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 $49, you get $100 toward window cleaning from KP Window Cleaning Services.

KP's professional gunk busters clarify crusted glass with biodegradable soaps, scaling OSHA-compliant ladders to relieve the most distant and difficult panes. Ample drop cloths and boot covers keep tracked dirt off floors, and whirling rags free windows from interior detritus and oily faceprints left from playing peekaboo with the mailman. Experienced hands restore exterior screens, performing minor repairs on tears and runs and preventing further damage. Suds flood sliding-door and window tracks, excavating trapped dirt and fossilized crumbs from pies left cooling on the sill. Industrial modifications prevent leaning ladders from damaging gutters, shingles, or walls as scaling soapmen clean glassy peaks.

KP Window Cleaning Services is not currently taking appointments, but will begin taking appointments again in August.