The demand from the public for energy-efficient homes will undoubtedly increase in the coming years, Sustain Worldwide has said.Anwar Harland-Khan, chief executive of the advocacy group, argued that the rise in consumer demand will lead to a premium price being placed on green properties.The comments follow the publication of Knight Franks Green Homes report into the proposed zero carbon directive of 2016. The paper claims that while the building industry is willing to cooperate with government targets, a clear definition of zero carbon is still need to help the industry prepare.Commenting on the issue, Mr Harland-Khan said The combination of legislation, increasing fuel costs and a more educated house buyer, means that the demand for green homes will undoubtedly increase.This will create an upper tier in housing and second home specs, which in turn will carry a premium.Homeowners wishing to upgrade their properties could also choose to invest in a new Franke kitchen sink or set of taps. James Max, an LBC (Londons Biggest Conversation) radio presenter, recently claimed that now is a good time for homeowners with a healthy disposable income to invest in their properties.