If they're not cleaned every few days, your windows will turn black and begin emitting a high-pitched scream that makes dogs pregnant. Prevent a neighborhood outbreak of puppies with today's Groupon: for $58, you get an exterior window cleaning for 10 windows (a $130 value) from Greenforce Clean Team, servicing homes in San Francisco, San Mateo, Oakland, and surrounding areas.

Greenforce, as its name suggests, specializes in eco-friendly cleaning with green products; Greenforce stays even more carbon neutral by donating to The Carbonfund for each trip made. The team has been cleaning the Bay Area since 1993, when the Internet was still a young, rampaging menace, destroying hillside farms with text-based role-playing maneuvers and ASCII color codes. Greenforce will work to clean 10 of your windows (up to 3'x5') with squeegees, specialized window-washing tools, and environmentally safe soap that is gentle on your family, your pets, your family's family of pets, your pet family, and the environment. The experienced pane purgers wield their chair, swing stage, boom lift, and water-fed pole system prowess to tackle a wide variety of jobs, ranging from seasonal dirt and grime removal to post-construction polishing. After a thorough exterior cleaning, chemically sensitive neighbors will once again be able to peep in windows without transforming into an evil alter ego that smells suspiciously of artificial pine, and glass will gleam as brightly as the day it was installed. Groupon holders also receive a 10 percent discount on any additional cleaning services (such as housekeeping, gutter cleaning, and carpet cleaning) scheduled for the same day as their exterior window cleaning.

Summer is a busy season for Greenforce Clean Team, so appointments should be scheduled well in advance.