Reducing heat losses is the basis for a rational renovation. When the facade or roof needs repairing, insulating at the same time decreases heating bills, improves comfort and eliminates a cause of mould. Renovating to the "Passivhaus" standard [2], however, often poses problems in renovation, i. e. anchoring thick insulation and detailing wall openings of window and door. Exterior insulation of historic buildings is often prohibited and interior insulation leaves thermal bridges.

Three examples are presented here: gutting the building to the structure (but still preserving much of its immense gray energy content), a gentle renovation of an historic building and a renovation including an innovative solar facade insulation system.