1) The document discusses approaches to retrofitting existing buildings in the UK to meet climate change targets through a holistic, stepped approach. It provides a case study of retrofitting a 1960s tower block in phases to an EnerPHit standard. 2) Initial measures included cavity wall insulation, window replacement, and roof insulation to reduce heating demands from over 200 kWh/m2 to around 150 kWh/m2. 3) Subsequent phases involved external wall insulation, ground floor insulation, and balcony glazing to further reduce demands to around 100 kWh/m2. 4) Final measures such as triple glazing windows and MVHR ventilation aim to achieve demands under 25 kWh/