COLUMN BUILDING SCIENCES
FIGURE 10 Metal Drip Edges. In high wind zones, it is recommended that metal
FIGURE 11 Asphalt Shingles. Asphalt shingles that are installed at eaves should be
drip edges be installed at roof eaves and roof rakes.
installed over an asphalt shingle starter strip that is adhered to the fully adhered
membrane underlayment or to the drip edge or both.
Roofing
Nails
Membrane
Underlayment
Slope
Second
Course
First
Course
Asphalt
Shingles
Asphalt Shingle
Starter Course
Flashing Over
Membrane
Underlayment
Along Rakes
Membrane
Underlayment
Self-Sealing Adhesive Strip
Cut Off Tabs; Install With the Cut Edge Placed
Downslope Along Eave Edge
Perimeter Flashing at Eave
Metal Perimeter Drip Edge Flashing
Bend to Form Closure at Corner
high wind zones are at roof edges. As noted earlier,
the pressures are more pronounced in sloping roofs.
In sloping roofs you win or lose the game at roof eaves
and roof rakes. That is where roofs experience the highest positive and negative air pressures. The structural
Precision Discharge Air Control
with the Rawal APR-E® Valve
Control any single or 2-stage DX system to a precise discharge
air setpoint with our electrically driven & electronically
controlled APR-E™. This Rawal Valve is an external compressor
unloader for aftermarket installations. The APR-E™ provides
modulation for any DX air-conditioning system and is easily
integrated into an existing BAS/BMS or with a stand-alone
controller for New or Retrofit Systems.
E
OBTAIN THY
FLEXIBILIT D
LE
IL
OF A CH STEM
WATER SYA
ON
ET!
DX BUDG
* Dew Point Control for
critical environments
* Applicable to any
VAV/MUA/DOAS systems
* Reset DAT to minimize
reheat for energy savings
RAWAL DEVICES, INC. | PHONE: 800.727.6447
FOR MORE INFORMATION VISIT: WWW.RAWAL.COM
SEND ALL INQUIRIES TO: SALES@RAWAL.COM
66
ASHRAE JOURNAL
ashrae.org
O CTO B E R 2020
connections connecting the roof deck layers to the wall
assemblies need to be robust (Photo 4 and Photo 5). We
were also here before ("Leiningen Versus The Ants
Redux," ASHRAE Journal, October 2011).
In high wind zones it is recommended that metal drip
edges be installed at roof eaves and roof rakes (Figure 10).
The following metal drip edge installation requirements
are recommended:
* Drip edges should overlap a minimum of 3 in.
(76 mm) at joints;
* Eave drip edges should extend a minimum of 0.5 in.
(13 mm) below sheathing and overlap the top of the roof
sheathing edge a minimum of 2 in. (51 mm);
* The drip edge should be mechanically fastened to the
roof deck at a maximum spacing of 4 in. (102 mm), and
the fasteners should be compatible with the flashing; and
* Drip edges at gables/rakes should be installed over
the fully adhered membrane underlayment.
Asphalt shingles that are installed at eaves should be
installed over an asphalt shingle starter strip that is
adhered to the fully adhered membrane underlayment
or to the drip edge or both (Figure 11).
Asphalt shingles that are installed at gables/rakes
should be installed set in a minimum 8 in. (203 mm)
wide strip of flashing cement.
Do all of this and you are in pretty good shape. Now for
the controversial part. Thought I would
leave it to the end. Unvented roofs resist
wind and rain and wildfire and pests
better than vented roofs. We will have a https://bit.ly/3bajige
Rate this Column
run at this some other time.
http://WWW.RAWAL.COM
https://www.bit.ly/3bajige
https://www.ashrae.org/