DOW™ High Performance Underlayment-LF (HPU-LF) extruded polystyrene foam insulation wraps your home like a blanket. If you don't need the insulation value of thicker insulation, HPU-LF insulation is for you. DOW™ HPU-LF insulation is specially formulated 1/4" and 3/8" thick extruded polystyrene foam boards sealed between select plastic facings and produced in continuous 50' long x 4' wide fan-fold sections. The inherent flexibility of HPU-LF insulation allows corner-wraps without breakage or reinforcement, providing sealing effectiveness and a smooth level surface for new siding.
Before covering an old wall with insulation and new siding, be sure the wall is sound. Do not install siding over walls that have deteriorated from moisture, insects etc.
How to install the fan-folded boards.
1. Cover the old siding completely with HPU-LF insulation. Butt the edges of the boards tightly together. After measuring, score panels with a utility knife, then snap off the excess piece over the edge of your work surface.
2. Measure the combined thickness of the insulation and new siding. Use this measurement to determine the thickness of the door and window jamb extensions. You may also need to extend sills. Be sure to extend flashings.
IMPORTANT: Have a qualified electrician extend outlets, light fixtures, doorbell buttons, etc.
3. Align the fan-folded boards along the bottom edge of your home or with the siding starter strip.
4. Nail boards directly over old siding. Use nails recommended for vinyl siding. Make sure nails go through the insulation, the old siding and into the framing. This nailing pattern will show you where to drive the siding nails later on. Space nails about 24" o.c. along each stud.
5. Apply the new siding and trim. Use nails recommended for vinyl siding. Be sure nails go through the insulation and into the underlying structure, not just the old siding.
6. Follow vinyl siding manufacturer's installation instructions.
NOTE: Do not overdrive nails. This can crush the insulation and can also cause a "wavy" siding installation.
