ASHRAE Journal - February 2011 - 10

letters	
Figure 4 by using indoor temperature rather than crawlspace  ground surface temperature and see the subfloor condensation  potential for places like Charleston, S.C., where outdoor summer dew points are near 75°F. Also, the underside of the groundcover is another condensing surface, for soil moisture. But this normally isn’t a concern  unless people roll the groundcover back to let the water out, or  if the water can grow stuff. Joe’s  crawlspace  discussion  has  one  other  little  flaw.  He  assumes there is a groundcover in place, and, therefore, crawlspace dew point is the same as outside dew point. In much of  the Southeast U.S., crawlspace groundcovers are not used, and  still not required by code.  About 20 years ago, I tried to publish a paper on the benefits  of installing a crawlspace groundcover, and a reviewer hacked  it by saying we don’t build houses without them. To that, and  20 years later, I say “Ha!” We still build them with naked soil.  Without a groundcover, crawlspace dew points can be much  higher than outside air. Joe’s reasoning is still good, but his simple method for determining potential is not so simple unless you  apply my tactic: “Install a groundcover, and call me in a week.” Joe, keep writing them. Craig DeWitt, P.E., Ph.D., Member ASHRAE, Clemson, S.C.

The Author Responds
Nice to connect with you again. It has been too long. Yes,  to  all  of  your  points.  I  got  lazy  about  the  subfloor  condensing surface, and you will be interested to know that I just got  smacked  by  Don  Gatley—another  legendary ASHRAE  Fellow—on the same point. Wow, I am shocked that crawlspaces  are still constructed without groundcovers. Just shocked, much  like Captain Renault. And Craig, you can be assured I will keep  writing them. Sometimes late, sorry Fred, Sarah and Rebecca. Joseph W. Lstiburek, P.Eng., Fellow ASHRAE, Somerville, Mass.

Economizer Control
Steven T. Taylor, P.E., Fellow ASHRAE, and C. Hwakong  Cheng, Member ASHRAE, authors of “Economizer High Limit  Controls and Why Enthalpy Economizers Don’t Work,” are to  be complimented on a comprehensive article on the heart of  economizer design: control selection. It is the first such article  that I am aware of in a widely read journal since the economizer  mandate in 90.1 was first published in 2004. However, I disagree  with the author’s dismissal of dew-point control.  The example given in the article is a case with low internal  latent  cooling  load  and  an  ideally  cool  required  supply  air 

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10	

ASHRAE	Journal	

	

	

