Dow Green Roof - Manual (Page 3)

I N F O R M A T I O N . C O M M E R C I A L . U S / C A N A D A
Figure 7: Option 3 – Drainage Layer Consisting of a Commercially
Available Mat and Filter*
Filter Fabric
Drainage Layer
Filter Fabric
STYROFOAM™ Brand
Foam Insulation
Fully Adhered
Waterproofing Membrane
Structural Concrete Deck
Planting Layer
Root Barrier Membrane
Regardless of the type of insulation,
where more than one layer of insulation
is required, follow these guidelines:
• The bottom layer of insulation (the
layer directly on the root barrier)
must be at least 2" (50 mm) thick.
• The bottom layer must be the
thickest or, at minimum, equal
to the top layer (e.g., 3" [75 mm]
bottom and 3" [75 mm] top).
• Lay succeeding layers of insulation
unbonded or unadhered.
• Stagger or offset all joints from
those of the underlying layer.
Note: These are guidelines only;
it is the responsibility of design-
ers and/or engineers to calculate
and accommodate live and dead
loads in a vegetative roof PMR
design. If required, contact a Dow
representative for additional
information on the live and dead
load design limits for STYROFOAM
™
Brand Extruded Polystyrene Foam
Insulation.
W H AT A R E T H E W E I G H T
R E C O M M E N D AT I O N S F O R
B A L L A S T A N D T H E
P L A N T I N G L AY E R ?
When designing a vegetative roof
PMR, the stone ballast typically
specified in a PMR is effectively
replaced by the planting layer to
minimize any potential for flotation.
As detailed in Dow literature and
Tech Solutions 508.1 (Ballast Design
Guide for PMR Systems [U.S.]), the
minimum stone ballast requirement
of 10-12 lb/ft
2 (50-60 kg/m 2 ) can be
replaced with a similar weight of a
dry and unsaturated planting layer,
with additional ballast required
around any penetration(s) and the
roof perimeter. Refer to Table 1 for
either weight or thickness of addi-
tional ballast, depending on the
thickness of insulation. For additional
literature, visit www.dowpmr.com
or call 1-866-583-BLUE (2583).
STYROFOAM™ THICKNESS, REQUIRED WEIGHT OF APPROXIMATE THICKNESS
IN (MM) STONE BALLAST, LB/FT 2 (KG/M 2 ) OF BALLAST, IN (MM)
Up to 2 (50) 12 (60) 1-3/4 (40)
3 (75) 17 (84) 2-1/4 (60)
4 (100) 22 (108) 3 (75)
5 (125) 27 (132) 3-1/2 (90)
6 (150) 32 (156) 4-1/4 (105)
7 (175) 37 (180) 5 (125)
8 (200) 42 (204) 5-1/2 (140)
TA B L E 1 : R E Q U I R E D B A L L A S T A R O U N D P E R I M E T E R S
A N D P E N E T R AT I O N S
WHAT TYPE OF STYROFOAM ™
BRAND INSULATION SHOULD
BE SPECIFIED?
The insulation must be able to perform
long term under both sustained (dead
loads from plantings, planters, etc.)
and cyclic loading (live loads from
maintenance vehicles, foot traffic,
etc.). Because the design of each
vegetative roof is unique, it is impor-
tant that the designers calculate
both the live and dead loads created
on the insulation layer. STYROFOAM
™
Brand Extruded Polystyrene Foam
Insulation is available in a range of
compressive strengths from 35-100
psi (240-690 kPa) to address the
specific design loading requirements
for each project.
For a vegetative roof PMR that is
exposed to limited pedestrian traffic
and minor landscape maintenance
using light power tools, typically
STYROFOAM
™ Brand ROOFMATE ™
Insulation or STYROFOAM ™ Brand
HIGHLOAD 40 Insulation may be
specified, depending on design loads
from the planting layer and other
dead loads. Where vehicular traffic
or large design loads are anticipated,
STYROFOAM
™ Brand HIGHLOAD 60
or STYROFOAM ™ Brand HIGHLOAD
100 Insulation may be required.
STYROFOAM
™ Brand PLAZAMATE ™
Insulation (U.S. only) is also available.
®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
*Not to scale. For reference purposes only.