READ COMPLETE INSTRUCTIONS BEFORE INSTALLATION!
• Ducts must be sealed and airtight; insulation secured properly with seams taped and corners reinforced.
• Substrate must be clean & dry. Installation works best at temperatures above 35° F (2° C).
• To improve adhesion in cold weather and on the duct bottoms, use MFM Spray Adhesive.
• For FlexClad-400, duct bottoms over 24” (60 cm) wide require use of pins.
• Top of duct must be sloped for drainage to prevent standing water.
• Use over metal duct or on rigid insulation only!
• Pressure sensitive adhesive: always roll firmly with a hand roller, especially on seams and duct bottoms.
STEP 1: Prepare the Surface
• Clean, primed metal ductwork, and rigid foil-faced insulation (polyiso board or FSK) are preferred substrates. FlexClad may also be installed over rigid, foil-faced EPS and extruded polystyrene (XPS) insulation. Do not use over non-rigid insulation!
• Surface must be free of dust, dirt, oil, dew, moisture, frost and other foreign material that will prevent proper adhesion. Wipe surface with acetone to remove oils, grease, hand prints, and processing lubricants.
• Insulation without a foil-facing, such as polyiso board insulation, requires the use of MFM Spray Adhesive.
• Prime bare metal surfaces with MFM Prime-A-Seal or asphalt primer.
• HINT: Use metal reinforcing strips on insulation corners to maintain shape for a neat appearance.
STEP 2: Measure & Cut
• Measure the length of FlexClad™ needed and cut with utility knife or scissors.
STEP 3: Use MFM Spray Adhesive 
• MFM Spray Adhesive improves adhesion in cool weather, on shaded surfaces, and in hard-to-reach areas.
• Apply a light coat of MFM Spray adhesive and let dry for a minimum of 30 seconds or until no longer wet.
STEP 4: Apply FlexClad
• Positioned pre-cut piece of FlexClad into place.
• Remove release paper from one end of FlexClad and stick membrane into position and align.
• Pull release paper from behind the membrane and continue to press
FlexClad into place.
• Roll entire surface firmly with a hand roller.
STEP 5: Applying More FlexClad
• Overlap FlexClad 3” (8 cm) on side laps and 6” (16 cm) on end laps.
• HINT: Use a tape measure to mark overlaps. Measure and press end of tape into membrane to leave an overlap mark.
• Firmly roll all seams and edges with a hand roller to ensure good adhesion!
• HINT: Use MFM Spray Adhesive on overlaps and edges for best adhesion.
• COOL WEATHER: Keep rolls of FlexClad in a warm place until ready to apply. Use MFM Spray Adhesive before applying FlexClad.
On ducts over 24” (60 cm) in width, pin bottom on 12” (30 cm) centers. Cover pins with a 3” (8 cm) square minimum of FlexClad. Duct work with air leaks will cause the FlexClad to “balloon,” creating adhesion problems and seam leaks. If this is a problem, a roof soffit vent may be added in a sheltered location to relieve air pressure.
PROPER INSTALLATIONS:
NOTE:
• Both FlexClad-250 and FlexClad-400 self-seal around punctures made by pins, screws, and other fasteners passing all ASTM D 1970 nail sealability tests.
• FlexClad-400 meets UL Class A fire tests when installed over a non-combustible surface.
• The lighter weight of FlexClad-250 may allow it to be installed without any pins. MFM recommends pins on duct bottoms when installed over foil-faced FSK insulation.
WARNINGS
• Follow instructions carefully. MFM not responsible for failure caused by improper installation, structural faults
or failure of underlying or adjacent materials.
• FlexClad is slippery when wet. Avoid falls by using proper safety equipment and monitoring devices.
• Aluminum FlexClad is reflective and can contribute to sunburn. Protect skin and eyes and avoid prolonged
exposure in direct sun.
• Store material in a dry place. Keep FlexClad in carton until use. Exposure of stored material to direct
sunlight or water will reduce adhesion.
• Do not install FlexClad over uncured caulks or sealants! Active solvents will cause the asphalt adhesive to
liquefy and run. It is the installers responsibility to ensure compatibility with all solvents, caulks and sealants.
For Technical Support contact MFM:
1-800-882-7663
Monday—Friday,
8:30 AM—4:30 PM Eastern Time
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