February	 2011



ASHRAE Journal - February 2011

Table of Contents for the Digital Edition of ASHRAE Journal - February 2011

ASHRAE Journal - February 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Thermal Coupling of Cooling and Heating Systems
10 Common Problems in Energy Audits
Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
A Guide to Wireless Technologies
Building Sciences
Solar NZEB Project
Emerging Technologies
People
Special Section
InfoCenter
Commissioning
Products
Washington Report
Classified Advertising
Advertisers Index
ASHRAE Journal - February 2011 - ASHRAE Journal - February 2011
ASHRAE Journal - February 2011 - Cover2
ASHRAE Journal - February 2011 - 1
ASHRAE Journal - February 2011 - 2
ASHRAE Journal - February 2011 - Contents
ASHRAE Journal - February 2011 - Commentary
ASHRAE Journal - February 2011 - 5
ASHRAE Journal - February 2011 - Industry News
ASHRAE Journal - February 2011 - 7
ASHRAE Journal - February 2011 - Letters
ASHRAE Journal - February 2011 - 9
ASHRAE Journal - February 2011 - 10
ASHRAE Journal - February 2011 - 11
ASHRAE Journal - February 2011 - 12
ASHRAE Journal - February 2011 - 13
ASHRAE Journal - February 2011 - 14
ASHRAE Journal - February 2011 - 15
ASHRAE Journal - February 2011 - Meetings and Shows
ASHRAE Journal - February 2011 - 17
ASHRAE Journal - February 2011 - Thermal Coupling of Cooling and Heating Systems
ASHRAE Journal - February 2011 - 19
ASHRAE Journal - February 2011 - 20
ASHRAE Journal - February 2011 - 21
ASHRAE Journal - February 2011 - 22
ASHRAE Journal - February 2011 - 23
ASHRAE Journal - February 2011 - 24
ASHRAE Journal - February 2011 - 25
ASHRAE Journal - February 2011 - 10 Common Problems in Energy Audits
ASHRAE Journal - February 2011 - 27
ASHRAE Journal - February 2011 - 28
ASHRAE Journal - February 2011 - 29
ASHRAE Journal - February 2011 - 30
ASHRAE Journal - February 2011 - 31
ASHRAE Journal - February 2011 - 32
ASHRAE Journal - February 2011 - 33
ASHRAE Journal - February 2011 - Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
ASHRAE Journal - February 2011 - 35
ASHRAE Journal - February 2011 - 36
ASHRAE Journal - February 2011 - 37
ASHRAE Journal - February 2011 - 38
ASHRAE Journal - February 2011 - 39
ASHRAE Journal - February 2011 - 40
ASHRAE Journal - February 2011 - 41
ASHRAE Journal - February 2011 - 42
ASHRAE Journal - February 2011 - 43
ASHRAE Journal - February 2011 - A Guide to Wireless Technologies
ASHRAE Journal - February 2011 - 45
ASHRAE Journal - February 2011 - 46
ASHRAE Journal - February 2011 - 47
ASHRAE Journal - February 2011 - 48
ASHRAE Journal - February 2011 - 49
ASHRAE Journal - February 2011 - Building Sciences
ASHRAE Journal - February 2011 - 51
ASHRAE Journal - February 2011 - 52
ASHRAE Journal - February 2011 - 53
ASHRAE Journal - February 2011 - 54
ASHRAE Journal - February 2011 - 55
ASHRAE Journal - February 2011 - 56
ASHRAE Journal - February 2011 - 57
ASHRAE Journal - February 2011 - 58
ASHRAE Journal - February 2011 - 59
ASHRAE Journal - February 2011 - 60
ASHRAE Journal - February 2011 - 61
ASHRAE Journal - February 2011 - Solar NZEB Project
ASHRAE Journal - February 2011 - 63
ASHRAE Journal - February 2011 - 64
ASHRAE Journal - February 2011 - 65
ASHRAE Journal - February 2011 - 66
ASHRAE Journal - February 2011 - 67
ASHRAE Journal - February 2011 - 68
ASHRAE Journal - February 2011 - 69
ASHRAE Journal - February 2011 - Emerging Technologies
ASHRAE Journal - February 2011 - 71
ASHRAE Journal - February 2011 - 72
ASHRAE Journal - February 2011 - 73
ASHRAE Journal - February 2011 - 74
ASHRAE Journal - February 2011 - 75
ASHRAE Journal - February 2011 - People
ASHRAE Journal - February 2011 - 77
ASHRAE Journal - February 2011 - InfoCenter
ASHRAE Journal - February 2011 - 79
ASHRAE Journal - February 2011 - 80
ASHRAE Journal - February 2011 - 81
ASHRAE Journal - February 2011 - 82
ASHRAE Journal - February 2011 - 83
ASHRAE Journal - February 2011 - 84
ASHRAE Journal - February 2011 - 85
ASHRAE Journal - February 2011 - Commissioning
ASHRAE Journal - February 2011 - 87
ASHRAE Journal - February 2011 - 88
ASHRAE Journal - February 2011 - 89
ASHRAE Journal - February 2011 - 90
ASHRAE Journal - February 2011 - Products
ASHRAE Journal - February 2011 - Washington Report
ASHRAE Journal - February 2011 - Classified Advertising
ASHRAE Journal - February 2011 - 94
ASHRAE Journal - February 2011 - 95
ASHRAE Journal - February 2011 - Advertisers Index
ASHRAE Journal - February 2011 - Cover3
ASHRAE Journal - February 2011 - Cover4
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