Nijenborgh 4 – the physics and chemistry building on Zernike – uses about 1.2 million euros worth of gas in a cold month. The old and poorly insulated construction still has single-pane windows and is very draughty. That needs to change, staff and students feel, so they spent last Friday applying insulating foil to the windows and sticking reflective foil behind the radiators. They hope to achieve a reduction in energy usage of about 30 percent.