ASHRAE Journal - March 2009 - (Page 13)

impact mitigated by an ERV having a reasonably high enthalpy recovery effectiveness. John Dieckmann, Member ASHRAE, Cambridge, Mass. The Author Responds You are basically saying that we can use good technology to compensate for a dumb ventilation rate decision, so I should just suck it up because the penalty for being dumb is not so bad. Well, why don’t we just use the good technology with a smart ventilation rate decision? You’re further saying that we should err on the side of safety with regard to these rates. Don’t you think that is what the ASHRAE 62 committees are already doing? Your approach is to add a safety factor on top of another safety factor. When does it stop? And based on what? Opinions from gadflies, activists and special interests? Don’t we already have that going on in our own ASHRAE committees? Joseph W. Lstiburek, Ph.D., P.Eng., Fellow ASHRAE, Somerville, Mass.  In November’s “Why Green Can Be Wash,” Joseph W. Lstiburek, Ph.D., P.Eng., comments that we should not use supply or return plenums. I agree with Joe on supply plenums, but question the basis of his comment regarding return air plenums (assuming the building is properly designed to have positive pressure). Several LEED reviewers make the same comment. I have seen a return duct after it has been in use for 15 years. It is coated with the same dust that accumulates in plenums. On what basis does Joe make the comment “Don’t use supply or return plenums?” When properly applied and constructed, return plenums save considerable energy (about 10% to 15% less supply air) and construction dollars (reduced ductwork and building height). James A. Kasulka, P.E., Member ASHRAE, Macon, Ga. The Author Responds In the May 2007 ASHRAE Journal, “The Hollow Building” covers the issues I have with return plenums in detail. BasiMarch 2009 cally, because they are not sealed at the perimeter they actually do not save energy, but rather are a huge energy penalty. Furthermore, they are an environmental nightmare, which is responsible for partload humidity problems and interstitial mold transfer. Finally, they do not save costs over the type of return approach I show in the aforementioned column and they do not save building height. They suck literally and figuratively. Joseph W. Lstiburek, Ph.D., P.Eng., Fellow ASHRAE, Somerville, Mass. www.info.hotims.com/23933-50 ASHRAE Journal 13 http://www.setra.com http://www.setra.com http://www.info.hotims.com/23933-50

Table of Contents Feed for the Digital Edition of ASHRAE Journal - March 2009

Contents Commentary Industry News Letters Meetings and Shows Special Section 2009 ASHRAE Technology Awards Feature Articles Heat Recovery for Office Tower Air Motion Control in the Hospital Operating Room Anniversary Feature: Five Defrost Methods for Commercial Refrigeration Groundwater Issues: Commercial Open Loop Heat Pump Systems Used Filters and Indoor Air Quality Building Sciences Emerging Technologies Washington Report Products Special Products People Classified Advertising Advertising Index

ASHRAE Journal - March 2009

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