House for a Runner is a single-storey rear extension with deep facade providing privacy and shading. Built-in benches offer post-run relaxation, while a panoramic skylight brightens the interior and helps check weather conditions before heading out. To ensure indoor comfort and wellbeing, we used traditional cavity wall construction with a twist for the internal walls. Insulated with foam blocks, these walls are fully separated from the cold site slab below. This innovation guarantees top thermal efficiency in a traditional build and allows rendering of internal walls, utilizing their thermal mass for cooling and heating.