An egress window is large enough for entry or exit in case of an emergency. If you're finishing a basement or adding a bedroom, you may want to take into account the building code for both safety and resale value. Does that mean a basement bedroom without an "egress-able" window is a big problem? Not necessarily. Peer agents, appraisers, and builders alike can't seem to agree on how important a code-adherent bedroom is for tax and/or market value—but if you have the opportunity to add a larger window + exterior window well or upgrade, why not suss it out?
Here are the requirements per the International Building Code (and Seattle's Department of Construction and Inspections):
Curious what it would take to make your retrofit your bedroom window? Start with a contractor who does foundation and/or general contracting work and get multiple quotes! Hoffman Rebuilding, After the Fire Construction, and Wu Construction are my go-tos. What are yours?
While we're talking planning...with contractors scheduling months out and remodel prices higher than ever, it pays to figure out exactly what you want before you embark on a project while being flexible later. I highly recommend starting with a floor plan (done by an appraiser or photographer) or "as-built sketch" (done by an architect, engineer, or house designer). The former costs as little as $150 and allows you to get a general sense of space/layout and play, while the full as-built may be sufficient for builders to use for their work (and may be several hundred or up to $2000). Either way, it pays to visualize that layout you *think* will be perfect. In the case of my house, Grant and I took several iterations to get the right flow for our daylight basement. Ping me for floor plan resources!