Energy-led retrofitting of solid wall dwellings - technical and user perspectives on airtightness

Mechanical ventilation with heat recovery (MVHR) is increasingly being promoted in the UK as a means of reducing the CO2 emissions from dwellings, and installers report growing activity in the retrofit market. In parallel with a survey of householder preferences and practices, the behaviour of a whole-house MVHR system installed in an experimental house, purpose built to typical 1930s standards, has been simulated. The range of air permeability values corresponded to those achieved in a retrofit upgrading process carried out on the house. In the house considered, air permeability, as measured in a 50 Pa pressurisation test, must be reduced below 5 m3/m2.h for MVHR to make an overall energy and CO2 saving. This required a level of disruption that would be unlikely to be tolerated by owners of solid wall dwellings.