance issues, it is difficult and expensive to improves the R value of the roofing, walls, and glazing but simple and much more efficient to reduce the heat gain, loss, and infiltration significantly. This is easily accomphlished with radiant barrier technology, 
If you have an older underperforming building, how do you improve the glazing R value? The glazing efficiency performance can be quickly and easily greatly improved by adding a see through radiant barrier window insert. This is much easier and more economically than a window replacement! You can improve the SHGC by almost half, reduce inflitration by two-thirds, reduce Uv by up to 90%, and energy use by as much as 30% with radiant barrier technology. You could not approach this performance with a R value enhancement plan. You could not keep the view or equal the improved comfort!
We can obtain similar and sometimes even better results with radiant barrier coating for roofing and walls! Improving the R value on roofing and walls can be very difficult, time consuming and expensive while better comfort, energy savings, and emission reductions can be achieved through coating roofing and walls with radiant barrier technology. 
Insulation is over emphasized and over valued. R value was developed by Fiberglass in the 70’s for thick materials over 1” testing. And – there is only one temperature used to test the measure for the R-value materials – 75F.  Therefore, if you live in a constant 75F with no wind and humidity, then you should use these materials. For R value you want to load all the heat and use thickness to control how long it takes for all this heat to load and transfer.  Why would anyone want this. Blocking heat load is the key to better performance. With radiant barrier coating we can coat to keep most heat out or in. 
Radiant barrier inserts and coatings deal with all methods of heat transfer. These coating work with reflectivity and emissivity to dramaticly reduce heat gain or loss. The solar reflectance is 73%, the visible light reflectance over 84%, and the infrared reflectance is over 67%. This will provide better results for our building owners and our planet than any R value enhancement,
Radiant barrier window treatments and coating have high emissivity.  Emissivity stops most of the heat that is landing on the surface and instead of being absorbed into the surface is rejected back out to the atmosphere. 
R value is NOT the best way to make our building envelopes more efficient. Radiant barrier technology can quickly put our planet on a better path for comfort, efficiency, and much less emissions!
Discussions
John Cockerill's picture
John Cockerill on Jan 6, 2023

The emphasis for renewables can be made far more economical, by employing conservation of energy requirements first, now and for the future.  It needs to be a two pronged approach.  Reduce requirements, convert to non poluting generation.

Jim Stack's picture
Jim Stack on Jan 9, 2023

Dennis.  I think both R value and Thermal barriers are important. Each in their own application. In a very cold place like I used to live in Upstate NY With many sub zero days so a radiant barrier would not help a lot. A high R50 roof and R30 walls makes a big differnce. I now live in Chandler AZ where it can be over 100F day and night for 100 plus days a year. I use a radiant barrier in my attic catherdral area. I use some added insulation and have 6 inch wall. I also use Solar Inflectors on my windows that I can reverse in a minute to reject heat in summer or make heat in winter. They are air tight so it stops convection of temperatures , IE Heat rises ,cold flows down . This lets our entire electric only  home run and produce extra electricity with a 4 kW solar system.  

Dennis Roberts's picture
Thank Dennis for the Post!
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