The Grade I Listed St Andrew’s Church in Much Hadham, a village in Hertfordshire that dates back to Saxon times has recently refurbished its historic bells. Part of the refurbishment was to improve the dilapidated sound insulation and thermal retention to the louvres in the church tower. The 8 ringing bells in the tower were taken off-site to be refurbished and re-tuned. Prior to them being rehung in the existing frame with new headstocks, wheels and fitting, it was suggested that secondary glazing was fitted into the louvre openings in the tower. Like many historic buildings, not all of the openings were plumb and true. Prior to the installation of the secondary glazing, timber frames were fitted to each opening to accept the secondary units ensuring they could support the weight of the new glazing of around 130-140kg. A 200mm cavity was used to enhance performance. 8 units were installed in the 4 openings of the church’s bell tower; a combination of the Series 42 fixed light units mullion coupled with the Series 80 3-pane horizontal slider with 10.8mm thick laminated glass. The fully assembled units could not be carried up the extremely narrow spiral stairs leading to the top of the tower. Therefore, the units were lifted 12 meters up with great care in sections via rope and pulley from the bottom of the tower up through a series of trapdoors across 3 floors.