This excellent top-level round-up of multiple UK retrofit programmes sadly reveals how many were really poorly done. The most recent was a politically driven voucher system that lasted less than a year. Bottom line? 1. Focus on the building thermal envelope and design stage overall energy model (ie take a holistic whole dwelling retrofit approach). 2. Ignoring the tricky bits at the corners and focusing on wall/roof/floor R-values is dumb. 3. (Mechanical) ventilation is key.
Or, as the report author put it: “the lessons from these schemes have been learned:
- the need to adopt a holistic, whole dwelling retrofit approach but prioritise the building envelope (‘fabric first’);
- the need to reduce demand before attempting to decarbonise building services;
- the need to pay attention to the corners, junctions, edges and interfaces, which are the places where retrofit goes wrong;
- that most retrofit risks are moisture risks; and
- the critical role of ventilation in protecting buildings and the health of occupants.”
The author closes with a warning New Zealand would do well to also take to heart: “Promising deep reductions in emissions by 2035 without a credible domestic retrofit programme is empty posturing.”