The owner of this nineteen thirties cottage was enthusiastic about renovating their home and adding features to make it more sustainable and more enjoyable to live in. Water collection for a thriving garden was a high priority as was bulk insulation for thermal comfort. The challenge was how to bring natural light and some winter sun into a building which was hard up against its northern neighbour. A contemporary version of dormer windows which we called ‘roof fins’ worked well. They were not only highly functional, but had a beautiful aesthetic effect on the interior geometry of the building.