The Tamar government headquarters will be environmentally friendly but officials could not say yesterday whether it will be carbon-neutral. Being carbon-neutral means carbon dioxide generated from the site will be offset by environmentally friendly measures. It is also not known where protesters will be allowed to gather until the detailed design is unveiled by the end of this year. An official promised to strike a balance between public rights and security issues. Rocco Yim, architect of The Door, said the design was environmentally friendly in various ways. Apart from the large green area for public use, there would be green roofs, sky gardens and vertical planting walls for the government and Legislative Council buildings. Water features, such as a lily pond and fish ponds, would give a cooling effect via evaporation to lower day-time temperatures. Rainwater would be collected for irrigation and the design of the actual 'door' would allow air to flow from the harbour to the business district. For energy efficiency, photovoltaic panels would convert sunlight into electricity on the rooftop to provide renewable energy for site usage. A computerised lighting system and service-on-demand escalator would avoid energy wastage. For example, office lighting would be automatically adjusted according to daylight penetrating the office. Materials such as a double-layered ventilated facade and special glass curtain wall would reduce temperatures inside and hence cut the use of air conditioning. Metal rather than bamboo scaffolding would be used in the 39-month construction period to minimise waste. Lawmaker Lee Wing-tat said the government headquarters should be carbon-neutral. He also urged the government to disclose the location intended for public protests. Director of administration Jennifer Mak Yee-ming said she could not comment on the carbon-free issue and the government was still deciding whether to demolish the existing government offices. The project is expected to be completed by May 2011.