Numerous types of windows exist, including single-hung. These windows contain two large sections oriented vertically, one atop the other, each containing a windowpane. Only one of these sections moves, usually the bottom one. When it comes to installation, technically speaking you can place a single-hung window any way you want. Horizontal installation of a single-hung window, however, can lean to some serious problems, most notably a high degree of moisture penetration and resultant issues.
When installed horizontally, a single-hung window opens by sliding side to side. If you own a single-hung window and want to install a side-opening window in a space whose length is longer than its height, using your single-hung window for this purpose may seem like a good idea. You can install a single-hung window horizontally just as easily as you can install it vertically, but really you should avoid horizontal installation.
The biggest problem with installing any window improperly arises from the window's orientation, including the horizontal installation of single-hung windows. All manufacturers design windows to work in a specific direction when it comes to preventing water and moisture from entering your home through or around the window. When you install a single-hung window horizontally, you orient it in the wrong direction. Because of this, the window can provide no protection from moisture. Copious amounts of water may leak into your home, and moss, mold and more may grow in the moisture that builds up around your window.
Numerous other problems may arise from improperly installing a window. Notably, manufacturers usually automatically void the product warranty if it's installed incorrectly. So, if you install your single-hung window sideways and things go pear-shaped, you can't return or exchange your window because you violated the terms of the warranty. Furthermore, when you install a single-hung window sideways, you orient the sill in the wrong direction, meaning, essentially, that the window has no sill. This can lead to a buildup of dirt, pollen, debris and other filth and allergens around your window.
You can purchase windows specifically for horizontal installation. If you want a horizontal window in your house and haven't yet purchased anything, stay away from single-hung windows and go with a horizontal unit. These windows contain sliding tracks so that the window opens by moving in a horizontal direction. Manufacturers orient the sill and seal on these windows specifically for horizontal installation. If you already own a single-hung window and want to save money, try returning your window or exchanging it for a horizontal sliding window.