Jalousie windows can consist of glass, acrylic or wooden louvres. The louvres are set in the frame and connect together on a track. If you experience closing problems with your windows, it can be due to your home settling. Issues due to settling often require more extensive measures to repair the window. But more minor causes, such as hardware and mechanism issues along with cleanliness, can also affect how well a window can close tightly.
While the windows may be perfectly squared and centered when installed, that can change as the home settles. In order for the window to continue to close correctly, the window may require an installation adjustment. The jambs must sit plumb. The top, bottom and middle widths should measure equally. The recourse is often to remove the window and reframe and square the opening. A skewed window opening may even require a new window install.
Jalousie window closing problems are sometimes caused by loose, broken or dry hardware. Tighten all screws connecting the lever handles or knobs to the windows. Inspect the hardware for any damage and replace it, if necessary. When closing the windows, pull or turn the hardware firmly. Engage the locks while holding onto the lever after it won't turn or pull any further. Keeping the lever or knob turned in tight may keep the window closed just enough so the locks can engage the window and move it in closer for a tighter seal. Apply a silicone spray to the hardware to keep it lubricated.
The mechanism behind each louvre -- consisting of various small parts -- may break and prevent the window from closing. Jalousie windows with motor operated louvres may experience problems with the motor malfunctioning. Contact the dealer for service or repair. The dealer can repair the window or offer a replacement, often for free if the window is still under warranty.
Dirt can become trapped between the louvres and inside of the frame. Buildup and larger pieces of debris can prevent the window from closing tightly. Clean the windows at least every three months to prevent such problems. If you live in areas with higher amounts of dust or near the ocean, where salt buildup is an issue, it may be necessary to clean the windows more often. Do not use chemicals to clean the windows as they may ruin the materials. Instead use warm water and a mild detergent.