Sheffield City Council in the UK identified some dwellings of non-standard construction that needed to be refurbished. The refurbishment mainly involved applying insulation and rendering to the exterior surfaces of external walls and replacing old windows. The main aims of the refurbishment for the Council were to improve the condition and appearance of the dwellings and reduce conductive heat loss through the fabric. Although no specific measures were taken to improve the air tightness of the houses it was thought to be interesting to see if an improvement in air tightness could be achieved as a by-product of the general refurbishment. This study performed a series of blower door air tightness tests on three dwellings, each of different non-standard construction, before and after refurbishment. The three houses displayed a wide range of air leakiness values prior to refurbishment. The worst house had nearly twice the leakage of the best house and all the houses were above the recommended good practice air tightness value for UK housing. After refurbishment the leakiness of each house had been reduced, although the improvements were of not of equal magnitude. Two of the three houses did meet the good practice air tightness as an additional benefit of the general refurbishment.