Unwashed windows accumulate layers of grime that can build up and block out the sun, causing light-hungry houseplants to turn to TV sets and birthday cakes. Keep the planted masses happy with today's Groupon: for $40, you get $80 worth of window-cleaning services from A Pane in the Glass. This Groupon is valid only for Spokane, Spokane Valley, Liberty Lake, and Veradale.

The window-cleaning whiz kids behind A Pane in the Glass supplement classic squeegee techniques with eco-friendly products and water that's filtered on-site to cleanse see-through walls inside and out. Hollow poles transmit the purified liquid directly from the water source to sullied panes, and because the water is starved for minerals, it then latches onto dirt and grime like a lonely burr on a comforting sweater. A Pane in the Glass charges per window; technicians bathe standard first-floor window panes thoroughly to remove mold, mildew, streaks, and suction-cup-footed plush cats for $5 each, and non-first-floor windows cost between $6 and $8 each. Use the online estimate form to receive a customized cleaning quote.