You have to love the amusing way in which "green" considerations impact on decisions of Government and the Parliamentary apparatus. When the House of Commons Commission was asked by Norman Baker MP if it would consider a flat fee for car parking on the Parliamentary Estate of £10 the answer was no.
There were no plans to introduce a punitive tax to discourage car usage for people who have to go to Parliament to work - those sort of taxes are just for the proles you see. Meanwhile, the seven year old escalator system in Portcullis House is having an estimated £327,000 spent on it this summer. When the work is complete it will have fancy motion sensors so that it operates in an energy efficienct way!