The effect of refurbishment and trickle vents on airtightness: the case of a 1930s semi-detached house

As UK homes are insulated and draught proofed in an attempt to reduce wintertime heating demand they become more airtight. Any reduction in infiltration could have a detrimental effect on indoor air quality. Controllable background ventilation provided by trickle vents is one method of maintaining indoor air quality.
A 1930s semi-detached 3-bedroom house was refurbished with double-glazed windows, trickle vents, doors and loft insulation. 167 blower door tests were carried out pre- and post-refurbishment between January and March 2017 to understand the repeatability of the test and quantify how trickle vents affect airtightness.
The refurbishment reduced air leakage by 29% from 20.8 to 14.7m3/h/m2 at 50Pa (with all windows and trickle vents closed), but still in excess of the current UK regulations for new builds (10m3/h/m2 at 50Pa). Opening trickle vents provided limited additional ventilation, only increasing air change rate by 1.8m3/h/m2 with all vents open. The test was found to be repeatable with a standard error of 0.07m3/h/m2 at 50Pa with no relationship between the test result and wind speed or direction.
The results lead to two important conclusions. Firstly, after refurbishing older homes of this type, infiltration rates are still well above recommendations for adequate indoor air quality. Secondly, the omission of trickle vents in older homes may not unduly diminish indoor air quality.