By 2010, Seattle was home to approximately of green roofs. Despite initial hiccups in the city stemming from weeds, lack of irrigation during dry summer months, and a need for continuous replanting, the project has continued to succeed as understanding around the best soils and plants and the need for monitoring and upkeep has increased. A 2010 survey of the green roofs in Seattle acknowledged that while the initial costs of implementing a green roof may deter businesses or homeowners, it is likely that green roofs actually preserve the roofing material and cut costs in the long run. In light of the success in Seattle, other cities such as Portland, Chicago, and Washington, D.C. have all made efforts to develop their own Green Factor programs.