Tools Needed: Tin snips #2 Phillips head screwdriver or #2 Phillips bit on electric drill.

  1. The U-channel is packed on top of the window. The angled side faces in towards the room. We supply it 1/4″ long so it can be trimmed to a snug fit. Hold the U-channel up to the top of the window opening, butt one end against the window stop and mark the other end. Start cutting the U-channel on the straight side. Cut to the corner and bend the cut part down, then cut the top, bend it down, then cut the angled side. Trial fit the U-channel exactly where it will be installed and trim if necessary. Start the screws in the predrilled holes about 3″ from each end and one in the middle if the window is wide enough. Peel paper backing off double faced tape and carefully press in place. Note: the tape has a very strong adhesive; it is very difficult to remove once pressed in place. If for some reason you intend to take off the U-channel at some future time leave the paper backing on and just use the screws.
  2. Now, you are ready to put in the Innerglass Window. Hold it by the sides towards the top and compress the expanders until the top of the window can fit in the opening. Slide it upward into the U-channel until it is in all the way. Move your hands down compressing the expanders and gently pushing the window into place. Push the window in by the sides working a little at a time along the sides so that you do not bend or twist the window too much. It is flexible but it is best not to tempt fate. Before the bottom is in you may need to trim the bottom weather-strip, but before you cut it, check the other side to make sure the weather-strip isn’t too short on that side.
  3. Mark the left and right window stops 1/3 way up just in front of the expander when the Innerglass window is in the proper position. Remove the Innerglass window. Drill a 3/32″ hole (1/8″ will work) parallel with the glass, slightly downwards so the pin will not fall out. Reinstall the Innerglass window and place the retaining pins in the holes.
  4. Check for gaps at sides and push the expander fin outward to seal. Gaps at the sill, if less than 1/16,” will seal as the bottom foam decompresses. If there is a gap at one corner reach up to the opposite top side compress the expander to get your fingers between it and the window frame and pull toward the other side to slightly rotate the window. If the gap is in the middle take the wood block and place it on the Interlock edge and tap the block downwards, move it over an inch and repeat until the bottom frame is conformed to the opening..

Installation of Windows with Mullions

Horizontal Mullions
  1. The horizontal mullions can be used with or without the vinyl cap. Take the cap off the mullion to expose the pocket holes. These should face upwards when the mullion is in the window. Place the mullion in the window, normally the top of the mullion is positioned to be even with the top of the lower sash, or at the height you specified in your order. Note that if your window is crooked the ends of the mullion may be at different heights from the sill.
  2. Use the long screws to fasten the ends of the mullion. One leg of the vinyl cap is slightly longer than the other; it should face you when it is in place. Put the vinyl cap back on the mullion.
  3. Trim the lower window U-channel to length. Pull off the paper backing of the tape on the U-channel and with the bent face towards you position it on the bottom of the mullion so that no wood can be seen (towards the room).
  4. Complete the rest of the installation as described on the Compression Window Installation instruction sheet.
Vertical Mullions
  1. Vertical Mullions are positioned so that the 1 1/8″ face is towards you. There are 2-3 sided vinyl pieces that surround the wood post. Trial fit the mullion post first, you may have to trim it slightly. Inside the vinyl is a double faced tape, peel the paper backing off when you are ready to attach it permanently to the wood post. After the trial fit attach the vinyl to the back of the post (facing towards the outside) the pocket holes should be facing you and visible.
  2. Place the post exactly in the middle of the opening using a measuring tape to get the same dimension on each side at the top and bottom. Screw in the 8×1 1/2 screws top and bottom. Fussiness here saves hassle later.
  3. Pull the paper off the tape and press the vinyl in place.
  4. Install the U-Channels centered on the post.
  5. Blocking pin holes should be drilled into the mullion post offset so they don’t run in to one another. Drill the holes carefully so you don’t break through the other side. The pins should be trimmed shorter with your tin snips.
  6. You may want to place an extra set of blocking pins behind the windows on the mullion post so that you can’t push the windows past the post.

Tall Window Installation

For windows over 5 ft tall we have included extra retaining pins. In some cases with tall windows under a high wind load they can bend and try to come out. To stop this add 1 more pin on each side that is 2/3 the up the side. Remember you already should have a pair of pins 1/3 the way up.