Window wells are about the unsexiest part of basement finishing you can imagine. But like taking steps to prevent water infiltration, installing subfloor, and insulating walls, it's one of those necessary "first step" sub-projects that let you get to the fun things like building that bar or installing a home theater.
Wells: Dig-Outs That Allow You To Have a Basement Window
Basements were not meant to have windows; so consider any fenestration you can get to be a nice plus, a bonus, pure lagniappe.
On one end of the spectrum are day-light basements, which have one or more sides at grade level (meaning, you can walk straight out and be on ground, no steps necessary). The other sides will be banked up against earth. On the day-light side, wells are not needed; you can install windows in the conventional fashion.
At the other end are basements that, except for the upper foot or so, are fully underground. When you install a window in such a basement, you need to dig a well on the exterior. The well is your opening to the outside world so that the window can bring in some measure of air and light. In some cases, these wells must be of specific dimensions in order to allow for exit in case of emergency.
If you don't support the earth in your dig-out, it will eventually collapse--onto your window. Wells are half-circular or rectangular galvanized steel or polyethylene shields that attach to the side of the house, supporting the earth and blocking debris and moisture from reaching the basement window.
What Are Well Covers?
Keeping these basement windows exposed means that anything that is outside at-grade (water, snow, leaves, dust, etc.) can reach your window. Windows are weather-resistant, but only to a point. Wells and covers act like a "storm door for your basement window," providing extra protection for this heavily battered area.
Covers are composed of transparent plastic (polycarbonate) and are either flat or bubble-shaped. Most tend to cost well under $100, with many even under $50.
Covers attach to the top of an existing well. As it turns out, energy efficiency experts tell us that well covers do a great job of saving you energy and money. The reason is because most basement windows are severely inadequate when it comes to holding in your precious heat and/or cold. Compounding the problem is the fact that basements tend to have a naturally lower temperature than at-grade or above-grade spaces.
Basement windows tend to get a real beating from water dripping off of roofs and from ground-flow rain, so they deteriorate quickly.
Egress Wells: Building Code Requires Specific Dimensions
If your local building code requires that your basement window provide egress (access to the outside in case of emergency), then window well dimensions will be large. Not only that, but egress window wells may need to have some kind of steps or ladder system for occupants to use for escape.
Horizontal dimensions should be large enough to allow the window (or door) to be fully opened. Total area of the well should be at least 9 square feet.
Outward from the house, it should project at least 36 inches. Height of the well should be no more than 44 inches.