ASHRAE Journal - February 2011 - 58

building sciences	
of this has to wait for some other time. Second, and most important to our story, is that its function is to transfer the stresses of the primary roof membrane to the metal deck. Stresses from the roof membrane are transferred to the coverboard, and the coverboard does the heavy lifting and handles these stresses finally getting them down to the metal deck. Next we have to deal with the potential for concentrated roof stresses at parapets. Figure 12a shows how the “old timers” did it—wood blocking and a cant anchored to the structural deck. Figure 12b shows how the “new pups” do it—a large backer rod supporting a bunch of extra membrane that lets things move when they have to move. As much as it pains this “old timer” to say this, with the newer more dimensionally stable membranes the “new pups” have it more right. Now on to the continuity stuff. All we have to do is apply the Baker Principles (Figure 5) to typical roofs and walls. To that end, with the help of my colleagues at the Skunk Works at Building Science Corporation, I have drawn up a few of the more common parapet constructions following the “Baker Principles”: the already discussed Steel Stud Parapet (Figure 12b), the Masonry Parapet (Figure 13), the Balloon Framed Steel Stud Parapet (Figure 14) and, finally, the Cantilevered Mini Parapet (Figure 15). All of the “good” series of parapet details presented follow the “Baker Principles” and a little bit of other stuff (Figure 12a, Figure 12b, Figure 13, Figure 14, and Figure 15): • Water control layer continuity: membranes continuous under the parapet flashing; • Air control layer continuity: an air control layer in the roof assembly is connected to the air control layer in the wall assembly; • Vapor control layer continuity: a vapor control layer in the roof assembly is connected to the vapor control layer in the wall assembly; • Thermal control layer continuity: the thermal control layer of the roof assembly is connected to an effective thermal control layer in the wall assembly. The thermal control layer in the wall assembly is exterior to the structure—just as in the roof assembly. • The roof membrane is fully adhered to a coverboard that is mechanically attached
58	 ASHRAE	Journal	

Figure 13:	The	Masonry	Parapet.	The	thing	to	note	here	is	that	the	concrete	deck	 is	the	air	control	layer	so	an	additional	one	is	not	necessary.	However,	joints	in	the	 concrete	deck	need	to	be	addressed	for	air	control	layer	continuity.

Figure 14:	The	Balloon	Framed	Steel	Stud	Parapet.	This	is	the	ugliest	parapet	to	 get	right.	Notice	the	use	of	spray	polyurethane	foam,	the	high	density	stuff,	to	 provide	air	control	layer	continuity	across	the	balloon	framed	exterior	steel	stud	 wall.	The	spray	foam	is	supported	by	horizontal	bridging	or	metal	blocking.	This	is	 a	tricky	thing	to	execute	and,	as	such,	we	design	into	the	upper	parapet	assembly	a	 pathway	for	drying	via	vapor	diffusion	to	provide	some	performance	redundancy.
ashrae.org	 	 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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