To maximize the efficiency of
THERMAX™ Polyisocyanurate
Insulation in metal buildings and
alternative applications such as
tilt-up concrete wall panels and
parking garage ceilings, joints
between boards must be properly
finished. Whether on the interior or
exterior, finished joints reduce air
leakage and moisture infiltration.
They also create a clean,
professional appearance in interior
applications.
Several joint closure systems
are recommended by Dow when
using any of the THERMAX™
product family:
• THERMAX™ Sheathing
• THERMAX™ Metal Building
Board
• THERMAX™ Heavy Duty
• THERMAX™ Heavy Duty Plus*
• THERMAX™ Light Duty
• THERMAX™ White Finish
All accessories are available for sale in
conjunction with insulation products. See
specific THERMAX™ product installation
guidelines for board attachment
procedures.
C L O S U R E S Y S T E M
C O M P O N E N T S
Each joint closure system uses
one or more of the following
components:
• THERMAX™ white foil tape
(for THERMAX™ Heavy Duty,
THERMAX™ Heavy Duty Plus,
THERMAX™ Light Duty or
THERMAX™ White Finish)
• THERMAX™ aluminum foil tape
(for THERMAX™ Sheathing and
THERMAX™ Metal Building
Board)
• Clip Strip
• Interlocking System
• J-Channel
• WEATHERMATE™ Straight
Flashing
• Construction-grade sealant and
adhesive**
• Shiplap board joint
Joint Closure Recommendations used in
Metal Building Applications
®™ Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
*Parking garage ceilings are a specialized application requiring additional design considerations. For assistance installing THERMAX™ products in this application, call 1-866-583-BLUE (2583).
** THERMAX™ Heavy Duty Plus Insulation is designed for use in walls only.
†
To produce a continuous air- and moisture-resistant seal, use Vulkem 116, Sikaflex 201, Dow Corning 790 or equivalent sealant. Your Dow representative can recommend an appropriate sealant and adhesive for your application.
P R O D U C T / I N S T A L L AT I O N I N F O R M A T I O N . C O M M E R C I A L . P R O T E C T I O N M A N A G E M E N T
Joint Closures From Dow
1" Base
2" Base
Top “T”
150' rolls
(16 rolls/box)
10' lengths; sold
in cartons of 20
(200 linear feet)
10' lengths; sold
in cartons of 20
(200 linear feet)
10' lengths; sold
in cartons of 20
(200 linear feet)
100' rolls
(6 rolls/box)
Varies
3" wide
Accommodates foam
thicknesses of 1",
1.5", 2", 2.5", 2.65",
3" and 3.2"
Base
1" section accommo-
dates foam thicknesses
from 1" to 1.75"
2" section accommo-
dates foam thicknesses
from 2" to 3.2"
Top “T” section
1", 1.5", 2", 2.5", 3"
and 3.2"
Accommodates foam
thicknesses of 1",
1.5", 2", 2.5", 2.65",
3" and 3.2"
4" and 6" widths
N/A – edge treatment
available on many
rigid foam insulation
products >/= 1.5"
thick
Strong and durable foil
tapes help prevent air
and water vapor infiltra-
tion at joints and seams
PVC closure effectively
and efficiently joins two
edges of THERMAX™
Insulation boards
• Two-part PVC closure
• Sections easily snap
into place for a secure
fit
• Base sections fasten
to concrete or masonry
walls or ceilings
• PVC closure
• Typically used when
other closure methods
will not cover the
joints between boards
(such as the joint
between the top and
bottom of THERMAX™
Insulation or at the
roof peak when
combining two
sections of board)
• High-density
polyethylene film facer
with butyl rubber
adhesive
• Resists water intrusion
at joints between
insulation boards in
standing seam metal
roofs and steel stud
construction
One of the most
thermally efficient joints
available
THERMAX™
White Foil Tape or
THERMAX™
Aluminum Foil Tape
Clip Strip
Interlocking System
J-Channel
WEATHERMATE™
Straight Flashing
For use on
THERMAX™ Insulation
that is applied on the
exterior side of back-up
wall only, e.g.
THERMAX™ installed
outboard of a Steel Stud
Framed Wall
Shiplap Board Joint
JOINT CLOSURE DESCRIPTION SIZES PACKAGE
DETAILS
C L O S I N G A T H E R M A X ™
J O I N T
OPTION 1
Requires square edge boards
1. Center THERMAX™ white foil
tape over dry, clean edge joint
and apply tape (Figure 1). When
installing THERMAX™
Sheathing or THERMAX™ Metal
Building Board, use aluminum
foil tape.
2. Use a squeegee or stiff bristle
brush to press the tape firmly to
the joint. Cut tape with a knife.
Do not tear tape.
Figure 1
Caulk Pocket
Interior Air Sealing with Tape
(4 pages)
(4 pages)
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