This basic idea (thermal mass energy storage) is perfectly sensible, and has a long history. https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org

This basic idea (thermal mass energy storage) is perfectly sensible, and has a long history. https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org/wiki/Trombe_wall Coupled with a well designed ventilation system, a Trombé wall can also be used for cooling.