Ashrae Journal - November 2008 - 28

Why Green Can Be Wash By Joseph W. Lstiburek, Ph.D., P.Eng., Fellow ASHRAE any “green” buildings don’t save energy (Figure 1). Why? They have too much glass, they are overventilated, they are leaky to air, they are fraught with thermal bridges and they rely on gimmicks and fads rather than physics. Basically, the current green and sustainability craze can be summed up as architects and engineers behaving badly. The good news is that most of this nonsense can be easily remedied. The bad news is that the failures are beginning to bubble to the surface, and we are in danger of ruining the “green brand.”* Before you can have a “green” building, you need a building that can stand up, not be blown away in a hurricane, not fall down in an earthquake, not burn, not leak rainwater, not be moldy, not rot, not corrode and otherwise be able to meet applicable building codes such as having a basic provision for ventilation like that specified by Standard 62.1. So what’s with all these “green” programs providing “points” for “durability” and “indoor air quality?” I mean it’s pretty pathetic if we have to reward architects and engineers when they provide details and specifications that should be basic to fundamental practice. If you design and install a controlled ventilation system that meets Standard 62, you get points. You get more points if you keep the rain out and design the building to dry if it becomes wet. And, you get still more points if the occupants are actually comfortable. Aren’t these code requirements? Shouldn’t these be “the standard of care?” Have we architects and engineers sunk so low that we now get points if we meet basic building requirements that all buildings should meet to be called buildings? Green programs waste a lot of time and money on stuff that is obvious and more time and money on stuff that is irrelevant or unimportant. How about focusing on stuff that is important? It’s become all about the points and the important stuff gets ignored. Chasing “green points” doesn’t get you good buildings that are truly green. You can get a Leadership in Energy and Environmental Design® (LEED) rating and not save any energy compared to traditional buildings. How can that possibly be green? How to Be Green M Editor’s Note: Letter s to the editor a re w elcome fo r this column. Send letters to the editor at fturner@ashrae.org. Letters should not exceed 250 words. No points for this. This is what the minimum requirement for a building should be. Now what’s next? That’s pretty easy. It’s energy. What are two of the greatest challenges facing the U.S.? Global warming and energy security. The key to both is energy conservation. Architect Edward Mazria likes to say “architects control the global thermostat.” I think he is right. Show me a building that meets code and the standard of care and saves energy, and I will show you a green building. A “real” green building, not a social statement that saps money, time and resources from the real problems facing the planet. Do you want to save serious energy and serious money? That’s easy. Use less glass. Windows and curtain walls are the most expensive component in a building and provide the worst energy performance. The more you use, the more energy and money you burn. Limit the glazing area to approximately 30%, and use good glass and frames (Figure 2). Then, don’t overventilate. This idea of getting green points by increasing the rates above those specified by Standard 62 is just madness. Whatever happened to source control? If you don’t use poorly chosen materials in the building, don’t do unwise things in the building and don’t connect the interior to exterior via the parking garage, Standard 62 works very well. Next, build an enclosure without big holes. Build tight, ventilate right. Tight is 2.0 L/s/m2 at 75Pa (0.39 cfm/ft2 at 0.3 in. w.c.).1 Right is Standard 62. How complicated can that be? Except, we don’t do it. Moving on, don’t insulate steel stud cavities, insulate them on the outside. Most of the time all that you will need is R-10 of continuous exterior insulation (that’s between 1.5 in. and 2 in. [40 mm and 50 mm] of rigid insulation). And, don’t use supply or return plenums. Use ducts to avoid air quality problems and to ensure air goes where you want it. How Not to Be Green So let’s start with a basic requirement that we need a building that meets code and the standard of care. That would be a building that is structurally sound, is fire-safe, has a controlled ventilation system, does not leak rainwater and is comfortable. Once we get an enclosure, we can condition it. Note to architects: before you can control air you must first enclose air. The enclosure comes first and is more important than all the systems within it. Mechanical engineers call themselves green and claim to do green design. However, when push comes to shove, few of them want to do the additional work necessary to design a mechanical system matched to a high performance enclosure. Of *“Michael Zatz, manager of the commercial building program for ENERGY STAR®, an EPA program to promote energy-e.cien t products and practices, says ENERGY STAR has a usersupport line that gets calls from green-building owners and managers who are disappointed in their building’s energy performance.”5 28 ASHRAE Journal ashrae.org November 2008

Ashrae Journal - November 2008

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